Since fast fine structures (FFS) superimposed on microwave bursts were found with high time resolution observations, they have been observed in extensive frequency range (Slottje 1978; Fu, et al. 1986; Stähli and Magun 1986; and Stepanov and Yurovsky 1991), and these results make understanding of the emission deepening. But, at the same time, the puzzling problem, these phenomena originate from sun or are only artificial, is often concerned and disputed (Benz and F ü rst 1987). As it was pointed out by Benz and F ü rst (1987), “the only really reliable way to study solar microwave fluctuation is to use two or more widely separated radio telescopes”. In this paper, some of FFS events superimposed on microwave bursts simultaneously obtained at Beijing Astronomical Observatory (BAO), Crimea Astrophysical Observatory (CAO) and Institute of Applied Physics, University of Bern (IAP), are presented at first time. It is a conclusive evidence of rapid radio fluctuation originating from sun and associated with flare appearance.

Variations on short time-scales have been found in solar flares at different wavelengths. Millisecond scale radio spikes are a quickly developing area of solar radio astronomy. The solar radio astronomy group of Beijing Astronomical Observatory (BAO) has found fine structures of microwave bursts with millisecond time-scale at 2840 MHz. In this paper, we briefly summarize the observations. A joint-observation network for observing solar radio bursts with high time resolution has also been established. The equipment in the network covers a frequency domain of more than 10:1, including 1.3, 2.0, 6, 10, 15, 20 cm, and meter wavelengths. In particular, a multi-channel polarimeter with super-fast sampling (10 μs) at 2600 MHz, an intensity interferometer with 1 ms sampling rate at 6 cm wavelength, and an auto-correlation radio spectrograph with 8 ms time constant at 21 cm wavelength are being established. We pay close attention to research on the spike emission features over wide bands, and their relationship to special characteristics in other spectral ranges.

Using the high time resolution of 1 ms, the data of solar microwave millisecond spike (MMS) event was recorded more than two hundred times at the frequency of 2.84 GHz at Beijing (Peking) Observatory since May 1981. A preliminary analysis was made. It can be seen from the data that the MMS-events have a variety of the fast activities such as the dispersed and isolated spikes, the clusters of the crowded spikes, the weak spikes superimposed on the noise background, and the phenomena of absorption. The marked differences from that observed with lower time resolution are presented. Using the data, a valuable statistical analysis was made. There are close correlations between MMS-events and hard X-ray bursts, and fast drifting bursts. The MMS events are highly dependent on the type of active regions and the magnetic field configuration. It seems to be crucial to find out the accurate positions on the active region where the MMS-events happen and to make co-operative observations at different bands during the special period when specific active regions appear on the solar disk.