Extreme Plasma Heating and Flows in Earth’s Ionosphere
 

During quiet times, Earth’s ionosphere is relatively cool by space standards, with temperatures of 2,000 K (~0.2 eV) or less. However, the ionosphere can be highly disturbed in the presence of the aurora, which during active periods deposits hundreds of GW into the high-latitude atmosphere via the ionosphere.  This energy comes from the magnetosphere in the form charged particle precipitation, Joule or frictional heating in the lower ionosphere, and wave-particle interactions at higher altitudes. The latter pathway can result in ion temperatures of the order of a million K – comparable the temperature of the solar corona. While such extremes have been measured for many decades in the magnetosphere, until recently they were not reported below 500 km altitude – within the main ionosphere – due to damping and dissipation caused by collisional interaction with the neutral atmosphere. High-time-resolution imaging of particle distribution functions made possible by recent satellite missions has in fact revealed the presence of extreme temperatures within the main ionosphere - typically in highly localized regions of the order or less than 1 km wide, which are traversed in only a fraction of a second in low Earth orbit.  This talk will describe a new generation of particle instrument that has made possible the detection and characterization of these extreme regions, and their importance to geophysics and plasma physics.