The Link Beteween CME-associated Dimmings and Magnetic Clouds

Cristina H. Mandrini1, Maria Soledad Nakwacki1, Gemma Attrill2, Lidia van Driel-Gesztelyi2, Sergio Dasso1, Pascal Demoulin3

1Instituto de Astronomia y Fisica del Espacio, Buenos Aires, Argentina
2Mullard Space Science Laboratory, University College, Holmbury St. Mary, UK
3Observatoire de Paris-Meudon, Meudon, France

Coronal dimmings are often present on both sides of erupting magnetic configurations. It has been suggested that dimmings mark the location of the footpoints of ejected flux ropes and, thus, their magnetic flux can be used as a proxy for the flux involved in the ejection. If so, this quantity can be compared to the flux in the associated interplanetary magnetic cloud to find clues about the origin of the ejected flux rope. In the context of this physical interpretation, we analyse several events, flares and coronal mass ejections (CMEs), for which we can find their interplanetary counterpart. We combine SOHO/Extreme Ultraviolet Imaging Telescope data and Michelson Doppler Imager magnetic maps to identify and measure the flux in the dimming regions. We model the associated clouds and compute their magnetic flux using in situ observations. We find that the magnetic fluxes of the dimmings and magnetic clouds are compatible in some cases; though this is not the case for large-scale events and eruptions that occur in regions that are not isolated from other flux concentrations. We conclude that, in these particular cases, a fraction of the dimmed regions could be formed by reconnection between the erupting field and the surrounding magnetic structures, via a “stepping” process that can explain other CME associated events.