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Title: A TYPE II RADIO BURST WITHOUT A CORONAL MASS EJECTION

Abstract

Type II radio bursts are thought to be a signature of coronal shocks. In this paper, we analyze a short-lived type II burst that started at 07:40 UT on 2011 February 28. By carefully checking white-light images, we find that the type II radio burst is not accompanied by a coronal mass ejection, only by a C2.4 class flare and narrow jet. However, in the EUV images provided by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, we find a wave-like structure that propagated at a speed of ∼600 km s{sup −1} during the burst. The relationship between the type II radio burst and the wave-like structure is, in particular, explored. For this purpose, we first derive the density distribution under the wave by the differential emission measure method, which is used to restrict the empirical density model. We then use the restricted density model to invert the speed of the shock that produces the observed frequency drift rate in the dynamic spectrum. The inverted shock speed is similar to the speed of the wave-like structure. This implies that the wave-like structure is most likely a coronal shock that produces the type II radio burst. We also examinemore » the evolution of the magnetic field in the flare-associated active region and find continuous flux emergence and cancellation taking place near the flare site. Based on these facts, we propose a new mechanism for the formation of the type II radio burst, i.e., the expansion of the strongly inclined magnetic loops after reconnecting with a nearby emerging flux acts as a piston to generate the shock wave.« less

Authors:
; ; ; ;  [1]
  1. School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China)
Publication Date:
OSTI Identifier:
22522454
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 804; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COSMIC RADIO SOURCES; DENSITY; IMAGES; JETS; MAGNETIC FIELDS; MASS; SHOCK WAVES; SOLAR CORONA; SOLAR FLARES; SUN; VELOCITY; VISIBLE RADIATION

Citation Formats

Su, W., Cheng, X., Ding, M. D., Chen, P. F., and Sun, J. Q., E-mail: xincheng@nju.edu.cn, E-mail: dmd@nju.edu.cn. A TYPE II RADIO BURST WITHOUT A CORONAL MASS EJECTION. United States: N. p., 2015. Web. doi:10.1088/0004-637X/804/2/88.
Su, W., Cheng, X., Ding, M. D., Chen, P. F., & Sun, J. Q., E-mail: xincheng@nju.edu.cn, E-mail: dmd@nju.edu.cn. A TYPE II RADIO BURST WITHOUT A CORONAL MASS EJECTION. United States. doi:10.1088/0004-637X/804/2/88.
Su, W., Cheng, X., Ding, M. D., Chen, P. F., and Sun, J. Q., E-mail: xincheng@nju.edu.cn, E-mail: dmd@nju.edu.cn. Sun . "A TYPE II RADIO BURST WITHOUT A CORONAL MASS EJECTION". United States. doi:10.1088/0004-637X/804/2/88.
@article{osti_22522454,
title = {A TYPE II RADIO BURST WITHOUT A CORONAL MASS EJECTION},
author = {Su, W. and Cheng, X. and Ding, M. D. and Chen, P. F. and Sun, J. Q., E-mail: xincheng@nju.edu.cn, E-mail: dmd@nju.edu.cn},
abstractNote = {Type II radio bursts are thought to be a signature of coronal shocks. In this paper, we analyze a short-lived type II burst that started at 07:40 UT on 2011 February 28. By carefully checking white-light images, we find that the type II radio burst is not accompanied by a coronal mass ejection, only by a C2.4 class flare and narrow jet. However, in the EUV images provided by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, we find a wave-like structure that propagated at a speed of ∼600 km s{sup −1} during the burst. The relationship between the type II radio burst and the wave-like structure is, in particular, explored. For this purpose, we first derive the density distribution under the wave by the differential emission measure method, which is used to restrict the empirical density model. We then use the restricted density model to invert the speed of the shock that produces the observed frequency drift rate in the dynamic spectrum. The inverted shock speed is similar to the speed of the wave-like structure. This implies that the wave-like structure is most likely a coronal shock that produces the type II radio burst. We also examine the evolution of the magnetic field in the flare-associated active region and find continuous flux emergence and cancellation taking place near the flare site. Based on these facts, we propose a new mechanism for the formation of the type II radio burst, i.e., the expansion of the strongly inclined magnetic loops after reconnecting with a nearby emerging flux acts as a piston to generate the shock wave.},
doi = {10.1088/0004-637X/804/2/88},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 804,
place = {United States},
year = {2015},
month = {5}
}