A survey of the cusp ion outflow’s kinetic energy flux measured by Polar and FAST during conjunction events

Polar and FAST conjunction events are selected from Polar cusp crossings in 1997. These conjunction events reveal a common pattern in which Polar observed significant ion kinetic energy flux in the upward direction at mid-altitudes (below 6 Re). Depending on the magnetic activity level, the maximum ion kinetic energy flux is on the order of 10-100 mW/m^2, when mapped to the ionosphere. It is an order of magnitude or more larger than the ion kinetic energy flux observed by FAST in conjunction at altitudes of <1 Re. Therefore, the ion outflows are significantly energized within the mid-latitude cusp. Also shown in the conjunction events is that the downward Poynting flux has enough wave energy to power the ion energization. The observed pattern suggests that the cusp at ionosphere altitudes is not a simple mapping of higher altitude particles. Instead, the mid-latitude cusp receives significant downward Poynting flux from higher altitude due to the solar wind/magnetosphere coupling. Within the mid-altitude cusp, the Poynting flux then supplies energy to power the ionosphere/magnetosphere coupling. Ion outflows are triggered and energized, forming a planetary wind that feeds the magnetosphere with ionospheric ions. During southward IMF, the wind convects anti-sunward and can affect the tail lobe, the nightside auroral region and the nightside plasma sheet.