Relating CME density derived from remote sensing data to CME sheath solar wind plasma pile up as measured in-situ

Manuela Temmer - Institute of Physics, University of Graz; Lukas Holzknecht - Institute of Physics, University of Graz, Austria; Mateja Dumbovic - Hvar Observatory, University of Zagreb, Croatia; Bojan Vrsnak - Hvar Observatory, University of Zagreb, Croatia; Nishtha Sachdeva - Climate and Space Sciences and Engineering Department, University of Michigan, United States; Stephan Heinemann - Institute of Physics, University of Graz, Austria; Karin Dissauer - Institute of Physics, University of Graz, Austria; Camilla Scolini - KU Leuven, Belgium; Eleanna Asvestari - Department of Physics, University of Helsinki, Finland; Astrid Veronig - Institute of Physics, University of Graz, Austria; Stefan Hofmeister - Institute of Physics, University of Graz, Austria

Session: Interplanetary CMEs and Solar Particle Events

Abstract

For better estimating the drag force acting on coronal mass ejections (CMEs) in interplanetary space and ram-pressure at planets, improved knowledge of the evolution of CME density/mass is highly valuable. We investigate a sample of 29 well observed CME-ICME events, for which we determine the de-projected 3D mass (STEREO-A and -B data), and the CME volume using GCS modeling (STEREO, SoHO). Expanding the volume to 1AU distance, we derive the density and compare the results to in-situ proton density measurements separately for the ICME sheath and magnetic structure. A fair agreement between calculated and measured density is derived for the magnetic structure as well for the sheath if taking into account mass pile up of solar wind plasma. We give evidence and observational assessment that during the interplanetary propagation of a CME 1) the magnetic structure has rather constant mass and 2) the sheath region at the front of the driver is formed from piled-up mass that is rather depending on the solar wind density ahead of the CME, than on the CME speed.