Scientific Highlights from the Swarm Electric Field Instruments

The Swarm mission brings a new perspective to ionospheric observations by virtue of its precision, multi-point measurements of key plasma parameters that include plasma density, electron and ion temperature, and ion drift velocity, from which electric field estimates are derived. Ion measurements are made using an orthogonal pair of Thermal Ion Imager sensors which image 2-D (energy/angle) distributions of rammed ion populations, providing ion drift and temperature estimates in three directions. Ion flows are resolved to ~10 m/s at 2 samples/s. We show examples of ion upflow at high latitudes, as well as vertical drift variations of order 1 m/s resolved through averaging of slowly-varying drifts near the equator. We also report occurences of highly anisotropic ion temperature at high latitudes, in most cases with temperature perpendicular to B exceeding that parallel to B, though with some exceptions. During the first two months of operation, the Swarm satellites followed each other in a "pearls on a string" arrangement, providing a picture of the time evolution, on a one-minute time scale, of regions of enhanced energy dissipation as determined via the Poynting vector. Finally we show examples of highly structured plasma flows associated with auroral arcs observed by ground-based cameras.