CONSTRAINING THE MASSES AND THE NON-RADIAL DRAG COEFFICIENT OF A SOLAR CORONAL MASS EJECTION

摘要

Decades of observations show that coronal mass ejections (CMEs) can deflect from a purely radial trajectory, however, no consensus exists as to the cause of these deflections. Many theories attribute. CME deflection to magnetic forces. We developed Forecasting a CMEs Altered Trajectory (ForeCAT), 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 degrees in latitude and 4 degrees.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, chi(2)(v), between the ForeCAT results and the observations, we determine an acceptable mass range between 4.5 x 10(14) and 1 x 10(15) g and a drag coefficient less than 1.4 with a best fit at 7.5 x 10(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 slightly slower than the Potential Field Source Surface model.