Pc 1-2 waves and associated ion distributions observed during three extended conjunctions between the Polar satellite and Antarctic ground stations

We present ground and satellite observations of Pc 1 and 2 waves and associated ion distributions that occurred during three extended intervals in spring 2003 when the Polar satellite traveled northward across the magnetic equator near local noon along outer magnetospheric flux tubes (L = 9 - 11) that mapped to near the location of an array of search coil magnetometers in Antarctica. Observations of < 1 eV to 25 keV ions by the TIDE, TIMAS, and Hydra instruments on Polar provide information on the ion populations associated with these waves. Steady, enhanced fluxes of anisotropic > 5 keV protons were observed throughout each of the intervals shown. Their presence appears to be a "necessary but not sufficient" condition for ion cyclotron instability, suggesting that the outer dayside magnetosphere is near marginal stability but needs an additional trigger to cause rapid wave growth. During each of these three intervals, bursts of ~ 0.5 ± 0.2 Hz Pc 1 waves often coincided with short-lived increases in the flux of < 1 keV ions. Pc 2 waves, with frequency below the inferred equatorial He+ gyrofrequency, also occurred on February 11, 2003 in association with an inferred strong enhancement in trapped < 200 eV He+ ions. During the other two passes compressions and/or twists of the magnetic field were also associated with several wave bursts. Our observations thus suggest that either additional lower energy ions or compressions/twists of the magnetic field can often be sufficient to cause rapid wave growth in the outer dayside magnetosphere. Poynting vectors calculated along the satellite trajectory indicate mixed equatorward/poleward wave propagation below ± 20 ° magnetic latitude, but consistently poleward propagation at higher latitudes.