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Astron. Astrophys. 364, 793-798 (2000)

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2. Observation

For a detailed study of the fine structures in the high-frequency part of decimetric and microwave bursts, new spectral observations (intensity and polarization) with high resolution in time and in frequency over a wide frequency range are needed. For this purpose, a broad band radio spectrometer is being developed by the solar radio astronomical community of China (Fu et al. 1995). It consists of 5 separate spectrometers covering the respective frequency range: 0.70-1.40 GHz, 1.00-2.00 GHz, 2.60-3.80 GHz, 4.00-5.20 GHz and 5.20-7.60 GHz. The 2.60-3.80 GHz component spectrometer started working in October 1996 at BAO. It has 120 frequency channels of 10 MHz bandwidth each, a time resolution of 8ms, high sensitivity and high accuracy measurement of circular polarization (Ji et al. 2000).

An overview of type IV-DCIM on May 3 1999 is given in Fig. 1, including a single frequency time profile, left- and right-handed circular dynamic spectra respectively. Fig. 2 shows a fine structure, which has a `M' appearance.

[FIGURE] Fig. 1. An overview of DCIM on May 3 1999 observed by BAO, top to bottom: a single frequency time profile, left- and right-handed dynamic spectra respectively. (the period between two triangle markers is given in the top panel in Fig. 2).

[FIGURE] Fig. 2. Dynamic spectra of the M burst, which is a fine structure of DCIM; top and second panel: data integrated into 200ms; third and bottom: data recoded with a resolution of 8ms.

This type IV-DCIM event lasted from 05:42 UT to about 06:49 UT. According to Solar-Geophysical Data (SGD), it was also recorded by the spectrometer over the range of 800-2000 MHz from 05:42 UT to 06:41 UT in Ondrejov Observatory. Moreover, a type 48C burst was detected by LEAR and SVTO at fixed frequency 2695 MHz and 4995 MHz, etc. On the other hand, a M4.4/2N flare was recorded by GOES and LEAR in the active region NOAA 8525 located at N15E32. This flare lasted from 05:36 UT to 06:32 UT in GOES X-ray at 1-8 Å (or from 05:34 UT to 07:45 UT in [FORMULA]), reaching its maximum around 06:02 UT (or 05:51 UT in [FORMULA]). In addition, there were some sudden ionospheric disturbances between 05:43 UT and 06:01 UT (maximum at 05:50 UT).

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© European Southern Observatory (ESO) 2000

Online publication: January 29, 2001