A Statistical Study on Solar Active Regions Producing Extremely Fast Coronal Mass Ejections

TL;DR

This study statistically analyzes the properties of solar active regions that produce extremely fast CMEs, identifying key parameters like PIL complexity as strong indicators of CME speed.

Contribution

It introduces an automated method to characterize active regions and correlates specific magnetic parameters with the likelihood of fast CME production.

Findings

Larger active regions tend to produce faster CMEs.

High PIL complexity strongly correlates with fast CME occurrence.

Over 80% of fast CMEs originate from regions with high PIL parameters.

Abstract

We present a statistical result on the properties of solar source regions that have produced 57 fastest front-side coronal mass ejections (CMEs) (speed 1500 km/s) occurred from 1996 June to 2007 January. The properties of these fast-CME-producing regions, 35 in total, are compared with those of all 1143 active regions (ARs) in the period studied. An automated method, based on SOHO/MDI magnetic synoptic charts, is used to select and characterize the ARs. For each AR, a set of parameters are derived including the areas (positive, negative and total, denoted by A_P, A_N and A_T respectively), the magnetic fluxes (positive, negative and total, F_P, F_N and F_T respectively), the average magnetic field strength (B_avg), quasi-elongation (e) characterizing the overall shape of the AR, the number and length of polarity inversion lines (PILs, or neutral lines, N_PIL and L_PIL respectively), and the average and maximum of magnetic gradient on the PILs (GOP_avg and GOP_max respectively). Our statistical analysis shows a general trend between the scales of an AR and the likelihood of producing a fast CME, i.e., the larger the geometric size (A_T), the larger the magnetic flux (F_T), the stronger the magnetic field (B_avg), and/or the more complex the magnetic configuration (N_PIL and L_PIL), then the higher the possibility of producing a fast CME. When all ARs are sorted into three equally-numbered groups with low, middle and high values of these parameters, we find that, for all these AR parameters, more than 60% of extremely fast CMEs are from the high-value group. The two PIL parameters are the best indicators of producing fast CMEs, with more than 80% from the high value group.