"Impulse Response Flares" and Gamma Rays
From RHESSI Wiki
(upload text) |
(links and figures) |
||
Line 25: | Line 25: | ||
judging from the timing between high- and low-energy photon arrival times. | judging from the timing between high- and low-energy photon arrival times. | ||
- | [[File:188f1.png| | + | [[File:188f1.png|600px|thumb|center| Figure 1: |
The first (left) and a very recent (right) gamma-ray burst associated with | The first (left) and a very recent (right) gamma-ray burst associated with | ||
a solar flare. | a solar flare. | ||
Line 50: | Line 50: | ||
The brevity of the two gamma-ray bursts shown in Figure 1 is striking, and | The brevity of the two gamma-ray bursts shown in Figure 1 is striking, and | ||
it calls to mind a series of [mm-wave radio] observations recorded at 86 GHz | it calls to mind a series of [mm-wave radio] observations recorded at 86 GHz | ||
- | at the [Hat Creek Observatory] [2]. | + | at the [http://bima.astro.umd.edu/ Hat Creek Observatory] [2]. |
We show examples of this in Figure 2. | We show examples of this in Figure 2. | ||
At such wavelengths we probably detect | At such wavelengths we probably detect | ||
Line 58: | Line 58: | ||
These could be from Π<sup>+</sup> or Π<sup>-</sup> mesons created | These could be from Π<sup>+</sup> or Π<sup>-</sup> mesons created | ||
similarly to the Π<sup>0</sup>s; these charged pions decay into charged | similarly to the Π<sup>0</sup>s; these charged pions decay into charged | ||
- | [muons] | + | [http://cosmic.lbl.gov/SKliewer/Cosmic_Rays/Muons.htm muons] |
and then into electrons and positrons, respectively; finally these can | and then into electrons and positrons, respectively; finally these can | ||
produce our favorite | produce our favorite | ||
- | [bremsstrahlung] | + | [http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/xrayc.html bremsstrahlung] |
radiation detectable as hard X-rays. | radiation detectable as hard X-rays. | ||
Both electrons and positrons can also radiate the gyrosynchtrotron | Both electrons and positrons can also radiate the gyrosynchtrotron | ||
Line 79: | Line 79: | ||
Such high-energy particles also can be accelerated in the corona, far from | Such high-energy particles also can be accelerated in the corona, far from | ||
the flare site, by a | the flare site, by a | ||
- | [CME]-driven | + | [http://en.wikipedia.org/wiki/Coronal_mass_ejection CME]-driven |
shock. | shock. | ||
In both scenarios the ultimate source of energy must be in stressed magnetic | In both scenarios the ultimate source of energy must be in stressed magnetic | ||
Line 95: | Line 95: | ||
If this is so, we may expect to see more such events with Fermi and | If this is so, we may expect to see more such events with Fermi and | ||
at even shorter radio wavelengths with the new | at even shorter radio wavelengths with the new | ||
- | [ALMA] | + | [http://en.wikipedia.org/wiki/Atacama_Large_Millimeter_Array ALMA] |
facility. | facility. | ||
Line 101: | Line 101: | ||
== References == | == References == | ||
- | [1] [Gamma-Ray Burst from a Solar Flare]] | + | [1] [http://adsabs.harvard.edu/abs/1959JGR....64..697P Gamma-Ray Burst from a Solar Flare]] |
- | [2] [Energetic Electron Populations in Solar Flares]] | + | [2] [http://adsabs.harvard.edu/abs/1994AIPC..294..199W Energetic Electron Populations in Solar Flares]] |
[[Category: Nugget]] | [[Category: Nugget]] |
Revision as of 10:24, 10 November 2012
Nugget | |
---|---|
Number: | 188 |
1st Author: | Hugh Hudson |
2nd Author: | Stephen White |
Published: | 12 November 2012 |
Next Nugget: | TBD |
Previous Nugget: | Glasgow Callisto |
List all |
Contents |
Introduction
The original observation of a solar gamma-ray burst by Peterson & Winckler [1], in 1958, has had a remarkable resonance in the ultra-modern data from [Fermi]. We show this in Figure 1, which compares the fairly primitive information available in 1958 (flare event SOL1958-03-20) with the much more complete information obtained for SOL2010-06-12, some half-a-century later. The new data show gamma rays above 100 MeV, inferred to have originated in (p,p) nuclear interactions resulting in the production of Π0 meson production; these particles then decay spontaneously into high-energy gamma-rays. The acceleration to such high energies required no more than a few seconds, judging from the timing between high- and low-energy photon arrival times.
The production of hard X-rays and gamma-rays in solar flares marks the [impulsive phase] of the event, during which the main energy release takes place. We now know this to be very common, almost a defining feature of a solar flare, although usually not so violent. For most flares the hard X-ray time profiles, at 10-100 keV photon energies, have a more extended time profile that often exhibits erratic and spiky behavior.
A new flare paradigm derived from the mm-waves radio observations?
The brevity of the two gamma-ray bursts shown in Figure 1 is striking, and it calls to mind a series of [mm-wave radio] observations recorded at 86 GHz at the Hat Creek Observatory [2]. We show examples of this in Figure 2. At such wavelengths we probably detect [gyrosychrotron radiation], in [sunspot]-strength magnetic fields, from primary electrons at many MeV. These could be from Π+ or Π- mesons created similarly to the Π0s; these charged pions decay into charged muons and then into electrons and positrons, respectively; finally these can produce our favorite bremsstrahlung radiation detectable as hard X-rays. Both electrons and positrons can also radiate the gyrosynchtrotron radiation observed at Hat Creek.
The radio and gamma-ray observations, though almost at opposite extremes of the radiation spectrum, may both be revealing the most energetic particles known to be accelerated in the flare itself. Note that the Fermi flare (Fig. 1, right panel) also produced white-light continuum in a two-footpoint structure implying closed magnetic fields. Such high-energy particles also can be accelerated in the corona, far from the flare site, by a CME-driven shock. In both scenarios the ultimate source of energy must be in stressed magnetic fields slowly built up in the lower solar atmosphere, and suddenly relaxing by the flare process.
Summary
We've speculated in this Nugget that we can identify two distinct radiation signatures with the same process: the prompt acceleration of primary protons to energies above 100 MeV in regions of intense magnetic fields. The impulse-response time profile of this process may reveal a somewhat different paradigm for flare energetics, one that has a characteristic temporal signature on a time scale of about 20 s. If this is so, we may expect to see more such events with Fermi and at even shorter radio wavelengths with the new ALMA facility.
References
[1] Gamma-Ray Burst from a Solar Flare]
[2] Energetic Electron Populations in Solar Flares]
RHESSI Nugget Date | 12 November 2012 + |
RHESSI Nugget First Author | Hugh Hudson + |
RHESSI Nugget Index | 188 + |
RHESSI Nugget Second Author | Stephen White + |