Accession Number : ADA526478


Title :   Toward Understanding the Early Stags of an Impulsively Accelerated Coronal Mass Ejection


Descriptive Note : Journal article


Corporate Author : IOANNINA UNIV (GREECE)


Personal Author(s) : Patsourakos, S ; Vourlidas, A ; Kliem, B


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a526478.pdf


Report Date : 09 Aug 2010


Pagination or Media Count : 16


Abstract : The expanding magnetic flux in coronal mass ejections (CMEs) often forms a cavity. Studies of CME cavities have so far been limited to the pre-event configuration or to evolved CMEs at large heights, and to two-dimensional imaging data. AIMS. Quantitative analysis of three-dimensional cavity evolution at CME onset can reveal information that is relevant to the genesis of the eruption. METHODS. A spherical model is simultaneously fit to Solar Terrestrial Relations Observatory (STEREO) Extreme Ultraviolet Imager (EUVI) and Inner Coronagraph (COR1) data of an impulsively accelerated CME on 25 March 2008, which displays a well-defined extreme ultraviolet (EUV) and white-light cavity of nearly circular shape already at low heights h approximately = 0.2R. The center height h(t)and radial expansion r(t) of the cavity are obtained in the whole height range of the main acceleration. We interpret them as the axis height and as a quantity proportional to the minor radius of a flux rope, respectively. RESULTS. The three-dimensional expansion of the CME exhibits two phases in the course of its main upward acceleration. From the first h and r data points, taken shortly after the onset of the main acceleration, the erupting flux shows an overexpansion compared to its rise, as expressed by the decrease of the aspect ratio from k = h/r approximately = 3 to k approximately = 3 to k approximately = (1.5-2). This phase is approximately coincident with the impulsive rise of the acceleration and is followed by a phase of very gradual change of the aspect ratio (a nearly self-similar expansion) toward k tilda 2.5 at h tilde 10R. The initial overexpansion of the CME cavity can be caused by flux conservation around a rising flux rope of decreasing axial current and by the addition of flux to a growing, or even newly forming, flux rope by magnetic reconnection. Further analysis will be required to decide


Descriptors :   *CORONAL MASS EJECTIONS , *CAVITIES , *ACCELERATED TESTING , *WHITE LIGHT , IMAGES , CONSERVATION , RANGE(EXTREMES) , ASPECT RATIO , CIRCULAR , SOLAR CORONA , ULTRAVIOLET PHOTOGRAPHY , PHOTOGRAPHIC EQUIPMENT , FLUX(RATE) , ULTRAVIOLET RADIATION , QUANTITATIVE ANALYSIS , DATA BASES , MAGNETIC FIELDS


Subject Categories : Astrophysics


Distribution Statement : APPROVED FOR PUBLIC RELEASE