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Fourier Power Spectra of Solar Noise Storms


We analyzed three noise storms recorded on 200 – 400 MHz Trieste Callisto radio spectra on 2 July 2012, 8 July 2012, and 16 July 2012 by the Fourier method. We divided intervals of the noise storms into five-minute intervals, and in these intervals we computed the mean Fourier spectra as a function of the wave numbers in the frequency and height-scale spaces. We found that these Fourier spectra, where the spectrum from the quiet-activity interval was subtracted, are power-law spectra. The mean power-law index of these spectra in the range \(\ln(k_{z}) = [1.8, 2.9]\) (where \(k_{z}\) is the wave number in the height-scale space) is \(-1.7\pm0.14\), \(-1.6\pm0.14\), and \(-1.5 \pm0.12\) for the 2 July 2012, the 8 July 2012, and the 16 July 2012 noise storms, respectively. It appears that as the number of Type-I bursts in the studied interval increases, the power-law index becomes closer to \(-5/3\); this is known as the Kolmogorov spectral index. The power-law index of the noise storms is very similar to that of the narrowband dm-spikes found in our previous studies. Furthermore, we found a break in the power spectra at \(\ln(k_{z}) \approx2.9\), and the mean power-law index values above this break are \(-2.9\pm0.46\), \(-3.1\pm0.65\), and \(-3.4\pm0.98\), respectively.

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This research was supported by Grants 16-13277S and 17-16447S of the Grant Agency of the Czech Republic. This work was supported by the Science Grant Agency project VEGA 2/0004/16 (Slovakia). Help of the Bilateral Mobility Projects SAV-16-03 and SAV-18-01 of the SAS and CAS is acknowledged. This article was created in the project ITMS No. 26220120029, based on the supporting operational Research and development program financed from the European Regional Development Fund. The authors are indebted to the Institute for Particle Physics and Astrophysics, ETH Zurich and FHNW Brugg/Windisch (Switzerland) as well as to the Astronomical Observatory of Trieste (OAT/INAF, host: A. Marassi) in Trieste (Italy) and the Crimean Astrophysical Observatory (CrAO, host: Yu.F. Yurovsky) in Nauchnyi (Crimea, Ukraine) for the Callisto data. This research has made use of NASA’s Astrophysics Data System.

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Correspondence to Ján Rybák.

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Karlický, M., Rybák, J. & Monstein, C. Fourier Power Spectra of Solar Noise Storms. Sol Phys 293, 143 (2018).

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  • Sun: activity
  • Sun: radio radiation