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Swarm is the fifth Earth Explorer mission approved in ESA’s Living Planet Programme, and was successfully launched on 22 November 2013. The Swarm mission aims to provide the best-ever survey of the geomagnetic field and its temporal evolution, covering a wide variety of Earth processes, ranging from the geodynamo to the magnetosphere-ionosphere-thermosphere coupling using a constellation of 3 identical satellites carrying sophisticated magnetometers and electric field instruments. This session invites contributions illustrating the achievements of Swarm for investigating all types of Earth and near-Earth processes, as well as contributions describing synergies with other missions and ongoing initiatives towards designing innovative new low-Earth orbit (LEO) magnetic field missions.

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Convener: Georgios Balasis | Co-conveners: Gauthier Hulot, Anja Strømme
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| Attendance Wed, 06 May, 08:30–12:30 (CEST)

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Chat time: Wednesday, 6 May 2020, 08:30–10:15

Chairperson: Georgios Balasis, Anja Strømme
D1115 |
EGU2020-9616
Kathy Whaler, Magnus Hammer, Chris Finlay, and Nils Olsen

The Swarm constellation provides information on both along- and across-track magnetic field gradients. Spatial changes of the magnetic vector field elements are described by a magnetic field gradient tensor, whose elements and their uncertainties can be estimated using the Virtual Observatory (VO) concept, whereby data within a cylinder centred on the VO with axis perpendicular to the Earth’s surface are reduced to a central point at satellite altitude. Recent experiments have shown that analysing data collected over a 4 month window provides the best compromise between reducing bias from the way the satellite orbits sample each VO cylinder and preserving information on temporal changes of the field, and that the data provide spatial information sufficient to resolve 300 non-overlapping VOs. We invert annual first differences of the 5 independent gradient tensor elements (providing estimates of secular variation, SV, gradients) at these 300 VOs over the Swarm era for advective velocity at the core-mantle boundary, forcing the flow to have minimal acceleration while providing an adequate fit to the data. We obtain flows similar to those from previous SV inversions but purely from the gradient information. The resolution of the SV gradients is higher than that of the SV itself, resulting in a ~30% increase in the number of effective flow parameters; this is thought to be because the gradients are less affected by long period external signals that are difficult to remove from the data, resulting in an improved signal to noise ratio. Although very little temporal change in the flow is required to reproduce even rapid changes in the magnetic field, we are able to isolate some robust flow changes, in particular regarding changes in the azimuthal flow acceleration, associated with the geomagnetic impulse in the Pacific region in around 2016.

How to cite: Whaler, K., Hammer, M., Finlay, C., and Olsen, N.: Core-mantle boundary flows obtained purely from Swarm secular variation gradient information, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9616, https://doi.org/10.5194/egusphere-egu2020-9616, 2020.

Chairperson: Georgios Balasis, Anja Strømme
D1116 |
EGU2020-7879
Alexey Kuvshinov, Alexander Grayver, Lars Tøffner-Clausen, and Nils Olsen

In this contribution, we report on our recent attempts to detect lateral variations of the electrical conductivity at mid mantle depths (400­ – 1600 km) using 6 years of Swarm, Cryosat-2 and observatory magnetic data. The approach involves a three-dimensional (3-D) inversion of matrix Q-responses. These responses relate spherical harmonic coefficients of external (inducing) and internal (induced) parts of the magnetic potential, derived for geomagnetic variations at periods longer than 1 day and hence mainly describing signals of magnetospheric origin (i.e. external also to satellites, as required). In addition to the inversion results, we discuss potential ways to improve the recovery of 3-D conductivity structures in the mantle.

How to cite: Kuvshinov, A., Grayver, A., Tøffner-Clausen, L., and Olsen, N.: Mapping 3-D mantle electrical conductivity using Swarm, Cryosat-2 and ground observatory data , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7879, https://doi.org/10.5194/egusphere-egu2020-7879, 2020.

Chairperson: Georgios Balasis, Anja Strømme
D1117 |
EGU2020-4651
| solicited
Alexander Grayver, Nils Olsen, Chris Finlay, and Alexey Kuvshinov

The continuous high-quality geomagnetic field measurements delivered by the Swarm satellite constellation trio have enabled reliable global mapping of the magnetic signature of ocean tides for several tidal constituents. These signals provide geophysical constraints on the average electrical conductivity profile of the upper mantle below the oceans. In principle, these signals can also sense lateral variations of the electrical conductivity in the oceanic upper mantle, although the amplitude of these effects is small. Additionally, the long-term changes in the climatology of the ocean can be potentially detected by the magnetic satellite signals. Both applications put additional demands on the accuracy and resolution of the extracted signals. This contribution discusses potential ways to meet the required demands and evaluates the feasibility of using the magnetic signature of ocean tides for studying these effects.

How to cite: Grayver, A., Olsen, N., Finlay, C., and Kuvshinov, A.: Oceanic tidal signals in satellite magnetic data: quo vadis?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4651, https://doi.org/10.5194/egusphere-egu2020-4651, 2020.

Chairperson: Georgios Balasis, Anja Strømme
D1118 |
EGU2020-13612
Jakub Velímský, Magnus D. Hammer, and Christopher C. Finlay

The magnetic signatures of the M2, and more recently also the N2, and O1 oceanic tides have been successfully extracted from satellite observations (Grayver & Olsen, 2019). The traditional method uses the spatial representation of the tidal signals by spherical harmonics. Here we present an alternative approach based on the concept of virtual observatories, motivated by similar development in the analysis of the core field (Mandea & Olsen 2006). All quiet-time, night-side vector magnetic field values observed by the satellite(s) in the proximity of a selected virtual observatory are parameterized by a scalar magnetic potential represented by a cubic harmonic polynomial in a local Cartesian coordinate system. The time-dependence of the polynomial coefficients is constrained by selected tidal frequency, taking into account also the phase and amplitude corrections. The local approach offers several advantages over the use of the global spherical-harmonic base. The disturbances from external field in the polar areas have no impact on the inversion at lower latitudes, and local error estimates can be also provided. In this initial report, we will explore the possibilities of the new technique in terms of resolution, the combination of datasets from multiple satellites and the use of NS and EW field differences from the Swarm A-C pair.

How to cite: Velímský, J., Hammer, M. D., and Finlay, C. C.: The magnetic signatures of oceanic tides in satellite data: A virtual-observatory approach, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13612, https://doi.org/10.5194/egusphere-egu2020-13612, 2020.

Chairperson: Georgios Balasis, Anja Strømme
D1119 |
EGU2020-13140
Angelo De Santis and the SAFE Team

Analysing ionospheric electron density and magnetic field data from several years of the Swarm three-satellite mission we define a dataset of anomalies statistically.  We then use a superposed epoch approach to study the possible relation with a corresponding dataset of earthquakes occurred in the same space-time domain. Two statistical quantities d and n are then established comparing the statistics of the real analyses with simulations to assess the effectiveness of the largest concentrations of anomalies as ionospheric precursors. In detail, d would show how much the real maximum concentration is above the expected typical maximum concentration of a random anomaly distribution; while n value measures how much the largest concentration deviates with respect a typical random deviation: the larger are the d and n values, the more the results of the analysis applied to real data deviate from randomness. The best cases for which the real analyses are well distinct from random simulations are selected when d≥1.5, because the anomaly density is equal to or larger than 50% of random distribution, and n≥4, because the probability to be random is equal to or less than 0.1%.  This is the case of Y magnetic field component with a search in the Dobrovolsky area around each considered earthquake epicentre. The electron density is slightly less effective in the correlation with earthquakes, but still better than a homogeneous random distribution of anomalies.

How to cite: De Santis, A. and the SAFE Team: Statistical analysis of Swarm satellite data for assessing the effectiveness of ionospheric precursors of earthquakes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13140, https://doi.org/10.5194/egusphere-egu2020-13140, 2020.

