ENERGETIC ION COMPOSITION AND CHARGE-STATE OF SOLAR-WIND PLASMA DURING NOVEMBER 3, 1993, MAGNETIC STORM

Measurements from the energetic particles and ion composition instrume nt on Geotail are used to investigate at high time resolution the ion composition and charge state of solar wind plasma (sampled in the magn etosheath) impacting the Earth during the geomagnetic storm which comm enced on November 3, 1993. This storm is one in a series of recurrent storms associated with a high-speed stream from a large coronal hole. Significant changes in the ion composition were found to start at simi lar to 0300 UT on November 4, 1993, near the leading edge of the high- speed stream, becoming very conspicuous near similar to 0500 UT when t he solar wind speed reached similar to 700 km/s. Changes noted include a large transient enhancement of He++ relative to Kf, a transient dec rease in the temperatures of both H+ and He++ populations, an apparent enhancement of magnesium-silicon ions relative to iron ions, and a po ssible shift of iron ions to higher charge states. These changes may b e associated with a coronal mass ejection embedded within the arrival of a new interplanetary sector. The time of these changes coincides we ll with the start of the second plunge in the Dsr index which ultimate ly leads to the minimum Dst for this geomagnetic storm, suggesting tha t these changes in composition and possibly charge state of the solar wind ions may be associated with factors which enhance the storm inten sity at Earth. These results suggest that this magnetic storm may be e xceptional for being a recurrent storm and yet being associated with C ME activities for its intensity enhancement.