FAST home page at CU.
 
 

Robert Ergun's home page.

The FAST satellite mission investigates plasma processes occurring in the low-altitude auroral acceleration region where magnetic field-aligned currents couple global magnetospheric current systems to the high latitude ionosphere. In the transition region between the hot tenuous magnetospheric plasma and the cold, dense ionosphere, these currents give rise to parallel electric fields, particle beams, plasma heating, and a host of wave-particle interactions. FAST was designed to study these auroral plasma processes at high time resolution. These processes include parallel electric fields, double layers, field-aligned electrons, Langmuir and whistler wave emissions, auroral kilometric radiation (AKR), ion conics, ion beams, and the formation of the auroral density cavity.

The FAST satellite was launched into an ~83^o inclination orbit with a 350 km perigee and 4175 km apogee in August, 1996. The satellite is oriented in a cartwheel attitude which has the spin axis nearly (negative) normal to the orbital plane. It is spin stabilized with a spin period of 5 s. The satellite crosses the auroral zones (which form ovals at ~65^o-70^o magnetic latitude North and South) four times an orbit. The orbit was designed to have a Northern apogee during January and February of 1997 for coordinated ground-based and optical observations.

The FAST instruments were designed to have high quantitative accuracy measurement of plasma particles and fields with one to three orders of magnitude higher resolution than previous auroral missions which have identified many of the auroral processes but were unable to resolve them fully in space or time. The spacecraft data system performs on-board evaluation of the measurements to select data ?snapshots? that are stored for later transmission to the ground.

New measurements from FAST show that upward and downward current regions in the auroral zone have complementary field and particle features defined by upward and downward directed parallel electric field structures and corresponding electron and ion beams. Direct measurements of wave particle interactions have led to several discoveries, including Debye-scale electric solitary waves associated with the acceleration of up-going electron beams and ion heating, and the identification of electrons modulated by ion cyclotron waves as the source of flickering aurora. Detailed quantitative measurements of plasma density, plasma waves, and electron distributions associated with auroral kilometric radiation source regions yield a consistent explanation for AKR wave generation. These initial results have been published in 20 articles in a special issue of Geophysical Research Letters in 1998. Prof. Robert Ergun leads the FAST effort at LASP.


 

Robert Ergun's home page.

FAST home page at CU.