Chairperson: Georgios Balasis, Anja Strømme
D1120 |
EGU2020-10018
| Highlight
Pierdavide Coïsson, Vladimir Truhlik, Janusz Mlynarczyk, Gauthier Hulot, Rémi Madelon, Olivier Bonnot, Pierre Vigneron, Dalia Burešová, Jaroslav Chum, Pawel Rzonca, and Andzej Kulak

New sessions of burst-mode acquisition of the Absolute Scalar Magnetometers (ASM) onboard Swarm satellites have been conducted during 2019 , with the aim of acquiring events covering various geophysical conditions, in terms of geomagnetic latitude, spacecraft Local Time and season, to better understand the conditions under which the ELF component of whistlers is excited and can be detected at satellite altitude and to provide an additional ionospheric monitoring.

Among all candidate events detected using an automatic algorithm specifically designed for that purpose, a selection of remarkable whistler events have been further studied. Firstly, from the estimation of the whistler dispersions, the origin times of the lightning discharge have been estimated and validated with ground data from the World ELF Radiolocation Array (WERA), providing the locations of the lightning strikes and their intensity in the ELF spectral band. These locations have also been validated using data from the World Wide Lightning Location Network (WWLLN) providing measurements.

Subsequently, to reconstruct the propagation path inside the ionosphere of the ELF component of the whistler, a dedicated ray-tracing algorithm has been designed. It uses a background ionosphere model of electron and ions based on the International Reference Ionosphere. For the purposes of producing a ionospheric representation as close as possible to the experimental conditions, the update of the main ionospheric parameters based on worldwide ionosonde data IRTAM has been applied, validating it by using ionosonde data available in the vicinity of specific whistler events. The in-situ electron density measurements of the Electric Field Instrument (EFI) of Swarm satellite have also been used to constrain the model in the topside ionosphere.

We present the recent results obtained during some of these burst sessions, and discuss the possibility offered by this new dataset to validate global ionospheric models and provide a new avenue in ionospheric research, that could be also pursued by the NanoMagSat mission.

How to cite: Coïsson, P., Truhlik, V., Mlynarczyk, J., Hulot, G., Madelon, R., Bonnot, O., Vigneron, P., Burešová, D., Chum, J., Rzonca, P., and Kulak, A.: Reconstructing the propagation of Whistlers observed in ELF during ASM burst sessions from the lightning strikes to their detection and validation of IRI model, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10018, https://doi.org/10.5194/egusphere-egu2020-10018, 2020.

Chairperson: Georgios Balasis, Anja Strømme
D1121 |
EGU2020-11130
Paola De Michelis, Giuseppe Consolini, Georgios Balasis, and Jerome Bouffard and the INTENS Team

The ionospheric environment is a complex system where dynamic phenomena, such as turbulence (fluid and magnetohydrodynamics) and plasma instabilities generally occur as a consequence of the coupling processes among solar wind, magnetosphere and ionosphere. It has been suggested that the turbulent character of the ionospheric plasma density also enters into the formation and dynamics of ionospheric inhomogeneities and irregularities, which essentially characterize the active equatorial, mid-latitude and polar regions. The ionospheric turbulence indirectly plays an important role also in the framework of space weather when due to the arrival of solar perturbations the plasma, the energetic particle distributions, the electric and magnetic fields within the magnetosphere and ionosphere are deeply modified thus paving the way for an increase in the ionospheric turbulence. Recent findings within the ESA funded project “Characterization of IoNospheric TurbulENce level by Swarm constellation (INTENS)” permitted us to investigate the role played by the turbulence on scales from hundreds of kilometers to a few kilometers in generating multi-scale plasma structures and inhomogeneities in the ionospheric environment at different latitudes. This presentation reports on the most promising results of the INTENS project regarding the investigation of turbulence and plasma conditions in the topside ionosphere using Swarm data.

How to cite: De Michelis, P., Consolini, G., Balasis, G., and Bouffard, J. and the INTENS Team: Turbulence and Plasma Inhomogeneity Observed by Swarm Constellation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11130, https://doi.org/10.5194/egusphere-egu2020-11130, 2020.

Chairperson: Georgios Balasis, Anja Strømme
D1122 |
EGU2020-3760
Andrew Yau, Andrew Howarth, H. Gordon James, David Knudsen, Richard Langley, and David Miles

The CASSIOPE Enhanced Polar Outflow Probe (e-POP) was originally envisioned as a low-cost, short-lifetime (18-month) small-satellite mission for investigating polar ion outflows and related magnetosphere-ionosphere coupling phenomena. However, e-POP is currently in its seventh year of continuing operation, as an addition to and as the fourth component of the Swarm constellation of satellites, under the European Space Agency Third Party Mission Programme.

Since 2017, the increased operation duty-cycle of e-POP has enabled the routine extension of its science operations to its full altitude range and to all latitudes, and made possible several new studies of important mid- and low-latitude topside ionospheric phenomena. In addition, the integrated e-POP and Swarm operation takes advantage of the synergy between the orbit characteristics and unique instrument capabilities between e-POP and Swarm, to enable or enhance a host of coordinated studies of magnetosphere-ionosphere coupling: including the Earth’s magnetic field and related current systems, auroral and upper atmospheric dynamics, and ionosphere-thermosphere and ionosphere-plasmasphere coupling processes. We present an overview of these new studies, focusing on their results on the effects of space weather in the ionosphere and upper atmosphere such as anomalous satellite orbit drag and ionospheric scintillation.

How to cite: Yau, A., Howarth, A., James, H. G., Knudsen, D., Langley, R., and Miles, D.: Integrated Science Operations of CASSIOPE e-POP with the Swarm Constellation for New Studies of Magnetosphere-Ionosphere Coupling, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3760, https://doi.org/10.5194/egusphere-egu2020-3760, 2020.

Chairperson: Georgios Balasis, Anja Strømme
D1123 |
EGU2020-12192
| Highlight
David Knudsen

The Thermal Ion Imagers on Swarm A-C, and the Suprathermal Electron/Ion Imager on ePOP (now “Swarm-E”) provide a unique view of charged particle distribution functions in the ionosphere at high time resolution (up to 100 images/s). Through high resolution, CCD-based imaging (~3000 pixels/image), ion drift velocity is derived from these images at a resolution of 20 m/s or better, and in general agreement with velocities derived from ground based radars [1] and an empirical convection model [2]. This talk reviews recent scientific applications of this technique, which are wide-ranging and include mechanisms of ion heating and upflow [3,4], M-I coupling via Alfven waves [5,6], electron acceleration and heating by Alfven waves [7,8, 9], intense plasma flows associated with “Steve” [10,11], and electrodynamics of large-scale FAC systems[ 12], among others. In addition, future opportunities made possible by these data will be discussed.

[1] Koustov et al. (2019), JGR, https://doi.org/10.1029/2018JA026245

[2] Lomidze et al. (2019), ESS, https://doi.org/10.1029/2018EA000546

[3] Shen and Knudsen (2020a), On O+ ion heating by BBELF waves at low altitude, JGR, in revision.

[4] van Irsel et al. (2020), Highly correlated ion upflow and electron temperature variations in the high latitude topside ionosphere, submitted to JGR.

[5] Pakhotin et al. (2020), JGR, https://doi.org/10.1029/2019JA027277

[6] Wu et al. (2020a), Swarm survey of Alfvenic fluctuations and their relation to nightside field-aligned current and auroral arcs systems, JGR, in revision.

[7] Liang et al. (2019), JGR, https://doi.org/10.1029/2019JA026679

[8] Wu et al. (2020b), e-POP observations of suprathermal electron bursts in the ionospheric Alfven resonator, GRL, submitted.  

