First MMS measurements of the High Frequency Magnetic Waves

International audience; The MMS mission was successfully launched on March 13, 2015 into an equatorial, highly elliptical orbit with a low altitude perigee and an apogee of 12 earth radii. Each satellite is equipped by a search-coil magnetometer (SCM) which measures the three components of the magnetic field fluctuations with a nominal frequency range from 1 Hz to 6 kHz. During the past months of the commissioning phase, the SCM waveforms have usually been gathered at 128 or 256 samples per second (S/s). Yet in a few cases, burst data corresponding to 8192 S/s were obtained. Since the launch, the orbit apogee has moved from dawn to dusk. These various conditions allow us to present high frequency wave measurements and wave polarization analysis in the dawn magnetosphere flank as well as associated with local and global dipolarization events in the night side. Furthermore, the SCM is not saturated due to a large amplitude spin modulation even at perigee since the MMS spin frequency is low (50 mHz). Thanks to the onboard spectra computed by the digital signal processor, we are able to continuously monitor the magnetic wave activity through the full SCM frequency range all along the orbit and notably in the radiation belt region. Thus some typical figures of the wave activity in the inner magnetosphere are also briefly described.