SHINE: Observational Tests of CME Initiation Models

Observational Tests of CME Initiation Models

SHINE 2000 Working Group 1

J. Klimchuk
2000 November 1

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Working Group 1 (Coronal Mass Ejections), led by Jim Klimchuk and Joe Gurman, addressed three main questions during the SHINE 2000 meeting in Lake Tahoe:

  1. What is the observational evidence for multiple classes of CMEs?

  2. What are the fundamental physical differences among the various CME initiation models that have been proposed?

  3. What are the key observations that can discriminate among the models?

Progress was made on all of these questions, especially the last (see below), but in the end it was clear that much more work needs to be done before definitive answers are available. This "work in progress" status is reflected in the three challenges that we set for ourselves for the coming year:

  1. Determine observationally whether there are two distinct classes of CMEs, as possibly suggested by acceleration profiles.

  2. Better define and quantify the observational predictions of the models.

  3. Devise and execute focussed observational studies to test the models.
A separate challenge was issued by Ron Turner, who announced an "All Clear Competition." To emphasize the importance of accurate forecasts of geomagnetically calm conditions, Ron will award a prize to the person who can correctly forecast the most clear days over the period of the competition. Might sound easy: since most days are clear, why not predict that every day will be storm free? The catch is that any storm occurring on a day forecast to be clear means immediate disqualification from the competition! Interested competitors should contact Ron.

1. The models

A variety of models for CME initiation have been proposed, and they can be classified in several different ways based on their physical attributes (e.g., Forbes 2000; Klimchuk 2000). The table below presents one such classification that was developed at the SHINE 2000 Workshop. It identifies five distinct types of CME initiation model:

  1. Breakout ( Antiochos 1998; Antiochos, DeVore, and Klimchuk 1999)

  2. Flux Rope ( Forbes and Isenberg 1991; Amari et al. 2000; Wu et al. 2000)

  3. Tether Cutting ( Sturrock et al. 1984; Moore et al. 2001)

  4. Flux Injection ( Chen 1989; Krall, Chen, and Santoro 2000)

  5. Mass Loading ( Wolfson and Saran 1998; Low 1999).
Only representative papers are cited. Additional references can be found in the Forbes and Klimchuk reviews.

2. The observables

The table also lists a number of observables that can be used to test the models:

  1. Is a multipolar magnetic field required, or is a simple bipolar field sufficient?

  2. Does the pre-eruption configuration necessarily contain a flux rope?

  3. Must the field be appreciably sheared near the neutral line?

  4. Must there be a converging flow toward the neutral line in the period leading up to the eruption?

  5. Is reconnection required, and if so, does it occur before or after the onset of the eruption? (This refers to vigorous reconnection with strong heating.)

  6. Does the reconnection take place above or below the sheared core field/flux rope/prominence?

  7. Are there requirements on the existence and/or distribution of mass?

Y in the table signifies "yes," and NR signifies "not required." Readers should consult the original references for a detailed interpretation of the table entries.

3. The matrix

Model Multi-polar Flux Rope Sheared NL Converg. Flow Recon. Timing Recon. Location Mass Distrib.
Breakout YNRYNRat/beforeaboveNR
Flux Rope NRYYY1after1belowNR
Tether Cutting NRNRYNRat/beforebelowNR
Mass Loading NRNRNRNRNRNRcavity

1 Forbes and Isenberg (1991)

2 Amari et al. (2000)

4. References

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Last revised - J.B. Gurman