Orientations Of Lasco Halo Cmes And Their Connection To The Flux Rope Structure Of Icmes
Abstract
Coronal mass ejections (CMEs) are the most important solar drivers of geomagnetic storms. They are observed by remote sensing, such as LASCO coronographic imaging on board SOHO spacecraft. Their interplanetary counterparts, ICMEs, can be detected in-situ, for example, by ACE and Wind spacecraft. An ICME usually exhibits a complex structure that very often includes a magnetic cloud (MC). MCs are distinctive magnetic features that can be commonly modeled as magnetic flux ropes which are capable of providing prolonged periods of southward interplanetary magnetic field at 1 AU, due to the poloidal and/or toroidal component of their internal magnetic field. It is thought that the orientation of a halo CME elongation corresponds to the orientation of the flux rope. Therefore, in this study we compare orientation angles of elongated halo CMEs observed by the LASCO instrument and the corresponding MCs, measured by Wind and ACE spacecraft. We characterize the ICME structures by using the Grad-Shafranov reconstruction technique and several ICME/MC fitting methods to obtain their axis orientations. The CME and MC angles are compared without taking into account handedness of the underlying flux rope field and the polarity of its axial field. We report that for about 64\% of CME-ICME events, we found a good correspondence between the orientation angles implying that for two thirds of interplanetary ejecta their orientations do not change more significantly (less than 45 deg rotation) while traveling from the sun to the near earth environment. We also briefly discuss the applications of our results to space weather forecast and possible future studies.
- Publication:
-
AAS/Solar Physics Division Meeting #37
- Pub Date:
- June 2006
- Bibcode:
- 2006SPD....37.2402Y