The Earth's magnetic field is continuously monitored by a large number of geomagnetic observatories and satellites in low Earth orbit. In the past years, there has been a growing interest in space weather events and in particular in their potential hazard for the activities and infrastructures of a modern, technologically based society. It is on, or just above, the surface of the Earth indeed that several important practical effects of space weather events are realized. Therefore, both ground-based magnetic observatories and magnetic measurements from satellites can play a significant role in the space weather era. They can be used to monitor space weather events, such as magnetic storms, substorms and geomagnetically induced currents, and furthermore they facilitate studies of dynamic solar-terrestrial events and of their interactions.
The aim of this session is to collect new ideas and results on how magnetic field measurements (from geomagnetic observatories and satellites such as CHAMP, Swarm, CSES, ePOP and so on) can improve our knowledge in the space weather domain and on how they can become useful for service providers, users, and critical infrastructure protection administrations.

Co-organized by ST4
Convener: Paola De Michelis | Co-conveners: Jerome Bouffard, Ioannis A. Daglis, Mioara Mandea
| Attendance Wed, 06 May, 16:15–18:00 (CEST)

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Chat time: Wednesday, 6 May 2020, 16:15–18:00

Chairperson: Paola De Michelis, Jerome Bouffard, Ioannis A. Daglis
D1150 |
Ari Viljanen and Liisa Juusola

Fast geomagnetic variations of periods from seconds to hours and days are primarily produced by currents in the ionosphere and magnetosphere. There is always an associated secondary (internal, telluric) current system induced in the conducting ground and contributing to the total variation field measured by ground magnetometers. Mathematically, it is possible to fully explain the variation field by two equivalent current systems, one at the ionospheric altitude and another just below the ground. In practice, this separation is feasible using dense magnetometer networks.

A common way in space physics has been to implicitly neglect the internal part and interpret the ground field only in terms of ionospheric currents. As known from previous studies, this is often a reasonable assumption, since a typical internal contribution is about 30%. However, the situation is much different when the time derivative of the magnetic field (dB/dt) is considered. For the north European IMAGE magnetometer network, the internal part exceeds the external one nearly at all stations. The largest effects due to telluric currents occur at coastal sites close to highly-conducting ocean water and at inland locations close to highly-conducting near-surface anomalies.

This finding gives a new viewpoint for studies of geomagnetically induced currents (GIC), which are closely related to dB/dt. One key question is to understand which are the ionospheric drivers of big GIC events. We will demonstrate how the telluric currents can strongly modify field variations and especially dB/dt, and how this is correspondingly seen in equivalent current patterns. Consequently, it is recommended that the field separation is performed whenever it is feasible, i.e. a dense observation network is available.

How to cite: Viljanen, A. and Juusola, L.: Telluric currents play a big role in interpreting geomagnetic variations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2309, https://doi.org/10.5194/egusphere-egu2020-2309, 2020.

D1151 |
Adamantia Zoe Boutsi, Georgios Balasis, and Ioannis A. Daglis

Geomagnetically Induced Currents (GIC) constitute an integral part of the space weather research and a subject of ever-growing attention for countries located in the low and middle latitudes. A series of recent studies highlights the importance of considering GIC risks for the Mediterranean region. The HellENIc GeoMagnetic Array (ENIGMA) is a network of 4 ground-based magnetometer stations in the areas of Thessaly, Central Greece, Peloponnese and Crete in Greece that provides geomagnetic measurements for the study of pulsations, resulting from the solar wind - magnetosphere coupling. ENIGMA magnetometer array enables effective remote sensing of geospace dynamics and the study of space weather effects on the ground (i.e. GIC). ENIGMA contributes data to SuperMAG, a worldwide collaboration of organizations and national agencies that currently operate approximately 300 ground-based magnetometers. In this presentation, we exploit ENIGMA data in order to study the spatio-temporal variations of the geomagnetic field that emanate during active geospace conditions. Moreover, we investigate the possibility that these variations produce hazardous currents and provide an estimation of their intensity, focusing on the most intense magnetic storms of the present solar cycle.

How to cite: Boutsi, A. Z., Balasis, G., and Daglis, I. A.: Preliminary investigation of the possibility of GIC development in Greece, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-437, https://doi.org/10.5194/egusphere-egu2020-437, 2020.

