Naval Research Lab
A STEREO Survey of Earth-directed CMEs
I will present the results of a STEREO imaging survey of Earth-directed coronal mass ejections (CMEs) perceived as magnetic clouds (MCs) by the Wind spacecraft from 2008-2012. Out of 48 Wind MCs, 31 can be definitively connected to CMEs that STEREO can track continuously from the Sun to Earth using its heliospheric imaging capabilities. A full 3-D reconstruction of each CME's morphology and kinematics is performed based on STEREO and SOHO/LASCO imagery, assuming an underlying flux rope structure for each CME. There are a number of interesting implications of the survey for space weather forecasting. For example, there is poor agreement between flux rope orientations inferred from imaging and MC orientations inferred from Wind data, which does not bode well for some ideas for predicting Bz in the future. The kinematics of this sample of events can be used to provide simple prescriptions for CME arrival time prediction, with 1-sigma uncertainties ranging from 4.6-11.7 hours depending on the distance from the Sun where a CME's velocity is measured, and on whether that velocity is a leading edge velocity or a velocity along the Sun-Earth line.