Abstract
AbstractThe magnetopause marks the outer edge of the Earth's magnetosphere and a distinct boundary between solar wind and magnetospheric plasma populations. In this study, we use global magnetohydrodynamic simulations to examine the response of the terrestrial magnetopause to fast‐forward interplanetary shocks of various strengths and compare to theoretical predictions. The theory and simulations indicate the magnetopause response can be characterized by three distinct phases; an initial acceleration as inertial forces are overcome, a rapid compressive phase comprising the majority of the distance traveled, and large‐scale damped oscillations with amplitudes of the order of an Earth radius. The two approaches agree in predicting subsolar magnetopause oscillations with frequencies 2–13 mHz but the simulations notably predict larger amplitudes and weaker damping rates. This phenomenon is of high relevance to space weather forecasting and provides a possible explanation for magnetopause oscillations observed following the large interplanetary shocks of August 1972 and March 1991.
Highlights
The Earth's magnetopause exists in a delicate balance between forces exerted between the impinging solar wind and the Earth's intrinsic magnetic field
The location and shape of the magnetopause was initially theoretically predicted to depend on the pressure exerted by a stream of charged particles from the Sun (Chapman & Ferraro, 1931) and its three dimensional geometry was derived based on solar wind dynamic pressure alone (Mead & Beard, 1964)
The enhanced dynamic pressure in the solar wind compresses the magnetopause boundary from its initial position near −10 RE to its final position near −6 RE
Summary
The Earth's magnetopause exists in a delicate balance between forces exerted between the impinging solar wind and the Earth's intrinsic magnetic field. The subsolar magnetopause is typically located approximately ten Earth radii (RE) upstream but, during periods of enhanced solar wind forcing, this can be compressed to half this distance and inside the drift paths of radiation belt electrons and protons (Shprits et al, 2006) and the orbits of geosynchronous satellites (Cahill & Winckler, 1999). The dynamics and location of the magnetopause are of wide relevance to the understanding of planetary magnetospheres and to space weather forecasting. The location and shape of the magnetopause was initially theoretically predicted to depend on the pressure exerted by a stream of charged particles from the Sun (Chapman & Ferraro, 1931) and its three dimensional geometry was derived based on solar wind dynamic pressure alone (Mead & Beard, 1964).
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