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Type: Artigo de periódico
Title: A microwave study of coronal ejecta
Author: Kundu, MR
Nindos, A
Raulin, JP
Shibasaki, K
White, SM
Nitta, N
Shibata, K
Shimojo, M
Abstract: Using Nobeyama 17 GHz data, we have studied the radio properties of 19 coronal jets identified in Yohkoh soft X-ray imaging telescope (SXT) X-ray observations. The radio data provide information on the physical conditions in the jets, which complements the data from the X-ray surveys. Microwave emission was associated with the majority of the X-ray jets in our sample. The radio emission typically came from the base or the base and lower part of the jets. We detected radio emission from almost all jets that showed flarelike activity at their bases. The jets that were not associated with radio emission did not show any significant increase in X-ray emission at their bases. The strongest radio emission came from two of the largest jets in our sample. Our data show a general correlation between the X-ray jet fluxes and the associated radio fluxes. The 17 GHz time profiles were gradual and unpolarized, implying that the emission was thermal. In a two-sided-loop jet (1992 July 22 event) and one anemone-type jet (1993 February 9 event), the observed microwave fluxes from the lower part of the jets were well above the fluxes calculated from the computed physical parameters of the soft X-ray-emitting material on the basis of thermal free-free emission. We interpret the large discrepancies in terms of the presence of lower temperature material, which cannot be detected by the SXT (the SXT is most sensitive to hot plasma above 2 x 10(6) K), but which produces strong microwave free-free emission. This is the first time that such material has been observed in two-sided-loop-type jets. We also observed motion of a jet-associated microwave source with a velocity of 55 km s(-1). The microwave motion occurred after the appearance of the X-ray jet. There is clear evidence that the microwave emission of that source was associated with the jet and not with the associated small hare.
Subject: Sun : activity
Sun : corona
Sun : radio radiation
Sun : X-rays, gamma rays
Country: EUA
Editor: Univ Chicago Press
Citation: Astrophysical Journal. Univ Chicago Press, v. 520, n. 1, n. 391, n. 398, 1999.
Rights: aberto
Identifier DOI: 10.1086/307454
Date Issue: 1999
Appears in Collections:Unicamp - Artigos e Outros Documentos

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