[9] Shen and Knudsen (2020b), Suprathermal electron acceleration perpendicular to the magnetic field in the topside ionosphere, JGR, in press.

[10] Archer et al. (2019), JGR, https://doi.org/10.1029/2019GL082687

[11] Nishimura et al. (2019), JGR, https://doi.org/10.1029/2019GL082460

[12] Olifer et al (2020), Swarm observations of dawn/dusk asymmetries between Pedersen conductance in upward and downward FAC regions, submitted to JGR.

 

How to cite: Knudsen, D.: Recent scientific findings based on high-resolution core plasma imaging of the ionosphere with Swarm and ePOP, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12192, https://doi.org/10.5194/egusphere-egu2020-12192, 2020.

Chairperson: Georgios Balasis, Anja Strømme
D1124 |
EGU2020-20871
| solicited
Johnathan Burchill

Properties and dynamics of ionosphere-thermosphere coupling may be investigated using observations from the Swarm electric field instruments (EFI). We illustrate this claim using measurements of vertical ion drift and electron temperature made by the EFIs, within the context of ambipolar diffusion parallel to the geomagnetic field. The associated ambipolar electric field is difficult to measure directly. Rather, under conditions where the ambipolar electric field is assumed to be specified, the ion-neutral momentum transfer collision frequency may be derived from the EFI measurements. In this talk, the theory, measurements and methodology of this approach are presented. Statistical analysis reveals highly-correlated ion upflow and electron temperature. Derived collision frequencies are found to be within an order of magnitude of empirical estimates at Swarm altitudes. We speculate on the feasibility of using this technique to examine the dynamics of ionosphere-thermosphere coupling using Swarm.

How to cite: Burchill, J.: Using Swarm to study ionosphere-thermosphere coupling, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20871, https://doi.org/10.5194/egusphere-egu2020-20871, 2020.

Chairperson: Georgios Balasis, Anja Strømme
D1125 |
EGU2020-11721
| Highlight
William Archer, Bea Gallardo-Lacour, Gareth Perry, Jean-Pierre St.-Maurice, Stephan Buchert, and Eric Donovan

Little is currently known about the optical phenomenon known as Steve. The first scientific publication on the subject suggests that Steve is associated with an intense subauroral ion drift (SAID). However, additional inquiry is warranted as this suggested relationship as it is based on a single case study. Here we present eight occurrences of Steve with coincident or near‐coincident measurements from the European Space Agency's Swarm satellites and show that Steve is consistently associated with SAID. When satellite observations coincident with Steve are compared to that of typical SAID, we find the SAID associated with Steve to have above average peak ion velocities and electron temperatures, as well as extremely low plasma densities.

How to cite: Archer, W., Gallardo-Lacour, B., Perry, G., St.-Maurice, J.-P., Buchert, S., and Donovan, E.: Steve: The optical signature of subauroral ion drifts, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11721, https://doi.org/10.5194/egusphere-egu2020-11721, 2020.

Chairperson: Georgios Balasis, Anja Strømme
D1126 |
EGU2020-19206
Octav Marghitu, Adrian Blăgău, and Joachim Vogt

Field-aligned currents (FACs) are closely related to aurora and a key component of the magnetosphere-ionosphere-thermosphere system. Large scale FAC structures, like Region 1 / Region 2, threading the whole auroral oval, as well as smaller scale FACs, associated with auroral arcs, are often assumed to consists of upward / downward current sheet pairs, uniform in longitudinal direction. While such a uniformity is consistent with the prevalent 1D symmetry of the auroral arcs and oval, longitudinal gradients may develop at times, for example when the 1D symmetry prepares to break, during the growth phase of auroral substorms. The Swarm mission provides optimum conditions to explore systematically longitudinal gradients in FACs, namely a proper spacecraft configuration, with the Swarm A / Swarm C pair lining up periodically with Swarm B at auroral latitudes, and high quality magnetic field data. The present report concentrates on a set of auroral events observed by the Swarm satellites, in this suitable configuration, during the first six months of the mission operational phase. At that time, the distance between Swarm A / Swarm C and Swarm B was in the range of a few 100 km, comparable to the length scale of electrojet currents associated with auroral arcs. Not surprising, longitudinal gradients in FACs are occasionally significant, a feature which is discussed with respect to the location, activity level, and substorm phase of the event.

How to cite: Marghitu, O., Blăgău, A., and Vogt, J.: Longitudinal Gradients in Field-Aligned Currents as Observed by Swarm, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19206, https://doi.org/10.5194/egusphere-egu2020-19206, 2020.

Chairperson: Georgios Balasis, Anja Strømme
D1127 |
EGU2020-1166
Ivan Pakhotin, Ian Mann, Kai Xie, David Knudsen, and Johnathan Burchill

Electromagnetic energy transfer in magnetosphere-ionosphere coupling (MIC) is an inherently multiscale process, where the relative contributions of various scale sizes, linked to various auroral phenomena, are largely unknown. While work in previous decades has largely focused on large scales, in recent years with the development of new instrumentation smaller scale electromagnetic disturbances have once again come into focus. Recent work by the authors has demonstrated evidence that small-scale processes appear to be so important as to potentially account for a global interhemispheric asymmetry in ionospheric energy input. This study attempts to statistically quantify the contribution of energy at the small and mesoscales using Poynting flux, calculated using the unprecedented ESA Swarm mission dataset of simultaneous electric and magnetic field measurements at 16 Hz, with statistics now spanning several years. We find important contributions at small scales to the total energy budget, while at the same time noting that there appears to be a limit above which energy content tends to drop off. In the context of previous observations from other spacecraft this may shed light on key small-scale processes happening in and around the auroral acceleration region, in particular discrete arcs and Alfvén wave reflection from the ionosphere, which are important in forming inputs to coupled magnetosphere-ionosphere-thermosphere modelling studies.

How to cite: Pakhotin, I., Mann, I., Xie, K., Knudsen, D., and Burchill, J.: Multi-scale Analysis of Electromagnetic Energy Input using Swarm: Quantifying Key Scales in Magnetosphere-Ionosphere Coupling, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1166, https://doi.org/10.5194/egusphere-egu2020-1166, 2019.

Chairperson: Georgios Balasis, Anja Strømme
D1128 |
EGU2020-6554
| Highlight
Claudia Stolle, Juan Rodríguez-Zuluaga, Chao Xiong, Yosuke Yamazaki, Guram Kervalishvili, and Lucas Schreiter

The Swarm three-satellite constellation mission provides high resolution and high-quality observations of the Earth’s magnetic field and of multiple parameters of the ionosphere, which lead to new knowledge on the Earth’s interior and space environment and help to investigate space weather effects on space technology. Several findings would otherwise not have been possible and demonstrate that missions like Swarm are indispensable for Earth and space exploration. In addition, aspects of longterm variations or enhanced understanding in temporal and spatial resolution on regional scales could be gained in combination with other missions. This presentation  focuses on recent achievements on the low latitude ionosphere. Examples include an empirical model of the occurrence of post-sunset equatorial plasma irregularities derived in combination with ten years of CHAMP geomagnetic data, an enhanced description of the Swarm irregularity observations together with regional maps of the South Atlantic ionosphere from GOLD, and the identification of differing GPS scintillation characteristics evoked by the irregularities in comparison with the lower orbit GOCE data. Equatorial electrojet and plasma data from Swarm also helped to empirically prove that Antarctic sudden stratospheric warming events, such as in September 2019, couple to the low latitude ionosphere through modified planetary waves.

How to cite: Stolle, C., Rodríguez-Zuluaga, J., Xiong, C., Yamazaki, Y., Kervalishvili, G., and Schreiter, L.: Recent achievements from the Swarm mission on the low latitude space environment and combinations with other satellite missions , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6554, https://doi.org/10.5194/egusphere-egu2020-6554, 2020.

