A Comprehensive Study of the Initiation and Early Evolution of a Coronal Mass Ejection from Ultraviolet and White-Light Data
In this work we analyze simultaneous UV and white-light (WL) observations of a slow CME that occurred on 2000 January 31. Unlike most CMEs studied in the UV so far, this event was not associated with a flare or filament eruption. Based on vector magnetograph data and magnetic field models, we find that field disruption in an active region (AR) was driven by flux emergence and shearing motions, leading to the CME and to post-CME arcades seen in the EUV. WL images, acquired by the Mark IV coronagraph at the Mauna Loa Observatory, allowed us to identify the CME front, bubble, and core shortly (about 1 hr) after the CME ejection. From polarized brightness (pB) Mauna Loa data we estimated the mass and electron densities of the CME. The CME mass increases with time, indicating that about 2/3 of the mass originates above 1.6 Rsolar. Analysis of the UV spectra, acquired by the Solar and Heliospheric Observatory Ultraviolet Coronagraph Spectrometer (SOHO UVCS) at 1.6 and 1.9 Rsolar, allowed us to derive the electron temperature distribution across the CME. The temperature maximizes at the CME core and increases between 1.6 and 1.9 Rsolar. This event was unusual, in that the leading edge and the CME core were hotter than the ambient corona. We discuss magnetic heating and adiabatic compression as explanations for the high temperatures in the core and leading edge, respectively.