Power-law spectra of 1-2 GHz narrowband dm-spikes

Twelve examples of clouds of narrowband dm-spikes, observed by the Ondrejov radiospectrograph in the 1-2 GHz frequency range, are analyzed. After transforming of the frequency scales to heights in the solar atmosphere, the indices of the power-law power spectra are determined. The derived power-law indices are scattered in a broad range of values (-0.80 - -2.85). In some cases they considerably deviate from the previously found value of -5/3. A change of the power-law index above log k approximate to 2.5 was also found in some cases. In the two longest events the time evolution of their power spectra as well as their indices were studied. While in most parts of the radio spectra the spectral index remains constant, in one part its absolute value increases with the spike intensity increase. Finally, the results, especially the broad range of power-law indices, are briefly discussed.