ST1.11

The propagation of Solar Energetic Particles (SEPs) has been described traditionally by means of a spatially 1D focussed transport approach. However in recent years a number of physical mechanisms that give rise to motion across the mean magnetic field have been studied. These include perpendicular transport associated with turbulence, guiding centre drifts and drift along the heliospheric current sheet. In this presentation such mechanisms will be reviewed and emphasis will be placed on how assumptions and scenarios based on a 1D approach need to be modified when looking at SEP propagation from a 3D perspective. Observables such as time intensity profiles and anisotropies obtained from 3D models will be discussed and compared with observations.

How to cite: Dalla, S.: Role of 3D propagation in shaping Solar Energetic Particle observables, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7635, https://doi.org/10.5194/egusphere-egu22-7635, 2022.

The energy released during a solar flare is efficiently transferred to energetic non-thermal particles, though the exact plasma properties of the acceleration region and the importance of individual acceleration mechanisms is not fully understood. Non-thermal acceleration of electrons in the solar atmosphere is observed from two main sources: in-situ detection of solar energetic electrons (SEEs) in interplanetary space and remote observation of high-energy emission (e.g. X-rays, radio) at the Sun itself. While these two populations are widely studied individually, a common flare-associated acceleration region has not been established. If such a region were to exist, its properties would also need to be determined based on both remote and in-situ observations.

We present preliminary results of a parameter search of the plasma properties and possible acceleration processes in a common solar acceleration region and compare the results of precipitating and escaping electrons. The number density, plasma temperature and the size of the acceleration region itself, as well as properties such as turbulence leading to acceleration, are variable parameters in a transport model code including collisional and non-collisional processes, simulating electrons in the Solar atmosphere and heliosphere. The results of these simulations produce electron time profiles, pitch-angle distributions and energy spectra at the Sun (corona and chromosphere), at 1 AU and other heliospheric locations with which to compare directly with observational data from modern instruments including those mounted on Solar Orbiter.  

The ultimate goal of this study is to model the precipitating and escaping electron populations and compare the resultant properties with observations of solar events where both remote and in-situ observations are available. With this forward modelling approach, we aim to constrain the plasma properties and transport effects present in the solar atmosphere and heliosphere.

How to cite: Pallister, R. and Jeffrey, N.: Simultaneous modelling of flare-accelerated electrons at the Sun and in the heliosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10114, https://doi.org/10.5194/egusphere-egu22-10114, 2022.

Energetic particle populations in the solar corona and in the heliosphere appear to have different characteristics even when produced in the same solar flare. It is not clear what causes this difference: properties of the acceleration region, the large-scale magnetic field configuration in the flare, or particle transport effects, such as scattering. We use a combination of non-linear force-free magnetohydrostatic simulations, magnetohydrodynamic and test-particle modelling to investigate magnetic reconnection, particle acceleration and transport in two solar flares events: an  M-class flare on  June 19th, 2013, and an X-class flare on September 6th, 2011. We show that, although in both events particles are energised at the same locations, the magnetic field structure around the acceleration region results in different characteristics between particle populations precipitating towards the photosphere and those ejected towards the upper corona and the heliosphere. We expect this effect to be ubiquitous when particles are accelerated close to the boundary between open and colsed magnetic fields and, therefore, may be key to solar flares with  substantial particle emission into the heliosphere. Furthermore, this analysis elucidates the mechanisms by which escaping particle populations can be created in flares.

How to cite: Browning, P. and Gordovskyy, M.: Energetic particle emission in two solar flares with open magnetic field, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8518, https://doi.org/10.5194/egusphere-egu22-8518, 2022.

We are examining a new kind of hybrid method for finding SEP (Solar Energetic Particle) event onset times and assessing their uncertainties. Determining these onset times accurately is important because they are needed to relate the in-situ particle measurements to remote-sensing observations of the associated activity phenomena at the Sun. Only by this, can one identify the actual region and acceleration processes that generated the event. Different methods have been used to determine this onset time; however, the most common ones do not provide reasonable uncertainties so far. The method presented here employs a combination of a statistical quality control scheme, the Poisson-CUSUM (cumulative sum) method, and statistical bootstrapping for calculating a distribution of the necessary parameters for the Poisson-CUSUM method.

The CUSUM method is a statistical quality control scheme, used also in many industries, that is designed to give an early warning when the inspected process or variable changes (Page, 1954). Poisson-CUSUM refers to a specific cumulative sum method that assumes that the monitored variable has a Poisson distribution. 

