TY  - JOUR
A1  - Qin, Murong
A1  - Hudson, Mary
A1  - Li, Zhao
A1  - Millan, Robyn
A1  - Shen, Xiaochen
A1  - Shprits, Yuri Y.
A1  - Woodger, Leslie
A1  - Jaynes, Allison
A1  - Kletzing, Craig
T1  - Investigating loss of relativistic electrons associated with EMIC Waves at low L values on 22 June 2015
JF  - Journal of geophysical research : Space physics
N2  - In this study, rapid loss of relativistic radiation belt electrons at low L* values (2.4-3.2) during a strong geomagnetic storm on 22 June 2015 is investigated along with five possible loss mechanisms. Both the particle and wave data are obtained from the Van Allen Probes. Duskside H+ band electromagnetic ion cyclotron (EMIC) waves were observed during a rapid decrease of relativistic electrons with energy above 5.2 MeV occurring outside the plasma sphere during extreme magnetopause compression. Lower He+ composition and enriched O+ composition are found compared to typical values assumed in other studies of cyclotron resonant scattering of relativistic electrons by EMIC waves. Quantitative analysis demonstrates that even with the existence of He+ band EMIC waves, it is the H+ band EMIC waves that are likely to cause the depletion at small pitch angles and strong gradients in pitch angle distributions of relativistic electrons with energy above 5.2 MeV at low L values for this event. Very low frequency wave activity at other magnetic local time can be favorable for the loss of relativistic electrons at higher pitch angles. An illustrative calculation that combines the nominal pitch angle scattering rate due to whistler mode chorus at high pitch angles with the H+ band EMIC wave loss rate at low pitch angles produces loss on time scale observed at L = 2.4-3.2. At high L values and lower energies, radial loss to the magnetopause is a viable explanation.
Y1  - 2019
U6  - https://doi.org/10.1029/2018JA025726
SN  - 2169-9380
SN  - 2169-9402
VL  - 124
IS  - 6
SP  - 4022
EP  - 4036
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Ripoll, Jean-Francois
A1  - Loridan, Vivien
A1  - Denton, Michael H.
A1  - Cunningham, Gregory
A1  - Reeves, G.
A1  - Santolik, O.
A1  - Fennell, Joseph
A1  - Turner, Drew L.
A1  - Drozdov, Alexander
A1  - Cervantes Villa, Juan Sebastian
A1  - Shprits, Yuri Y.
A1  - Thaller, Scott A.
A1  - Kurth, William S.
A1  - Kletzing, Craig A.
A1  - Henderson, Michael  G.
A1  - Ukhorskiy, Aleksandr Y.
T1  - Observations and Fokker-Planck Simulations of the L-Shell, Energy, and Times
JF  - Journal of geophysical research : Space physics
N2  - The evolution of the radiation belts in L-shell (L), energy (E), and equatorial pitch angle (alpha(0)) is analyzed during the calm 11-day interval (4-15 March) following the 1 March 2013 storm. Magnetic Electron and Ion Spectrometer (MagEIS) observations from Van Allen Probes are interpreted alongside 1D and 3D Fokker-Planck simulations combined with consistent event-driven scattering modeling from whistler mode hiss waves. Three (L, E, alpha(0)) regions persist through 11 days of hiss wave scattering; the pitch angle-dependent inner belt core (L similar to <2.2 and E < 700 keV), pitch angle homogeneous outer belt low-energy core (L > similar to 5 and E similar to < 100 keV), and a distinct pocket of electrons (L similar to [4.5, 5.5] and E similar to [0.7, 2] MeV). The pitch angle homogeneous outer belt is explained by the diffusion coefficients that are roughly constant for alpha(0) similar to <60 degrees, E > 100 keV, 3.5 < L < L-pp similar to 6. Thus, observed unidirectional flux decays can be used to estimate local pitch angle diffusion rates in that region. Top-hat distributions are computed and observed at L similar to 3-3.5 and E = 100-300 keV.
KW  - radiation belts
KW  - wave-particle interactions
KW  - electron lifetime
KW  - pitch angle diffusion coefficient
KW  - hiss waves
Y1  - 2018
U6  - https://doi.org/10.1029/2018JA026111
SN  - 2169-9380
SN  - 2169-9402
VL  - 124
IS  - 2
SP  - 1125
EP  - 1142
PB  - American Geophysical Union
CY  - Washington
ER  -