Slowly Drifting Radio Structures in Solar Flares

We present the data of high-frequency drift radio structures observed by the spectrometer of the Purple Mountain Observatory (PMO) over the frequency range of 4.5-7.5GHz in the solar flare of March 18, 2003. Such structures have been observed to have fine features consisting of short pulses, but drift with time as a whole. The drifting structures take place before the soft X-ray maximum, almost at the maximum of hard X-ray flux of 25-50keV. For the first time, drifts toward higher frequencies are detected in this kind of radio structures near 6GHz.