Connecting Coronal Mass Ejections and Magnetic Clouds: A Case Study Using an Event from 22 June 2009

Solar Physics - On 27 June 2009 the Wind and Advanced Composition Explorer (ACE) spacecraft near Earth detected a magnetic cloud (MC). The MC can be traced back to a slow coronal mass ejection...     

Sunskirting comets discovered with the LASCO coronagraphs over the decade 1996–2008

In addition to an unprecedented number of Kreutz sungrazing comets, the LASCO coronagraphs have discovered some 238 unrelated “sunskirting” comets over the 12 years from 1996 to 2008. This new class is organized in several groups, and at least two comets have further been found periodic. This article presents the photometry and the heliocentric light curves of these 238 sunskirting comets. The bulk of them exhibit a continuous increase of the brightness as the comet approaches the Sun, reach a peak before perihelion and then progressively fade with a large variety of brightness gradients. However some of them have peak brightness either at or post-perihelion, whereas a quite large number are approximately flat. Likewise for the sungrazers, we find a color effect prominent between 8 and 40R_⊙ (solar radii) which we interpret as resulting from the emission lines of the Na I doublet (D lines). We finally characterize the different groups of sunskirters on the basis of their cumulative distribution function of the peak brightness and of their fragmentation history.