SOHO: An unfortunate omission



The article by R. Schmidt et al. in the March 29 issue of Eos reports both the welcome news that the SOHO and Cluster payloads have been chosen and the surprising announcement that the planned solar wind and interplanetary magnetic field instruments were not selected for flight. For the reasons outlined below, we deeply regret this decision and urge the national agencies to alter this decision and rectify the situation.

The solar wind is still very much an object of study. The source and energization of the solar wind is but poorly understood. The originally planned payload of SOHO provided the opportunity to study the solar surface in considerable detail while monitoring the solar wind at 1 AU and thereby leading to the solution of this mystery. No other present or planned mission will provide undisturbed solar wind data continuously or nearly so. If the Wind spacecraft of the International Solar-Terrestrial Physics (ISTP) project were used, it would be only by diverting it from its role of studying the extended foreshock region and of providing measurements of the solar wind on the streamlines that intersect the magnetosphere. Moreover, we need both spacecraft for these studies, the SOHO spacecraft for providing early warning or forecasting and the Wind spacecraft for monitoring near-Earth conditions for nowcasting. Not only the solar wind itself but also the solar wind control of magnetospheric activity are vital active research topics that require the highest-quality data sets.