Multi-Site Spectrographic and Heliographic Observations of Radio Fine Structure on April 10, 2001

Abstract

We present results of the first simultaneous observations of zebra patterns (ZPs) with super-fine spiky structure in the microwave range made at two observatories similar to 1000 km apart (Beijing and Nanjing, China). The fine structure was recorded by a spectra polarimeter in the 5.2 - 7.6 and 2.8 - 3.6 GHz ranges at the Huairou station and by the spectrometer in the 4.5 - 7.5 GHz range at the Purple Mountain Observatory. Simultaneously, the locations of radio sources were observed by the Siberian Solar Radio Telescope (SSRT) at 5.7 GHz. For a general analysis of the April 10, 2001 event, the Solar and Heliospheric Observatory/Michelson Doppler Imager (SOHO/MDI) data and Transition Region and Coronal Explorer (TRACE) images in EUV 171 angstrom line were used. The circular polarization degree was very weak for the burst background radio emission and moderate to strong for the fine structure. The polarization sign in all the cases probably corresponds to the extraordinary wave mode. Estimations of the magnetic field values in the whistler model for fine structure agree well with the extrapolated values from magnetic maps. Given the possibility of wave transformation in the perpendicular magnetic field and the spiky structure of the ZP, the whistler wave model appears to be the most appropriate explanation for the zebra stripe phenomenon.