On the semi-annual variation of relativistic electrons in the outer radiation belt

Abstract. The nature of the semi-annual variation in the relativistic electron fluxes in the Earth’s outer radiation belt is investigated using Van Allen Probes (MagEIS and REPT) and GOES (EPS) data during solar cycle 24. We perform wavelet and cross-wavelet analysis in a broad energy and spatial range of electron fluxes and examine their phase relationship with the axial, equinoctial and Russell-McPherron mechanisms. It is found that the semi-annual variation in the relativistic electron fluxes exhibits pronounced power in the 0.3–4.2 MeV energy range at L-shells higher than 3.5 and, moreover, it exhibits an in-phase relationship with the Russell-McPherron effect indicating the former is primarily driven by the latter. Furthermore, the analysis of the past 3 solar cycles with GOES/EPS indicates that the semi-annual variation at geosynchronous orbit is evident during the descending phases and coincides with periods of a higher (lower) HSS (ICME) occurrence.

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On the semi-annual variation of relativistic electrons in the outer radiation belt

Annales Geophysicae ◽

10.5194/angeo-39-413-2021 ◽

2021 ◽

Vol 39 (3) ◽

pp. 413-425

Author(s):

Christos Katsavrias ◽

Constantinos Papadimitriou ◽

Sigiava Aminalragia-Giamini ◽

Ioannis A. Daglis ◽

Ingmar Sandberg ◽

...

Keyword(s):

Relativistic Electron ◽

High Speed ◽

Radiation Belt ◽

Annual Variation ◽

Phase Relationship ◽

Relativistic Electrons ◽

Solar Cycles ◽

Outer Radiation Belt ◽

Interplanetary Coronal Mass Ejection ◽

Cross Wavelet Analysis

Abstract. The nature of the semi-annual variation in the relativistic electron fluxes in the Earth's outer radiation belt is investigated using Van Allen Probes (MagEIS and REPT) and Geostationary Operational Environmental Satellite Energetic Particle Sensor (GOES/EPS) data during solar cycle 24. We perform wavelet and cross-wavelet analysis in a broad energy and spatial range of electron fluxes and examine their phase relationship with the axial, equinoctial and Russell–McPherron mechanisms. It is found that the semi-annual variation in the relativistic electron fluxes exhibits pronounced power in the 0.3–4.2 MeV energy range at L shells higher than 3.5, and, moreover, it exhibits an in-phase relationship with the Russell–McPherron effect, indicating the former is primarily driven by the latter. Furthermore, the analysis of the past three solar cycles with GOES/EPS indicates that the semi-annual variation at geosynchronous orbit is evident during the descending phases and coincides with periods of a higher (lower) high-speed stream (HSS) (interplanetary coronal mass ejection, ICME) occurrence.

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On the semi-annual variation of relativistic electrons in the outer radiation belt

10.5194/egusphere-egu21-13458 ◽

2021 ◽

Author(s):

Sigiava Aminalragia-Giamini ◽

Christos Katsavrias ◽

Constantinos Papadimitriou ◽

Ioannis A. Daglis ◽

Ingmar Sandberg ◽

...

Keyword(s):

Relativistic Electron ◽

Radiation Belt ◽

Annual Variation ◽

European Space Agency ◽

Phase Relationship ◽

Radiation Environment ◽

Relativistic Electrons ◽

Solar Cycles ◽

Outer Radiation Belt ◽

Horizon 2020

The nature of the semi-annual variation in the relativistic electron fluxes in the Earth&#8217;s outer radiation belt is investigated using Van Allen Probes (MagEIS and REPT) and GOES (EPS) data during solar cycle 24. We perform wavelet and cross-wavelet analysis in a broad energy and spatial range of electron fluxes and examine their phase relationship with the axial, equinoctial and Russell-McPherron mechanisms. It is found that the semi-annual variation in the relativistic electron fluxes exhibits pronounced power in the 0.3 &#8211; 4.2 MeV energy range at L-shells higher than 3.5 and, moreover, it exhibits an in-phase relationship with the Russell-McPherron effect indicating the former is primarily driven by the latter. Furthermore, the analysis of the past 3 solar cycles with GOES/EPS indicates that the semi-annual variation at geosynchronous orbit is evident during the descending phases and coincides with periods of a higher (lower) HSS (ICME) occurrence.This work has received funding from the European Union's Horizon 2020 research and innovation programme &#8220;SafeSpace&#8221; under grant agreement No 870437 and from the European Space Agency under the &#8220;European Contribution to International Radiation Environment Near Earth (IRENE) Modelling System&#8221; activity under ESA Contract No 4000127282/19/NL/IB/gg.

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Radial diffusion coefficients database in the frame of SafeSpace project

10.5194/egusphere-egu21-10563 ◽

2021 ◽

Author(s):

Christos Katsavrias ◽

Ioannis A. Daglis ◽

Afroditi Nasi ◽

Constantinos Papadimitriou ◽

Marina Georgiou

Keyword(s):

Diffusion Coefficients ◽

Radiation Belt ◽

Field Measurements ◽

Radial Diffusion ◽

Relativistic Electrons ◽

Outer Radiation Belt ◽

Horizon 2020 ◽

Research And Innovation ◽

The Difference ◽

Cycle 24

Radial diffusion has been established as one of the most important mechanisms contributing the acceleration and loss of relativistic electrons in the outer radiation belt. Over the past few years efforts have been devoted to provide empirical relationships of radial diffusion coefficients (DLL) for radiation belt simulations yet several studies have suggested that the difference between the various models can be orders of magnitude different at high levels of geomagnetic activity as the observed DLL have been shown to be highly event-specific. In the frame of SafeSpace project we have used 12 years (2009 &#8211; 2020) of multi-point magnetic and electric field measurements from THEMIS A, D and E satellites to create a database of calculated DLL. In this work we present the first statistics on the evolution of DLL during the various phases of Solar cycle 24 with respect to the various solar wind parameters and geomagnetic indices.This work has received funding from the European Union's Horizon 2020 research and innovation programme &#8220;SafeSpace&#8221; under grant agreement No 870437.

