Necessity of substorm expansions in the initiation of steady magnetospheric convection

Steady magnetospheric convection (SMC) events occur during enhanced solar wind driving of the magnetosphere and are characterized by quasi‐stable convection, without any substorm expansions, for several hours. Previous research has hinted that a substorm onset may be required before the magnetospher...

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Bibliographic Details
Published in:Geophysical research letters 2012-08, Vol.39 (15), p.n/a
Main Authors: Kissinger, J., McPherron, R. L., Hsu, T.-S., Angelopoulos, V., Chu, X.
Format: Article
Language:English
Subjects:
Atmospheric sciences
balanced reconnection
Convection
Earth sciences
Earth, ocean, space
Exact sciences and technology
Flanks
Flux
Geophysics
High pressure
Magnetism
Magnetospheres
modes of magnetospheric response
Signatures
SMC
Solar wind
Stability
steady magnetospheric convection
substorms
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Summary:Steady magnetospheric convection (SMC) events occur during enhanced solar wind driving of the magnetosphere and are characterized by quasi‐stable convection, without any substorm expansions, for several hours. Previous research has hinted that a substorm onset may be required before the magnetosphere can enter the SMC mode of response. For the first time, we show statistically that nearly all SMC events are preceded by a substorm. Only 1% of SMC events occur without any preceding substorm signatures. The typical magnetospheric reaction to enhanced solar wind driving is a substorm. After this occurs, we find that the duration and stability of southward IMF determines whether a particular substorm will transition into an SMC event or not. The initial substorm sets up a high pressure region in the inner magnetosphere that causes flux diversion to the flanks, which allows closed flux from the nightside x‐line to return to balance the dayside reconnection rate. Key Points Clear AL substorms precede 92% of SMC events Only 1% of SMCs have no preceding substorm signatures After a substorm, magnetosphere stabilizes into SMC under continued IMF driving
ISSN:0094-8276
1944-8007
DOI:10.1029/2012GL052599