Microwave Burst of November 17, 1991: Evidence of Fragmented Particle Injection into a Coronal Loop

Abstract

The unusual event of November 17, 1991 07:04 UT, observed at 2.5 and 2.85 GHz, is analysed. The event reveals the sophisticated superfine time structure including sudden reductions and quasi-periodic pulsations. We shown that the sudden reductions (≈ 30–100 ms) can be driven by upward injected ≳ 100 keV electron beams filling the loss-cone of the coronal magnetic trap. The nonlinear oscillations of Langmuir waves provide the best fit for the pulsation observed. A reduced steady-state level of the pulsation phase is connected with quasi-continuous injection of electrons. The physical parameters of the radio source are found for the event.