Turbulent plasma model of the narrowband dm-spikes

Starting from radio spectrum features of the narrowband dm-spikes, it is su ggested that they are generated at positions in the solar are atmosphere wh ere the upper hybrid frequency is equal to the low harmonics of the electro n cyclotron frequency. It is assumed that a radio source plasma is in a tur bulent state. The upper hybrid waves are generated by an anisotropic electr on beam which propagates along magnetic loop lines. Collisional damping and turbulent changes of plasma parameters in the radio source cause strong in tensity-frequency variations of the upper hybrid waves. These waves are the n transformed into observed narrowband dm-spikes. Using this model, the art ificial radio spectra are computed. It is shown that a chain of narrowband spikes is generated at a one cyclotron harmonic, in one turbulent magnetic flux tube. On the other hand, a cloud of spikes (or their harmonic clouds) results from a superposition of many chains of spikes generated in many tur bulent magnetic flux tubes (in several cyclotron harmonics). Finally, furth er features of the narrowband dm-spikes are discussed in the framework of t he proposed model.