Quasi-periodic Radio Bursts Associated with Fast-mode Waves near a Magnetic Null Point

Journal Article · Tue Aug 01 04:00:00 EDT 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/AA7D53· OSTI ID:22663307

Kumar, Pankaj ^[1]; Nakariakov, Valery M. ^[2]; Cho, Kyung-Suk ^[3]

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1. Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
2. Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, CV4 7AL (United Kingdom)
3. Korea Astronomy and Space Science Institute (KASI), Daejeon, 305-348 (Korea, Republic of)

This paper presents an observation of quasi-periodic rapidly propagating waves observed in the Atmospheric Image Assembly (AIA) 171/193 Å channels during the impulsive phase of an M1.9 flare that occurred on 2012 May 7. The instant period was found to decrease from 240 to 120 s, and the speed of the wavefronts was in the range of ∼664–1416 km s{sup −1}. Almost simultaneously, quasi-periodic bursts with similar instant periods, ∼70 and ∼140 s, occur in the microwave emission and in decimetric type IV and type III radio bursts, and in the soft X-ray emission. The magnetic field configuration of the flare site was consistent with a breakout topology, i.e., a quadrupolar field along with a magnetic null point. The quasi-periodic rapidly propagating wavefronts of the EUV emission are interpreted as a fast magnetoacoustic wave train. The observations suggest that the fast-mode waves are generated during the quasi-periodic magnetic reconnection in the cusp region above the flare arcade loops. For the first time, we provide evidence of a tadpole wavelet signature at about 70–140 s in decimetric (245/610 MHz) radio bursts, along with the direct observation of a coronal fast-mode wave train in EUV. In addition, at AIA 131/193 Å we observed quasi-periodic EUV disturbances with periods of 95 and 240 s propagating downward at apparent speeds of 172–273 km s{sup −1}. The nature of these downward propagating disturbances is not revealed, but they could be connected to magnetoacoustic waves or periodically shrinking loops.

• OSTI ID: 22663307
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 844; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
DISTURBANCES
EMISSION
EXTREME ULTRAVIOLET RADIATION
FAST MAGNETOACOUSTIC WAVES
MAGNETIC FIELDS
MAGNETIC RECONNECTION
MAGNETOACOUSTICS
MHZ RANGE
MICROWAVE RADIATION
OSCILLATIONS
PERIODICITY
SOFT X RADIATION
SOLAR RADIO BURSTS
SUN
TOPOLOGY
VELOCITY