The Library

Spatially resolved microwave pulsations of a flare loop

Tools

Melnikov, V. F. (Victor Fedorovich), Reznikova, V. E., Shibasaki, K. (Kiyoto) and Nakariakov, V. M. (Valery M.). (2005) Spatially resolved microwave pulsations of a flare loop. Astronomy & Astrophysics, Vol.439 (No.2). pp. 727-736. ISSN 0004-6361

PDF
WRAP_Nakariakov_99_Spatially_resolved.pdf - Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader
Download (396Kb)

Official URL: http://dx.doi.org/10.1051/0004-6361:20052774

Abstract

A microwave burst with quasi-periodic pulsations was studied with high spatial resolution using observations with
the Nobeyama Radioheliograph (NoRH). We found that the time profiles of the microwave emission at 17 and 34 GHz exhibit
quasi-periodic (with two well defined periods P 1 = 14–17 s and P 2 = 8–11 s) variations of the intensity at diﬀerent parts of an observed flaring loop. Detailed Fourier analysis shows the P 1 spectral component to be dominant at the top, while the P 2 one near the feet of the loop. The 14–17 s pulsations are synchronous at the top and in both legs of the loop. The 8–11 s pulsations at the legs are well correlated with each other but the correlation is not so obvious with the pulsations at the loop top. For this P 2
spectral component, a definite phase shift, P 2 /4 ≈ 2.2 s, between pulsations in the northern leg and loop top parts of the loop have been found. The length of the flaring loop is estimated as L = 25 Mm (≈34 ) and its average width at half intensity at 34 GHz as about 6 Mm (≈8 ). Microwave diagnostics shows the loop to be filled with a dense plasma with the number density n 0 ≈ 10 11 cm −3, penetrated by the magnetic field changing from B 0 ≈ 100 G near the loop top up to B 0 ≈ 200 G near the north footpoint. A comparative analysis of diﬀerent MHD modes of the loop demonstrates the possibility of the simultaneous existence of two modes of oscillations in the loop: the global sausage mode, with the period P 1 = 14–17 s and the nodes at the footpoints, and a higher harmonics mode (possibly with the radial wave number l > 1), with P 2 = 8–11 s.

Item Type:

Journal Article

Subjects:

Q Science > QB Astronomy

Divisions:

Faculty of Science > Physics

Library of Congress Subject Headings (LCSH):

Solar flares, Magnetohydrodynamics, Solar oscillations, Solar radiation

Journal or Publication Title:

Astronomy & Astrophysics

Publisher:

EDP Sciences

ISSN:

0004-6361

Official Date:

August 2005

Dates:

Date	Event
August 2005	Published

Volume:

Vol.439

Number:

No.2

Page Range:

pp. 727-736

Identification Number:

10.1051/0004-6361:20052774

Status:

Peer Reviewed

Access rights to Published version:

Open Access

Funder:

Royal Society (Great Britain), Leverhulme Trust (LT), Rossiĭskiĭ fond fundamentalʹnykh issledovaniĭ [Russian Foundation for Basic Research] (RFBR)

Grant number:

04-02-39029 (RFFI), 04-02-16753 (RFFI)

References:

Asai, A., Shimojo, M., Isobe, H., et al. 2001, ApJ, 562, L103
Aschwanden, M. J. 1987, Sol. Phys., 111, 113
Aschwanden, M. J., Fletcher, L., Schrijver, C. J., & Alexander, D.
1999, ApJ, 520, 880
Dulk, G. A., & Marsh, K. A. 1982, ApJ, 259, 350
Edwin, P. M., & Roberts, B. 1982, Sol. Phys., 76, 239
Edwin, P. M., & Roberts, B. 1983, Sol. Phys., 88, 179
Fleishman, G. D., & Melnikov, V. F. 2003, ApJ, 587, 823
Grechnev, V. V., White, S. M., & Kundu, M. R. 2003, ApJ, 588, 1163
Kane, S. R., Kai, K., Kosugi, T., et al. 1983, ApJ, 271, 376
Kiplinger, A. L., Dennis, B. R., Frost, K. J., & Orwig, L. E. 1983, ApJ,
273, 783
Melnikov, V. F., Shibasaki, K., & Reznikova, V. E. 2002a, ApJ, 580,
L185
Melnikov, V. F, Reznikova, V. E., & Shibasaki, K. 2002b, Proc. of
Intern. Conf. Active processes on the Sun and stars, ed. V. V.
Zaitsev, & L. V. Yasnov, 225
Melnikov, V. F., Reznikova, V. E., Yokoyama, T. & Shibasaki, K.
2002c, in Solar Variability: From Core to Outer Frontiers (10th
European Solar Physics Meeting, 9–14 September 2002, Prague),
ed. A. Wilson, ESA SP-506, 339
Melnikov, V. F., Gary, D. E., & Nita, G. M. 2005, ApJ, in press
Melrose, D. B., & Brown, J. C. 1976, MNRAS, 176, 15
Nakajima, H., Kosugi, T., Kai, K., & Enome, S. 1983, Nature, 305,
292
Nakariakov, V. M. 2003, in Dynamic Sun, ed. B. N. Dwivedi, 314
Nakariakov, V. M., Ofman, L., DeLuca, E. E., Roberts, B., & Davila,
J. M. 1999, Science, 285, 862
Nakariakov, V. M., Melnikov, V. F., & Reznikova, V. E. 2003, A&A,
412, L7
Nita, G. M., Gary, D. E., & Lee, J. W. 2004, ApJ, 605, 528
Nobeyama, Radioheliograph Catalog of Events. NRO, Minamimaki,
Minamisaku, Nagano 384–1305, Japan, 2002
Ramaty, R., Schwartz, R. A., Enome, S. & Nakajima, N. 1994, ApJ,
436, 941
Razin, V. A. 1960a, Izv. VUZov Radiofizika, 3, 584
Razin, V. A. 1960b, Izv. VUZov Radiofizika, 3, 921
Rosenberg, H. 1970, A&A, 9, 159
Sakai, J.-I., & de Jager, C. 1996, Space Sci. Rev., 77, 1
Shibasaki, K. 2001, ApJ, 557, 326
Twiss, R. Q. 1954, Phyl. Mag., 45, 249
Urpo, S., et al. 1992, Solar Radio Flares 1989-1991, HUT Report 11,
Ser. A
Zaitsev, V. V., & Stepanov, A. V. 1975, Issled. Geomagn. Aeron. Fiz.
Solntsa, 37, 3
Zaitsev, V. V., & Stepanov, A. V. 1982, Sov. Astron. Lett., 8, 132
Zaitsev, V. V., Stepanov, A. V. 1989, Sov. Astron. Lett., 15, 66
Zaitsev, V. V., Stepanov, A. V., Urpo, S., & Pohjolainen, S. 1998,
A&A, 337, 887
Zaqarashvili, T. V. 2003, A&A, 399, L15