The Slowest Flare
From RHESSI Wiki
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have occurred. | have occurred. | ||
This happens with about half of the M-class flares, and it happened this | This happens with about half of the M-class flares, and it happened this | ||
- | time as well [ | + | time as well (see the |
- | + | [http://sdowww.lmsal.com/sdomedia/ssw/media/ssw/ssw_client/data/ssw_service_120717_073119_84874/www/ movies] | |
- | + | pages). | |
Furthermore, since this flare occurred near the west limb, an associated | Furthermore, since this flare occurred near the west limb, an associated | ||
- | CME almost always means an SEP - a | + | CME almost always means an SEP - a [http://en.wikipedia.org/wiki/Solar_energetic_particlessolar particle event]. |
This too was observed. | This too was observed. | ||
Finally, even better, another (more powerful and more impulsive) flare | Finally, even better, another (more powerful and more impulsive) flare | ||
Line 61: | Line 61: | ||
In such a case we may see | In such a case we may see | ||
[http://science.nasa.gov/science-news/science-at-nasa/2001/ast27mar_1/ "CME cannibalism"], | [http://science.nasa.gov/science-news/science-at-nasa/2001/ast27mar_1/ "CME cannibalism"], | ||
- | a phenomenon | + | a phenomenon that may occur when a later faster ejection overtakes |
- | that | + | an earlier slow ejection out in the [http://helios.gsfc.nasa.gov/heliosph.htmlheliosphere], in this case |
- | an earlier slow ejection out in the | + | about halfway between the Sun and the orbit of Earth. |
- | about halfway | + | |
== Energetics == | == Energetics == | ||
- | Such an event appears to have no "impulsive phase" | + | Such an event appears to have no [http://hesperia.gsfc.nasa.gov/hessi/flares.htm "impulsive phase"] |
- | hard X-ray and microwave signatures of | + | with hard X-ray and microwave signatures of powerful energy release into non-thermal particle acceleration. |
- | + | The non-impulsive behavior here may or may not reflect the presence of non-thermal particles, | |
simply because the longer time scale of the event may make them | simply because the longer time scale of the event may make them | ||
less detectable | less detectable | ||
- | This event, well-observed by both RHESSI and | + | This event, well-observed by both RHESSI and [http://fermi.gsfc.nasa.gov/ Fermi] in hard |
X-rays, provides an excellent test case for this question: can | X-rays, provides an excellent test case for this question: can | ||
slow CMEs also be associated with non-thermal energy release? | slow CMEs also be associated with non-thermal energy release? | ||
+ | A detailed study of these data might be rewarding. | ||
In a sense the answer is obvious, because we can see the SEPs. | 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? | But do we see hard X-rays and/or microwaves as well? | ||
+ | Figure 3 shows time series of GOES, the GOES temperature, and the | ||
+ | [http://lasp.colorado.edu/home/about/quick-facts-sdo-eve/EVE] observation of the | ||
+ | He II 304 A line (the line that dominates the AIA image shown in Figure 1). | ||
+ | |||
+ | [[File:180f3.png|thumb|left|500px|Figure 3: | ||
+ | Some time series of data from the flare: top, the GOES soft X-ray light curve; middle, the temperature | ||
+ | inferred from the GOES data, and bottom, the He II 304 emission. | ||
+ | ]] | ||
+ | |||
== Conclusion == | == Conclusion == |
Revision as of 20:20, 22 July 2012
Nugget | |
---|---|
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.
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 (see the movies pages). Furthermore, since this flare occurred near the west limb, an associated CME almost always means an SEP - a particle event. 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 may occur when a later faster ejection overtakes an earlier slow ejection out in the [2], in this case about halfway between the Sun and the orbit of Earth.
Energetics
Such an event appears to have no "impulsive phase" with hard X-ray and microwave signatures of powerful energy release into non-thermal particle acceleration. The non-impulsive behavior here 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 in hard X-rays, provides an excellent test case for this question: can slow CMEs also be associated with non-thermal energy release? A detailed study of these data might be rewarding. 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? Figure 3 shows time series of GOES, the GOES temperature, and the [3] observation of the He II 304 A line (the line that dominates the AIA image shown in Figure 1).
Conclusion
RHESSI Nugget Date | 23 July 2012 + |
RHESSI Nugget First Author | Sam Freeland + |
RHESSI Nugget Index | 180 + |
RHESSI Nugget Second Author | Hugh Hudson + |