The Flare that Time Forgot

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RHESSI, over its lifetime in space thus far, has detected many, many flares.
RHESSI, over its lifetime in space thus far, has detected many, many flares.
Often a single event inspires a single paper, and then a flood of literature
Often a single event inspires a single paper, and then a flood of literature
-
even if it's not very typical
+
even if it's not very typical.
-
The Masuda flare [1] would be a case in point, and we've had Nuggets on this
+
The Masuda flare [1] would be a case in point - there have been many follow-up papers, and we've also had several Nuggets on this
topic before:  
topic before:  
[http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/An_Alternative_View_of_the_Masuda_Flare "An alternative view..."],
[http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/An_Alternative_View_of_the_Masuda_Flare "An alternative view..."],
[http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/Acceleration_without_Heating "Acceleration without heating"],
[http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/Acceleration_without_Heating "Acceleration without heating"],
-
[http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/Acceleration-region_Densities "Acceleration-region densities"], etc.
+
[http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/Acceleration-region_Densities "Acceleration-region densities"], etc., etc.
-
In spite of this it is generally held that this particular event was of quite
+
 
-
a rare type.
+
But, there was only really the one event, and many have commented how unusual it was.
 +
Was this type of event worth the fuss?
 +
The more examples one can find, the less atypical it will seem, but [https://en.wikipedia.org/wiki/Yohkoh Yohkoh] only detected
 +
that one clear example in its whole decade of observations.
Thus we were amazed when a retrospective view of the RHESSI flares disclosed  
Thus we were amazed when a retrospective view of the RHESSI flares disclosed  
that the very first M-class flare observed by RHESSI looks very much like
that the very first M-class flare observed by RHESSI looks very much like
Line 27: Line 30:
See  
See  
[http://sprg.ssl.berkeley.edu/~tohban/browser/?show=qlpcr+qli02+qli03+qli04+qli05+grwa&date=20020220&time=095921&bar=1 Browser]
[http://sprg.ssl.berkeley.edu/~tohban/browser/?show=qlpcr+qli02+qli03+qli04+qli05+grwa&date=20020220&time=095921&bar=1 Browser]
-
for a concise overview.
+
for a concise overview of the event.
== How do we know nobody studied this one? ==
== How do we know nobody studied this one? ==
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The RHESSI book [2] has an extensive index, which makes use of the now-standard
The RHESSI book [2] has an extensive index, which makes use of the now-standard
IAU target designation scheme.
IAU target designation scheme.
-
A flare, in this scheme, has an identifier such as SOL2002-02-20T10:04 (with
+
A flare, in this scheme, has an identifier with the fixed pattern SOL2002-02-20T10:04 (and also with
the option of an extension for location).  
the option of an extension for location).  
This makes it easy to search any database, and (for example) a Google search
This makes it easy to search any database, and (for example) a Google search
-
just brought up an entire page of SOL2002-07-23 - but none of the
+
just brought up an entire page of SOL2002-07-23 - but none of our
"Flare that Time Forgot".
"Flare that Time Forgot".
-
The RHESSI index has one entry, for a study of the  
+
The RHESSI index has only one entry for it, a study of the  
[http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/Solar_Hard_X-ray_Albedo albedo patch],
[http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/Solar_Hard_X-ray_Albedo albedo patch],
but nothing concerning the interesting coronal developments.
but nothing concerning the interesting coronal developments.
Line 51: Line 54:
== The flare ==
== The flare ==
-
A couple of images show some of the attributes of this flare.
+
Images show some of the attributes of this flare.
Figure 1 shows soft, medium, and hard X-ray images via two imaging algorithms.
Figure 1 shows soft, medium, and hard X-ray images via two imaging algorithms.
They show the familiar cusp to be present at 25-50 keV, and above it a  
They show the familiar cusp to be present at 25-50 keV, and above it a  
significant 50-keV source.
significant 50-keV source.
-
In other words, it is possibly a much-sought-for Masuda event, and there it was  
+
In other words, it is probably another example of the much-sought-for Masuda phenomenon, and there it was  
on RHESSI's plate 11 years ago!
on RHESSI's plate 11 years ago!
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We discovered this event accidentally, while doing systematic pipeline processing.
We discovered this event accidentally, while doing systematic pipeline processing.
-
This is recommended - a throwaway paper describing a "gee whiz" event may or may not be worthwhile;  
+
Doing an extensive standard survey of events is usually a good idea, but too seldom done.
-
in cases where the phenomenon discussed is not typical, it may still be important, but in the case of
+
A throwaway paper describing a "gee whiz" event may or may not be worthwhile;  
-
solar flares we have major systematic uncertainties in how things work.
+
in cases where the phenomenon discussed is not typical, it may still be important, but it may
 +
also confuse people.
 +
In our understanding of solar flares we have major systematic uncertainties in how things really work.
Thus typical patterns are interesting, and routine analyses of many events together are  
Thus typical patterns are interesting, and routine analyses of many events together are  
certainly worthwhile.
certainly worthwhile.
It is especially nice when they [https://en.wikipedia.org/wiki/The_Three_Princes_of_Serendip serendipitiously]  
It is especially nice when they [https://en.wikipedia.org/wiki/The_Three_Princes_of_Serendip serendipitiously]  
suggest the identification of the Masuda phenomenon, for which we
suggest the identification of the Masuda phenomenon, for which we
-
have few good examples.
+
have had too few good examples.
== References ==
== References ==
Line 84: Line 89:
[1] [http://adsabs.harvard.edu/abs/1994Natur.371..495M "A loop-top hard X-ray source in a compact solar flare as evidence for magnetic reconnection"]
[1] [http://adsabs.harvard.edu/abs/1994Natur.371..495M "A loop-top hard X-ray source in a compact solar flare as evidence for magnetic reconnection"]
-
[2] [http://adsabs.harvard.edu/abs/2011SSRv..159....1E "Preface"]
+
[2] [http://books.google.co.uk/books/about/High_energy_Aspects_of_Solar_Flares_a_RH.html?id=RRs-MwEACAAJ&redir_esc=y "High Energy Aspects of Solar Flares"]

