The Equator‐S satellite often remained close to the magnetopause for long periods on the morningside of the magnetosphere. The combination of this coverage, slow magnetopause crossings (∼1–2 km/s), and high‐resolution (64–128 Hz) magnetic field data allows very close inspection of the region adjacent to the magnetopause. Strong signatures consistent with mirror‐like structures were observed on a large minority (30%) of the orbits. For the majority of these passes the signatures start close, or adjacent, to the magnetopause, despite a variety of upstream solar wind conditions, suggesting that in most cases the plasma depletion layer (PDL) was either narrow or absent. Without extensive plasma data the PDL cannot be observed directly. Using high‐resolution magnetic field data, however, we have surveyed the occurrence of electromagnetic ion cyclotron (EMIC) waves in the magnetosheath, which have been used by previous authors as a proxy for PDL occurrence. Only a very small number (11) of the 130 documented crossings showed the presence of an ion cyclotron signature in the adjacent magnetosheath, supporting the hypothesis that the PDL is rare in this region. Two of these crossings had proton number density data available, although the wave signatures were exceptionally weak and short‐lived. In these cases we find no clear evidence for a region of plasma depletion, suggesting that the relationship between a PDL and short bursts of EMIC wave occurrence may not be straightforward.