Chairperson: Georgios Balasis, Anja Strømme
D1129 |
EGU2020-8072
Martin Rother, Monika Korte, Jürgen Matzka, Achim Morschhauser, Claudia Stolle, and Foteini Vervelidou

The Earth's core magnetic field model Mag.num was the parent model for the GFZ IGRF 13 candidate submission. The model is based on geomagnetic ground observatory and Swarm satellite observations. Epochs 2020.0 and beyond were not covered by the data available at the time of submission and our results were based on predictions. In this study, we investigate the effect of the more recent available data on our results of the 2020.0 epoch and the predicted secular variation by generating an updated Mag.num version. We especially focus on the spatial and temporal patterns of the local geomagnetic field minimum of the South Atlantic Anomaly (SAA). Recently, global geomagnetic field models have shown that an additional, although shallow, secondary minimum at Earth's surface has developed since around 2005. The location and significance of the secondary minimum and of the saddle point between the two minima are assessed also in view of the respective differences among the candidate models.

How to cite: Rother, M., Korte, M., Matzka, J., Morschhauser, A., Stolle, C., and Vervelidou, F.: Earth's core magnetic field model Mag.num and the IGRF 13 candidate, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8072, https://doi.org/10.5194/egusphere-egu2020-8072, 2020.

Chairperson: Georgios Balasis, Anja Strømme
D1130 |
EGU2020-9775
William Brown, Ciarán Beggan, Grace Cox, and Susan Macmillan

2020 marks the start of a new 5-year cycle and updated releases of the World Magnetic Model (WMM) and International Geomagnetic Reference Field (IGRF). These models provide a reference for the up-to-date internal geomagnetic field in 2020, and a prediction of its secular variation for the next 5 years, to 2025. While similar in some aspects, the two models have different specifications and many different users across diverse fields. They provide references to be used primarily for navigation (WMM) and geomagnetic coordinate systems (IGRF).

BGS produces the WMM in collaboration with the US’ NOAA/NCEI, while the IGRF is produced by an IAGA Div. V-MOD task force, this time consisting of fifteen teams across nine nations, including BGS. Here we present a summary of the production of the updated WMM2020 and IGRF-13, and BGS efforts to enable access to these models.

We also present a retrospective analysis of the predictive components of the candidate models for previous IGRF epoch’s secular variation. Recent epochs have seen notable geomagnetic jerks and the acceleration of the North magnetic dip pole, features not well represented by the constant SV format of models such as the IGRF. We assess the range of candidate models submitted for previous IGRF epochs, assess the accuracy of physically derived predictions versus mathematical extrapolations, and discuss the implications given the range of candidate models submitted for IGRF-13 secular variation over the next five years.

How to cite: Brown, W., Beggan, C., Cox, G., and Macmillan, S.: The new WMM2020 and IGRF-13 models, and a retrospective analysis of IGRF secular variation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9775, https://doi.org/10.5194/egusphere-egu2020-9775, 2020.

Chairperson: Georgios Balasis, Anja Strømme
D1131 |
EGU2020-3869
Zdenek Martinec, Javier Fullea, and Jakub Velimsky

Conventional methods of seismic tomography, surface topography and gravity data analysis constrain distributions of seismic velocity and density at depth, all depending on temperature and composition of the rocks within the Earth. WINTERC-grav, a new global thermochemical model of the lithosphere-upper mantle constrained by state-of-the-art global waveform tomography, satellite gravity (geoid and gravity anomalies and gradiometric measurements from ESA's GOCE mission), surface elevation and heat flow data has been recently released. WINTERC-grav is based upon an integrated geophysical-petrological approach where all relevant rock physical properties modelled (seismic velocities and density) are computed within a thermodynamically self-consistent framework allowing for a direct parameterization of the temperature and composition variables. In this study, we derive a new three dimensional distribution of the electrical conductivity in the Earth's upper mantle combining WINTERC-grav's thermal and compositional fields along with laboratory experiments constraining the conductivity of mantle minerals and melt. We test the derived conductivity model over oceans by simulating a tidally induced magnetic field. Here, we concentrate on the simulation of M2 tidal magnetic field induced by the ocean M2 tidal flow that is modelled by two different assimilative barotropic models, TPXO8-atlas (Egbert and Erofeeva, 2002) and DEBOT (Ein\v spigel and Martinec, 2017). We compare our synthetic results with the M2 tidal magnetic field estimated from 5 years of Swarm satellite observations and CHAMP satellite data by the comprehensive inversion of Sabaka et al. (2018).

How to cite: Martinec, Z., Fullea, J., and Velimsky, J.: Probing the oceanic upper mantle using M2 tidal magnetic field, waveform tomography, satellite gravity field, surface elevation and heat flow data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3869, https://doi.org/10.5194/egusphere-egu2020-3869, 2020.

Chairperson: Georgios Balasis, Anja Strømme
D1132 |
EGU2020-8277
Aaron Hornschild, Jan Saynisch-Wagner, Christopher Irrgang, Johannes Petereit, and Maik Thomas

Electrically conducting sea-water moves through Earth's magnetic field and generates electromagnetic signals itself. These signals can be detected by space borne Earth observation technologies, like the Swarm satellite magnetometer mission. In contrast to already successfully detected ocean tidal magnetic signatures, the magnetic signals from ocean circulation are still unidentified in observations. However, the electromagnetic signals from the ocean circulation would be an additional, interesting source of information.
We propose, that satellite altimetry can be helpful in order to detect magnetic signals from ocean circulation. Sea surface height measurements allow to estimate depth-integrated current velocities by using the geostrophic approximation, which describes a balance between sea surface height gradients and horizontal currents. With the resulting integrated electric current density, the magnetic signals from ocean circulation can be calculated using an electromagnetic induction solver. In a further step, the estimations are a basis for the  separation of magnetometer observations and for data assimilation.
Therefore, it is necessary that the geostrophic approach reflects the realistic time behavior of electromagnetic signals from ocean circulation. Ocean model data allows to verify this approach with respect to the identification of magnetic signals from ocean circulation in satellite magnetometer observations. We present this analysis and report about the feasibility of this approach regarding the Swarm mission and possible future missions.

How to cite: Hornschild, A., Saynisch-Wagner, J., Irrgang, C., Petereit, J., and Thomas, M.: Detection of Magnetic Signals from Ocean Circulation with Satellite Altimetry and Magnetometer, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8277, https://doi.org/10.5194/egusphere-egu2020-8277, 2020.

Chat time: Wednesday, 6 May 2020, 10:45–12:30

Chairperson: Gauthier Hulot, Anja Strømme
D1133 |
EGU2020-13913
Magnus Hammer, Christopher Finlay, Ciaran Beggan, William Brown, and Grace Cox

The ESA Swarm DISC Geomagnetic Virtual Observatories (GVO) project aims to apply the virtual observatory concept to Swarm magnetic field measurements. The Virtual Observatory concept is a data processing method which mimics the behavior of magnetic monthly-mean time-series measured at ground observatories but at fixed locations on a uniform global grid at satellite altitude instead. Here we present several new GVO data products consisting of the average time-series of vector magnetic field values, regularly distributed in space and time which are suitable for monitoring the geomagnetic field. The GVO products consist of an equal-area grid with separation spacing of 300 km and cadence of either 1 month or 4 months. Various levels of processing are applied to remove the effects of altitude change and satellite local-time differences to produce a consistent time series. It is known that monthly time-series can have strong local-time artifacts which are removed with four-monthly averages, though with a loss of temporal resolution. The GVO products are designed to make Swarm magnetic data more accessible to researchers studying the physics of the core dynamo process, and related phenomenon such are secular variation, geomagnetic jerks and rapid core dynamics. In addition, the GVO data products also provide valuable information for investigating magnetospheric and ionospheric magnetic signals on timescales of months and longer.

