Three Dimensional Configuration and Evolution of Coronal Mass Ejections

H. CREMADES

Copernicus GmbH

Lugar: Katlenburg-Lindau, Germany; Año: 2005 p. 107

3-936586-40-3

Coronal mass ejections (CMEs) are a direct consequence of the dynamic nature of the Sun. They represent fundamental powerful processes in which energy is transferred from the Sun into interplanetary space, including geospace. Their origin, three-dimensional structure, and internal magnetic field configuration are to date not well understood. The unprecedented data provided by the Solar and Heliospheric Observatory (SOHO) allow for the first time the resolution of fine structures within CMEs, which can help to deduce their three-dimensional configuration.From a detailed investigation of the full set of SOHO/LASCO (Large Angle Spectroscopic Coronagraph) observations from 1996 to the end of 2002, a set of “structured CMEs” has been identified, i.e. events which exhibit white-light fine structures, likely indicative of their internal magnetic field configuration and possible 3D structure. Their source regions in the low corona and photosphere have been inferred by means of complementary analyses of data from the EUV Imaging Telescope (EIT) and Michelson Doppler Imager (MDI) onboard SOHO, and ground-based Hα measurements.From the characteristic pattern of the CMEs’ source regions in both solar hemispheres, a generic scheme of three-dimensional configurations is deduced. According to the scheme, the projected white-light topology of a CME depends primarily on the heliographic position and orientation of the source region’s underlying neutral line that separates opposite magnetic polarities. The cylindrical geometry found in the structured CMEs implies that they are organized along an axial direction. Furthermore, the typical dimensions of structured events exhibiting extreme projections (viewed along their axis or perpendicular to it) were investigated. These events originated from limb and near-limb regions. The measured dimensions indicate that these CMEs would be better approximated by elliptic cones, rather than by the classical cone of circular cross section. The dimensions of halo CMEs originating near Sun center are expected to agree with those obtained for the structured events. In order to understand the CME topology better, an elliptical cone model was developed as an improvement to an existing circular cone model, in an effort to fit and reproduce a set of halo CMEs from LASCO.