MINIS Observations During the Geomagnetic Storm of 21 January 2005: ULF Waves

The MINIS balloon campaign was successfully conducted in January 2005 to investigate relativistic electron loss mechanisms. The MINIS campaign provided multi-point measurements of electron precipitation up to MeV energies, including simultaneous measurements at different longitudes and hemispheres. Two balloons, each carrying an X-ray spectrometer for measuring the bremsstrahlung produced as electrons precipitate into the atmosphere, were launched from Churchill, Manitoba. Four balloons, each carrying an X- ray spectrometer, and a 3-axis electric field instrument providing DC electric field and VLF measurements in 3 frequency bands, were launched from the South African Antarctic Station (SANAE IV). An X 7.1 solar flare occurred at 0636 UT on 20 January 2005. A CME from this flare arrived at the Earth 34 hours later. An SSC began at ~1650 UT followed by a geomagnetic storm with a Dst perturbation of ~-100nT. The arrival of the CME initiated an interval of very strong relativistic electron precipitation. The second and third Southern payloads and the first Northern payload made observations in both hemispheres of several extensive relativistic electron precipitation events that occurred from 1700 to 2000 UT on 21 January 2005. ULF waves are thought to play a significant role in the acceleration and precipitation of these particles. This paper will present a preliminary review of the ULF spectra observed by the electric and magnetic field detectors. The status of efforts to determine the payload motion well enough to obtain ULF wave data from the on-board magnetometer will also be discussed.