**Abstract**

Two new, previously unknown types of dissipative streaming instabilities (DSI) are substantiated. They follow from new approach, which allows solving in general form the classical problem of an initial perturbation development for streaming instabilities (SI). SI is caused by relative motion of the streams of plasma components. With an increase in level of dissipation SI transforms into a DSI. The transformation occurs because dissipation serves as a channel for energy removal for the growth of the negative energy wave of the stream. Until recently, only one type of DSI was known. Its maximal growth rate depends on the beam density *nb* and the collision frequency *<sup>ν</sup>* in the plasma as � ffiffiffiffiffiffiffiffiffi *nb=ν* p . All types of conventional beamplasma instabilities (Cherenkov, cyclotron, etc.) transform into it. The solution of the problem of the initial perturbation development in systems with weak beamplasma coupling leads to a new type of DSI. With an increase in the level of dissipation, the instability in these systems transforms to the new DSI. Its maximal growth rate is � ffiffiffiffiffi *nb* p *=ν*. The second new DSI develops in beam-plasma waveguide with over-limiting current of e-beam. Its growth rate � *nb=ν*. In addition, the solutions of abovementioned problem provide much information about SI and DSI, significant part of which is unavailable by other methods.

**Keywords:** beam-plasma instability, dissipative instability, development of initial perturbation, growth rate, absolute/convective instability
