Recurrent geomagnetic storms and relativistic electron enhancements in the outer magnetosphere: ISTP coordinated measurements

TLDR

New ISTP constellation measurements demonstrate the causes and effects of recurrent geomagnetic activity during recent solar minimum conditions. Solar wind and Yohkoh soft X‑ray data are used to identify coronal holes and high‑speed streams that drive magnetospheric acceleration during recurrent geomagnetic activity. WIND and POLAR data show that even modest geomagnetic storms rapidly enhance relativistic electron fluxes in the outer radiation belt, and that quiet solar minimum conditions still produce coronal holes and high‑speed streams capable of intense particle acceleration, as evidenced by a long‑lasting >1 MeV electron event in March 1996 that contributed to Anik E1 failure.

Abstract

New, coordinated measurements from the International Solar‐Terrestrial Physics (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 E1) operational failure.