Talk:CMEless Flares

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Correspondence with Dick Canfield

Hi Hugh,

Enjoyed your latest nugget, but have to remark -- your claim that the TRACE movie of the event in the Nugget shows the usual flare morphology: two ribbons and a loop arcade is (in the words of the memorable Chang-Hyuk An) "hard to believe". In particular, the late-phase loops look very non-potential -- much different from the standard arcade that one sees in an eruptive event!

Best wishes,

Dick

+++++++++

Well, that is an interesting comment and so I'll put it into our "discussion" section. I think you're right, standard arcades can look pretty potential, but appearances can be deceptive. I know of a couple of examples when a proper arcade formed - the ground state of the field, one might argue - but then the arcade erupted!

Anyway, I think these flares have been ignored for too long. If interested you might check out the Wang & Zhang 2007 article we cite; it is about the magnetic environment.

Cheers

Hugh

Correspondence with Nariaki Nitta

Hi Hugh,

I enjoy reading this nugget as usual. However, if you wrote a paper like this, I would complain a little as enumerated below.

1. It would be nice to repeat the list of CMEless X-class flares as compiled by Gopalswamy et al. (2009), since the reference is not free.

2. What do you want to say about the hard X-ray spectral behavior of flares associated with CMEs? I see flares without CMEs usually show the soft-hard-soft pattern, but you also published in one of your nuggets (http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/SEPs_Link_not_Confirmed) some examples of X-class flares with major CMEs without the soft-hard-harder pattern. Ask Gerry and Allan. I don't think these spectral behaviors distinguish flares associated and not associated with CMEs.

3. Hasn't higher CME association of longer duration flares been known for decades, starting from seminal papers by Sheeley, Kahler, etc.?

4. Concerning the two-ribbon morphology, you should remember the TRACE observations of flares associated with fast CMEs and unimpressive (or loosely [perhaps incorrectly] associated) CMEs by Mei Zhang and Golub (http://adsabs.harvard.edu/abs/2003ApJ...595.1251Z). These authors pointed out that foot-point separation distinguishes flares associated with and without fast CMEs.

5. Now we are reminded that we need to include the energy that goes to a CME. There are several X-class flares associated with CMEs but those CMEs may be just small jets or streamer "puffs", perhaps different beasts from real CMEs [I used the term "unimpressive" following Ed Cliver]. CME visibility also depends on the angle between the ejection and the plane of the sky, causing observational bias in some cases. It would be easy to discuss just whether a certain solar phenomenon is associated with a CME, thanks to the excellent catalog, but wouldn't it be a clear next step to go beyond it and to discuss CME properties?

6. My favorite X-class flare without a (major) CME is the 27-Nov-1999 event. Without purchasing reference [0], I vaguely remember Gopal's list does not include it, since the CME catalog does show an associated CME. The movies is http://cdaw.gsfc.nasa.gov/CME_list/UNIVERSAL/1999_11/jsmovies/1999_11/19991127.125405.p256s/c2_rdif.html. I would like to know opinions of CME experts (such as Angelos) whether this outflow traceable up to only ~4 Rsun is a CME.

7. I have a movie of Yohkoh SXT images for the 27-Nov-1999 event (http://www.lmsal.com/nitta/movies/19991127_12/sxt_flare/SXT_991127_12.html). It clearly shows an ejection confined by overlying field, similar to the famous TRACE/RHESSI example published by Ji et al. (http://adsabs.harvard.edu/abs/2003ApJ...595L.135J). Perhaps the turbulent motions seen in CMEless flares as described by Zhang and Golub (2003, item 4) may represent collisions of outflows and overlying fields. I have more SXT and TRACE examples of both confined and full-blown ejections in http://www.lmsal.com/nitta/movies/ejecta/index.html.

8. There is a speculation that all flares conform to the standard model, but the overlying and surrounding field may play a role in determining whether (and what kind of) a CME will result. At the last SPD meeting, I was interested in the posted by Oscar Olmedo and Jie Zhang (http://adsabs.harvard.edu/abs/2009SPD....40.2207O).

Cheers, Nariaki

++++++++++

1. Good idea, I'll put a link to the table. Meanwhile it's on my presentations page under the heading CMEless somewhere. It is essentially the same list as the Wang-Zhang list

2. That Nugget wasn't a very good one, but I accept the point that SHS is sometimes not observable

3. Yes, this is just a confirmation (didn't I say that?)

4. Hmm. Have tried to forget that paper. These arcades and ribbons are also morphologically different; I have already had fan-mail from Canfield about that.

5. Good idea.

6. Gopal's list starts in 2000. Also omitted is the de la Beaujardiere event and probably other Yohkoh ones

7. I see that this was X1.4. All of the Gopal events are below X2 as well. I had forgotten about the Zhang & Golub paper and will reread it. The abstract says good things.

8. The standard model involves a CME. How can flares without CMEs conform to it?

p.s. - Nuggets aren't publishable archive-type papers. We are only accountable to ourselves here, I'm afraid, and I prefer readability here to accountability anyway. :)


Correspondence with Dave Webb

Hugh,

A nice nugget with mostly expected results. But I have two problems with your statements: 1) The so-called "standard model", CHSKP, of flares is for eruptive flares only not all flares! Thus, it would apply to the CME flares. I think Shibata-san has helped to try to apply this model to all flares which I think is wrong. So I would not call this application to all X flares a "discrepancy".

That's right, only a discrepancy if you think that reconnection is important for flares. The CME-related effects would be from the reconnection, then.

2) "Probably the simple conclusion is the right one: there is an energy threshold for a coronal disruption (as a CME) from a flaring solar active region." This is sort of OK in the context of your article but clearly there are CMEs that are associated with lesser GOES flares from ARs and of course away from ARs associated with filament eruptions. Going back to Hundhausen's work comparing SMM CMEs with GOES and Yohkoh obs., it is clear that the GOES class (energy) of a flare does not correlate well with any parameter of the assoc. CME!

Hundhausen's work was a bit misleading, I think. It took little account of flare longitudes and projection effects, emphasizing the plane-of-the-sky approximation. It furthermore did not reveal the correlations found in the newer work by Joan Burkepile and by Brian Dennis. These have gone a long way towards setting the record straight.

On the other hand your statement certainly seem to apply to the bigger flare-CMEs and we now recognize the close relationship bet. the GOES rise and peak curves and the accleration phase of a CME (eg, Zhang et al.). So maybe we are headed for a different 2-classes of CMEs, those closely related to (an energy threshold) AR flares and those that are not.

Don't forget our dimming paper! We anticipated the Zhang et al. result with X-ray dimming.

You mean two classes of flare, right? That is what this seems to show. If one starts with CMEs, and could really characterize their energy properly, then one could look at the quiet-Sun events and maybe draw a similar but inverted conclusion. But the situation is now pretty clear for the energetic events.


Please note that Jie Zhang is coming through with an entirely separate Nugget on this topic, one emphasizing the environmental factors.


--Hhudson 15:37, 21 August 2009 (UTC)

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