On Monday, March 6, 1989, a very large and complex sunspot group, Region 5395, rotated into view around the east limb of the Sun and quickly gained attention when it produced an X15/3B flare (N35, E69). The event began a period of high solar activity that lasted two weeks and had many important consequences at Earth and in near‐Earth space. From March 6–19, Region 5395 produced 11 X‐class and 48 M‐class X ray flares. Prolonged proton events occurred that lasted several days and had an unusually high proportion of lower‐energy particles. The solar activity produced an historically “great” magnetic storm, long‐lasting Polar Cap Absorption events, and a major Forbush decrease, which is a decrease of the galactic cosmic ray flux observed at Earth. The ionosphere was greatly disturbed.

Abstract. New, coordinated measurements from the International Solar-TerrestrialPhysics (ISTP) constellation of spacecraft are presented to show the causes and effects of recurrent geomagnetic activity during recent solar minimum conditions. It is found using WIND and POLAR data that even for modest geomagnetic storms, relativistic electron fluxes are strongly and rapidly enhanced within the outer radiation zone of the Earth' s magnetosphere. Solar wind data are utilized to identify the drivers of magnetospheric acceleration processes. Yohkoh solar soft X-ray data are also used to identify the solar coronal holes that produce the high-speed solar wind streams which, in turn, cause the recurrent geomagnetic activity. It is concluded that even during extremely quiet solar conditions (sunspot minimum) there are discernible coronal holes and resultant solar wind streams which can produce intense magnetospheric particle acceleration. As a practical consequence of this Sun-Earth connection, it is noted that a long-lasting E> 1MeV electron event in late March 1996 appears to have contributed significantly to a major spacecraft (Anik E 1) operational failure.

In deriving auroral electrojet 2.5‐min magnetic activity indices for 1970, simple statistics were kept that tabulated the time and frequency of contribution of index values by each of the 11 geomagnetic observatories whose records were used in the derivation. Systematic patterns were noted in the times of most frequent observation of extreme H deviations by each station for both quiet and disturbed hours. On the average, AL was most often derived from records of stations located about 3¼ hours past local geomagnetic midnight, LGM (peak westward electrojet effect); a second prominent time of occurrence of extreme negative H values came at 11¼ hours after LGM; AU was most often derived from stations located 6½ hours before LGM (peak eastward electrojet effect); and a second prominent time of occurrence of extreme positive H values came at about 6¼ hours after LGM. The secondary peak times of index contribution are shown to be consistent with quiet time current sources apparently equatorward of the auroral zone. The UT daily pattern of average hourly values of AU is shown to vary seasonally, being lowest in winter, intermediate during equinoctial months, and highest during summer. No clear diurnal UT dependence can be seen in disturbed hour averages of AU. The average hourly AL values for disturbed hours are not clearly differentiated by season but appear to have a broad span of higher values from 1200 to 2100 UT. A composite map is included of regions within which auroral electrojet currents would produce the systematic extreme H deviations revealed in the derivation of 1970 AE(11). Preliminary analyses of AE indices for 1966 through 1971 give results that agree with these conclusions.

A very intense flux of electrons, evident in the magnetosphere earlier this year, may have caused a satellite failure (or at least exacerbated the situation) leading to the loss of pager service to 45 million customers, research has shown. The electrons, known as highly relativistic electrons (HREs), were especially numerous in the weeks preceding the failure. Researchers say HREs have triggered spacecraft anomalies in the past through a process of deep dielectric charging when fluxes are elevated. They therefore believe this energetic electron environment could have been behind the failure in the attitude control system of the Galaxy 4 spacecraft at 2200 UT on May 19,1998. A backup system also failed, either at the same time or earlier, so operators were unable to maintain a stable Earth link [Silverstein, 1998].

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