DYNAMICS EXPLORER OBSERVATIONS OF THE PRODUCTION OF ELECTRON CONICS

Several mechanisms have been proposed as the cause of electron conics, including perpendicular, oblique, and parallel heating, as well as acceleration by both stochastic and oscillating parallel electric fields. While the conic distributions and various wave modes have been observed together. been made of the actual acceleration mechanism while it is in progress. This study reports on data obtained by DE-1, which measured conics at high altitudes (greater than or equal to 10,000 km) over the auroral oval, and DE-2, which simultaneously measured electron distributions at low altitudes (similar to 900 km) in the same latitude/local time region. The DE-2 electron distributions often show the low-altitude signature of a downward field-aligned beam, which has spread to pitch angles of about 55 degrees as a result of the magnetic mirror force, along with an upward-moving electron conic distribution localized in the same pitch-angle range. Even though the electron conics observed by DE-2 have energies of only several hundred eV, compared to the several keV conics observed by DE-1, these observations nevertheless support models in which field-aligned bursts and electron conics occur on the same field line, with the conic being the result of the magnetic mirroring of the part of the downward electron beam that lies just outside the loss cone.