D1152 |
Venera Dobrica, Dumitru Stanica, Crisan Demetrescu, and Cristiana Stefan

A recent model of the Romanian lithosphere electric properties, based on magnetotelluric transects carried out in the past 50 years across main tectonic units, is used to assess the geoelectric hazard represented by geomagnetically induced currents (GICs) for certain space weather events. Based on the geomagnetic field recordings and on information regarding the underground electric conductivity, the surface geoelectric field associated to geomagnetic variations during several large geomagnetic storms of the solar cycle 23 (1986-1996) is determined using the plane wave approximation for the depth propagation of the geomagnetic disturbance. A comparison to the territory of the European continent is done as well.   

How to cite: Dobrica, V., Stanica, D., Demetrescu, C., and Stefan, C.: The geoelectric structure of the Romanian underground and its contribution to the geoelectric hazard during the solar cycle 23 , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19917, https://doi.org/10.5194/egusphere-egu2020-19917, 2020.

D1153 |
Malcolm Dunlop, Junying Yang, Xiangcheng Dong, Mervyn Freeman, Neil Rogers, Jim Wild, Colin Forsyth, Jinbin Cao, Hermann Lühr, and Chao Xiong

The orientation of field-aligned current sheets (FACs) can be inferred from dual-spacecraft correlations of the FAC signatures between two Swarm spacecraft (A and C), using the maximum correlations obtained from sliding data segments. Statistical analysis of both the correlations and the inferred orientations shows clear trends in magnetic local time (MLT) which reveal behaviour of both large and small scale currents. The maximum correlation coefficients show distinct behaviour in terms of either the time shift, or the shift in longitude between Swarm A and C for various filtering levels. The lower-latitude FACs show the strongest correlations for a broad range of MLT centred on dawn and dusk, with a higher correlation coefficient on the dusk-side and lower correlations near noon and midnight, and broadly follow the mean shape of the auroral boundary for the lower latitudes corresponding to Region 2 FACs (and are most well-ordered on the dusk side). Individual events sampled by higher altitude spacecraft (e.g. the 4 Cluster spacecraft), in conjunction with Swarm (mapping both to region 1 and 2), also show two different domains of FACs: time variable, small-scale (10s km), and more stationary large-scale (>100 km) FACs. We investigate further how these FAC regimes are dependent on geomagnetic activity, focusing on high activity events. Both the statistical trends, and individual conjugate events, show comparable effects seen in the ground magnetometer signals (dH/dt) during storm/substorm activity and show distributions that are similar.

How to cite: Dunlop, M., Yang, J., Dong, X., Freeman, M., Rogers, N., Wild, J., Forsyth, C., Cao, J., Lühr, H., and Xiong, C.: Field-aligned current ordering in ground and space measurements, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19203, https://doi.org/10.5194/egusphere-egu2020-19203, 2020.

D1154 |
Karl Laundal, Jesper Gjerloev, Sam Yee, Slava Merkin, Heikki Vanhamäki, Liisa Juusola, and Jone Reistad

The auroral electrojet is traditionally measured remotely with magnetometers on ground or in low Earth orbit. The long distance, more than 100 km, means that smaller scale sizes are not detected. Because of this, the spatiotemporal characteristics of the electrojet are not known. Recent advances in measurement technology give hope of remote detections of the magnetic field in the mesosphere, very close to the electrojet. We present a prediction of the magnitude of these disturbances, inferred from the spatiotemporal characteristics of magnetic field-aligned currents. We also discuss how a constellation of small satellites carrying the Microwave Electrojet Magnetogram (MEM) instrument (Yee et al., 2020), could be used to essentially image the equivalent current at unprecedented spatial resolution. 

How to cite: Laundal, K., Gjerloev, J., Yee, S., Merkin, S., Vanhamäki, H., Juusola, L., and Reistad, J.: Electrojet estimates from mesospheric magnetic field measurements, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19826, https://doi.org/10.5194/egusphere-egu2020-19826, 2020.

D1155 |
Jeng-Hwa Yee, Jesper Gjerloev, Viacheslav Merkin, and Karl Laundal

The Zeeman effect of the O2 118 GHz spectral radiance measurements can be utilized to remotely measure the magnetic field perturbations at altitudes close to the auroral electrojets. The technique has been demonstrated using the measurements provided by the Microwave Limb Souncer onboard the Aura spacecraft.  The derived current-induced magnetic field perturbations were found to be highly correlated with those coincidently obtained by ground magnetometers and to be consistent with the well-known auroral electrojet current distribution thereby providing a strong argument for the validity of the technique. With today's technology, a 118 GHz instrument, can be miniaturized allowing it to fly on small satellites such as CubeSats.  A constellation of small satellites with each one carrying a number of these identical mini-radiometers would have the ability to provide simultaneous multipoint measurement of the magnetic field perturbations at altitudes close to the electrojet, thereby greatly advancing our understanding of the ionospheric current system.  In this paper, we present the Zeeman magnetic field sensing technique, the requirements and specifications of the instrument, and an example of a cost effectively cubesat mission that provides unprecedented measurements of the evolution and structure of the auroral electrojet system.

