Mirror mode structures observed in the dawn‐side magnetosheath by Equator‐S

Abstract

The Equator‐S satellite was ideally positioned to make magnetic field observations in the dawn‐side magnetosheath, relatively close to the magnetopause. The magnetosheath data were particularly rich in compressional signatures, consistent with mirror mode structures, which occurred during ∼30% of orbits crossing into the magnetosheath. In most, although not all cases, strongly compressive signatures extended up to the magnetopause boundary, with no increase in the underlying magnetic field magnitude on the time scale of ten to thirty minutes. The proximity and character of mirror‐like fluctuations near the magnetopause suggest that in the dawn‐side magnetosheath the plasma depletion layer (PDL) is of narrower extent than is generally observed closer to the subsolar point, or is absent.