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Electron loss rates from the outer radiation belt caused by the filling of the outer plasmasphere: The calm before the storm

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Electron loss rates from the outer radiation belt caused by the filling of the outer plasmasphere: The calm before the storm. / Borovsky, J. E.; Denton, Michael H.
In: Journal of Geophysical Research, Vol. 114, No. A11203, 11.2009, p. 1-12.

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Borovsky JE, Denton MH. Electron loss rates from the outer radiation belt caused by the filling of the outer plasmasphere: The calm before the storm. Journal of Geophysical Research. 2009 Nov;114(A11203):1-12. doi: 10.1029/2009JA014063

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@article{af12fa411a8f48d785a512839f0117ec,
title = "Electron loss rates from the outer radiation belt caused by the filling of the outer plasmasphere: The calm before the storm",
abstract = "Measurements from seven spacecraft in geosynchronous orbit are analyzed to determine the decay rate of the number density of the outer electron radiation belt prior to the onset of high-speed-stream-driven geomagnetic storms. Superposed-data analysis is used with a collection of 124 storms. When there is a calm before the storm, the electron number density decays exponentially before the storm with a 3.4-day e-folding time: beginning about 4 days before storm onset, the density decreases from ∼4 × 10−4 cm−3 to ∼1 × 10−4 cm−3. When there is not a calm before the storm, the number density decay is very small. The decay in the number density of radiation belt electrons is believed to be caused by pitch angle scattering of electrons into the atmospheric loss cone as the outer plasmasphere fills during the calms. This is confirmed by separately measuring the density decay rate for times when the outer plasmasphere is present or absent. While the radiation belt electron density decreases, the temperature of the electron radiation belt holds approximately constant, indicating that the electron precipitation occurs equally at all energies. Along with the number density decay, the pressure of the outer electron radiation belt decays, and the specific entropy increases. From the measured decay rates, the electron flux to the atmosphere is calculated, and that flux is 3 orders of magnitude less than thermal fluxes in the magnetosphere, indicating that the radiation belt pitch angle scattering is 3 orders weaker than strong diffusion. Energy fluxes into the atmosphere are calculated and found to be insufficient to produce visible airglow.",
keywords = "Radiation belt, plasmasphere DCS-publications-id, art-971, DCS-publications-credits, iono, DCS-publications-personnel-id, 123",
author = "Borovsky, {J. E.} and Denton, {Michael H.}",
note = "Copyright (2009) American Geophysical Union. Further reproduction or electronic distribution is not permitted",
year = "2009",
month = nov,
doi = "10.1029/2009JA014063",
language = "English",
volume = "114",
pages = "1--12",
journal = "Journal of Geophysical Research",
issn = "0148-0227",
publisher = "American Geophysical Union",
number = "A11203",

}

RIS

TY - JOUR

T1 - Electron loss rates from the outer radiation belt caused by the filling of the outer plasmasphere: The calm before the storm

AU - Borovsky, J. E.

AU - Denton, Michael H.

N1 - Copyright (2009) American Geophysical Union. Further reproduction or electronic distribution is not permitted

PY - 2009/11

Y1 - 2009/11

N2 - Measurements from seven spacecraft in geosynchronous orbit are analyzed to determine the decay rate of the number density of the outer electron radiation belt prior to the onset of high-speed-stream-driven geomagnetic storms. Superposed-data analysis is used with a collection of 124 storms. When there is a calm before the storm, the electron number density decays exponentially before the storm with a 3.4-day e-folding time: beginning about 4 days before storm onset, the density decreases from ∼4 × 10−4 cm−3 to ∼1 × 10−4 cm−3. When there is not a calm before the storm, the number density decay is very small. The decay in the number density of radiation belt electrons is believed to be caused by pitch angle scattering of electrons into the atmospheric loss cone as the outer plasmasphere fills during the calms. This is confirmed by separately measuring the density decay rate for times when the outer plasmasphere is present or absent. While the radiation belt electron density decreases, the temperature of the electron radiation belt holds approximately constant, indicating that the electron precipitation occurs equally at all energies. Along with the number density decay, the pressure of the outer electron radiation belt decays, and the specific entropy increases. From the measured decay rates, the electron flux to the atmosphere is calculated, and that flux is 3 orders of magnitude less than thermal fluxes in the magnetosphere, indicating that the radiation belt pitch angle scattering is 3 orders weaker than strong diffusion. Energy fluxes into the atmosphere are calculated and found to be insufficient to produce visible airglow.

AB - Measurements from seven spacecraft in geosynchronous orbit are analyzed to determine the decay rate of the number density of the outer electron radiation belt prior to the onset of high-speed-stream-driven geomagnetic storms. Superposed-data analysis is used with a collection of 124 storms. When there is a calm before the storm, the electron number density decays exponentially before the storm with a 3.4-day e-folding time: beginning about 4 days before storm onset, the density decreases from ∼4 × 10−4 cm−3 to ∼1 × 10−4 cm−3. When there is not a calm before the storm, the number density decay is very small. The decay in the number density of radiation belt electrons is believed to be caused by pitch angle scattering of electrons into the atmospheric loss cone as the outer plasmasphere fills during the calms. This is confirmed by separately measuring the density decay rate for times when the outer plasmasphere is present or absent. While the radiation belt electron density decreases, the temperature of the electron radiation belt holds approximately constant, indicating that the electron precipitation occurs equally at all energies. Along with the number density decay, the pressure of the outer electron radiation belt decays, and the specific entropy increases. From the measured decay rates, the electron flux to the atmosphere is calculated, and that flux is 3 orders of magnitude less than thermal fluxes in the magnetosphere, indicating that the radiation belt pitch angle scattering is 3 orders weaker than strong diffusion. Energy fluxes into the atmosphere are calculated and found to be insufficient to produce visible airglow.

KW - Radiation belt

KW - plasmasphere DCS-publications-id

KW - art-971

KW - DCS-publications-credits

KW - iono

KW - DCS-publications-personnel-id

KW - 123

U2 - 10.1029/2009JA014063

DO - 10.1029/2009JA014063

M3 - Journal article

VL - 114

SP - 1

EP - 12

JO - Journal of Geophysical Research

JF - Journal of Geophysical Research

SN - 0148-0227

IS - A11203

ER -