Traveling Convection Vortices: Origin and Characteristics

Traveling Convection Vortices (TCVs) represent the ionospheric
equivalent of the more familiar atmospheric weather cyclones and
anticyclones. High-latitude ground magnetometers and radars provide
observations indicating that TCVs stir up convection swirls as they
propagate antisunward through the dayside auroral ionosphere. Riometers
and photometers record transient increases in radio wave absorption and
optical emissions during the events. Because their signatures are most
prominant on magnetic field lines that map to the outer dayside
magnetosphere, statistical studies of TCVs offer important insights into
the nature of the transient solar wind-magnetospheric interaction at the
magnetopause. Past studies have variously attributed TCVs to bursty
reconnection, impulsive penetration, the Kelvin-Helmholtz instability, and
pressure-pulse driven waves on the magnetopause, as well as to interchange
instabilities somewhat deeper within the magnetosphere. We compare the
results of numerical simulations and analytical models for each proposed
mechanism with case and statistical studies of TCV characteristics to
identify their predominant generation mechanism(s).

Feb. 2000