Tracking intense geomagnetic storms to the interplanetary medium: May 15, 2005

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

Perugia

Congreso; International Union of Geodesy and Geophysics (IUGG) XXIV General Assembly; 2007

IUGG

On May 15, 2005, at 02:38 UT an interplanetary shock was recorded by ACE. The followinginterplanetary structure produced an important geomagnetic storm (minimal value of the Dst index -263 nT). Analysis of interplanetary (plasma and magnetic) observations has shown that these disturbances could correspond to the arrival of at least one magnetic cloud. The main trigger of the geomagnetic storm is definitively the fast halo CME of May 13 (LASCO) observed consequently to the flare occuring at 17:22 UT in the active region 10759. However the analysis of the complexity of the magnetic cloud parameters (ACE) leads us to different possible scenarios for the interpretation, either the existence of two clouds produced by two different events on May 15 (eruption of filaments observed by HASTA), OR the presence of a complex cloud resulting from the interaction of the fast CME of May 13 with a previous one occuring on May 11 and triggered by a flare in another active region (10758). The helicity and the orientation of the candidate CMEs and the magnetic clouds are compared in both cases.