Halo CMEs far from Central Meridian: Why are they Geoeffective?

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

Ubatuba-SP, Brasil

Workshop; 2009 ILWS: The Influence of Solar Variability on Geophysical and Heliospheric Phenomena; 2009

International Living With a Star

Fast halo CMEs are considered as the most geoeffective solar events. When the halo CME comes with velocities higher than 1000 km/s and originating from the Western hemisphere close to the solar center, a large disturbance is expected at terrestrial environment. However, large disturbances have been also associated to halo CMEs from regions located far from central solar meridian, as Hallowing storm, related to CMEs from active regions farther than E80 and resulting a Dst index below -400 nT. In this work we have selected all halo CMEs of solar cycle 23, as observed by the Solar and Heliospheric Observatory (SOHO) mission, with solar source at solar limb (±90º) looking for the possibility of connection between solar limb and terrestrial environment. For this task, we have analyzed not only solar atmosphere and the terrestrial surface, but every link in the Sun-Earth chain.