Near-Sun Speed of CMEs and the Magnetic Non-potentiality of their Source Active Regions

TL;DR

This study demonstrates that the maximum speed of CMEs from active regions can be predicted using vector magnetogram data, with certain magnetic parameters providing better upper-limit estimates.

Contribution

It introduces a method to predict CME speed upper limits from AR magnetic parameters, highlighting the significance of magnetic twist and free energy proxies.

Findings

CME speed increases with AR magnetic parameters.

Magnetic twist and free energy proxies better predict CME speed limits.

The study uses data from 189 CMEs and vector magnetograms.

Abstract

We show that the speed of the fastest coronal mass ejections (CMEs) that an active region (AR) can produce can be predicted from a vector magnetogram of the AR. This is shown by logarithmic plots of CME speed (from the SOHO LASCO CME catalog) versus each of ten AR-integrated magnetic parameters (AR magnetic flux, three different AR magnetic-twist parameters, and six AR free-magnetic-energy proxies) measured from the vertical and horizontal field components of vector magnetograms (from the {\it Solar Dynamics Observatory's Helioseismic and Magnetic Imager}) of the source ARs of 189 CMEs. These plots show: (1) the speed of the fastest CMEs that an AR can produce increases with each of these whole-AR magnetic parameters, and (2) that one of the AR magnetic-twist parameters and the corresponding free-magnetic-energy proxy each determine the CME-speed upper-limit line somewhat better than any of the other eight whole-AR magnetic parameters.