The storm of March 1989 revisited: A fresh look at the event

Abstract Some new features of the well known geomagnetic storm of March 1989 are presented in this paper. They include more detailed description of the geophysical situation in the Eastern hemisphere (Siberian sector) as well as more careful consideration of the dynamics of the energetic particle precipitation during the event. More attention is given to the peculiarities of the geomagnetic activity at that time. Change of the magnetospheric configuration during active phase of the storm is especially noteworthy. Intriguing feature of this storm is the impulsive powerful solar proton event (SPE) with simultaneous impulsive intense precipitation of the protons with “soft” energetic spectra (1–40 MeV) appearing in a time interval between 02 and 12 UT of March 13 at the background of a previously existing moderate energetic proton flux. Intensity of this impulsive SPE was very high (up to 5300 pfu for protons with E  > 10 MeV). Most probably this SPE was caused by the impulsive solar X-ray flare (N28, W02) classified as X-1.4. It is worth to note that this peak of the proton fluxes was recorded at the same time (07:45 UT) when the Quebec energetic system was collapsed. Simultaneous sharp decrease of the geomagnetic indices AU, AL and PC (Polar Cap index) with a fast recovery time was recorded. Precipitation of more soft particles ( E  = 30–30,000 eV) was studied by the data of the DMSP 8 and 9 satellites. Equatorward protrusion of the soft particles precipitation boundary reached such lower geomagnetic latitudes as 45 degrees. A specific feature of this storm was absence of the satellite measurements of the solar wind and Interplanetary Magnetic Field (IMF) during several days including active phase of the event. Under these circumstances more important became the data obtained by ground-based geophysical observations especially at the high-latitudes. A special attention was given to the elements of the storm whose peaks were close to time of technological catastrophe (07–45 UT of March 13 1989).