Unusual Type III Burst Dynamics Produced by Diverging Magnetic Fields
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frequencies that are proportional to the square root of the ambient | frequencies that are proportional to the square root of the ambient | ||
electron density. | electron density. | ||
- | The plasma density in the [https://en.wikipedia.org/wiki/Corona | + | The plasma density in the [https://en.wikipedia.org/wiki/Corona solar corona] |
- | solar corona] generally decreases outwards from the solar surface. | + | generally decreases outwards from the solar surface. |
The emission frequency is therefore related to the height that | The emission frequency is therefore related to the height that | ||
corresponds to the requisite background density, and type III bursts | corresponds to the requisite background density, and type III bursts | ||
Line 26: | Line 26: | ||
move outward. | move outward. | ||
- | [[File:311f1.png| | + | === Source Region Splitting === |
+ | |||
+ | A series of type III bursts have recently been observed to exhibit | ||
+ | a curious splitting behavior by the | ||
+ | [http://mwatelescope.org Murchison Widefield Array (MWA)], | ||
+ | a new and very powerful low-frequency radio interferometer (Ref. [1]). | ||
+ | In these bursts the source region splits from one component at | ||
+ | higher frequencies (smaller heights), into two increasingly-separated | ||
+ | components at lower frequencies (larger heights). | ||
+ | The two components also repetitively move apart at a few | ||
+ | tenths of light speed in observations at individual frequencies. | ||
+ | This motion, shown in Figure 1, lasts around 2 seconds and occurs | ||
+ | many times over several minutes. | ||
+ | |||
+ | |||
+ | [[File:311f1.png|600px|thumb|center|Figure 1: | ||
Source splitting motion at 108 MHz, beginning at 2015/09/21 | Source splitting motion at 108 MHz, beginning at 2015/09/21 | ||
05:16:53.70 UT. The dashed line in the left panel denotes the slit | 05:16:53.70 UT. The dashed line in the left panel denotes the slit |
Revision as of 17:36, 23 November 2017
Nugget | |
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Number: | 311 |
1st Author: | Patrick McCauley |
2nd Author: | |
Published: | 27 November 2017 |
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Introduction
Type III solar radio bursts are widely believed to be caused by electron beams accelerated away from the Sun during solar flares. Fast electrons stimulate oscillations in the ambient plasma, which in turn produce radio emission. This plasma emission occurs at specific frequencies that are proportional to the square root of the ambient electron density. The plasma density in the solar corona generally decreases outwards from the solar surface. The emission frequency is therefore related to the height that corresponds to the requisite background density, and type III bursts are characterized by a rapid drift to lower frequencies as the beams move outward.
Source Region Splitting
A series of type III bursts have recently been observed to exhibit a curious splitting behavior by the Murchison Widefield Array (MWA), a new and very powerful low-frequency radio interferometer (Ref. [1]). In these bursts the source region splits from one component at higher frequencies (smaller heights), into two increasingly-separated components at lower frequencies (larger heights). The two components also repetitively move apart at a few tenths of light speed in observations at individual frequencies. This motion, shown in Figure 1, lasts around 2 seconds and occurs many times over several minutes.
References
[1] "Type III Solar Radio Burst Source Region Splitting Due to a Quasi-Separatrix Layer"
[2] "Tracing Electron Beams in the Sun's Corona with Radio Dynamic Imaging Spectroscopy"
RHESSI Nugget Date | 27 November 2017 + |
RHESSI Nugget First Author | Patrick McCauley + |
RHESSI Nugget Index | 311 + |