How to cite: Yee, J.-H., Gjerloev, J., Merkin, V., and Laundal, K.: Remote Sensing of Magnetic Fields Induced by Electrojets From Space: Measurement Techniques and Sensor Design Requirements, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20938, https://doi.org/10.5194/egusphere-egu2020-20938, 2020.

D1156 |
Lucia Santarelli, Paola De Michelis, and Giuseppe Consolini

The features of the horizontal intensity of the geomagnetic field fluctuations during a geomagnetically disturbed period are analyzed. The Empirical Mode Decomposition (EMD) method is applied to separate short timescale (T<200 min) and long timescale (T>200 min) magnetic field fluctuations, which have been suggested to be related to different physical processes. The magnetic fluctuations at long timescales (T>200 min) seem to show a large degree of correlation between solar wind parameters and magnetospheric dynamics proxies, while the magnetic field fluctuations at short timescales (T<200 min) seem to be essentially related to internal magnetospheric processes and not directly driven by interplanetary changes.

Daily maps of the short timescale magnetic field fluctuations during a selected period are analyzed in order to investigate their contribution to the total magnetic signal. The aim is to evaluate the role that the internal magnetospheric processes have on the magnetic signal recorded on the ground and to investigate their dependence on the geomagnetic activity level. A comparison between the two hemispheres is also shown. The obtained results can be useful in the Space weather framework. They show the magnetic field fluctuation forecasting requires the development of models that take into account not only the solar wind parameters but also the internal dynamics of the magnetosphere that although triggered by changes of the interplanetary conditions is not directly driven by solar wind/interplanetary magnetic field.

How to cite: Santarelli, L., De Michelis, P., and Consolini, G.: Short timescale magnetic field fluctuations and their impact on space weather forecasting , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11647, https://doi.org/10.5194/egusphere-egu2020-11647, 2020.

D1157 |
Svetlana Riabova and Alexander Spivak

Temporal variations of the electric field in near-surface layer of the Earth are determined by many factors, among which strong disturbances of the magnetic field should be especially noted. Magnetic storms cause an increase in the ionospheric electric field, which leads to variations in the gradient of the electric field potential near the Earth's surface. We consider the effect of magnetic storms in variations in the electrical characteristics of the atmosphere at Geophysical observatory «Mikhnevo» of Sadovsky Institute of Geosphere Dynamics of Russian Academy of Sciences and at Center for geophysical monitoring of Moscow of Sadovsky Institute of Geosphere Dynamics of Russian Academy of Sciences. We used data from the continuous monitoring of three components of the magnetic field, vertical components of the atmospheric electric field and atmospheric current carried out in fair weather. Experimental data processing and analysis show that accompanying magnetic storms with geomagnetic K index more or equal 5 increased variations in the electric field and vertical atmospheric current are characterized by different morphological structures. It is currently difficult to interpret the data. Nevertheless, the research results can be of great help in the development and verification of theoretical and computational models for generating variations in the electric field as a result of strong geomagnetic disturbances.

How to cite: Riabova, S. and Spivak, A.: Variations of electrical characteristics of near-surface atmosphere of the Earth during magnetic storm, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20128, https://doi.org/10.5194/egusphere-egu2020-20128, 2020.

D1158 |
Anna Morozova, Rania Rebbah, and M. Alexandra Pais

Geomagnetic field (GMF) variations from external sources are classified as regular diurnal or occurring during periods of disturbances. The most significant regular variations are the quiet solar daily variation (Sq) and the disturbance daily variation (SD). These variations have well recognized daily cycles and need to be accounted for before the analysis of the disturbed field. Preliminary analysis of the GMF variations shows that the principal component analysis (PCA) is a useful tool for extraction of regular variations of GMF; however the requirements to the data set length, geomagnetic activity level etc. need to be established.

Here we present preliminary results of the PCA-based Sq extraction procedure based on the analysis of the Coimbra Geomagnetic Observatory (COI) measurements of the geomagnetic field components H, X, Y and Z between 2007 and 2015. The PCA-based Sq curves are compared with the standard ones obtained using 5 IQD per month. PCA was applied to data sets of different length: either 1 month-long data set for one of 2007-2015 years or data series for the same month but from different years (2007-2015) combined together. For most of the analyzed years the first PCA mode (PC1) was identified as SD variation and the second mode (PC2) was identified as Sq variation.

