Solar type III bursts with high-frequency cut-off

Background: Solar activity often manifests in type III bursts. Some of them can have high-frequency cut-off. The origin of this phenomenon is unclear until now. Materials and Methods: New results in the study of solar bursts with high-frequency cut-off observed with the UTR-2 radio telescope are presented. The bursts were associated with the emergency of a new group of solar spots behind the solar limb relative to an observer on the Earth. Results: We have identified the radio events with type III by analyzing its frequency drift rate, duration and flux depending on frequency. The cut-off feature is considered in the context of specific effects of radio wave propagation between the burst sources moving behind the solar limb and the ground-based radio instruments. Conclusions: The role of tunnel-like cavities with low density in the solar corona can be crucial for the emergence of solar decameter bursts with high-frequency cut-off.