scholarly journals Electric and magnetic radial diffusion coefficients using the Van Allen probes data

2016 ◽  
Vol 121 (10) ◽  
pp. 9586-9607 ◽  
Author(s):  
Ashar F. Ali ◽  
David M. Malaspina ◽  
Scot R. Elkington ◽  
Allison N. Jaynes ◽  
Anthony A. Chan ◽  
...  
Keyword(s):  
Diffusion Coefficients ◽  
Radial Diffusion ◽  
Van Allen Probes

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>

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>

scholarly journals Magnetic field power spectra and magnetic radial diffusion coefficients using CRRES magnetometer data

2015 ◽  
Vol 120 (2) ◽  
pp. 973-995 ◽  
Author(s):  
Ashar F. Ali ◽  
Scot R. Elkington ◽  
Weichao Tu ◽  
Louis G. Ozeke ◽  
Anthony A. Chan ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Diffusion Coefficients ◽  
Power Spectra ◽  
Radial Diffusion ◽  
Magnetometer Data

scholarly journals Optimization of Radial Diffusion Coefficients for the Proton Radiation Belt During the CRRES Era

2021 ◽  
Vol 126 (3) ◽  
Author(s):  
Alexander R. Lozinski ◽  
Richard B. Horne ◽  
Sarah A. Glauert ◽  
Giulio Del Zanna ◽  
Jay M. Albert
Keyword(s):  
Diffusion Coefficients ◽  
Radiation Belt ◽  
Radial Diffusion ◽  
Proton Radiation

scholarly journals Simulating radial diffusion of energetic (MeV) electrons through a model of fluctuating electric and magnetic fields

2006 ◽  
Vol 24 (10) ◽  
pp. 2583-2598 ◽  
Author(s):  
T. Sarris ◽  
X. Li ◽  
M. Temerin
Keyword(s):  
Magnetic Fields ◽  
Test Particle ◽  
Diffusion Coefficients ◽  
Radial Diffusion ◽  
Particle Simulation ◽  
Quiet Time ◽  
Earth’S Magnetosphere ◽  
Electric And Magnetic Fields ◽  
Earth's Magnetosphere ◽  
Diffusion Rates

Abstract. In the present work, a test particle simulation is performed in a model of analytic Ultra Low Frequency, ULF, perturbations in the electric and magnetic fields of the Earth's magnetosphere. The goal of this work is to examine if the radial transport of energetic particles in quiet-time ULF magnetospheric perturbations of various azimuthal mode numbers can be described as a diffusive process and be approximated by theoretically derived radial diffusion coefficients. In the model realistic compressional electromagnetic field perturbations are constructed by a superposition of a large number of propagating electric and consistent magnetic pulses. The diffusion rates of the electrons under the effect of the fluctuating fields are calculated numerically through the test-particle simulation as a function of the radial coordinate L in a dipolar magnetosphere; these calculations are then compared to the symmetric, electromagnetic radial diffusion coefficients for compressional, poloidal perturbations in the Earth's magnetosphere. In the model the amplitude of the perturbation fields can be adjusted to represent realistic states of magnetospheric activity. Similarly, the azimuthal modulation of the fields can be adjusted to represent different azimuthal modes of fluctuations and the contribution to radial diffusion from each mode can be quantified. Two simulations of quiet-time magnetospheric variability are performed: in the first simulation, diffusion due to poloidal perturbations of mode number m=1 is calculated; in the second, the diffusion rates from multiple-mode (m=0 to m=8) perturbations are calculated. The numerical calculations of the diffusion coefficients derived from the particle orbits are found to agree with the corresponding theoretical estimates of the diffusion coefficient within a factor of two.

scholarly journals Calculating ultra-low-frequency wave power of the compressional magnetic field vs. <i>L</i> and time: multi-spacecraft analysis using the Van Allen probes, THEMIS and GOES

2016 ◽  
Vol 34 (6) ◽  
pp. 565-571 ◽  
Author(s):  
Theodore E. Sarris ◽  
Xinlin Li
Keyword(s):  
Diffusion Processes ◽  
Low Frequency ◽  
Time History ◽  
Energetic Particles ◽  
Radial Diffusion ◽  
Wave Power ◽  
Frequency Wave ◽  
Wave Numbers ◽  
Van Allen Probes ◽  
History Of

Abstract. Ultra-low-frequency (ULF) pulsations are critical in radial diffusion processes of energetic particles, and the power spectral density (PSD) of these fluctuations is an integral part of the radial diffusion coefficients and of assimilative models of the radiation belts. Using simultaneous measurements from two Geostationary Operational Environmental Satellites (GOES) geosynchronous satellites, three satellites of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft constellation and the two Van Allen probes during a 10-day period of intense geomagnetic activity and ULF pulsations of October 2012, we calculate the PSDs of ULF pulsations at different L shells. By following the time history of measurements at different L it is shown that, during this time, ULF wave power is not enhanced uniformly throughout the magnetosphere but instead is mostly enhanced in the outer L shells, close to the magnetopause, and to a lesser extent in the inner magnetosphere, closer to the plasmapause. Furthermore, by using phase differences between two GOES geosynchronous satellite pairs, we estimate the daily-averaged distribution of power at different azimuthal wave numbers. These results can have significant implications in better defining the effect of radial diffusion in the phase space density of energetic particles for different wave numbers or L shell distributions of ULF power.

scholarly journals Bayesian Inference of Quasi‐Linear Radial Diffusion Parameters using Van Allen Probes

2020 ◽  
Vol 125 (5) ◽  
Author(s):  
Rakesh Sarma ◽  
Mandar Chandorkar ◽  
Irina Zhelavskaya ◽  
Yuri Shprits ◽  
Alexander Drozdov ◽  
...  
Keyword(s):  
Bayesian Inference ◽  
Radial Diffusion ◽  
Diffusion Parameters ◽  
Van Allen Probes
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