Radial Evolution of CME Deflection and Angular Momentum
Abstract
Understanding the trajectory of a coronal mass ejection (CME), including any deflection from a radial path, is essential for space weather predictions. Kay et al. (2015a) developed a model, Forecasting a CME's Altered Trajectory (ForeCAT), of CME deflection due to magnetic forces that reproduces the general trends in the magnitude and direction of observed CME deflections. ForeCAT can also reproduce the deflection of individual observed CMEs (Kay et al. 2015b). The deflecting CMEs tend to show a rapid increase in the angular momentum close to the Sun, followed by little to no increase at farther distances. Here we quantify the distance at which the CME deflection is 'determined,' which we define as the distance after which the background solar wind has negligible influence on the total deflection. We determine this distance by calculating the radial distance at which the CME reaches either 90% of its total deflection or angular momentum at 1 AU. We consider a wide range in CME mass and velocity parameter space and find that the deflection is typically determined by 2 Rs. This implies that non-magnetic forces must be responsible for any observed interplanetary deflections where the CME actually accelerates and that it is absolutely essential to accurately describe the solar environment below 2 Rs to obtain accurate predictions of CME deflections.
- Publication:
-
Solar Heliospheric and INterplanetary Environment (SHINE 2015)
- Pub Date:
- July 2015
- Bibcode:
- 2015shin.confE.167K