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In-situ density of ICMEs versus CME 3D geometry and mass derived from remote sensing data

Using stereoscopic data from STEREO-SECCHI instruments COR1, and COR2, we derive the de-projected mass and its evolution for a sample of coronal mass ejections (CMEs). A significant mass increase can be found of the order of 2% – 6%, most prominent over the distance range 10Rs-15Rs. At a distance of about 20Rs it is assumed that the CME mass evolution more or less ceases and that a final mass is reached (cf., Bein et al., 2013). However, numerical studies reveal that there should be a significant increase of CME mass in interplanetary space (e.g., Lugaz et al., 2005). By applying the forward fitting model (Thernisien et al., 2006, 2009) on COR2 data, for some well observed events out of this sample, we obtain the geometry of the CMEs and their volume. Working under the assumption that the CME undergoes self-similar expansion and combining it with solar wind density assumptions, we will have a look at the CME mass development and derive the CME density (plasma composition of 90%H and 10%He) for the distance of 1AU. The results are compared to in-situ proton density data measured for the associated flux ropes. From this we may draw important conclusions on the possible CME mass increase in interplanetary space.

coronal mass ejections, solar-terrestrial relations

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