Three frontside full halo coronal mass ejections with a nontypical geomagnetic response

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

Space Weather

American Geophysical Union

Año: 2009 vol. 70 p. 6003 - 6013

1539-4964

We analyze three frontside full halo coronal mass ejections (CMEs) that occurred in the year 2000 (close to the activity maximum of the solar cycle 23), together with associated solar and heliospheric phenomena as well as their impact on the Earth’s magnetosphere. Even though all three were fast full halos (with plane of the sky speeds higher than 1100 km/s), the geomagnetic response was very different for each case. After analyzing the source regions of these halo CMEs, it was found that the halo associated with the strongest geomagnetic disturbance was the one that initiated farther away from disk center (source region at W66); while the other two CMEs originated closer to the central meridian but had weaker geomagnetic responses. Therefore, these three events do not fit into the general statistical trends relating the location of the solar source and the corresponding geoeffectivity. We investigate possible causes of such a non-typical behavior. Non-radial direction of eruption, passage through a leg of an interplanetary flux rope and strong compression at the eastern flank of a propagating ICME during its interaction with the ambient solar wind are found to be important factors that have a direct influence on the resulting north–south interplanetary magnetic field (IMF) component and thus on the CME geoeffectiveness. We also find indications that interaction of two CMEs could help in producing long-lasting southward IMF component. Finally, we are able to explain successfully the geomagnetic response using plasma and magnetic filed in situ measurements from the L1 point. Our results have important implications for space weather forecasting.