A solar microwave type-M burst

A microwave M-type burst observed by Beijing Astronomical observatory on 19 98 April 15 is studied and analysed in this paper. It is composed of two co ntinuous inverted U-type bursts, the sources moving to and fro within one m agnetic arch from reflection by the magnetic mirror around one footpoint of the same magnetic arch. At a low time resolution (0.2s) the records show t he U-type morphology while the true motion is revealed by the high time res olution (8 ms) records. By comparing the two constituent Ii-type bursts, we see that the magnetic arch is probably at the descending phase of evolutio n, Its possible configuration in space is discussed.