Deriving CME density from remote sensing data and comparison to insitu measurements 

Manuela Temmer Submitted: 20201125 23:20
We determine the 3D geometry and deprojected mass of 29 wellobserved coronal mass ejections (CMEs) and their interplanetary counterparts (ICMEs) using combined STEREOSOHO whitelight data. From the geometry parameters we calculate the volume of the CME for the magnetic ejecta (fluxrope type geometry) and sheath structure (shelllike geometry resembling the (I)CME frontal rim). Working under the assumption that the CME mass is roughly equally distributed within a specific volume, we expand the CME selfsimilarly and calculate the CME density for distances close to the Sun (1530 Rs) and at 1AU. Specific trends are derived comparing calculated and insitu measured proton densities at 1AU, though large uncertainties are revealed due to the unknown mass and geometry evolution: i) a moderate correlation for the magnetic structure having a mass that stays rather constant (~0.560.59), and ii) a weak correlation for the sheath density (~0.26) by assuming the sheath region is an extra mass  as expected for a mass pileup process  that is in its amount comparable to the initial CME deprojected mass. High correlations are derived between insitu measured sheath density and the solar wind density (~ 0.73) and solar wind speed (~0.56) as measured 24 hours ahead of the arrival of the disturbance. This gives additional confirmation that the sheathplasma indeed stems from piledup solar wind material. While the CME interplanetary propagation speed is not related to the sheath density, the size of the CME may play some role in how much material could be piled up.
Authors: M. Temmer, L. Holzknecht, M. Dumbovic, B. Vrsnak, N. Sachdeva, S.G. Heinemann, K. Dissauer, C. Scolini, E. Asvestari, A. M. Veronig, S. J. Hofmeister
Projects: None

Publication Status: accepted for publication in JGR Space
Last Modified: 20201130 16:54


