Constraining the Masses and the Non-Radial Drag Coefficient of a Solar Coronal Mass Ejection

Abstract

Decades of observations show that CMEs can deflect from a purely radial trajectory yet no consensus exists as to the cause of these deflections. Many of theories attribute the CME deflection to magnetic forces. We developed ForeCAT (Kay et al. 2013(Kay et al. , 2015, a model for CME deflections based solely on magnetic forces, neglecting any reconnection effects. Here we compare ForeCAT predictions to the observed deflection of the 2008 December 12 CME and find that ForeCAT can accurately reproduce the observations. Multiple observations show that this CME deflected nearly 30 • in latitude (Byrne et al. 2010;Gui et al. 2011) and 4.4 • in longitude . From the observations, we are able to constrain all of the ForeCAT input parameters (initial position, radial propagation speed, and expansion) except the CME mass and the drag coefficient that affects the CME motion. By minimizing the reduced chi-squared, χ 2 ν , between the ForeCAT results and the observations we determine an acceptable mass range between 4.5x10 14 and 1x10 15 g and the drag coefficient less than 1.4 with a best fit at 7.5x10 14 g and 0 for the mass and drag coefficient. ForeCAT is sensitive to the magnetic background and we are also able to constrain the rate at which the quiet sun magnetic field falls to be similar or to or fall slightly slower than the Potential Field Source Surface model. Subject headings: Sun: coronal mass ejections (CMEs)

Using the Coronal Evolution to Successfully Forward Model CMEs' In Situ Magnetic Profiles

“…This paper and previous work (Capannolo et al, ; Kay, dos Santos et al, ; Kay et al, ; Kay, Gopalswamy, Xie, et al, ) have shown that ForeCAT can reproduce the deflection and rotation of observed CMEs, given the correct input parameters. Future work will allow ForeCAT to be useful for actual predictions.…”

The Deflection of the Cartwheel CME: ForeCAT Results

“…The peculiarity of this CME definitely lives in the reversal in latitudinal deflection, very different than previous CME successfully matched by ForeCAT (Kay et al 2015a(Kay et al , 2016(Kay et al , 2017. We show in this work how ForeCAT can still reproduce the complex CME trajectory after taking into account magnetic tension and magnetic forces only, if we include an appropriate initial nonradial velocity and a linear angular width expansion law.…”

“…ForeCAT has successfully matched several observed CME trajectories (Kay et al 2015a(Kay et al , 2016(Kay et al , 2017. Here, we explore a more complex CME, ejected on 2008 April 9 (during solar minimum of cycle 24) at 9:25 UT.…”

USING ForeCAT DEFLECTIONS AND ROTATIONS TO CONSTRAIN THE EARLY EVOLUTION OF CMEs

“…For all free parameters, the behavior at distances below the coronagraph field-of-view is largely unconstrained. To determine tighter constraint on these unknown paramters, as done in Kay et al (2015a) and Pisharody et al (2016), we determine a best fit to the observations by sampling parameter space for the unknown ForeCAT input parameters. We determine the reduced chi-squared, χ 2 ν ,…”