First interferometric observations of solar microwave millisecond spike bursts

We report observations, with one-dimensional spatial resolution, of solar microwave millisecond spikes at 2.8 GHz. The observations were made with the Owens Valley frequency-agile interferometer with 20 ms time resolution. We find that the spikes occur at a position different from that of the underlying gyrosynchrotron radio burst source. All of the spikes during the rising part of the burst come from the same one-dimensional location to within ± 1", despite the fact that rapid evolution in the sense and degree of circular polarization was observed. The one-dimensional position of the spikes is consistent with a location over a large sunspot, suggesting that the emission occurs in a region of strong, converging magnetic field. The observations support the suggestion that the spikes are due to the electron-cyclotron maser mechanism.