Physics – Plasma Physics
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufmsh41a1912m&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #SH41A-1912
Physics
Plasma Physics
[7509] Solar Physics, Astrophysics, And Astronomy / Corona, [7519] Solar Physics, Astrophysics, And Astronomy / Flares, [7534] Solar Physics, Astrophysics, And Astronomy / Radio Emissions, [7845] Space Plasma Physics / Particle Acceleration
Scientific paper
A compact flare was observed with Nobeyama Radio Heliograph (NoRH) near the west limb around 2:56 UT on 10 March 2011. Its duration was only one minute. The peak values of microwave flux at 17GHz and 34GHz were 210 and 133 SFU, respectively. This level corresponds to the fifth intense flare observed with NoRH in this solar cycle as of the end of July, 2011. However, any significant enhance was not found in GOES X-ray light curve during the flare period. Since the GOES background level was around C1 at that time, so we can say the upper limit of this flare was C1. In SDO EUV images, any significant change was not observed during the flare. From microwave images, this flare might occur slightly behind the west limb. We check STEREO-A SECCHI EUV images during the flare period. Again, there was almost no signature of a flare. Summarizing these observations, any significant enhance of thermal emissions was not observed in this flare. Only microwave emissions are detected. Unfortunately RHESSI was in the shadow of the earth during this flare. What causes the relatively intense microwave emissions? Considering that the brightness temperature was about 19 MK (the third highest temperature in this cycle as of the end of July 2011), the microwave emissions should be gyro-synchrotron emissions by high-energy electrons. Fleishman et al. (2011) reported a cold tenuous flare with acceleration, but without heating. This flare seems to be similar. However, footpoint regions, i.e., strong magnetic field regions, were occulted in the case of this flare. Additionally, in higher-frequency range like 34GHz, intense microwave emissions were detected. It is more difficult to understand these observational results. We summarize the characteristics of this unique flare and discuss what kind of process/situation produced it.
Goto Tomotsugu
Kawate Tomoko
Masuda Seiji
Shimojo Miki
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