The magnetopause at high time resolution: structure and lower-hybrid waves

Equator-S made many magnetopause crossings between 06 00 and 10 40 LT, taki ng magnetic field data at 64 or 128 vectors/s. This allows structure within the shortest crossings to be examined, and examples having an exceptionall y smooth ramp in \B\ are presented. These crossings show no significant str ucture at sub-kilometre scales. Strong electromagnetic wave activity did no t occur within the ramp, although some crossings have extremely low amplitu de compressional waves in part of the field ramp close to the magnetosphere , with frequencies close to the lower hybrid frequency. These initial resul ts suggest that physical processes on sub-km scales play no role in determi ning the structure of the current layer.