By randomly choosing samples from the particle flux preceding the event, we acquire a distribution of different values for the estimated mean flux and for the standard deviation of the background measurements. These two distributions produce a set of possible onset times via the Poisson-CUSUM method, allowing us to evaluate the uncertainty of an onset time by the precision of our set of candidate onset times, and also to identify the most likely onset time. In addition, we apply the new method to energetic particle observations of the Solar Orbiter spacecraft that come with high energy and time resolution, and perform velocity dispersion analyses. 

• S. PAGE, CONTINUOUS INSPECTION SCHEMES, Biometrika, Volume 41, Issue 1-2, June 1954, Pages 100–115, https://doi.org/10.1093/biomet/41.1-2.100

How to cite: Palmroos, C., Dresing, N., Gieseler, J., Vainio, R., and Asvestari, E.: Determining SEP Event Onset Times and Evaluating Their Uncertainty Using a Poisson CUSUM-Bootstrap Hybrid Method, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12111, https://doi.org/10.5194/egusphere-egu22-12111, 2022.

Modeling of time profiles of solar energetic particle (SEP) observations typically considers transport along a large-scale magnetic field with a fixed path length from the source to the observer.  Chhiber et al. (2021) pointed out that the path length along a turbulent magnetic field line is longer than that along the large scale field, and that the path along the particle gyro-orbit can be substantially longer again; they also considered the global variation in these quantities.  Here we point out that variability in the turbulent field line path length can affect the fits to SEP data and the inferred mean free path and injection profile.  To explore such variability, we perform Monte Carlo simulations in representations of homogeneous 2D MHD + slab turbulence in spherical geometry and trace trajectories of field lines, particle guiding centers, and full particle orbits, considering ion injection from a narrow or wide angular region near the Sun, corresponding to an impulsive or gradual solar event, respectively. We analyze our simulation results in terms of path length statistics within and among square-degree pixels in heliolatitude and heliolongitude at 0.35 and 1 AU from the Sun.  For a given representation of turbulence, there are systematic effects on the path lengths vs. heliolatitude and heliolongitude.  Field line path lengths relate to the fluctuation amplitudes experienced by the field lines, which in turn partly relate to the local topology of 2D turbulence.  Particles from an impulsive event that arrive at a distant angular separation (up to ~25 degrees from the mean field connection) generally have longer path lengths, not because of the angular distance per se but because of strong magnetic fluctuations experienced to drive the guiding field lines to such angular distances and because of the associated scattering of the particles.  We describe the effects of such path length variations on observed time profiles of solar energetic particles, both in terms of path length variability at specific locations and motion of the observer with respect to turbulence topology during the course of the observations.  This research was partially supported by Thailand Science Research and Innovation grant RTA6280002 and the Parker Solar Probe mission under the ISOIS project (contract NNN06AA01C) and a subcontract to University of Delaware from Princeton University (SUB0000165).  Additional support is acknowledged from the NASA LWS program (NNX17AB79G) and HSR program (80NSSC18K1210 & 80NSSC18K1648).

How to cite: Sonsrettee, W., Chuychai, P., Seripienlert, A., Tooprakai, P., Sáiz, A., Ruffolo, D., Matthaeus, W. H., and Chhiber, R.: Magnetic Field Line Path Length Variations and Effects on Solar Energetic Particle Transport, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3394, https://doi.org/10.5194/egusphere-egu22-3394, 2022.

In this work, we model the energetic storm particle (ESP) event of 14 July 2012 using the energetic particle acceleration and transport model named PARADISE (PArticle Radiation Asset Directed at Interplanetary Space Exploration), together with the solar wind and coronal mass ejection (CME) model named EUHFORIA (EUropean Heliospheric FORcasting Information Asset).  The CME generating the ESP event is simulated by using the spheromak model of EUHFORIA, which approximates the CME’s magnetic field as a linear force-free spheroidal magnetic field. The energetic particles are modelled by injecting a seed population of 50 KeV protons continiously at the CME-driven shock wave. The simulation results illustrate both the capabilities and limitations of the utilised models.  

We find that for energies below 1 MeV, the simulation results agree well with the upstream and downstream components of the ESP event observed by the Advanced Composition Explorer (ACE).  This suggests that these low-energy protons are mainly the result of interplanetary particle acceleration. In the downstream region, the sharp drop in the energetic particle intensities is reproduced at the entry into the following magnetic cloud, illustrating the importance of a magnetised CME model.

