Fourier Analysis of Radio Bursts Observed with Very High Time Resolution

Abstract

Numerous solar radio bursts were observed in 2000 -2001 using the Toruń radio spectrograph with its unique time resolution of 80 microseconds. This high time resolution enables an in-depth analysis of the time evolution of the power spectra and Fourier spectral indices of selected short radio bursts. We analyze the power-spectrum parameters and variability for two millisecond radio dm-spike events and one drifting pulsation structure (DPS) event, for which the structures of the recorded signals were analyzed with an effective time resolution of 0.0008 s in five adjacent frequency bands of their radio spectra.We found that Fourier spectral indices varied rapidly when radio fine structures were recorded. Otherwise they remained close to zero, indicating the presence of noise. For the 10 -40 Hz frequency interval of the power spectra the mean values of the Fourier spectral indices varied up to −1.51 for the dm-spikes and up to −1.53 for the DPS event. Crosscorrelation coefficients of radio fluxes in adjacent frequency bands varied between 0.12 and 0.60 for dm-spikes and between 0.77 and 0.94 for the DPS event. The shortest fine structure found in the studied events lasted 0.001 s.These results are entirely new for dm-radio spikes and confirm a single previous result found for the DPS events. On the basis of our results, we propose that dm-spikes and DPS events are physically similar and that both are signatures of cascades of interacting plasmoids of different sizes.

Oscillations and Waves in Radio Source of Drifting Pulsation Structures

“…For an interval of periods shorter than 1 s the authors found that the periods are distributed according to the power-law function with the power-law index from −1.3 to −1.6. The power-law distribution with the similar power-law index was also found in the 0.025-0.1 s period interval in DPS from the 12 July 2000 flare, observed with the very high time resolution (80 µs) by the 1352-1490 MHz Torun Radiospectrograph (Dabrowski, Karlický, and Rudawy, 2015).…”

High resolution observations with Artemis-IV and the NRH

“…If such drifts are interpreted in terms of exciter motion, the local scale height has to be less than predicted by quiet-Sun models. Indeed, this is expected to be the case within disturbed structures such as interacting plasmoids, as proposed by Dabrowski et al (2015), where density gradients are higher.…”

New Eyes Looking at Solar Activity: Challenges for Theory and Simulations – Placing It into Context

“…The Torun radio spectrograph data, with a high time-resolution of 80 microseconds, were used to study the time evolution of power spectra and Fourier spectral indices in selected short radio bursts (Dabrowski, Karlický, and Rudawy, 2015). The results suggest that dmspikes and drifting pulsation structure (DPS) events are physically similar and that both are signatures of cascades of interacting plasmoids of different sizes.…”

“…The observations were obtained by the Badary Broadband Microwave Spectropolarimeter (BBMS) and compared with the SSRT interferometer data. The fine-structures of radio bursts observed by the Solar Broadband Radio Spectrometer (SBRS) at Huairou and the IZMIRAN spectrograph were studied in detail by Chernov et al (2015). These observations help in testing the different theoretical models of fine-structure formation, as, for example, several mechanisms have been proposed for just the generation of zebra structures.…”