Revision as of 19:24, 14 October 2013


Nugget
Number:
1st Author: Paulo Simões
2nd Author: Hugh Hudson
Published: October 14, 2013
Next Nugget: TBD
Previous Nugget: The Post-Burst Increase
List all



Contents

Introduction

RHESSI, over its lifetime in space thus far, has detected many, many flares. Often a single event inspires a single paper, and then a flood of literature even if it's not very typical. The Masuda flare [1] would be a case in point - there have been many follow-up papers, and we've also had several Nuggets on this topic before: "An alternative view...", "Acceleration without heating", "Acceleration-region densities", etc., etc.

But, there was only really the one event, and many have commented how unusual it was. Was this type of event worth the fuss? The more examples one can find, the less atypical it will seem, but Yohkoh only detected that one clear example in its whole decade of observations. Thus we were amazed when a retrospective view of the RHESSI flares disclosed that the very first M-class flare observed by RHESSI looks very much like a Masuda flare! Somehow nobody picked up on this one, in spite of its newsworthiness. See Browser for a concise overview of the event.

How do we know nobody studied this one?

The RHESSI book [2] has an extensive index, which makes use of the now-standard IAU target designation scheme. A flare, in this scheme, has an identifier with the fixed pattern SOL2002-02-20T10:04 (and also with the option of an extension for location). This makes it easy to search any database, and (for example) a Google search just brought up an entire page of SOL2002-07-23 - but none of our "Flare that Time Forgot". The RHESSI index has only one entry for it, a study of the albedo patch, but nothing concerning the interesting coronal developments. By contrast everybody's favorite SOL2002-07-23 has no fewer than 79 entries, and featured in Bob Lin's final chapter of the book specifically because of its Masuda-like properties. The "flare that time forgot" of course had not made the top-10 list of RHESSI flares.

The flare

Images show some of the attributes of this flare. Figure 1 shows soft, medium, and hard X-ray images via two imaging algorithms. They show the familiar cusp to be present at 25-50 keV, and above it a significant 50-keV source. In other words, it is probably another example of the much-sought-for Masuda phenomenon, and there it was on RHESSI's plate 11 years ago!

Fig. 1: RHESSI images from the flare using two inversion techniques: CLEAN at the top, and MEM at the bottom. From left to right, increasing energies (6-12, 25-50, and 50-100 keV). the simple structure seen in soft X-rays becomes more complicated with time, revealing a Masuda-type "above the loop top" source at high energies. Note that this appearance is in the early phase of the flare, as it was for Masuda's original event SOL1992-01-13 (Browser).

A conclusion

We discovered this event accidentally, while doing systematic pipeline processing. Doing an extensive standard survey of events is usually a good idea, but too seldom done. A throwaway paper describing a "gee whiz" event may or may not be worthwhile; in cases where the phenomenon discussed is not typical, it may still be important, but it may also confuse people. In our understanding of solar flares we have major systematic uncertainties in how things really work. Thus typical patterns are interesting, and routine analyses of many events together are certainly worthwhile. It is especially nice when they serendipitiously suggest the identification of the Masuda phenomenon, for which we have had too few good examples.

References

[1] "A loop-top hard X-ray source in a compact solar flare as evidence for magnetic reconnection"

[2] "High Energy Aspects of Solar Flares"

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