The Slowest Flare
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A search of the GOES database reveals that in fact this event had the | A search of the GOES database reveals that in fact this event had the | ||
longest start-to-peak time interval of any M or X-class flare in | longest start-to-peak time interval of any M or X-class flare in | ||
- | the present Hale cycle [http://en.wikipedia.org/wiki/Solar_cycle link], in fact since1995. | + | the present Hale cycle [http://en.wikipedia.org/wiki/Solar_cycle link], in fact since1995 (FIgure 2). |
+ | |||
+ | [[File:180f2.png|thumb|left|300px|Figure 2: | ||
+ | Histogram of the rise times (start to peak) of all of the tabulated GOES M-class and X-class flares | ||
+ | since 1995. | ||
+ | The red asterisk shows the location of our flare, somewhat above the general trend of the histogram. | ||
+ | ]] | ||
== What else went with this event? == | == What else went with this event? == |
Revision as of 20:08, 22 July 2012
Nugget | |
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Number: | 180 |
1st Author: | Sam Freeland |
2nd Author: | Hugh Hudson |
Published: | 23 July 2012 |
Next Nugget: | TBD |
Previous Nugget: | Flare Nimbus |
List all |
Contents |
Introduction
A remarkable flare, distinguishable by its very slow rise phase, has just occurred (SOL2012-07-17T17:15, M1.7) near the W limb of the Sun. According to the NOAA database from the GOES X-ray photometers, using the standard definitions of start and peak time, it took this flare 5.2 hours to develop. We show an overview from SDO/AIA and RHESSI in Figure 1. Please refer to the extensive movies showing many dynamic features of this event.
![](/~tohban/wiki/images/thumb/8/81/180f1.png/600px-180f1.png)
A skeptic might want to describe this as a coincidental superposition of smaller events, perhaps on different parts of the Sun but in fact the movies linked above show that the entire flare evolution consisted of a single organic process. A search of the GOES database reveals that in fact this event had the longest start-to-peak time interval of any M or X-class flare in the present Hale cycle link, in fact since1995 (FIgure 2).
What else went with this event?
Because this flare was a major gradual event, we might expect a CME to have occurred. This happens with about half of the M-class flares, and it happened this time as well [link]. Figure 1 shows images from the flare and the CME. [probably a panel from the AIA three-color movie, plus a frame from the C2 movie] Furthermore, since this flare occurred near the west limb, an associated CME almost always means an SEP - a solar particle event [link]. This too was observed. Finally, even better, another (more powerful and more impulsive) flare occurred about a day and a half later (SOL2012-07-19, M7.7), in the same active region. In such a case we may see "CME cannibalism", a phenomenon that occurs when a later faster ejection overtakes an earlier slow ejection out in the heliosphere [link], in this case about halfway to the distance of the Earth.
Energetics
Such an event appears to have no "impulsive phase" [link] with hard X-ray and microwave signatures of particle energy release. That may or may not reflect the presence of non-thermal particles, simply because the longer time scale of the event may make them less detectable This event, well-observed by both RHESSI and Fermi [link] in hard X-rays, provides an excellent test case for this question: can slow CMEs also be associated with non-thermal energy release? In a sense the answer is obvious, because we can see the SEPs. But do we see hard X-rays and/or microwaves as well?
Conclusion
RHESSI Nugget Date | 23 July 2012 + |
RHESSI Nugget First Author | Sam Freeland + |
RHESSI Nugget Index | 180 + |
RHESSI Nugget Second Author | Hugh Hudson + |