How to cite: Hammer, M., Finlay, C., Beggan, C., Brown, W., and Cox, G.: Geomagnetic Virtual Observatories: Global monitoring of geomagnetic secular variation with Swarm data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13913, https://doi.org/10.5194/egusphere-egu2020-13913, 2020.

Chairperson: Gauthier Hulot, Anja Strømme
D1134 |
EGU2020-9957
Grace Cox, Will Brown, Ciaran Beggan, Magnus Hammer, and Chris Finlay

Geomagnetic Virtual Observatories (GVOs) use satellite measurements to provide estimates of the mean internally-generated magnetic field (MF) over a specified period (usually one or four months) at a fixed location in space, mimicking the mean values obtained at ground-based observatories (GOs). These permit secular variation (SV) estimates anywhere on the globe, thereby mitigating the effects of uneven GO coverage. Current GVO estimates suffer from two key contamination sources: first, local time sampling biases due to satellite orbital dynamics, and second, MFs generated in regions external to the Earth such as the magnetosphere and ionosphere. Current methods to alleviate this contamination have drawbacks:Averaging over four months removes the local time sampling bias at the cost of reduced temporal resolution

  1. Stringent data selection criteria such as night-time, quiet-time only data greatly reduce, but do not entirely remove, external MF contamination and result in a small subset (<5%) of the available data being used
  2. Removing model predictions for external MFs from the measurements also reduces noise, however such parameterisations cannot fully describe these physical systems and some of their signal remains in the data.

Here we present an alternative approach to denoising GVOs that uses principal component analysis (PCA). This method retains monthly resolution, uses all available vector satellite data and removes contamination from orbital effects and external MFs. We present an application of PCA, implemented in an open-source Python package called MagPySV, to new GVOs calculated as part of a Swarm DISC project.  The denoised data will be incorporated into a new GVO data set that will be available to the geomagnetism community as an official Swarm product.  

How to cite: Cox, G., Brown, W., Beggan, C., Hammer, M., and Finlay, C.: Denoising Swarm Geomagnetic Virtual Observatories using principal component analysis, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9957, https://doi.org/10.5194/egusphere-egu2020-9957, 2020.

Chairperson: Gauthier Hulot, Anja Strømme
D1135 |
EGU2020-18876
Wojciech Jarmolowski, Pawel Wielgosz, Anna Krypiak-Gregorczyk, and Beata Milanowska

Three Swarm satellites are equipped with Langmuir Probes (LP) measuring in-situ electron density of Earth electric field and POD GNSS receivers determining topside total electron content (TEC) in the upper ionosphere. It is proved that different events on the Earth and in its atmopshere have their own impact on Earth electric field, and the earthquakes are in this group. Many strong earthquakes induce tsunamis, which are also suspected as contributing to the gravity waves having an impact on the ionospheric TEC. These reasons encourage to the study on the sensitivity of Swarm LP and POD GNSS data to the abovementioned phenomena. Referring to the sensitivity of TEC data derived from GNSS stations to Earthquakes, sensitivity of GNSS and LP data at around 500 km high orbit is analyzed here. A similar orbital height can be found in case of many LEO missions equipped at least with GNSS POD receivers, which makes Swarm especially interesting data acquisition platforms.

The investigation of Swarm data in view of Tsunamis and earthquakes is difficult due to several factors. There are only three satellites, the two of which fly almost together, which gives in fact only two points of the survey. The orbital repetition period is long, which seriously limits the number of comparable observations in terms of the location and time of the day. Finally, the number of large earthquakes and tsunami events in time of Swarm science mission is low, and many Earthquakes do not coincide sufficiently with Swarm passes in time and space. All these factors, however, doesn’t exclude an opportunity of analyzing of Swarm data passes above the earthquakes of magnitude nearby 8, linked with the tsunamis reaching several decimeters.

Swarm LP data is detrended and analyzed before the earthquakes and also during the earthquakes and resulting tsunami events. The GNSS POD topside TEC from Swarm is analyzed together as a background for LP data. In-situ electron density disturbances occurring during a pass close to the earthquake is compared to selected STEC measurements between LEO and GNSS satellites. Additionally absolute STEC values from selected nearby ground stations are analyzed in order to  find existing correlations for detected disturbances in the electric and magnetic fields. All the observations are sparse in time and space, and therefore, leave some unanswered questions and uncertainties. However, several interesting perturbations over earthquake/tsunami events are observable in both Swarm LP data and GNSS TEC data.

How to cite: Jarmolowski, W., Wielgosz, P., Krypiak-Gregorczyk, A., and Milanowska, B.: Analysis of Swarm Electric Field Data in View of Tsunami Events and related Earthquakes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18876, https://doi.org/10.5194/egusphere-egu2020-18876, 2020.

Chairperson: Gauthier Hulot, Anja Strømme
D1136 |
EGU2020-4981
Constantinos Papadimitriou, Georgios Balasis, Adamantia-Zoe Boutsi, Omiros GIannakis, Anastasios Anastasiadis, Ioannis A. Daglis, Paola De Michelis, and Giuseppe Consolini

Recently, many novel concepts originated in dynamical systems or information theory have been developed, partly motivated by specific research questions linked to geosciences, and found a variety of different applications. This continuously extending toolbox of nonlinear time series analysis highlights the importance of the dynamical complexity to understand the behavior of the complex solar wind – magnetosphere – ionosphere - thermosphere coupling system and its components. Here, we propose to apply such new approaches, mainly a series of entropy methods to the time series of the Earth's magnetic field measured by the Swarm constellation. Swarm is an ESA mission launched on November 22, 2013, comprising three satellites at low Earth polar orbits. The mission delivers data that provide new insight into the Earth's system by improving our understanding of the Earth's interior as well as the near-Earth electromagnetic environment. We show successful applications of methods originated in information theory to quantitatively studying complexity in the dynamical response of the topside ionosphere, at Swarm altitudes, focusing on the most intense magnetic storms of the present solar cycle.

How to cite: Papadimitriou, C., Balasis, G., Boutsi, A.-Z., GIannakis, O., Anastasiadis, A., Daglis, I. A., De Michelis, P., and Consolini, G.: Dynamical Complexity of Magnetic Storms at Swarm Altitudes Using Entropy Measures, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4981, https://doi.org/10.5194/egusphere-egu2020-4981, 2020.

Chairperson: Gauthier Hulot, Anja Strømme
D1137 |
EGU2020-5070
Georgios Balasis, Michael A. Balikhin, Sandra C. Chapman, Giuseppe Consolini, Ioannis A. Daglis, Reik V. Donner, Juergen Kurths, Milan Palus, Jakob Runge, Bruce Tsurutani, Dimitris Vassiliadis, Simon Wing, Rune Floberghagen, Jesper W. Gjerloev, Jay Johnson, Massimo Materassi, Tommaso Alberti, Adamantia Zoe Boutsi, Constantinos Papadimitriou, and Anja Strømme

Learning from successful applications of methods originating in statistical mechanics or information theory in one scientific field (e.g. atmospheric physics or weather) can provide important insights or conceptual ideas for other areas (e.g. space sciences) or even stimulate new research questions and approaches. For instance, quantification and attribution of dynamical complexity in output time series of nonlinear dynamical systems is a key challenge across scientific disciplines. Especially in the field of space physics, an early and accurate detection of characteristic dissimilarity between normal and abnormal states (e.g. pre-storm activity vs. magnetic storms) has the potential to vastly improve space weather diagnosis and, consequently, the mitigation of space weather hazards. This presentation reports on the progress of a largely interdisciplinary International Team, combining expertise from both space physics and nonlinear physics communities, which was selected for funding by the International Space Science Institute (ISSI) in 2019. The Team attempts to combine advanced mathematical tools and identify key directions for future methodological progress relevant to space weather forecasting using Swarm, SuperMAG, and other space/ground datasets. By utilizing a variety of complementary modern complex systems based approaches, an entirely novel view on nonlinear magnetospheric variability is obtained. Taken together, the multiplicity of recently developed approaches in the field of nonlinear time series analysis offers great potential for uncovering relevant yet complex processes interlinking different geospace subsystems, variables and spatio-temporal scales. The Team provides a first-time systematic assessment of these techniques and their applicability in the context of geomagnetic variability.

