IMAP-3 Experiment

Magnetic field measurements onboard the INTERBALL AURORAL spacecraft.
Magnetic field measurements onboard the INTERBALL-2 (Auroral Probe) is carried out by the IMAP-3 instrument. The IMAP-3 magnetic field experiment onboard the INTERBALL-2 spacecraft is aimed to study the following processes in the Earth's plasma environment: The IMAP-3 was designed and manufactured under cooperation of IZMIRAN (, NPL SDS (Bulgaria) and PIC GPI of RAS.

PI: V.A.Styazhkin,
Co-i: V.G.Petrov (data processing and archiving,, A.Bochev.

The IMAP-3 instrument is designed to measure three components of the DC magnetic field in two ranges: +/- 6800 nT with resolution 1 nT and +/- 68000 nT with resolution 10 nT. Usually magnetometer data are transmitted to the scientific SSNI telemetry system with rate of one vector per 3 seconds, during special intervals data are transmitted to telemetry with rates 2 or 8 vectors/s depending on the instrumentís operating mode.

The INTERBALL-2 spacecraft has been successfully launched on 29 August 1996. The IMAP-3 was initially tested on the 9th of Sept and started to work regularly on the 14th of Sept.

Fig. 1 shows measured Bx (directed to the Sun) and Byz (perpendicular to the direction to the Sun) components of the magnetic field and Tsyganenko model magnetic field components. There are good agreement in Bx component and reasonable agreement in Byz. We cannot calculate now By and Bz components separately due to absence of the spacecraft attitude data.

Fig. 2 shows magnetic field perturbation (deviation from undisturbed main field). At 21:30-21:40 variations up to +/- 30 nT mainly in By component are seen. Spacecraft at that moment was near midnight, so By component was directed along L-shell and it is reasonably to consider this variation as produced by field-align currents.