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| Titel |
A linear perturbation analysis of magnetopause motion in the Newton-Busemann limit |
| VerfasserIn |
M. P. Freeman, N. C. Freeman, C. J. Farrugia |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 13, no. 9 ; Nr. 13, no. 9, S.907-918 |
| Datensatznummer |
250011975
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| Publikation (Nr.) |
 copernicus.org/angeo-13-907-1995.pdf |
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| Zusammenfassung |
| The response of the magnetopause surface to
time-varying solar wind dynamic pressure is examined. We argue that to a first
approximation the magnetopause surface may be considered as analogous to an
elastic membrane. Upon displacement from equilibrium resulting from a change in
applied external pressure, it moves to a new equilibrium under the equation of
motion of a forced, damped, simple harmonic oscillator. We derive this equation
of motion by linearising for small perturbations the momentum equation for flow
past a nonrigid ellipsoidal body in the Newton-Busemann limit. Though our
approach is only an approximation to the real dynamics of the magnetopause
boundary, it serves to demonstrate the importance of inertia in the system
response. It allows us to estimate the natural eigenperiod of magnetopause
oscillation as typically around 7 min, the precise value depending on solar wind
conditions. However, the magnetopause eigenoscillation is furthermore found to
be strongly damped, regardless of solar wind conditions. One consequence of
these properties is that short-period fluctuations in the solar wind dynamic
pressure elicit a suppressed magnetospheric response. We outline other
theoretical expectations by which our model may be tested against observation,
and discuss the implications of our findings for current interpretations of
spacecraft observations made in the dynamic magnetopause environment. |
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