EDP Sciences
Free access
Volume 385, Number 2, April II 2002
Page(s) 671 - 685
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20020172

A&A 385, 671-685 (2002)
DOI: 10.1051/0004-6361:20020172

Discovery of unusual large group delay in microwave millisecond oscillating events

G. D. Fleishman1, 2, Q. J. Fu1, G.-L. Huang3, V. F. Melnikov1, 4 and M. Wang1

1  Beijing Astronomical Observatory, National Astromonical Observatories, Beijing 100012, PR China
    e-mail: fuqj@cenpok.net
2  Ioffe Institute for Physics and Technology, 194021 St.Petersburg, Russia
3  Purple Mountain Observatory, National Astromonical Observatories, Nanjing 210008, PR China
    e-mail: guangli@public1.ptt.js.cn
4  Radiophysical Research Institute, 603950 Nizhny Novgorod, Russia
    e-mail: meln@nirfi.sci-nnov.ru

(Received 13 March 2001 / Accepted 17 January 2002 )

Two events demonstrating periodic narrowband millisecond pulsations of radio emission both in intensity and polarization degree are analyzed. Large time delays between  L- and R-polarization components are found. The radio emission is shown to be generated as unpolarized by a plasma mechanism at the second harmonic of the upper-hybrid frequency. Observed oscillations of the radiation polarization degree arise due to group delay between extraordinary and ordinary modes along the line of sight. The theoretically predicted dependence of the group delay on frequency (~ f-3) agrees excellently with the observed delay frequency dependence. Physical parameters of the emission source and "delay site" are determined within the proposed model.

Key words: Sun: radio radiation -- Sun: flares -- Sun: general

Offprint request: G. D. Fleishman, gregory@sun.ioffe.rssi.ru

SIMBAD Objects in preparation

© ESO 2002