Analysis of solar narrow band dm-spikes observed at 1420 and 2695 MHz

Abstract

Abstract. Using both linear and nonlinear methods, narrow band dm-spikes recorded at 1420 and 2695 MHz on June 6, 2000, July 8, 2000, July 12, 2000, July 20, 2000, and March 28, 2001 were analyzed. In particular their time profiles were studied statistically. The mean characteristic times of the ascending and of the decaying parts of their profiles are comparable, even if the dispersion of the values is very broad. For selected spikes at 1420 MHz a more precise fitting technique using exponential profiles was applied. While in the decaying part the exponential trend can be generally found, in the ascending part the exponential form can be confirmed only in few cases. The ascending and decaying phase of spikes presumably correspond to the source instability evolution and the plasma wave absorption. Furthermore, durations and polarization values of both 1420 and 2695 MHz spikes were determined and compared with the results in literature. All the analyzed spike events were located near the solar disk center. The polarization values and their trend in spike groups and the nearly constant duration suggest that the polarization originates at the source itself or near it. Selected time series of spikes were tested with respect to low-dimensional determinism and nonlinearity. We found that spikes recorded at fixed frequencies are not governed by a linear stochastic process, as the underlying physical system contains nonlinear signatures.

High Spectral Resolution Observation of Decimetric Radio Spikes Emitted by Solar Flares – First Results of the Phoenix-3 Spectrometer

“…Obviously, higher spectral resolution has not resulted in a power-law distribution. The distribution found here is in conflict mainly with the result published by Nita, Fleishman, and Gary (2008) and partially with Meszarosova et al (2000). The discrepancy may be attributed to the following reasons: − Nita, Fleishman, and Gary (2008) studied the distribution of peak flux density, contrary to the total flux distribution here.…”

High resolution observations with Artemis-IV and the NRH

“…In Fig. 6a we plot data from Table 1 of Dabrowski et al (2011), together with our results and those of Melnik et al (2011Melnik et al ( , 2014; the curve is a power law with α = 1.32, which is the average of the power reported by Guedel & Benz (1990;α = 1.34) and by Mészárosová et al (2003) and Rozhansky et al (2008;α = 1.29). This plot indicates a reasonable power law fit up to ∼2 GHz.…”

“…For a relative bandwidth of 2% (see previous section) and δt ∼ 0.005 s (half the SAO time resolution), this gives a value of ∼4 s −1 as an approximate upper limit to the measurable relative drift rate. (Guedel & Benz 1990;Mészárosová et al 2003;Rozhansky et al 2008). Panel b): instantaneous bandwidth versus frequency; the line is a plot of the empirical power law fit D f ∝ 0.66 f 0.42 by Csillaghy & Benz (1993).…”

Fourier Analysis of Radio Bursts Observed with Very High Time Resolution

“…They are characterized by very high brightness temperatures (T b ≈ 10 15 K) and short durations (≤ 0.1 s) (Benz, 1986). Their observational parameters have been described in several papers, e.g., in Mészárosová et al (2003). As shown by Karlický, Sobotka, and Jiřička (1996) and by Karlický, Jiřička, and Sobotka (2000), Fourier spectra of the spikes have a power-law form and show that there is no characteristic frequency bandwidth of the spikes.…”