This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870405 (EUHFORIA 2.0).

How to cite: Wijsen, N., Aran, A., Scolini, C., Lario, D., Afanasiev, A., Vainio, R., Pomoell, J., Sanahuja, B., and Poedts, S.: Observation-based modelling of the energetic storm particle event of 14 July 2012, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5899, https://doi.org/10.5194/egusphere-egu22-5899, 2022.

Fluxes of solar energetic particles (SEPs) are associated with solar flares and coronal/interplanetary shock waves. In the case of shocks, particles are thought to get accelerated to high energies via the diffusive shock acceleration mechanism. In order to be efficient, this mechanism requires an enhanced level of magnetic turbulence in the vicinity of the shock front, in particular, in the so-called foreshock region upstream of the shock. This turbulence enhancement can be produced self-consistently, i.e., by the accelerated particles themselves via streaming instability. This idea underlies the SOLar Particle Acceleration in Coronal Shocks (SOLPACS) Monte-Carlo simulation code, which we developed earlier to simulate acceleration of protons in coronal shocks. In the present work, we apply SOLPACS to model an energetic storm particle (ESP) event measured by the STEREO A spacecraft on November 10, 2012. All but one main SOLPACS input parameters are fixed by the in-situ plasma measurements from the spacecraft. Comparison of a simulated proton energy spectrum at the shock with the observed one then allows us to fix the last simulation input parameter related to efficiency of particle injection to the acceleration process. Subsequent comparison of simulated proton time-intensity profiles in a number of energy channels with the observed ones shows a very good correspondence throughout the upstream region. Our results give support for the quasi-linear formulation of the foreshock. This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870405 (EUHFORIA 2.0).

How to cite: Afanasiev, A., Talebpour Sheshvan, N., Vainio, R., Dresing, N., Trotta, D., Hietala, H., and Nyberg, S.: Self-consistent Monte-Carlo modeling of the November 10, 2012 energetic storm particle event, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11915, https://doi.org/10.5194/egusphere-egu22-11915, 2022.

This report presents the results of observations of Solar Particle Events (SPE) in July-October 2021 that have been simultaneously detected by the MGNS (Mercury Gamma-ray and Neutron Spectrometer) instrument on board the MPO spacecraft of the BepiColombo mission which is currently on a cruise phase to Mercury, as well as by science instruments that are operated in near-Mars orbit: HEND (High Energy Neutron Detector) instrument onboard Mars Odyssey mission, FREND (Fine Resolution Epithermal Neutron Detector) instrument and Liulin-MO dosimeter onboard ExoMars TGO (Trace Gas Orbiter) mission. This location of the spacecrafts, allowed for stereoscopic observation of SPEs, in addition during the period July-October 2021 Mars is on the opposite side of the Sun from Earth, when it is difficult to observe these SPEs by instruments on a near-Earth group of spacecrafts for Solar monitoring. The report will present an analysis of the energy spectra deposition and analysis of time profiles. In particular it shows the Forbush decrease of GCR in effect of the arrival of the dense solar plasma to the SPE observation locations. The MGNS, HEND and FREND instrument developed and manufactured at the Space Research Institute of the Russian Academy of Sciences and are a Russian-made and Russian-funded contribution by the Russian Federal Space Agency (ROSCOSMOS) to the BepiColombo, Mars Odyssey and ExoMars TGO missions, respectively. Liulin-MO has been developed in Space Research and Technology Institute at the Bulgarian Academy of Sciences with participation of Institute of Biomedical Problems of the Russian Academy of Sciences (Moscow) and Institute for Space Research (Moscow).

Acknowledgements

The work in Bulgaria is supported by grant KP-06-Russia 24 for bilateral projects of the National Science Fund of Bulgaria and Russian Foundation for Basic Research.

How to cite: Kozyrev, A., Litvak, M., Malakhov, A., Mitrofanov, I., Semkova, J., Koleva, R., Benghin, V., Krastev, K., Matviichuk, Y., Tomov, B., Maltchev, S., Bankov, N., Shurshakov, V., and Drobyshev, S.: Observation of solar particle events from MGNS experiment onboard BepiColombo mission, HEND experiment onboard Mars Odyssey mission, and also FREND and Liulin-MO experiments onboard TGO mission during July-October 2021, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11521, https://doi.org/10.5194/egusphere-egu22-11521, 2022.

