Solar Sources Related to the Largest DST Variations of Solar Cycle 23

CID, C.; CERRATO, Y.; SAIZ, E.; GONZÁLEZ, W.; PALACIOS, J.; ARAN, A.; CREMADES, H.; DASSO, S.; LATHUILLERE, C.; MANDRINI, C.H.; MENVIELLE, M.; POEDTS, S.; RODRIGUEZ, L.; SANAHUJA, B.; SCHMIEDER, B.; ZHUKOV, A.

Ubatuba

Workshop; 2009 International Living with a Star Workshop: The Influence of Solar Variability on Geophysical and Heliospheric Phenomena; 2009

Geomagnetic storms are the consequences in the terrestrial environment of solar disturbances. Throughout solar cycle 23, Dst index varied more than 100 nT in one hour only for seven times. Different stages of these events from the Sun to the terrestrial environment are carefully analyzed. This detailed study reveals that every event included in the table could be related to interaction among structures. In some cases a faster CME overtakes a slower previous one and a shock from the second ICME appears inside the first ICME; in other cases an ICME passes a high speed stream from a coronal hole; and sometimes, both solar emissions (either from a coronal hole or a CME) keep their magnetic structure as they travel far from the Sun, but the rear one compresses the one ahead. In any case, interaction produces large variation on Bz and then an increase in the geoeffectiveness of the event.