Confined X-class Flares vs.

Eruptive onesNon-CME associated X-class Flares

vs. CME-associated ones

Yuming Wang1, 2 & Jie Zhang1

1 Computational & data Science, College of Science, George Mason University, Fairfax, VA 22030, USA

2 School of Earth & Space Sciences, University of Science & Techonology of China,Hefei, Anhui 230026, P. R. China

2007 September

(Adapted from Shibata et al. 1995)

Lin & Forbes, 2000

Flux rope catastrophe model

Antiochos et al., 1999

Breakout model

Lin et al., 2004

C M X

15% 24% 100% Harrison, 1995

290 flares, 86-87

55% 100% Andrews, 2003

229 flares, 96-99

16-25% 42-55% 90-92%4 events

Yashiro et al., 2005

1301 flares, 96-01

89%11 events

Wang & Zhang, 2007

104 X flares, 96-04

An incomplete list of the CME association of flares

Question

Why could strong energy releases in corona be either confined or eruptive?

Why are not some X-class flares associated with coronal mass ejections?

11 (~10%) X-class flares were confined (not associated with CMEs).

Some cases were reported by Feynman & Hundhausen (1994), Green et al. (2002), Yashiro et al. (2005) and so on.

Another question: Why these confined X-class flares occurred only in solar maximum and decline phase? At least, it is true for the last solar cycle.

Select 4 eruptive flares similar to the confined flares in soft X-ray for comparison.

Two sets of events have similar profiles in soft X-ray flux recorded by GOES.

The rise time is no more than 13 minutes.

The intensity is no stronger than X2.0.

Identify the source regions of flares in MDI magnetograms

4 confined events

Segmented MDI magnetogram remapped on Carrington rotation map.

Red asterisks, diamonds, and blue lines denote the flare site, centroid of magnetic flux, and associated neutral line, respectively.

4 eruptive events

displacement

≤ 17 Mm

≥ 22 Mm Close to edge

Close to center

A confined event

PFSS model is used to extrapolate coronal magnetic field, in which MDI synoptic charts with resolution of 3600x1080 are adopted as input boundary condition and spheric harmonic coefficients are calculated to 225 order.

1.0 Rs

1.1 Rs

1.5 Rs

Low corona

High corona

An eruptive event

Confined Events

Eruptive Events

≤ 5.68

≥ 7.11

confined

eruptive

Conclusions:

(1) The displacement for all the confined events is smaller than that for eruptive events, which implies that the overlying arcades are weaker in the edge of an active region than in the center.

(2) The flux ratio of low-corona to high-corona is smaller for confined events than eruptive events (no significant difference between the two sets of events in individual values of coronal fluxes), which means that there probably is a critical point, above/below which a flare is eruptive/confined.

The inner flux rope has a tendency to erupt due to Lorentz self-force (hoop force).

It is suggested that the magnetic gradient along the height in the overlying field may decide whether the flux rope instability leads to a confined event or to a CME.

A weak gradient favors confinement.

[Torok & Kliem, 2005].

Initial configuration (Adapted from Torok & Kliem, 2007)

Question: If there is only a flare but no CME, what happens to the inner flux rope or what is its fate?

[Nindos & Andrews 2004]

|alpha| Coronal Helicity

A statistical comparison between CME and non-CME flares78 available ARs from Andrews (2003) 229 events

All non-CME flares do not exceed X-class

What does the helicity stand for?

Next step

1. Extend to M-class flares

2. Investigate more parameters