Magnetic Field/Electric Field Instruments
ELECTROSTATIC ANALYZERS
The Electrostatic Analyzers ("ESAs") measure the direction and energy of charged particles in the polar ionosphere. These particles are primarily electrons (-) and protons (+), but can also include oxygen and helium as well. Changes in the solar wind and the local "space weather" of the Earth can accelerate these particles to high energies; when they hit the upper layers of our atmosphere, aurora can be the result. These instruments tell us how many particles were present, their direction in space, and if the particle masses are known, their velocities as well. With this information, scientists can infer what processes may have caused these particles to "precipitate" towards the Earth and relate these to changes in the solar wind that surrounds the Earth. Additional information available at "http://sprg.ssl.berkeley.edu/PolarCusp/instruments2/B.html" [Summary provided by the Silver Space Sciences Laboratory]