Medium energy electron (MEE) (>30 keV) precipitation into the Earth's atmosphere is acknowledged as a relevant part of solar forcing as collisions between electrons and atmospheric gasses initiate several chemical reactions which can reduce ozone concentration. Ozone is critically important in the middle atmosphere energy budget as changes in ozone concentration impact temperature and winds. There is an ongoing debate to which extent the existing geomagnetic parameterizations represent a realistic precipitating flux level, especially when considering the high energy tail of MEE (>300 keV). An improved quantification might be achieved by a better understanding of the driving processes of MEE acceleration and precipitation, alongside optimized data handling. In this study, the bounce loss cone fluxes are inferred from MEE precipitation measurements by the Medium Energy Proton and Electron Detector (MEPED) on board the Polar Orbiting Environmental Satellite (POES) and the Meteorological Operational Satellite Program of Europe (METOP) at tens of keV to a couple hundred keV. It investigates MEE precipitation in contexts of different solar wind structures: corotating interaction regions (CIRs) associated with high-speed solar wind streams (HSSs), and coronal mass ejections (CMEs), during an eleven-year period from 2004 – 2014. The objective of this study is to explore general features of the MEE precipitating spectrum in the context of its solar wind driver: the intensity of MEE alongside the intensity and delayed response of its high energy tail.

How to cite: Salice, J., Tyssøy, H. N., Smith-Johnsen, C., and Babu, E. M.: Solar Wind Structures and their Effects on the High-Energy Tail of the Precipitating Energetic Electron Spectrum, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2745, https://doi.org/10.5194/egusphere-egu22-2745, 2022.

Investigating the motion of charged particles in time- and space-dependent electromagnetic fields is central to many areas of space and astrophysical plasmas. Here we present results of studying the energy changes of particle orbits that are trapped in inhomogeneous magnetic fields with rapidly shortening field lines. These so-called collapsing magnetic trap (CMT) models can be useful for explaining the acceleration of particles below the reconnection region in a solar flare. For both 2D and 3D CMT models (e.g. Giuliani et al. 2005; Grady & Neukirch, 2009), betatron acceleration was considered to be the dominant energisation mechanism. We present new results that have been obtained using an improved version of the 3D CMT model by Grady and Neukirch (2009). Our investigations show that a sizeable portion of particle orbits can gain a significant amount of energy that is not explained by the betatron effect. The other mechanism at play appears to be Fermi acceleration at loop tops, where the particle passes through the region of field that is collapsing the most rapidly. 

We show that the particles that experience this effect the most have initial positions that are related to specific regions of the magnetic field model and it is these particle orbits whose energy gains are not adequately explained by betatron acceleration alone. In fact, some particle orbits seem to gain energy almost entirely as a result of this Fermi acceleration. One can also show that for suitable initial conditions the same effect can be seen in the 2D CMT model given by Giuliani et al. (2005). This updated understanding of the systems at play for particle acceleration in a CMT can, for example, inform any changes made to future CMT models by accounting for the large number of particles that see energy gains due to Fermi acceleration. 

Giuliani, P. et al., ApJ 635, 636

Grady, K. & Neukirch, T., A&A 508, 1461 

How to cite: Mowbray, K. and Neukirch, T.: Particle Energisation in Collapsing Magnetic Traps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11965, https://doi.org/10.5194/egusphere-egu22-11965, 2022.

On October/November 2021 the Heavy Ion Sensor onboard Solar Orbiter observed data connected to three interplanetary shock events: Oct 30, Nov 3 and Nov 27. During all three events, the flux of suprathermal particles, defined as those having an energy larger than twice the energy of the solar wind component, showed remarkable intensification. We discuss those changes and specifically how particles of different mass/charge and energy/charge distribution before the shock are affected differently by the interaction with the shock front itself. From these three expampes, it appears that intensifications are stronger for species already having a seed population in the suprathermal regime.

How to cite: Livi, S., Owen, C., Louarn, P., Fedorov, A., Alterman, B., Lepri, S., Raines, J., Galvin, A., Kistler, L., Allegrini, F., Ogasawara, K., Wurz, P., Bruno, R., D'Amicis, R., and Collier, M.: Preferential Acceleration of Suprathermal Particles at Shocks, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5984, https://doi.org/10.5194/egusphere-egu22-5984, 2022.

