Possible storm-intensity enhancing factor for the November 3, 1993 magnetic storm Original Research Article

The storm which started on November 3, 1993 was a recurrent storm and had a slightly higher intensity than the other storms in the series. Measurements from the energetic particles and ion composition (EPIC) instrument on Geotail were used to seek the cause for storm intensity enhancement. Significant changes in the ion composition and charge state of solar wind plasma (sampled in the magnetosheath) impacting the Earth were found, which include (1) a large transient enhancement of He++ relative to H+, (2) a transient decrease in the temperatures of both H+ and He++ populations, (3) an apparent enhancement of magnesium-silicon ions relative to iron ions, and (4) a possible shift of iron ions to higher charge states. These changes are likely due to a direct impact of a coronal mass ejection (CME), implying that this magnetic storm is slightly more intense than the others in the series because it is associated with both a high-speed stream from a large coronal hole and with a direct impact of a CME.