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

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

<p>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. Τhis 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.</p>

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

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

<p>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.</p>

Simulations of the Relativistic Radiation Belt Electrons Using the VERB-3D Code

2021 ◽  
Author(s):  
Dedong Wang ◽  
Yuri Shprits ◽  
Alexander Drozdov ◽  
Nikita Aseev ◽  
Irina Zhelavskaya ◽  
...  
Keyword(s):  
Space Weather ◽  
Radiation Belt ◽  
Model Performance ◽  
Dynamic Evolution ◽  
Relativistic Electrons ◽  
Outer Radiation Belt ◽  
Chorus Waves ◽  
Van Allen Probes ◽  
Radiation Belt Electrons ◽  
Simulation Results

<p>Using the three-dimensional Versatile Electron Radiation Belt (VERB-3D) code, we perform simulations to investigate the dynamic evolution of relativistic electrons in the Earth’s outer radiation belt. In our simulations, we use data from the Geostationary Operational Environmental Satellites (GOES) to set up the outer boundary condition, which is the only data input for simulations. The magnetopause shadowing effect is included by using last closed drift shell (LCDS), and it is shown to significantly contribute to the dropouts of relativistic electrons at high $L^*$. We validate our simulation results against measurements from Van Allen Probes. In long-term simulations, we test how the latitudinal dependence of chorus waves can affect the dynamics of the radiation belt electrons. Results show that the variability of chorus waves at high latitudes is critical for modeling of megaelectron volt (MeV) electrons. We show that, depending on the latitudinal distribution of chorus waves under different geomagnetic conditions, they cannot only produce a net acceleration but also a net loss of MeV electrons. Decrease in high‐latitude chorus waves can tip the balance between acceleration and loss toward acceleration, or alternatively, the increase in high‐latitude waves can result in a net loss of MeV electrons. Variations in high‐latitude chorus may account for some of the variability of MeV electrons. </p><p>Our simulation results for the NSF GEM Challenge Events show that the position of the plasmapause plays a significant role in the dynamic evolution of relativistic electrons. We also perform simulations for the COSPAR International Space Weather Action Team (ISWAT) Challenge for the year 2017. The COSPAR ISWAT is a global hub for collaborations addressing challenges across the field of space weather. One of the objectives of the G3-04 team “Internal Charging Effects and the Relevant Space Environment” is model performance assessment and improvement. One of the expected outputs is a more systematic assessment of model performance under different conditions. The G3-04 team proposed performing benchmarking challenge runs. We ‘fly’ a virtual satellite through our simulation results and compare the simulated differential electron fluxes at 0.9 MeV and 57.27 degrees local pitch-angle with the fluxes measured by the Van Allen Probes. In general, our simulation results show good agreement with observations. We calculated several different matrices to validate our simulation results against satellite observations.</p>

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

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

<p>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.</p><p>This work has received funding from the European Union's Horizon 2020 research and innovation programme “SafeSpace” under grant agreement No 870437 and from the European Space Agency under the “European Contribution to International Radiation Environment Near Earth (IRENE) Modelling System” activity under ESA Contract No 4000127282/19/NL/IB/gg.</p>

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

2021 ◽  
Author(s):  
Christos Katsavrias ◽  
Constantinos Papadimitriou ◽  
Sigiava Aminalragia-Giamini ◽  
Ioannis A. Daglis ◽  
Ingmar Sandberg ◽  
...  
Keyword(s):  
Relativistic Electron ◽  
Radiation Belt ◽  
Annual Variation ◽  
Phase Relationship ◽  
Relativistic Electrons ◽  
Solar Cycles ◽  
Outer Radiation Belt ◽  
Cross Wavelet Analysis ◽  
Cycle 24 ◽  
Broad Energy

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.

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

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.

Superposed Epoch Analyses of electron-driven and proton-driven magnetic dips

2021 ◽  
Author(s):  
Hui Zhu ◽  
Lunjin Chen
Keyword(s):  
Statistical Characteristics ◽  
Relativistic Electrons ◽  
Magnetic Fluctuations ◽  
Inner Magnetosphere ◽  
Superposed Epoch Analysis ◽  
Van Allen Probes ◽  
Epoch Analysis ◽  
The Relationship ◽  
Statistical Results

<p>In this study, we use the Van Allen Probes data statistically to investigate the features of magnetic dips by the means of superposed epoch analysis. Based on the different max values of electron and proton plasma betas, we categorize the dips into two types: electron-driven dips and proton-driven dips. Superposed epoch analysis on two types of magnetic dips suggests the correlation between the magnetic fluctuations and plasma betas. Moreover, the occurrence of the butterfly distributions of relativistic electrons driven by the magnetic dips is confirmed by the statistical results. Our results reveal the statistical characteristics of magnetic dips and build up the relationship among the magnetic fluctuations and several parameters, indicating the potentially important role of magnetic dips in the dynamics of the inner magnetosphere.</p>

Radial diffusion coefficients database in the frame of SafeSpace project

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

<p>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 (D<sub>LL</sub>) 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 D<sub>LL</sub> have been shown to be highly event-specific. In the frame of SafeSpace project we have used 12 years (2009 – 2020) of multi-point magnetic and electric field measurements from THEMIS A, D and E satellites to create a database of calculated D<sub>LL</sub>. In this work we present the first statistics on the evolution of D<sub>LL </sub>during the various phases of Solar cycle 24 with respect to the various solar wind parameters and geomagnetic indices.</p><p>This work has received funding from the European Union's Horizon 2020 research and innovation programme “SafeSpace” under grant agreement No 870437.</p>

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