Solar electrons beams are accelerated in the corona, and can travel out into the solar wind and beyond. These beams of non-thermal electrons evolve as a function of distance from the Sun, interacting with the background plasma and growing Langmuir waves as they propagate. Subsequent radio emission is also seen in the form of type III bursts. Around 1 AU, we detect in-situ electrons up to 10-20 keV together with local Langmuir waves. However, previous studies suggest that higher energy electrons interact with Langmuir waves close to the Sun and so these electrons would not propagate scatter-free. Through beam-plasma structure simulations we study the interactions between these electron beams and the background plasma of the solar corona and the solar wind at different distances from the Sun, up to 130 solar radii. This allows us to determine what is the maximum electron velocity responsible for Langmuir wave production and growth, and consequently which electron energies are affected by wave-particle interactions as a function of distance from the Sun. We also vary the spectral index of the electron velocity distribution α and the electron beam density n_beam to identify what role they play in determining the relevant electron velocities at which wave-particle interactions occur. Understanding the mechanisms driving the change in the maximum electron velocity will permit more accurate predictions in electron onset as well as arrival times, relevant for space weather applications and the understanding of the subsequent emissions at radio and X-ray wavelength. Moreover, our radial predictions can be tested against in-situ electron and plasma measurements from the instruments on-board the Solar Orbiter and Parker Solar Probe spacecrafts.

How to cite: Lorfing, C. and Reid, H.: Evolution of solar accelerated electron beams as a function of distance from the Sun, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9873, https://doi.org/10.5194/egusphere-egu22-9873, 2022.

The particle flux in the near-Earth environment can increase by orders of magnitude during geomagnetically active periods. This leads to intensification of particle precipitation into Earth’s atmosphere. The process potentially further affects atmospheric chemistry and temperature.

In this research, we concentrate on ring current electrons and investigate precipitation mechanisms on a short time scale using a numerical model based on the Fokker-Planck equation. We focus on understanding which kind of geomagnetic storm leads to stronger electron precipitation. For that, we considered two storms, corotating interaction region (CIR) and coronal mass ejection (CME) driven, and quantified impact on ring current. We validated results using observations made by POES satellite mission, low Earth orbiting meteorological satellites, and Van Allen Probes, and produced a dataset of precipitated fluxes that covers energy range from 1 keV to 1 MeV.

How to cite: Grishina, A., Shprits, Y., Wutzig, M., Allison, H., Aseev, N., Wang, D., and Szabo-Roberts, M.: Ring Current Electron Precipitation During Storm Events, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11023, https://doi.org/10.5194/egusphere-egu22-11023, 2022.

Observations of Energetic Electron Substorm Injection Signatures by Cluster and BepiColumbo During an Earth Flyby

We present an analysis of the energetic electron signatures observed by BepiColumbo and Cluster during the Bepi flyby of Earth on 10 April 2020, as well as other spacecraft. After closest approach, the SIXS instrument on Bepi observed two separate substorm injection fronts, while Cluster RAPID/IES also observed a sequence of energetic electron signatures. Bepi and Cluster were in a particularly favourable configuration during this event, with Bepi moving rapidly radially outward near the nightside equatorial plane while the four Cluster spacecraft cut the same region in a north/south direction in a string of pearls configuration. The coincidence of this favourable geometry with the substorm activity is highly fortuitous and appears to show a complicated sequence of spatially and temporally separated injections and drift echoes.

How to cite: Grande, M., Sanches-Cano, B., Nakamura, R., Vainio, R., Miyoshi, Y., Dandouras, I., Johnson, R., Oleynik, P., Nakamura, S., Perry, C., Johnson, P., Huovelin, J., Maguire, S., and Heyner, D.: Observations of Energetic Electron Substorm Injection Signatures by Cluster and BepiColumbo During an Earth Flyby, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8067, https://doi.org/10.5194/egusphere-egu22-8067, 2022.

The Earth is continuously exposed to galactic cosmic rays. The flux of these particles is altered by the magnetized solar wind in the heliosphere and the Earth's magnetic field. If cosmic rays hit the atmosphere they can form secondary particles. The total flux measured within the atmosphere depends on the atmospheric density above the observer. Therefore, the ability of a particle to approach an aircraft depends on its energy, the altitude and position of the aircraft. The latter is described by the so-called cut-off rigidity.
The radiation detector of the detector system NAVIDOS (NAVIgation DOSimetry) is the DOSimetry Telescope (DOSTEL) measuring the count and dose rates in two semiconductor detectors. From 2008 to 2011 two instruments were installed in two aircraft. First we corrected the data for pressure variation by normalizing them to one flight level and determined their dependence on the cut-off rigidity by fitting a Dorman function to the observation. The latter was used to compute the yield function, that describes the ratio of incoming primary cosmic rays, approximated by a force field solution, to the measured count and dose rate for a particular instrument. As for neutron monitors the sensitivity increases substantially above a rigidity of about 1 GV.
We received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 870405. 

