Plasma waves observed in the cusp turbulent boundary layer: An analysis ofhigh time resolution wave and particle measurements from the Polar spacecraft

The boundary layer located in the cusp and adjacent to the magnetopause is a region that is quite turbulent and abundant with waves. The Polar spacecr aft's orbit and sophisticated instrumentation are ideal for studying this r egion of space. Our analysis of the waveform data obtained in this turbulen t boundary layer shows broadband magnetic noise extending up to a few kiloh ertz (but less than the electron cyclotron frequency); sinusoidal bursts (a few tenths of a second) of whistler mode waves at around a few tens of her tz, a few hundreds of hertz, and just below the electron cyclotron frequenc y; and bipolar pulses, interpreted as electron phase-space holes. In additi on, bursts of electron cyclotron harmonic waves are occasionally observed w ith magnetic components. We show evidence of broadband electrostatic bursts covering a range of similar to3 to similar to 25 kHz (near but less than t he plasma frequency) occurring in packets modulated at the frequency of som e of the whistler mode waves. On the basis of high time resolution particle data from the Polar HYDRA instrument, we show that these bursts are consis tent with generation by the resistive medium instability. The most likely s ource of the whistler mode waves is the magnetic reconnection site closest to the spacecraft, since the waves are observed propagating both toward and away from the Earth, are bursty, which is often the. case with reconnectio n, and do not fit on the theoretical cold plasma dispersion relation curve.