Using Coronal Dimming to Study CME Initiation

The aim of this project is to study the initiation of coronal mass ejections (CMEs) using data from the Solar Dynamics Observatory (SDO). It is notoriously difficult to observe the initiation of CMEs which cause space weather, in routinely available space based data. However, observing the onset of CMEs in the low corona is needed to study the source region and the initiation process. Coronal dimming has been identified as an observable tool which can be the first detection of a CME hours before they are observed in coronagraph observations. The identification of coronal dimming also leads directly to the source regions and studies of the initiation process.

Data from SDO consists of full disk, high cadence and high spatial resolution data covering a wide range of temperatures in the Sun’s atmosphere, which has not been available in the past. This project will use SDO and other related datasets to identify coronal dimming (i.e. CME source regions) and thus study the initiation of CMEs. Coronal dimming has until recently only been investigated in coronal lines, where the mass loss that leads to the CME has been restricted. However, it has been shown by Bewsher et al (2008), that using data from multiple temperatures is needed to successfully predict the occurrence of CMEs from observations of coronal dimming.

This project will exploit work done by Bewsher in developing an algorithm to automatically identify coronal dimming, but has not yet applied to SDO data.

Numerous models of CME inititation have been proposed (e.g. Dynamo model, Klimchuk (1990), mass loading model, Low (1996), tether release model, Forbes & Isenberg (1991), magnetic breakout model, Antiochos et al. (1999)) and the properties of CME initiation identified from data will be compared to the theoretical models.