Observation of intense poynting flux in the dayside cusp region during ion outfows

Abstract

Polar spacecraft data was used to take inventory of the different wave and particle energy forms present in the dayside intermediate-altitude cusp region during periods of intense Poynting flux seen in the major geomagnetic storms in October and November 2003. From this inventory, the energy budget of this region during northward and southward IMF was inferred. Dominant forms of energy in this region include Poynting flux in three frequency bands, large upgoing ion fluxes , and energetic particle fluxes perpendicular to the magnetic field. Hydra particle data from Polar showed out owing ions with high energies simultaneous to intense Poynting flux. Filtering the Poynting flux over three time scales revealed that only the energy from the low-frequency Poynting flux is consistently sufficient to account for the ion kinetic energy flux seen during these intervals. The presence of field-aligned current structures in the magnetic field data suggests that the low-frequency Poynting flux associated with these structures may be powering the energization of upgoing ions. The electric and magnetic field data were used to detect Alfven waves, and Alfvenic Poynting flux is consistently another of the important forms of energy present. Moderate fluxes of ions energized perpendicular to the magnetic field (as seen in the Hydra data) may be indicative of ion cyclotron or kinetic Alfven waves heating the ions perpendicular to the field.