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Author Morioka, A. ♦ Misawa, H. ♦ Obara, T. ♦ Miyoshi, Y. ♦ Masuda, S. ♦ Iwai, K. ♦ Kasaba, Y.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword ASTROPHYSICS, COSMOLOGY AND ASTRONOMY ♦ ACCELERATION ♦ ELECTRON DENSITY ♦ INTERFACES ♦ MAGNETIC FIELDS ♦ SOLAR CORONA ♦ SOLAR RADIO BURSTS ♦ SUN ♦ TRAPPING
Abstract Solar micro-type III radio bursts are elements of the so-called type III storms and are characterized by short-lived, continuous, and weak emissions. Their frequency of occurrence with respect to radiation power is quite different from that of ordinary type III bursts, suggesting that the generation process is not flare-related, but due to some recurrent acceleration processes around the active region. We examine the relationship of micro-type III radio bursts with coronal streamers. We also explore the propagation channel of bursts in the outer corona, the acceleration process, and the escape route of electron beams. It is observationally confirmed that micro-type III bursts occur near the edge of coronal streamers. The magnetic field line of the escaping electron beams is tracked on the basis of the frequency drift rate of micro-type III bursts and the electron density distribution model. The results demonstrate that electron beams are trapped along closed dipolar field lines in the outer coronal region, which arise from the interface region between the active region and the coronal hole. A 22 year statistical study reveals that the apex altitude of the magnetic loop ranges from 15 to 50 R{sub S}. The distribution of the apex altitude has a sharp upper limit around 50 R{sub S} suggesting that an unknown but universal condition regulates the upper boundary of the streamer dipolar field.
ISSN 0004637X
Educational Use Research
Learning Resource Type Article
Publisher Date 2015-08-01
Publisher Place United States
Journal Astrophysical Journal
Volume Number 808
Issue Number 2


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