How to cite: Balasis, G., Balikhin, M. A., Chapman, S. C., Consolini, G., Daglis, I. A., Donner, R. V., Kurths, J., Palus, M., Runge, J., Tsurutani, B., Vassiliadis, D., Wing, S., Floberghagen, R., Gjerloev, J. W., Johnson, J., Materassi, M., Alberti, T., Boutsi, A. Z., Papadimitriou, C., and Strømme, A.: Complex system perspectives of geospace electromagnetic environment research, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5070, https://doi.org/10.5194/egusphere-egu2020-5070, 2020.

Chairperson: Gauthier Hulot, Anja Strømme
D1138 |
EGU2020-8796
Alexandra Antonopoulou, Constantinos Papadimitriou, Georgios Balasis, Adamantia Zoe Boutsi, Konstantinos Koutroumbas, Athanasios Rontogiannis, and Omiros Giannakis

Ultra-low frequency (ULF) magnetospheric plasma waves play a key role in the dynamics of the Earth’s magnetosphere and, therefore, their importance in Space Weather studies is indisputable. Magnetic field measurements from recent multi-satellite missions (e.g. Cluster, THEMIS, Van Allen Probes and Swarm) are currently advancing our knowledge on the physics of ULF waves. In particular, Swarm satellites, one of the most successful mission for the study of the near-Earth electromagnetic environment, have contributed to the expansion of data availability in the topside ionosphere, stimulating much recent progress in this area. Coupled with the new successful developments in artificial intelligence (AI), we are now able to use more robust approaches devoted to automated ULF wave event identification and classification. The goal of this effort is to use a deep learning method in order to classify ULF wave events using magnetic field data from Swarm. We construct a Convolutional Neural Network (CNN) that takes as input the wavelet spectra of the Earth’s magnetic field variations per track, as measured by each one of the three Swarm satellites, and whose building blocks consist of two convolution layers, two pooling layers and a fully connected (dense) layer, aiming to classify ULF wave events in four different categories: 1) Pc3 wave events (i.e., frequency range 20-100 MHz), 2) non-events, 3) false positives, and 4) plasma instabilities. Our primary experiments show promising results, yielding successful identification of more than 95% accuracy. We are currently working on producing larger training/test datasets, by analyzing Swarm data from the mid-2014 onwards, when the final constellation was formed, aiming to construct a dataset comprising of more than 50000 wavelet image inputs for our network.

How to cite: Antonopoulou, A., Papadimitriou, C., Balasis, G., Boutsi, A. Z., Koutroumbas, K., Rontogiannis, A., and Giannakis, O.: A Deep Learning Technique for Automated Detection of ULF Waves in Swarm Time Series, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8796, https://doi.org/10.5194/egusphere-egu2020-8796, 2020.

Chairperson: Gauthier Hulot, Anja Strømme
D1139 |
EGU2020-7122
Leonie Pick, Joachim Vogt, Adrian Blagau, and Nele Stachlys

Auroral field-aligned currents (FACs) are of key importance for the electromagnetic coupling and the energy transport in the magnetosphere-ionosphere system. We use Swarm multi-spacecraft magnetic and electric field measurements from a selection of auroral oval crossing events to advance our understanding of the spatial scales and the electromagnetic energy flux (Poynting flux) associated with sheets of auroral FACs. Our study comprises the derivation of a scale-dependent correlation function based on dual-satellite vectorial magnetic field perturbation time series, in order to identify and analyze planar current structures. Applying concepts from multi-point boundary crossing analysis to data from Swarm-A and Swarm-C, a correlation measure is constructed using the mean square deviation of the observed magnetic perturbations and an empirical pattern function. Peak correlations indicate the positions and the scales of auroral FAC sheets, which we contextualize with the magnetic local time, the geomagnetic latitude, and geomagnetic activity indices (e.g., AL). In a parallel strand of work, we estimate the associated Poynting flux from the combination of the magnetic field perturbations and those of the electric field as deduced from the observed cross-track ion drift velocity. We assess the quality of our Swarm-based estimate by a comparison to the Poynting flux given by the “Cosgrove-PF” empirical model, which is based on FAST data from 1996 to 2001 and available from NASA’s Community Coordinated Modeling Center. Connecting both strands of work, we check to what degree this data-model comparison depends on the current sheets’ spatial scale. Throughout the study, we adopt a framework for describing planar magnetic structures that facilitates error analysis and accommodates not only boundary analysis, but also single-spacecraft polarization techniques.

How to cite: Pick, L., Vogt, J., Blagau, A., and Stachlys, N.: Update on scales and energetics of auroral field-aligned currents as observed by Swarm, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7122, https://doi.org/10.5194/egusphere-egu2020-7122, 2020.

Chairperson: Gauthier Hulot, Anja Strømme
D1140 |
EGU2020-9644
Abiyot Workayehu, Heikki Vanhamäki, and Anita Aikio

We present statistical investigation of the high-latitude ionospheric current systems in the Northern hemisphere (NH) and Southern hemisphere (SH) during low (Kp < 2) and high (Kp ≥ 2) geomagnetic activity levels. Nearly four years of vector magnetic field measurements are analyzed from the two parallel flying Swarm A and C satellites using the spherical elementary current system (SECS) method. The ionospheric horizontal and field-aligned currents (FACs) for each auroral oval crossing are calculated. The mean values of FACs, as well as the horizontal curl-free (CF) and divergence-free (DF) currents in 1o magnetic latitude by 1 h magnetic local time grid cells, are calculated for each hemisphere and activity level. To estimate the NH/SH current ratios for the two activity levels, we remove seasonal bias in the number of samples and in the Kp distribution by bootstrap resampling.

Averaging over all seasons, we found that for the low activity level the currents in the NH are stronger than in the SH by 12 ± 4 % for FAC, 9 ± 2% for the horizontal CF current and 8 ± 2% for the horizontal DF current. During the high activity level, the hemispheric differences are not statistically significant.

When making the statistical analysis for the four seasons separately, we find a seasonal dependence in the hemispheric asymmetry. During low Kp conditions, both FACs and horizontal currents are larger in the NH than SH with the largest difference observed in winter. In winter, the currents in the NH are larger than the SH by 21 ± 5 %  for FAC, 14 ± 3% for the horizontal CF current and 10±3%  for the horizontal DF current. During the high activity level, the asymmetry is smaller compared to the low activity level with the largest and smallest hemispheric differences observed in autumn and summer, respectively. In autumn, the currents in the NH are larger than the SH by 8 ± 5%  for FAC, 9 ± 2%  for the horizontal CF current and 8 ± 3%  for the horizontal DF current. Interestingly, during high Kp conditions, the NH/SH ratio of horizontal current is >1 in autumn and <1 in spring.

The physical mechanism producing the hemispheric asymmetry is not known. One hypothesis is that the local ionospheric conditions, such as magnetic field strength or daily variations in insolation may play a role. We present preliminary results indicating that only a small part of the seasonal dependence in the NH/SH total current ratios can be explained by variations in the background conductances caused by solar irradiance and affected by local hemispheric values of the magnetic field.

 

 

 

How to cite: Workayehu, A., Vanhamäki, H., and Aikio, A.: Hemispheric asymmetry in field-aligned and ionospheric horizontal currents from the Swarm satellite measurements, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9644, https://doi.org/10.5194/egusphere-egu2020-9644, 2020.

