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Fast ionospheric feedback instability and substorm onsetA study suggesting that the Alfven resonator can play an important role in modifying the ionosphere on the time and space scales required to play a significant role in substorm formation is presented. Although the effect of magnetosphere-ionosphere coupling on the onset of substorms has been studied, the effects due to gradients of the Alfven speed along auroral field line were neglected. The large increase of the Alfven speed with altitude above the ionosphere creates an effective resonant cavity, which can lead to fluctuations in the electric and magnetic fields as well as in particle fluxes in the range 0.1 to 1 Hz. Such fluctuations can be observed from the ground as PiB pulsations associated with substorm onset. These fluctuations can be excited by a fast feedback instability, which can grow on time scales much less than the Alfven travel time between the ionosphere and the plasma sheet. The instability enhances the value of both the Pedersen and Hall conductivity, and may play a role in preparing the ionosphere for substorm onset.
Document ID
19950011840
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Lysak, Robert L.
(Minnesota Univ. Minneapolis, MN, United States)
Grieger, John
(Minnesota Univ. Minneapolis, MN, United States)
Song, Yan
(Minnesota Univ. Minneapolis, MN, United States)
Date Acquired
August 16, 2013
Publication Date
June 1, 1992
Publication Information
Publication: ESA, Substorms 1
Subject Category
Geophysics
Accession Number
95N18255
Funding Number(s)
CONTRACT_GRANT: NAGW-2653
Distribution Limits
Public
Copyright
Other
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