Study of a sequence of substorm onsets on the basis of coordinated ground-satellite observations

Abstract

We present the results of simultaneous ground-satellite observations of a sequence of three substorms occurred on December 9, 1996. We used the data of various types of optical and geophysical spacecraft instruments including UVI and VIS images on the POLAR spacecraft, DMSP-F12 images of the auroral displays, the WIND satellite IMF and the solar wind data. Ground based data included the data of IMAGE magnetometer network and low-light-level all-sky TV observations at Loparskaya (65.0° N, 114.2° E geomagnetic) located on the Kola Peninsula in northwest Russia. The observations provided remarkably similar views of periodic onsets leading to substorms with 75 min duration. The interplanetary magnetic field (IMF) conditions that preceded the three onsets were very different. The first onset took place for a slightly positive and constant IMF BZ component, the second for a slightly negative IMF BZ , and the third for a ∼40 min interval of strong negative constant IMF BZ (∼ −13 nT). There were no obvious IMF or solar wind plasma triggers.