Chairperson: Gauthier Hulot, Anja Strømme
D1141 |
EGU2020-11746
Renata Lukianova, Vladimir Frolov, and Alexander Ryabov

It has long been a goal of active experiments to understand the response of the ionosphere to the high-power high-frequency (HF) radio wave pumping. The altitudes of 400-500 km are of particular interest since they correspond to the transition from the region, in which the most intense plasma heating and artificial ionospheric turbulence are observed, to the region where the disturbed plasma escapes to the magnetosphere. No observational data on the properties of plasma turbulence induced by the high-power HF pumping at this altitudinal range existed, until the emergence of a multi-satellite low-orbiting SWARM mission.

A series of experiments were conducted with a conjunction between the midlatitude SURA ionospheric heating facility and the SWARM satellites. We present the first observations made by SWARM on the plasma perturbations and electric currents induced in the F2 region ionosphere by the O‐mode radio wave pumping. In the heated region, significant effects include a localized increase of the electron temperature accompanied by stratification of the electron density and the magnetic signatures of field‐aligned currents (FAC) of 0.01-0.02 μA/m2 densities. The upward FAC is confined within the central part of the artificially perturbed magnetic flux tube, while the return downward current flows through the ambient plasma adjoining to the boundary of the HF-disturbed region. The spatial structure and amplitude of FACs indicate the current system is likely associated with the unipolar diffusion and excitation of eddy electric currents in the topside ionosphere. Similar effects are revealed in the laboratory experiment but not previously observed in space. The spaceborne experimental information is being accumulated and further analysis is underway.

This study was supported by the Russian Foundation for Basic Research, grant 20-05-00166. 

How to cite: Lukianova, R., Frolov, V., and Ryabov, A.: SWARM observations of the artificial ionospheric plasma disturbances and field‐aligned currents induced by the SURA power HF heating, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11746, https://doi.org/10.5194/egusphere-egu2020-11746, 2020.

Chairperson: Gauthier Hulot, Anja Strømme
D1142 |
EGU2020-21247
Spencer Hatch, Stein Haaland, Karl Magnus Laundal, Therese Moretto Jørgensen, Andrew Yau, Lindis Bjoland, Jone Peter Reistad, Anders Ohma, and Kjellmar Oksavik

The polar cap ionosphere (here defined as the region above 80° magnetic latitude) is the primary source region of cold plasma outflows observed in the magnetosphere. The two factors controlling cold plasma outflows are the availability of plasma in the polar cap ionosphere, and transport from the ionosphere to the magnetosphere. Some statistical studies have indicated that the former of these two factors, availability of cold plasma, is the limiting factor. We use 15 years of electron density measurements made by Swarm and CHAMP spacecraft, corrected for variations in observation altitude and solar activity, to investigate how variations in solar wind driving and local hemispheric season affect the polar cap ionosphere electron density Ne. We show that the dependence of Ne on the By component of the interplanetary magnetic field is apparently antisymmetric in the two hemispheres, that Nestatistically decreases with decreasing Dst index (i.e., increasing geomagnetic activity) and that Ne is apparently insensitive to the AE index. We also show that Ne distributions around March and September equinoxes display weak evidence of hemispheric asymmetry. We show that during local summer, observed Ne distributions under high solar wind driving conditions are relatively lower than Ne distributions under low solar wind driving conditions. During local winter the reverse is true, with Ne distributions under low solar wind driving conditions being relatively lower than Ne distributions under high solar wind driving conditions. Thus solar wind driving and seasonal effects may apparently both constructively and destructively interfere. Altitude variation in Swarm and CHAMP Nemeasurements is accounted for via an empirical scale height derived from 1687 conjunctions between Swarm B and either Swarm A or Swarm C during 2013–2019. The approximately linear dependence of Ne on F10.7 measurements is also accounted for. Swarm Ne measurements are additionally corrected using the Lomidze et al. (2018) calibrations.

How to cite: Hatch, S., Haaland, S., Laundal, K. M., Jørgensen, T. M., Yau, A., Bjoland, L., Reistad, J. P., Ohma, A., and Oksavik, K.: Hemispheric and seasonal variations in the cold plasma outflow source region: polar cap ionosphere electron density at 350–500 km, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21247, https://doi.org/10.5194/egusphere-egu2020-21247, 2020.

Chairperson: Gauthier Hulot, Anja Strømme
D1143 |
EGU2020-14042
Martin Fillion, Gauthier Hulot, Patrick Alken, Arnaud Chulliat, and Pierre Vigneron

A new multi-spacecraft method to recover estimates of the average three-dimensional current density in the Earth's ionosphere is presented. It is demonstrated using the ESA's Swarm satellite constellation and by taking advantage of the favorable geometrical configurations during the early phase of the mission. The current density vector is calculated inside prisms whose vortices are defined by the satellite positions. The mathematical formalism differs from previous approaches such as the one known as the ”curlometer”. It makes use of the well-known curl-B technique and involves an inverse problem which allows for error propagation through the calculation. Data from the vector field magnetometers of the three satellites are used and special care is taken to characterize the errors on these data. The method is applied in the low- and mid-latitude F-region on 15 February 2014. It provides latitudinal profiles of the full current density vector together with the associated error bars in the morning and evening sectors. We observe several dynamical features such as clear signatures of field-aligned interhemispheric currents, potential signatures of the wind dynamo current system as well as mid-latitude east-west currents.

How to cite: Fillion, M., Hulot, G., Alken, P., Chulliat, A., and Vigneron, P.: Derivation of the full current density vector in the Earth's ionosphere low- and mid-latitude F region using ESA's Swarm satellites, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14042, https://doi.org/10.5194/egusphere-egu2020-14042, 2020.

Chairperson: Gauthier Hulot, Anja Strømme
D1144 |
EGU2020-10515
Gauthier Hulot, Pierre Vigneron, Jean-Michel Léger, and Thomas Jager

Satellites of the ESA Swarm mission carry Absolute Scalar Magnetometers (ASM) that provide the nominal 1 Hz scalar data of the mission and allow the calibration of the nominal fluxgate vector magnetometry payload. ASM instruments, however, also provide independent 1 Hz experimental self-calibrated ASM-V vector data. More than six years of such data have been produced since the launch of the mission in November 2013. They allow the construction of global geomagnetic field models fully capable of capturing the fast temporal evolution of the core field, illustrating the ability of the ASM instruments to operate as a stand-alone instrument for advanced geomagnetic investigations. In this presentation we will provide the latest update on the ASM-V data (soon to be released as a new Swarm product), report on our ongoing efforts to further use these data to improve the nominal data of the mission, and discuss the prospect offered by the planned use of a miniaturized version of this ASM on board the satellites of the NanoMagSat constellation. This nano-satellite project is currently undergoing a 6 months consolidation study funded by the ESA Scout mission program. With a launch planned in 2024, it aims at forming the basis of a low-cost constellation for permanent long-term monitoring of the geomagnetic field and ionospheric environment from space.

How to cite: Hulot, G., Vigneron, P., Léger, J.-M., and Jager, T.: On the self-calibrated absolute vector data produced by the ASM absolute magnetometers on board the Swarm satellites, results and prospect, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10515, https://doi.org/10.5194/egusphere-egu2020-10515, 2020.

Chairperson: Gauthier Hulot, Anja Strømme
D1145 |
EGU2020-9850
Enkelejda Qamili, Jerome Bouffard, Filomena Catapano, Christian Siemes, Jan Miedzik, Lars Tøffner-Clausen, Stephan Buchert, Lorenzo Trenchi, Anja Stromme, and Pierre Vogel

The European Space Agency (ESA) Swarm mission, launched in November 2013, continue to provide the best ever survey of the geomagnetic field and its temporal evolution. These high quality measurements of the strength, direction and variation of the magnetic field, together with precise navigation, accelerometer, electric field, plasma density and temperature measurements, are crucial for a better understanding of the Earth’s interior and its environment. This paper will provide an overview of the Swarm Instruments and data quality status and product evolution after six years of operations, focusing on the most significant payload investigations to improve science quality, data validation activities and results along with future validation/calibration plans.

