During shot explosions, which result in the formation of a hot plasma, electromagnetic radiation takes place in a very wide range, up to the radio waveband. But to date, those physical mechanisms that could explain the origin of such radiation are unknown. It is known that plasma resonance is longitudinal, but longitudinal resonance can not radiate transverse radio waves. There were no other resonances other than plasma resonances in an unmagnetized plasma. However, it turns out that in a bounded unmagnetized plasma there can also exist a transverse resonance with respect to the propagation direction of the waves. It is this resonance that can be associated with the loss of electromagnetic waves in explosions of the flow of charges. This resonance can be used to create high-power lasers and to heat the plasma.