Interplanetary Shock‐Induced Magnetopause Motion: Comparison Between Theory and Global Magnetohydrodynamic Simulations.

The 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. Plain Language Summary: The Earth's magnetic field carves out an approximately spherical region of space called a magnetosphere which charged particles streaming from the Sun are unable to directly penetrate. In this study we use computer simulations and theory to examine how the edge of the magnetosphere, the magnetopause, moves following the impact of interplanetary shock waves originating at the Sun. These shocks act to shift the magnetopause to a more tightly compressed position and we find that the magnetopause notably features large‐scale oscillations of decreasing magnitude before settling into a new stable location. When very large shock waves strike, the magnetopause can be compressed inside geosynchronous orbits and will therefore expose telecommunication satellites to increased radiation levels in the solar wind. These results provide an explanation for periodic magnetopause motion observed when large shock waves struck the Earth in August 1972 and in March 1991. Key Points: The response of the terrestrial magnetopause to fast‐forward interplanetary shocks is studied using theory and global magnetohydrodynamic simulationsTheory and simulations predict large‐scale damped oscillations with amplitudes up to an Earth radius and frequencies 2–13 mHzThis phenomenon may explain magnetopause oscillations observed following the large interplanetary shocks of August 1972 and March 1991 [ABSTRACT FROM AUTHOR]