Solar wind control of the magnetopause shape, location, and motion

TLDR

We verify that the subsolar magnetopause position follows the pressure balance between solar‑wind dynamic pressure and the magnetopause. We assembled a database of 1,821 magnetopause crossings and quantified how IMF Bz, Birkeland current strength, and the subsolar magnetopause location together shape the dayside magnetosphere. The analysis shows that the magnetopause location scales with solar‑wind dynamic pressure and IMF orientation, that pressure variations drive self‑similar motion on hourly timescales, and that dayside magnetopause cross‑sections are oblate.

Abstract

We have assembled a data set of 1821 magnetopause crossings. Separate fits to subsets of this data set determine the magnetopause location as a function of solar wind dynamic pressure and interplanetary magnetic field orientation. Solar wind dynamic pressure variations produce self‐similar magnetopause motion on time scales of one hour or longer. We verify the pressure balance relationship between the solar wind dynamic pressure and the location of the subsolar magnetopause. We quantify the relationship between the IMF B z , region l Birkeland current strength, the position of the subsolar magnetopause, and the shape of the dayside magnetosphere. Cross sections of the dayside magnetopause in planes perpendicular to the Earth‐Sun line are oblate.