Data for studying the theta auroral events are provided by six instruments from the ISTP/GGS Polar and Wind satellites and the ground-based SuperDARN radars.
Auroral images were taken by the Earth camera of the Visible Imaging System (VIS) on-board the Polar spacecraft.
The Earth camera has a 20° × 20° field of view and a time resolution of 12 s.
Its wavelength passband of 124-149 nm, principally responds to the atomic oxygen emissions at 130.4 and 135.6 nm and molecular nitrogen Lyman-Birge-Hopfield (LBH) emissions.
A detailed description of the instrumentation has been given by Frank et al. [1995].
The particle measurements from Polar are provided by the DuoDeca Electron Ion Spectrometer (DDEIS) of Hydra [Scudder et al., 1995], as well as from the Imaging Electron Sensor (IES) and the Imaging Proton Sensor (IPS) of the Comprehensive Energetic Particle and Pitch Angle Distribution Experiment (CEPPAD) [Blake et al., 1995].
Hydra DDEIS has twelve electrostatic analyzers capable of sampling electrons and positive ions with energy per unit charge from 2 eV to 35 keV at high time resolution (0.5 s).
The field of view of each detector is 10°.
CEPPAD IES measures electrons from 20 to 400 keV and IPS measures ion spectra over the energy range of 20-1500 keV.
Both sensors have almost a full 4
sr field of view, in each 6 s spin period.
Ion composition data were obtained from the Toroidal Imaging Mass-Angle Spectrograph (TIMAS) [Shelley et al., 1995].
TIMAS samples ions with energies from 15 eV/e to 32 keV/e.
It covers 4 × 0.98 sr in a half spin with an angular resolution of 11.25° × 11.25°.
The electric field measurements were acquired with the Electric Field Instrument (EFI) [Harvey et al., 1995].
EFI consists of three dipoles measuring 3-d electric fields from potential differences between three pairs of spherical sensors.
Two pairs of the sensors are held at separation distances of 100 m and 130 m by wire booms that move in the satellite's spin plane and the other pair is held at a separation of 14 m by a pair of rigid booms, aligned with the spin axis.
Data are sampled at a rate of 40 s-1 by all three sensors.
Corrections are made for DC offsets and fields induced by the spacecraft's - VSC × B motion and by a transformation of the measurements into a reference frame which corotates with the Earth.
Interplanetary magnetic field data are provided by the Wind Magnetic Field Investigation (MFI) [Lepping et al., 1995] on-board the Wind spacecraft.
MFI consists of dual, wide range (±0.001 to ±65536 nT) triaxial flux gate magnetometers.
Measurements of ionospheric convection were acquired with the SuperDARN HF radar network [Greenwald et al., 1995].
These radars detect backscatter from F-region ionospheric irregularities.
Studies by Ruohoniemi et al. [1987] and others have shown that the drift motion of F-region irregularities is equal to that of the F-region plasma.
Therefore the measurements may be used to determine plasma convection, the ionospheric electric field, and the high latitude potential pattern.
Please send questions, comments, or suggestions about the paper to:
Shen-Wu Chang
Department of Physics and Astronomy, The University of Iowa, Iowa City, IA 52242
Phone:(319)335-3828; Fax:(319)335-1753;
swc@space-theory.physics.uiowa.edu