Abstract:

During the May 2-3, 1998 CME event, iron charge distributions were measured on the ACE spacecraft in both solar energetic particles and the solar wind. Surprisingly, common signatures can be found, even though the energy of these two particle populations differ by about two orders of magnitude. At the beginning of the event in the energetic particles on May 2, iron with ionic charge states of at least Q=14 was detected nearly simultaneously in solar energetic particles by the SEPICA instrument, and in the solar wind by the SWICS instrument. The onset in the solar wind data was somewhat more gradual, beginning approximately two hours before the rather sudden onset in the solar energetic particles. The sudden occurrence of high iron charge states coincided approximately with the magnetic cloud associated with the CME. Later, during the cloud passage, periods of high and unusually low, iron ionization states occurred in the solar wind. In addition, at the end of the measurement period, iron with high charge states again appeared in both energetic particles and the solar wind. Transport and acceleration scenarios will be discussed as possible explanations of this unusual event.