Submerged Flare Acoustic Sources
From RHESSI Wiki
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{{Infobox Nugget | {{Infobox Nugget | ||
|name = Nugget | |name = Nugget | ||
| - | |title = Submerged Flare Acoustic Sources | + | |title = Submerged Flare Acoustic Sources |
|number = 388 | |number = 388 | ||
| - | |first_author = | + | |first_author = Charles LINDSEY |
|second_author = Angel MARTÍNEZ | |second_author = Angel MARTÍNEZ | ||
|publish_date = 13 September 2020 | |publish_date = 13 September 2020 | ||
| - | |next_nugget = TBD | + | |next_nugget = TBD |
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::387]]}} | |previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::387]]}} | ||
}} | }} | ||
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comparable in fact to the ubiquitous photospheric variability due to | comparable in fact to the ubiquitous photospheric variability due to | ||
[https://www.mps.mpg.de/phd/solar-physics-lecture-2013-part-2 convection] | [https://www.mps.mpg.de/phd/solar-physics-lecture-2013-part-2 convection] | ||
| - | and the | + | and the |
[https://solarscience.msfc.nasa.gov/Helioseismology.shtml "p-mode" global oscillations]. | [https://solarscience.msfc.nasa.gov/Helioseismology.shtml "p-mode" global oscillations]. | ||
| - | Recently an extraordinarily impulsive flare, | + | Recently an extraordinarily impulsive flare, SOL2016-07-23, produced |
an acoustic event that has led to the discovery described here (Ref. [2]). | an acoustic event that has led to the discovery described here (Ref. [2]). | ||
| + | Figure 1 shows one frame from a [movie] | ||
| + | that shows the development of the ripples. | ||
| + | |||
| + | [[File:388f1.png|600px|thumb|center|'''Figure 1''': | ||
| + | Left, the sunspot group where SOL2016-07-23 appeared, and (right) one frame | ||
| + | of the [movie] showing concentric ripples emanating from somewhere within | ||
| + | (and it turns out, below) the flare region. | ||
| + | The movie has a time acceleration of 200x and also has enhanced | ||
| + | amplitudes for the observed ripples, for clearer recognition. | ||
| + | ]] | ||
== Solar Acoustic Holography == | == Solar Acoustic Holography == | ||
| + | |||
| + | This subject may sound forbiddingly arcane, but in essence it is simple: | ||
| + | one observes the ripples, and then propagates them analytically | ||
| + | back through the solar interior, knowing the speed of sound, until they | ||
| + | converge on the source. | ||
| + | The analogy with optical ray tracing exact. | ||
| + | The source location (and its shape) can be estimated in all three dimensions, | ||
| + | and for this flare the source is quite compact, close to the resolution | ||
| + | limit imposed by the diffraction of the acoustic wave front, and (surprise!) | ||
| + | at a significant depth below the photosphere (Ref. [3]): 1150 +- 200 km, | ||
| + | to be precise. | ||
| + | Figure 2 shows the layout graphically. | ||
| + | |||
| + | [[File:388f2.png|600px|thumb|center|'''Figure 2''': | ||
| + | ]] | ||
| + | |||
| + | |||
== A deep source == | == A deep source == | ||
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[2] [https://ui.adsabs.harvard.edu/abs/2020ApJ...895L..19M "Ultra-impulsive Solar Flare Seismology"] | [2] [https://ui.adsabs.harvard.edu/abs/2020ApJ...895L..19M "Ultra-impulsive Solar Flare Seismology"] | ||
| + | |||
| + | [3] [https://ui.adsabs.harvard.edu/abs/2020ApJ...901L...9L "Submerged Sources of Transient Acoustic Emission from Solar Flares"] | ||
Revision as of 21:10, 29 September 2020
| Nugget | |
|---|---|
| Number: | 388 |
| 1st Author: | Charles LINDSEY |
| 2nd Author: | Angel MARTÍNEZ |
| Published: | 13 September 2020 |
| Next Nugget: | TBD |
| Previous Nugget: | Circular Ribbon Flare at Microwaves |
| List all | |
Contents |
Introduction
A major new discovery about solar flares appeared as recently as 1997, when a set of concentric, expanding ripples appeared on the solar surface immediately following the flare SOL1996-07-09 (see earlier Nuggets No. 26 and No. 127). These phenomena hold great interest because they come from acoustic waves launched by the flare that surprisingly penetrate into the Sun's deep interior, and that contain substantial fractions of the flare's total energy. At present no broadly accepted theory exists.
These events are hard to detect because the ripples have small amplitudes, comparable in fact to the ubiquitous photospheric variability due to convection and the "p-mode" global oscillations. Recently an extraordinarily impulsive flare, SOL2016-07-23, produced an acoustic event that has led to the discovery described here (Ref. [2]). Figure 1 shows one frame from a [movie] that shows the development of the ripples.
Solar Acoustic Holography
This subject may sound forbiddingly arcane, but in essence it is simple: one observes the ripples, and then propagates them analytically back through the solar interior, knowing the speed of sound, until they converge on the source. The analogy with optical ray tracing exact. The source location (and its shape) can be estimated in all three dimensions, and for this flare the source is quite compact, close to the resolution limit imposed by the diffraction of the acoustic wave front, and (surprise!) at a significant depth below the photosphere (Ref. [3]): 1150 +- 200 km, to be precise. Figure 2 shows the layout graphically.
A deep source
Conclusions
References
[1] "X-ray flare sparks quake inside Sun"
[2] "Ultra-impulsive Solar Flare Seismology"
[3] "Submerged Sources of Transient Acoustic Emission from Solar Flares"
| RHESSI Nugget Date | 13 September 2020 + |
| RHESSI Nugget First Author | Charles LINDSEY + |
| RHESSI Nugget Index | 388 + |
| RHESSI Nugget Second Author | Angel MARTÍNEZ + |
