Rights statement: © 2013 The Authors. Journal of Geophysical Research: Space Physics published by Wiley on behalf of American Geophysical Union. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
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Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Case studies of the impact of high-speed solar-wind streams on the electron radiation belt at geosynchronous orbit
T2 - flux, magnetic field and phase space density
AU - Hartley, Dave
AU - Denton, Michael
AU - Green, Janet
AU - Onsager, Terrance
AU - Rodriguez, Juan
AU - Singer, Howard
N1 - © 2013 The Authors. Journal of Geophysical Research: Space Physics published by Wiley on behalf of American Geophysical Union. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
PY - 2013/11
Y1 - 2013/11
N2 - Investigation of electron radiation belt dropouts has revealed the importance of a number of loss processes, yet there remains a lack of quantitative detail as to how these processes wax and wane between events. The overarching aim of this study is to address the issue of electron radiation belt dropouts. This is achieved using in situ observations at geostationary orbit from GOES-13 (pitch-angle-resolved electron data and magnetic field measurements) to examine the outer electron radiation belt during three high-speed stream-driven storms. Analysis and interpretation are aided by calculation of the phase space density (PSD) as a function of the three adiabatic invariants. Our results confirm the importance of outwards adiabatic transport as a mechanism for causing electron dropouts at GEO, however study of the pitch-angle distributions indicates that other loss mechanisms are also likely to be occurring during these HSS-driven storms. Two of the studied events exhibit similar evolutionary structure in their pitch-angle distributions, (i) highly peaked distributions immediately prior to the dropout (ii) sharp transitions between peaked and isotropic and then subsequent butterfly distributions, and (iii) isotropic distributions at minimum flux shortly afterwards (dusk). We also address the difficulty in interpreting PSD calculations by comparing the T96 model magnetic field with that measured by GOES-13. Our results are intended as a first step in quantifying the timeline of events that occur in the radiation belts following the arrival of a HSS - particularly timely given the increase in HSS-occurrence expected in the declining phase of the current solar cycle.
AB - Investigation of electron radiation belt dropouts has revealed the importance of a number of loss processes, yet there remains a lack of quantitative detail as to how these processes wax and wane between events. The overarching aim of this study is to address the issue of electron radiation belt dropouts. This is achieved using in situ observations at geostationary orbit from GOES-13 (pitch-angle-resolved electron data and magnetic field measurements) to examine the outer electron radiation belt during three high-speed stream-driven storms. Analysis and interpretation are aided by calculation of the phase space density (PSD) as a function of the three adiabatic invariants. Our results confirm the importance of outwards adiabatic transport as a mechanism for causing electron dropouts at GEO, however study of the pitch-angle distributions indicates that other loss mechanisms are also likely to be occurring during these HSS-driven storms. Two of the studied events exhibit similar evolutionary structure in their pitch-angle distributions, (i) highly peaked distributions immediately prior to the dropout (ii) sharp transitions between peaked and isotropic and then subsequent butterfly distributions, and (iii) isotropic distributions at minimum flux shortly afterwards (dusk). We also address the difficulty in interpreting PSD calculations by comparing the T96 model magnetic field with that measured by GOES-13. Our results are intended as a first step in quantifying the timeline of events that occur in the radiation belts following the arrival of a HSS - particularly timely given the increase in HSS-occurrence expected in the declining phase of the current solar cycle.
KW - radiation belt
KW - dropout
KW - GEO
KW - transport
KW - phase space density
KW - high-speed stream
U2 - 10.1002/2013JA018923
DO - 10.1002/2013JA018923
M3 - Journal article
VL - 118
SP - 6964
EP - 6979
JO - Journal of Geophysical Research: Space Physics
JF - Journal of Geophysical Research: Space Physics
SN - 2169-9402
IS - 11
ER -