Microwave type III pair bursts in solar flares

Journal Article · Tue Mar 01 04:00:00 EST 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/819/1/42· OSTI ID:22886978

Tan, Baolin; Tan, Chengming ^[1]; Mészárosová, Hana; Karlický, Marian ^[2]; Huang, Guangli ^[3]

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1. Key Laboratory of Solar Activity, National Astronomical Observatories of Chinese Academy of Sciences, Beijing 100012 (China)
2. Astronomical Institute of the Academy of Sciences of the Czech Republic, CZ-25165 Ondřejov (Czech Republic)
3. Purple Mountain Observatory of Chinese Academy of Sciences, Nanjing 210008 (China)

A solar microwave type III pair burst is composed of normal and reverse-sloped (RS) burst branches with oppositely fast frequency drifts. It is the most sensitive signature of the primary energy release and electron accelerations in flares. This work reports 11 microwave type III pair events in 9 flares observed by radio spectrometers in China and the Czech Republic at a frequency of 0.80–7.60 GHz during 1994–2014. These type III pairs occurred in flare impulsive and postflare phases with separate frequencies in the range of 1.08–3.42 GHz and a frequency gap of 10–1700 MHz. The frequency drift increases with the separate frequency (f{sub x}), the lifetime of each burst is anti-correlated to f{sub x}, while the frequency gap is independent of f{sub x}. In most events, the normal branches are drifting obviously faster than the RS branches. The type III pairs occurring in flare impulsive phase have lower separate frequencies, longer lifetimes, wider frequency gaps, and slower frequency drifts than that occurring in postflare phase. Also, the latter always has strong circular polarization. Further analysis indicates that near the flare energy release sites the plasma density is about 10{sup 10}--10{sup 11} cm{sup −3} and the temperature is higher than 10{sup 7} K. These results provide new constraints to the acceleration mechanism in solar flares.

• OSTI ID: 22886978
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 819; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCELERATION
EMISSION
GHZ RANGE 01-100
PLASMA DENSITY
POLARIZATION
RELICT RADIATION
SOLAR CORONA
SOLAR FLARES
SOLAR RADIO BURSTS
SUN