Typical Profiles and Distributions of Plasma and Magnetic Field Parameters in Magnetic Clouds at 1AU

RODRIGUEZ L.; MASÍAS-MEZA, J.J.; DEMOULIN, P.; ZHUKOV, A. N.; MIERLA, M.; KILPUA, E.; LACATUS, D.; PARASCHIV, A.; DASSO, S.; GULISANO A.M.; WEST, M.; JANVIER, M.

SOLAR PHYSICS

SPRINGER

Lugar: Berlin; Año: 2016 vol. 291

0038-0938

Magnetic clouds (MCs) are a subset of interplanetary coronal mass ejections(ICMEs). They are important because of their simple internal magnetic field configuration,which resembles a magnetic flux rope, and because they represent one of the most geoeffectivetypes of solar transients. In this study, we analyze their internal structure using asuperposed epoch method on 63 events observed at L1 by the Advance Composition Explorer(ACE), between 1998 and 2006. In this way, we obtain an average profile for eachplasma and magnetic field parameter at each point of the cloud. Furthermore, we take afixed time-window upstream and downstream from the MC to also sample the regions precedingthe cloud and the wake trailing it.We then perform a detailed analysis of the internalcharacteristics of the clouds and their surrounding solar wind environments. We find thatthe parameters studied are compatible with log-normal distribution functions. The plasmaβ and the level of fluctuations in the magnetic field vector are the best parameters to definethe boundaries of MCs. We find that one third of the events shows a peak in plasma densityclose to the trailing edge of the flux ropes. We provide several possible explanations for thisresult and investigate if the density peak is of a solar origin (e.g. erupting prominence material)or formed during the magnetic cloud travel from the Sun to 1 AU. The most plausibleexplanation is the compression due to a fast overtaking flow, coming from a coronal holelocated to the east of the solar source region of the magnetic cloud.