Coronal Signatures of a Flare Generated Type-II Solar Radio Burst

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1 8th East-Asia School and Workshop on Laboratory, Space, and Astrophysical Plasmas July 30 (Mon), 2018 ~ August 03 (Fri), 2018 Coronal Signatures of a Flare Generated Type-II Solar Radio Burst V. Vasanth and Y. J. Moon School of Space Research, Kyung Hee University, Yongin, South Korea

2 The sudden enhancements of non-thermal radio emission from the solar corona due to energetic electrons are observed as solar radio bursts. They follow the solar activities such as flares and CMEs. It is well known that there exist five types of radio bursts at the metric wavelength, including type-i, II, III, IV and V (Wild and McCready, 1950; Melrose, 1980; Mclean and Labrum, 1985).

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5 Type II burst Type II burst is importance in studying the near sun and near earth effects i.e. It can observed from sun to earth. Type II bursts identification! payne-scott et al., 1947 wild and McCready, (1950)! classification of radio bursts. Type II radio bursts! drifts slowly from high to low frequency.! signature of shock wave in the corona Metric (m) Type II burst Deca-Hectometer (DH) Type II burst Kilo metric (km) Type II burst! MHz,! 14 1 MHz and! 1 MHz 20 KHz. The m-type-ii bursts are not observed below 20 MHz due to ionospheric cut off frequencies. Type II bursts occurring in this three regime gives characteristic and information about the activities taking place near sun to near earth.

6 Example of a IP t-iis frequency range MHz Example of a coronal t-iis Typical frequency range MHz

7 111 1

8 Type II Solar Radio Burst on 6th March 2014 ORFEES MHz Learmonth MHz The composite dynamic spectrum of the type II solar radio bursts observed with fundamental ( MHz) and harmonic ( MHz) bands. The total radio flux profiles recorded by NRH observations at 270, 228, 173 and 150 MHz plotted over the dynamic spectrum

9 The type II radio burst is associated with a weak C-class flare located around S07E64, which starts at 9:23 UT, peaks at 9:25 UT and ends at 9:30 UT according to the RHESSI X-ray flux at 6 12 kev and kev bands, indicating the emission from the non-thermal electrons

10 Speed LASCO ~ 252 km/s STEREO-B ~ 280 km/s. Angular width ~ 61

11 Position of STEREO instruments

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13 The EUV images showed fastly propagating wave, probably the shock wave, that moved outward and generated the type-ii burst. Both the flare energy release and onset of EUV wave occurred simultaneously around 9:23 UT. Therefore the wave is most likely generated by the flare pressure pulse. The EUV wave at AIA 171 Å has two components one propagating perpendicular and another along parallel to the flare region. While the parallel propagating component gets reflected backward from the other leg of the flare loops, the perpendicular component freely propagates outward. In AIA 211 Å images it is observed as a freely propagating outward moving structure

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15 The line-up of type-iii radio sources from higher to lower frequencies simultaneously at all frequency channels implies the propagation of electron beam along the open filed loop or large scale loop structure

16 In the case of type-ii radio burst, the observed NRH data shows shift of radio sources from higher to lower frequencies with time.

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18 In the ST-B EUVI image the radio sources are located at lower heights than the frontal eruptive structure. This height difference between CME leading edge and the shock wave implies that the type-ii burst is not driven by the CME.

19 Summary The type-ii radio burst is observed with both fundamental and harmonic structures in the frequency range between MHz ( MHz) in harmonic (fundamental) band with a life time of 5 min between 09:26 09:31 UT. The speed of the type-ii radio burst is estimated by employing 2xSaito electron density model and it is found to be 650 km/s. The radio source positions reveal that the radio burst is excited at the outward moving EUV wave. The eruption is also accompanied by a weak CME observed in LASCO C2 (STEREO-B) FOV with a sky plane speed of 252 (280) km/s. The observed CME is independent of the shock wave as confirmed by the location of NRH radio source inside the angular span of CME-leading edge in ST-B EUVI images. Therefore the observed type-ii radio burst and the EUV wave are probably ignited by the flare.

20 THANK YOU FOR YOUR ATTENTION 8th East-Asia School and Workshop on Laboratory, Space, and Astrophysical Plasmas July 30 (Mon), 2018 ~ August 03 (Fri), 2018