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>

scholarly journals The "SafeSpace" Radial Diffusion Coefficients Database: Dependencies and application to simulations

2021 ◽  
Author(s):  
Christos Katsavrias ◽  
Afroditi Nasi ◽  
Ioannis A. Daglis ◽  
Sigiava Aminalragia-Giamini ◽  
Nourallah Dahmen ◽  
...  
Keyword(s):  
Solar Wind ◽  
Diffusion Coefficients ◽  
Low Frequency ◽  
Field Measurements ◽  
Radial Diffusion ◽  
Wind Pressure ◽  
Relativistic Electrons ◽  
Interplanetary Coronal Mass Ejections ◽  
Outer Radiation Belt ◽  
Semi Empirical

Abstract. Radial diffusion has been established as one of the most important mechanisms contributing to both the acceleration and loss of relativistic electrons in the outer radiation belt. In the framework of the SafeSpace project we have used 9 years (2011–2019) of multi-point magnetic and electric field measurements from THEMIS A, D and E satellites to create a database of accurately calculated radial diffusion coefficients (DLL) spanning an L* range from 3 to 8. In this work we investigate the dependence of the DLL on the various solar wind parameters, geomagnetic indices and coupling functions, and moreover, on the spatial parameters L* and Magnetic Local Time (MLT), during the solar cycle 24. The spatial distribution of the DLL reveals important MLT dependence rising from the various Ultra Low Frequency (ULF) wave generation mechanisms. Furthermore, we investigate via a superposed analysis, the dependence of the DLL on solar wind drivers. We show that the Interplanetary Coronal Mass Ejections (ICME) driven disturbances accompanied by high solar wind pressure values combined with intense magnetospheric compression produce DLLB  values comparable or even greater than the ones of DLLE. This feature cannot be captured by semi-empirical models and introduces a significant energy dependence on the DLL. Finally, we show the advantages of the use of accurately calculated DLL by means of numerical simulations of relativistic electron fluxes performed with the Salammbô code and significant deviations of several semi-empirical model predictions depending on the level of geomagnetic activity and L-shell.

ULF Wave Power During Geomagnetic Storms and Implications for Radial Diffusion Processes

2021 ◽  
Author(s):  
Jasmine Sandhu ◽  
Jonathan Rae ◽  
John Wygant ◽  
Aaron Breneman ◽  
Sheng Tian ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Diffusion Coefficients ◽  
Radiation Belt ◽  
Geomagnetic Storms ◽  
Radial Diffusion ◽  
Ulf Waves ◽  
Wave Power ◽  
Outer Radiation Belt ◽  
Large Variability ◽  
Ulf Wave

<p>Ultra Low Frequency (ULF) waves drive radial diffusion of radiation belt electrons, where this process contributes to and, at times, dominates energisation, loss, and large scale transport of the outer radiation belt. In this study we quantify the changes and variability in ULF wave power during geomagnetic storms, through a statistical analysis of Van Allen Probes data for the time period spanning 2012 – 2019. The results show that global wave power enhancements occur during the main phase, and continue into the recovery phase of storms. Local time asymmetries show sources of ULF wave power are both external solar wind driving as well as internal sources from coupling with ring current ions and substorms.</p><p>The statistical analysis demonstrates that storm time ULF waves are able to access lower L values compared to pre-storm conditions, with enhancements observed within L = 4. We assess how magnetospheric compressions and cold plasma distributions shape how ULF wave power propagates through the magnetosphere. Results show that the Earthward displacement of the magnetopause is a key factor in the low L enhancements. Furthermore, the presence of plasmaspheric plumes during geomagnetic storms plays a crucial role in trapping ULF wave power, and contributes significantly to large storm time enhancements in ULF wave power.</p><p>The results have clear implications for enhanced radial diffusion of the outer radiation belt during geomagnetic storms. Estimates of storm time radial diffusion coefficients are derived from the ULF wave power observations, and compared to existing empirical models of radial diffusion coefficients. We show that current Kp-parameterised models, such as the Ozeke et al. [2014] model, do not fully capture the large variability in storm time radial diffusion coefficients or the extent of enhancements in the magnetic field diffusion coefficients.</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>

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

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

<p>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.</p><p>This work is supported by ESA’s Science Core Technology Programme (CTP) under contract No. 4000127282/19/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.

Radial Diffusion as a Potential Source and Loss Mechanism of Relativistic Electrons in the Outer Radiation Belt

2006 ◽  
Author(s):  
Y. Y. Shprits ◽  
R. M. Thorne ◽  
R. Friedel ◽  
G. D. Reeves ◽  
J. Fennell ◽  
...  
Keyword(s):  
Radiation Belt ◽  
Radial Diffusion ◽  
Relativistic Electrons ◽  
Loss Mechanism ◽  
Outer Radiation Belt ◽  
Potential Source

Methodology for calculation of radial diffusion coefficients for a relativistic electron population from hybrid-Vlasov simulation

2021 ◽  
Author(s):  
Harriet George ◽  
Emilia Kilpua ◽  
Adnane Osmane ◽  
Urs Ganse ◽  
Solene Lejosne ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Radiation Belt ◽  
Time Derivative ◽  
Distribution Functions ◽  
Radial Diffusion ◽  
Outer Radiation Belt ◽  
Electron Population ◽  
Radial Diffusion Coefficient

<p>The relative importance of radial diffusion and local acceleration to the dynamics of outer radiation belt electron populations is an open question in radiation belt physics. A key component of this discussion is the calculation of the radial diffusion coefficients, which quantify the effect of radial diffusion on an electron population. However, there is currently a broad range of radial diffusion coefficient values in the literature, which presents difficulties when determining the dominant process governing radiation belt energisation. Here we develop a methodology for the calculation of radial diffusion coefficients using Vlasiator, a 5D hybrid-Vlasov simulation of near-Earth space, and calculate the radial diffusion coefficients for a 10 MeV electron population at multiple locations within the outer radiation belt.</p><p> </p><p>Vlasiator currently models ions as velocity distribution functions and electrons as a magnetohydrodynamic fluid, so the drift motion of the electron population can not be directly studied. However, the ion dynamics accurately determine the magnetic field in the inner magnetosphere, and the spatial and temporal magnetic field variations can be used to calculate the radial diffusion coefficient of a population according to principles outlined in Lejosne et. al. 2020.<span>  </span>Four magnetic field isocontours in the outer radiation belt are used to model the guiding centre drift contours of an electron population, and the corresponding Roederer L-star coordinates are calculated from the magnetic flux through each of these drift contours. The variation of the L-stars over time are calculated from population-specific variables and the Lagrangian magnetic field time derivative along the magnetic isocontours. The radial diffusion coefficients for the 10 MeV electron population are then calculated at each of these L-stars and compared to the literature. This methodology produces radial diffusion coefficients from Vlasiator that have the expected L-shell dependence and are consistent with the literature, including studies based on satellite measurements of radiation belt electrons. These results indicate that this is a valid methodology for the calculation of radial diffusion coefficients, and can therefore be extended to evaluate the radial diffusion coefficients in different solar wind conditions and at more L-stars.</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>

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