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On the effect of ULF waves on the outer radiation belt during geomagnetic storms

10.5194/egusphere-egu21-5977 ◽

2021 ◽

Author(s):

Christopher Lara ◽

Pablo S. Moya ◽

Victor Pinto ◽

Javier Silva ◽

Beatriz Zenteno

Keyword(s):

Relativistic Electron ◽

Radiation Belt ◽

Geomagnetic Storms ◽

Cumulative Effect ◽

Radiation Belts ◽

Ulf Waves ◽

Relativistic Electrons ◽

Relative Role ◽

Outer Radiation Belt ◽

Ulf Wave

The inner magnetosphere is a very important region to study, as with satellite-based communications increasing day after day, possible disruptions are especially relevant due to the possible consequences in our daily life. It is becoming very important to know how the radiation belts behave, especially during strong geomagnetic activity. The radiation belts response to geomagnetic storms and solar wind conditions is still not fully understood, as relativistic electron fluxes in the outer radiation belt can be depleted, enhanced or not affected following intense activity. Different studies show how these results vary in the face of different events. As one of the main mechanisms affecting the dynamics of the radiation belt are wave-particle interactions between relativistic electrons and ULF waves. In this work we perform a statistical study of the relationship between ULF wave power and relativistic electron fluxes in the outer radiation belt during several geomagnetic storms, by using magnetic field and particle fluxes data measured by the Van Allen Probes between 2012 and 2017. We evaluate the correlation between the changes in flux and the cumulative effect of ULF wave activity during the main and recovery phases of the storms for different position in the outer radiation belt and energy channels. Our results show that there is a good correlation between the presence of ULF waves and the changes in flux during the recovery phase of the storm and that correlations vary as a function of energy. Also, we can see in detail how the ULF power change for the electron flux at different L-shell We expect these results to be relevant for the understanding of the relative role of ULF waves in the enhancements and depletions of energetic electrons in the radiation belts for condition described.

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Association of chorus waves and source/seed electrons with the enhancement of relativistic electrons in the outer Van Allen belt

10.5194/egusphere-egu2020-1014 ◽

2020 ◽

Author(s):

Afroditi Nasi ◽

Ioannis A. Daglis ◽

Christos Katsavrias ◽

Wen Li

Keyword(s):

Relativistic Electron ◽

Radiation Belt ◽

Geomagnetic Disturbance ◽

Relativistic Electrons ◽

Outer Radiation Belt ◽

Inner Magnetosphere ◽

Superposed Epoch Analysis ◽

Chorus Waves ◽

Substorm Activity ◽

Epoch Analysis

Local acceleration driven by whistler-mode chorus waves is fundamentally important for the acceleration of seed electrons in the outer radiation belt to relativistic energies. &#932;his mechanism strongly depends on substorm activity and on the source electron population injected by the substorms into the inner magnetosphere. In our work we use Van Allen Probes data to investigate the features of source electrons, seed electrons and chorus waves for events of enhancement versus events of depletion of relativistic electrons in the outer Van Allen belt. To that end we calculate the electron phase space density (PSD) for five values of the first adiabatic invariant corresponding to source and seed electrons, and we perform a superposed epoch analysis of 28 geomagnetic disturbance events, out of which, 20 result in enhancement and 8 in depletion of relativistic electron PSD. Our results indicate that events resulting in significant enhancement of relativistic electron PSD in the outer radiation belt are characterized by statistically stronger and more prolonged storm and substorm activity, leading to more efficient injections of source but mostly seed electrons to the inner magnetosphere, and also to more pronounced and long-lasting chorus and Pc5 wave activity. The effect of these parameters in the acceleration of electrons seems to be determined by the abundance of seed electrons at the region of L*=4-5.

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Identification of interplanetary parameter schemes which drive the variability of the magnetospheric radiation environment

10.5194/egusphere-egu2020-632 ◽

2020 ◽

Author(s):

Christos Katsavrias ◽

Afroditi Nasi ◽

Constantinos Papadimitriou ◽

Sigiava Aminalragia-Giamini ◽

Ingmar Sandberg ◽

...

Keyword(s):

Solar Wind ◽

Radiation Belt ◽

Solar Energetic Particle ◽

Radiation Environment ◽

Relativistic Electrons ◽

Outer Radiation Belt ◽

Core Technology ◽

Cycle 24 ◽

Solar Wind Parameters ◽

Time And Energy

The energetic particles of the outer radiation belt are highly variable in space, time and energy, due to the complex interplay between various mechanisms that contribute to their energization and/or loss. Previous studies have focused on the influence of solar wind and magnetospheric processes on the electron population dynamics, showing that the eventual effect of the various interplanetary drivers results from different combinations of IMF and solar wind parameters. Yet, all of these studies were limited in temporal, spatial and energy coverage. In this work, we take advantage of a large dataset, which includes multipoint measurements of electron fluxes covering a large energy range and various orbits (e.g. Van Allen Probes, GOES, HIMAWARI, SREM monitors, etc.), as well as approximately the whole solar cycle 24 to deduce specific interplanetary parameter schemes that drive enhancements or depletions of relativistic electrons in the outer radiation belt. Our study also investigates parameters which are correlated to the Solar Energetic Particle (SEP) environment with the long-term goal of connecting the two sets of results for coherent merging of environment models.This work is supported by ESA&#8217;s Science Core Technology Programme (CTP) under contract No. 4000127282/19/IB/gg.

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