How to cite: Romaneehsen, L., Burmeister, S., Bernd, B., Herbst, K., Marquardt, J., Senger, C., and Wallmann, C.: Yield function of the DOSimetry TELescope (DOSTEL) count and dose rates aboard an aircraft, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12121, https://doi.org/10.5194/egusphere-egu22-12121, 2022.

Within the wider scope of improving Space weather forecast by the EUHFORIA project, we present an updated version of the AtRIS code designed to simulate the count rates and dose deposits of space weather events in the atmosphere. As more and more of modern technological infrastructure is sensitive to radiation exposure space weather forecast can develop into a critical tool to protect it from possible damage. Thereby, AtRIS can be applied  to analyse the impact of past Solar Energetic Particle (SEP) events, complementary to the analysis and comparisons of measurements both at top the  atmosphere and at ground level by e.g. NAVIDOS and DOSTEL. AtRIS thereby is designed as a framework of the well established GEANT4 code, offering   the possibility to implement the atmospheric composition in a layer-wise model. Furthermore, it offers the possibility to select the thickness of the  shielding between 0 and 20 mm of aluminium. Here we will present the physics implemented into AtRIS, its validation, and show preliminary results for  selected past events utilising different layers of shielding.The Kiel team received funding from the European Union’s Horizon 2020 research and  innovation programme under grant agreement No 870405.

How to cite: Pohland, P., Vogt, A., Banjac, S., Burmeister, S., Giese, H., Heber, B., Herbst, K., Romaneehsen, L., and Wallmann, C.: Presenting the AtRIS code as a future tool to investigate the atmospheric impactof SEP events, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12744, https://doi.org/10.5194/egusphere-egu22-12744, 2022.

Medium energy electron (MEE) (30-1000 keV) precipitation enhances the production of nitric (NO_x) and hydrogen oxides (HO_x) throughout the mesosphere, which can destroy ozone (O₃) in catalytic reactions. The dynamical effect of the direct mesospheric O₃ reduction has long been an outstanding question, partly due to the concurrent feedback from the stratospheric O₃  reduction. To overcome this challenge, the Whole Atmosphere Community Climate Model (WACCM) version 6 is applied in the specified dynamics mode for the year 2010, with and without MEE ionization rates. The results demonstrate that MEE ionization rates can modulate temperature, zonal wind and the residual circulation affecting NO_x transport. The required fluxes of MEE to impose dynamical changes depend on the dynamical preconditions. During the Northern Hemispheric winter, even weak ionization rates can modulate the mesospheric signal of a sudden stratospheric warming event. The result is a game changer for the understanding of the MEE direct effect.

How to cite: Nesse Tyssøy, H., Zúñiga, H. D. L., Smith-Johnsens, C., and Maliniemi, V.: The medium energy electron direct effect on mesospheric dynamics during a sudden stratospheric warming event in 2010, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7106, https://doi.org/10.5194/egusphere-egu22-7106, 2022.

Energetic particle precipitation (EPP) into the atmosphere, lead to chemical reactions producing NOx gases. Auroral electrons deposit their energy at altitudes throughout the upper mesosphere and lower thermosphere. During the winter the EPP-produced NOx gases can survive for months and be transported down to the stratosphere, where it can destroy ozone through catalytic reactions. Studies comparing the NO density estimated by chemistry climate models and observations suggest that the estimation of NO-production by auroral forcing is overestimated during quiet times and underestimated during active time. This study provides an intercomparison of different auroral forcing estimates. We compare fluxes from the Total energy detector (TED) onboard the NOAA Polar Orbiting Environmental Satellites (POES) and Meteorological Operational satellite (MetOp), sensor for precipitating particles (SSJ) from Defense Meteorological spacecraft Program (DMSP), alongside a Kp-driven auroral model. The data over a full year was sorted by the daily Kp and evaluated as function of geomagnetic latitude and magnetic local time. Discrepancies are evaluated in respect to geographical bias, as well as geometric factors of the satellites. Furthermore, the observations are compared to the Kp-driven auroral model.

How to cite: Eide, H. D., Tyssøy, H. N., Tesema, F., and Babu, E. M.: What is the flux of low energy electron precipitation in the lower thermosphere?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11792, https://doi.org/10.5194/egusphere-egu22-11792, 2022.