First Measurements of the Mass of Coronal Mass Ejections from the EUV Dimming Observed with STEREO EUVI A+B Spacecraft
Markus J. Aschwanden Submitted: 2009-04-03 17:21
The masses of Coronal Mass Ejections (CMEs) have traditionally
been determined from white-light coronagraphs, based on the Thomson
scattering of electrons, which depends on the (generally unknown)
angle of the CME propagation direction. Here we develop a new method
of measuring CME masses from the EUV dimming seen with EUV imaging
telescopes in multiple temperature filters. As a test we investigate
8 CME events with previous mass determinations from STEREO/COR2,
of which 5 cases are fully detected with EUVI, 2 partially, and 1 not,
using an automated multi-wavelength detection code.
We find CME masses in the range of m_CME = (2-7) x 1015 g.
The agreement between the two EUVI/A and B spacecraft is m_A/m_B
=1.3 ± 0.6 and the consistency with white-light measurements by
COR2 is m_EUVI/m_COR2 = 1.1±0.3.
The consistency between EUVI and COR2 implies no significant
mass backflows (or inflows) at r < 4 R☉ and adequate
temperature coverage for the bulk of the CME mass in the range of
T = 0.5-3.0 MK. The temporal evolution of the EUV dimming
allows us also to model the evolution of the CME density n_e(t),
volume V(t), height-time h(t), and propagation speed
v(t) in terms of an adiabatically expanding self-similar
geometry. We determine e-folding EUV dimming times of
1.3±1.4 hr. We test the adiabatic expansion model in terms of
the predicted detection delay (0.7 hr) between EUVI
and COR2 for the fastest CME event (2008-Mar-25) and find good agreement with the observed delay ( 0.8 hr).
Authors: Aschwanden,M.J., Nitta,N.V., Wuelser,J.P., Lemen,J.R., Sandman,A., Vourlidas,A., Colaninno,R.C.
Publication Status: ApJ, subm. 2009 Apr 3
Last Modified: 2009-04-04 09:20