CHARACTERISTICS OF ELECTROMAGNETIC PROTON CYCLOTRON WAVES ALONG AURORAL FIELD LINES OBSERVED BY FAST IN REGIONS OF UPWARD CURRENT

Preliminary studies from FAST observations indicate that auroral ion c yclotron waves (ICWs) above the helium cyclotron frequency (Omega(He+) ) occur at all MLTs have amplitudes sometimes >1 V/m and often have a magnetic component even above the proton cyclotron frequency (Omega(p) ) with amplitudes up to 2nT. Waves with transverse amplitudes greater than 100 mV/m often exhibit large spiky downward pointing field-aligne d components with amplitudes that may exceed that of transverse fluctu ation. The ratio of electric to magnetic fluctuation amplitude (E-1/B- 1) is dose to c. Using the 3 dimensional electric and magnetic field m easurements available from FAST it is demonstrated that these waves ar e in most cases polarized transverse to the ambient magnetic field (B- 0) and have linear polarization with wavelengths perpendicular to B(0 )ranging from hundreds of meters to kilometers. Calculations of the Po ynting vector associated with these ICWs indicates Poynting fluxes dir ected downwards along B(0 )for waves below the local ap and generally upwards for waves observed close to and above this frequency with flux es which may exceed 10% of the total field-aligned electron beam energ y flux.