How to cite: Qamili, E., Bouffard, J., Catapano, F., Siemes, C., Miedzik, J., Tøffner-Clausen, L., Buchert, S., Trenchi, L., Stromme, A., and Vogel, P.: Six years of Swarm: instruments and data quality status, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9850, https://doi.org/10.5194/egusphere-egu2020-9850, 2020.

Chairperson: Gauthier Hulot, Anja Strømme
D1146 |
EGU2020-13403
Filomena Catapano, Stephan Buchert, Igino Coco, Ewa Slominska, Enkelejda Qamili, Lorenzo Trenchi, and Jerome Bouffard

Swarm is a three-satellite constellation mission launched by ESA in 2013 flying at an altitude of about 510 km for Swarm Bravo, and 460 km for Alpha and Charlie. The three satellites carry identical instruments continuously collecting ground-breaking data on the various components of the magnetic field and on the near-Earth environment and their dynamics. The Electric Field Instrument (EFI)  is composed by the Thermal Ion Imager (TII) and two Langmuir Probes (LPs) which measure the electron density, temperature and spacecraft potential with the cadence of 2Hz. The scope of this work is to provide an updated status of the L1B data derived from LP measurements, describing some of anomalies affecting the data products as well the outcomes of recent investigations aiming at further improving the science quality of the LP-based Swarm data.

How to cite: Catapano, F., Buchert, S., Coco, I., Slominska, E., Qamili, E., Trenchi, L., and Bouffard, J.: Swarm Langmuir Probe measurements : analysis and characterization of the data quality, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13403, https://doi.org/10.5194/egusphere-egu2020-13403, 2020.

Chairperson: Gauthier Hulot, Anja Strømme
D1147 |
EGU2020-22239
Jose M G Merayo, John L Joergensen, Peter S Joergensen, Matija Herceg, Mathias Benn, and Troelz Denver

Since launch in November 2013, the Swarm constellation of three satellites provides detailed measurements of the magnetic field of the Earth. To ensure the high accuracy of magnetic vector observation by Vector Field Magnetometer (VFM), the Swarm inertial attitude is determined by the micro Advanced Stellar Compass (μASC). Besides its primary function of attitude determination, the µASC is also capable of detecting particles with energies high enough to penetrate its camera shielding, where particles passing the focal plane CCD detector leave detectable ionization tracks. The typical shielding employed requires the minimum energy to penetrate >15MeV for electrons, > 80MeV for protons and >~GeV for heavier elements.

The signature of passing particle will only persist in one frame time, but the signature differs between electrons and protons. To ensure full attitude performance operations even during the most intense CMEs, the signatures are removed before star tracking. By counting the signatures, and using a model for the flux transport through the shielding, an accurate measure of the instantaneous high energy particle flux is achieved at each update cycle (250ms).

With this feature installed on all three Swarm spacecrafts, a hitherto unprecedented accurate mapping of the proton population around Earth is achieved at two distances, 450 and 530km.

The superrelativistic protons measured by the μASC (g>>1), travel at speeds very close to c, and bouncing between the North and South Earth sphere, encounters complex field structures for at least some of the time. The bounce period is much smaller than the Earth rotation period, and an east-west drift component is caused by the magnetic field gradient.

We will present observations of the trapped proton fluxes and show how the magnetic field affects their motion shells. Slightly deformed particle drift shells due to the magnetic field structure (for orbits with L>1.07) and the differential east-west drift as measured by the Swarm Alpha and Charlie satellites will be discussed.

How to cite: Merayo, J. M. G., Joergensen, J. L., Joergensen, P. S., Herceg, M., Benn, M., and Denver, T.: Earth inner drift shells as observed by the Advanced Stellar Compass on Swarm, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22239, https://doi.org/10.5194/egusphere-egu2020-22239, 2020.

Chairperson: Gauthier Hulot, Anja Strømme
D1148 |
EGU2020-22445
Lorenzo Trenchi, Jerome Bouffard, Anja Stromme, Octav Marghitu, Kirsti Kauristie, Adrian Blăgău, Joachim Vogt, Balázs Heilig, and Péter Kovács

This presentation illustrates the recent results obtained in the context of scientific ESA Swarm projects. The project “Swarm data quality Investigation of Field-Aligned Current products, Ionosphere, and Thermosphere system” (SIFACIT) has been recently extended in order to achieve two additional objectives: To provide to users an open-source program package to estimate Field Aligned Current (FAC) density and quality indicators, using single- and multi-s/c methods from Swarm data; To study the Joule heating of the ionosphere–thermosphere system on multiple scales, using Swarm data, together with conjugate ground information and simulations.

The other project illustrated here is EPHEMERIS (nEw sPace weatHER inforMation Exploited from the SwaRm observatIonS). This project is investigating the Midlatitude Ionospheric Trough (MIT) with Swarm data, and will also develop a new MIT Swarm data product based on Swarm L1b Langmuir Probe (LP) data. The second part of the project will develop a quasi-real-time intermittency index (IMI) for the detection of ionosphere plasma irregularities along the Swarm orbit, which can be responsible for errors and loss of lock in GPS signals. A statistical comparison of the IMI index with GPS signal from ground based receivers will be performed, in order to identify the ionospheric irregularities at Swarm altitude responsible for scintillations in GPS signals.

How to cite: Trenchi, L., Bouffard, J., Stromme, A., Marghitu, O., Kauristie, K., Blăgău, A., Vogt, J., Heilig, B., and Kovács, P.: Recent results from scientific ESA Swarm projects, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22445, https://doi.org/10.5194/egusphere-egu2020-22445, 2020.

Chairperson: Gauthier Hulot, Anja Strømme
D1149 |
EGU2020-19908
Martin Pačes, Daniel Santillan Pedrosa, and Ashley Smith

VirES for Swarm [1] is a data manipulation and retrieval interface for the ESA Swarm constellation mission data products. It includes tools for studying various geomagnetic models by comparing them to the Swarm satellite measurements at given space weather and ionospheric conditions.

The list of the provided Swarm products is growing and it currently includes MAG (both, LR and HR), EFI, IBI, TEC, FAC, EEF, and IPD products as well as the collection of L2 SHA Swarm magnetic models, all synchronized to their latest available versions.

VirES provides access to the Swarm measurements and models either through an interactive visual web user interface or through a Python-based API (machine-to-machine interface). The latter allows integration of the users' custom processing and visualization.

The API allows easy extraction of data subsets of various Swarm products (temporal, spatial or filtered by ranges of other data parameters, such as, e.g., space weather conditions) without needing to handle the original product files. This includes evaluation of composed magnetic models (MCO, MLI, MMA, and MIO) and calculation of residuals along the satellite orbit.

The Python API can be exploited in the recently opened Virtual Research Environment (VRE), a JupyterLab based web interface allowing writing of processing and visualization scripts without need for software installation. The VRE comes also with pre-installed third party software libraries (processors and models) as well as the generic Python data handling and visualization tools.

A rich library of tutorial notebooks has been prepared to ease the first steps and make it a convenient tool for a broad audience ranging from students and enthusiasts to advanced scientists.

Our presentation focuses on the introduction of the new Virtual Research Environment and recent VirES evolution.

[1] https://vires.services

How to cite: Pačes, M., Santillan Pedrosa, D., and Smith, A.: VirES for Swarm – Virtual Research Environment, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19908, https://doi.org/10.5194/egusphere-egu2020-19908, 2020.