Transient MHD activity in the multiple-mirror trap GOL-3 at the stage of plasma cooling after decay of the net current was studied. Such events are diagnosed as short bursts (generally shorter than 5 cycles) of oscillations of azimuthal magnetic field with the frequency within 0.1 [divided by] 1 MHz. Earlier transient events at the plasma decay stage were also observed. At that time an existence of long-lived internal current structures in the GOL-3 plasma was supposed.

The paper presents new results from the magnetic diagnostics. Azimuthal and longitudinal mode localization agrees with the assumption that the magnetic field is generated by filaments with the current in the range of 1 [divided by] 50 A in nearly uniform azimuthal distribution. Statistical analysis shows that the main oscillation frequencies are grouped near the inversed time of the Alfven wave propagation along the trap. Power dependence of the pulse probability on its amplitude with the index = -1.87 was found. Relationships of MHD activity on the regime of plasma heating and on a degree of the beam stabilization at the exit receiver are discussed.