Millisecond Radio Spikes in the Decimetric Band

Abstract

We present the results of the analysis of thirteen events consisting of dm-spikes observed in Toruń between 15 March 2000 and 30 October 2001. The events were obtained with a very high time resolution (80 microseconds) radio spectrograph in the 1352 -1490 MHz range. These data were complemented with observations from the radio spectrograph at Ondřejov in the 0.8 -2.0 GHz band. We evaluated the basic characteristics of the individual spikes (duration, spectral width, and frequency drifts), as well as their groups and chains, the location of their emission sources, and the temporal correlations of the emissions with various phases of the associated solar flares. We found that the mean duration and spectral width of the radio spikes are equal to 0.036 s and 9.96 MHz, respectively. Distributions of the duration and spectral widths of the spikes have positive skewness for all investigated events. Each spike shows positive or negative frequency drift. The mean negative and positive drifts of the investigated spikes are equal to −776 MHz s −1 and 1608 MHz s −1 , respectively. The emission sources of the dm-spikes are located mainly at disk center. We have noticed two kinds of chains, with and without frequency drifts. The mean durations of the chains vary between 0.067 s and 0.509 s, while their spectral widths vary between 7.2 MHz and 17.25 MHz. The mean duration of an individual spike observed in a chain was equal to 0.03 s. While we found some agreement between the global characteristics of the groups of spikes recorded with the two instruments located in Toruń and Ondřejov, we did not find any one-to-one relation between individual spikes.

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.…”

The Storm of Decameter Spikes During the Event of 14 June 2012

“…At frequencies 0.8 -2 GHz, spikes with positive and negative drift rates were observed. The extreme values were equal to 1608 MHz s −1 and 776 MHz s −1 (Dabrowski, Rudawy, and Karlický, 2011), respectively; • the spike fluxes in most cases are not higher than 100 s.f.u. (where 1 s.f.u = 10 −22 W m −2 Hz −1 ) (Benz et al, 1992;Melnik et al, 2014).…”

“…• spikes are observed simultaneously with different types of radio bursts (Type II, III, IIIb, IV bursts); • spike durations decrease with the increase of the observational frequency, namely from one second at frequencies 12.5 -30 MHz (Ellis and McCulloch, 1967;Baselian et al, 1974;de La Noe, 1975;Sawant, Bhonsle, and Alurkar, 1976) to 400 -100 ms at frequencies 145 -345 MHz (McKim Malville, Aller, and Jensen, 1967;Markeev and Chernov, 1970;Bakunin and Chernov, 1985), 155 -36 ms at frequencies 0.3 -2 GHz (Droege, 1977;Guedel and Benz, 1990;Dabrowski, Rudawy, and Karlický, 2011) and less than 100 ms (instrumental resolution) at frequencies 6 -8 GHz (Benz et al, 1992); • spike bandwidths increase with the increase of the observational frequency, viz. from tens of kHz at frequencies 20 -100 MHz (Ellis and McCulloch, 1967;Warwick and Dulk, 1969;Baselian et al, 1974;de La Noe, 1975) to 1.5 -4 MHz at frequencies 100 -300 MHz (Elgaröy, 1967;Markeev and Chernov, 1970), 10 MHz at frequency 0.8 -2 GHz (Droege, 1977;Dabrowski, Rudawy, and Karlický, 2011), and even up to 100 MHz at frequency 6.4 -8.6 GHz (Benz et al, 1992); • spike frequency-drift rates vary within wide limits.…”

“…from tens of kHz at frequencies 20 -100 MHz (Ellis and McCulloch, 1967;Warwick and Dulk, 1969;Baselian et al, 1974;de La Noe, 1975) to 1.5 -4 MHz at frequencies 100 -300 MHz (Elgaröy, 1967;Markeev and Chernov, 1970), 10 MHz at frequency 0.8 -2 GHz (Droege, 1977;Dabrowski, Rudawy, and Karlický, 2011), and even up to 100 MHz at frequency 6.4 -8.6 GHz (Benz et al, 1992); • spike frequency-drift rates vary within wide limits. At frequencies lower than 100 MHz, the spikes drift rates are small (20 -150 kHz s −1 ) or practically zero (Ellis and McCulloch, 1967;Warwick and Dulk, 1969;Baselian et al, 1974;de La Noe, 1975).…”

Evolution of electron beam pulses of short duration in the solar corona

“…These are events with enhanced radio emission with durations of the order of tens of milliseconds [Vlasov et al (2002); Krucker et al (1997), Bouratzis et al (2015)], that surpass the solar radio emission of the quiet sun (Benz, 2009). The study of solar radio spikes has been of interest for some decades and has been considered to be important for understanding the physical processes occurring in the solar corona and their possible association to other large energy releasing events such as solar flares and coronal mass ejections [Chen et al (2015), Aschwanden and Guedel (1992), Dabrowski et al (2003), Tan et al (2012), Tan (2013), Dabrowski et al (2011)]. Recently, unusual radio bursts of millisecond durations were also observed to be associated with the solar flares (Oberoi et al, 2009).…”