How to cite: Morozova, A., Rebbah, R., and Pais, M. A.: Separation of the daily quiet variation from the geomagnetic field observations with the principal component analysis, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3423, https://doi.org/10.5194/egusphere-egu2020-3423, 2020.

D1159 |
Wu Yingyan

The geomagnetic field shows a regular diunal variation at the middle and low latitudes during geomagnetic quiet time, which is called as solar quiet daily variation (Sq). It is mainly generated from the ionosphere dynamic current system in the E-region of ionosphere, which is controlled by the ionospheric diunal and semi-diunal tidal wind field. The variation of the Sq field is greatly related to the latitude and the local time, and its amplitude and the phase vary very slowly in the whole year. Furthermore, a significant day-to-day (DTD) variation is usually seen in the amplitude and the phase of the Sq. It is greatly related to many factors such as the conductivity and the wind field in the ionosphere, and states of the magnetosphere.

This work is primarily to investigate the seasonal variation of the amplitude of the Sq field on both north-and-south sides of the Sq current, by using of the hourly data of the geomagnetic horizontal field from 75 observatories at mid-and-low latitudes. The result indicates that there is a significant seasonal variation in the amplitude of Sq(H) at all observatories, which shows a great enhancement during equinoxes months. However, a notable latitudinal asymmetry is clearly seen between the northside and southside observatories. The amplitude of Sq(H) reaches the maximum value in autumn at northside observatories, but in spring at southside observatories. This latitudinal asymmetry is most likely to reflect the tilt of the ionosphere current vortex.


How to cite: Yingyan, W.: The latitudinal asymmetry of the seasonal variation of the amplitude of the Sq field, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13424, https://doi.org/10.5194/egusphere-egu2020-13424, 2020.

D1160 |
Anatoly Soloviev and Artem Smirnov

The most regular of all daily geomagnetic field variations is the so-called solar quiet, or Sq, variation. It is attributed to the two current vortices flowing in the E-region of the dayside ionosphere. We present an investigation of the time-dependent parameters of Sq variation for the historical minimum of solar activity in 2008. We apply "Measure of Anomalousness" algorithm to detection of magnetically quiet days. The global maps of seasonal Sq amplitudes of the three orthogonal components are derived using 75 INTERMAGNET and 46 SuperMAG stations at low and middle latitudes. The global Sq amplitudes are compared to the previous Coupled Magnetosphere-Ionosphere-Thermosphere (CMIT) model simulations and show good agreement. Significant variability was found in Sq(X) and Sq(Y) based on the solar activity and latitude, while almost no difference is observed in Sq(Z) for across all latitudes and seasons. We analyze equivalent Sq current system using observatory data from the Australian mainland and narrow European-African latitudinal segment. Sq current system also strongly depends on solar activity, as current vortices are strongest in the local summer-hemisphere and disintegrate during local winter. The dynamics of Sq variation along the solar cycles 23 and 24 is also discussed and compared to Swarm-based spherical harmonic Sq model.

How to cite: Soloviev, A. and Smirnov, A.: Solar quiet daily (Sq) geomagnetic variation during minimum of solar cycle 23/24, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5276, https://doi.org/10.5194/egusphere-egu2020-5276, 2020.

D1161 |
Dragos Constantinescu, Hans-Ulrich Auster, Magda Delva, Olaf Hillenmaier, Werner Magnes, and Ferdinand Plaschke

Measuring the in situ magnetic field using space borne instruments requires either a magnetically clean platform and/or a very long boom for accommodating magnetometers sensors at a large distance from the spacecraft body. This significantly drives up the costs and time for building the spacecraft. Here we present an alternative sensor configuration and an algorithm allowing for ulterior removing of the spacecraft generated disturbances from the magnetic field measurements, thus lessening the need for a magnetic cleanliness program.

The Service Oriented Spacecraft Magnetometer (SOSMAG) onboard the Korean Geostationary Satellite GEO-KOMPSAT-2A (GK-2A) uses for the first time a multi-sensor configuration for onboard data cleaning. To remove the AC disturbances, a combination of the measurements from sensors placed at different positions from the disturbance sources is processed onboard. Sensor biases due to daily temperature variations are also removed using the specific SOSMAG sensor arrangement. 


How to cite: Constantinescu, D., Auster, H.-U., Delva, M., Hillenmaier, O., Magnes, W., and Plaschke, F.: Cleaning magnetometer data using multi sensor configuration, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17741, https://doi.org/10.5194/egusphere-egu2020-17741, 2020.