Solar radio blips and X-ray kernels

A detailed comparison is made between hard X-ray spikes and decimetric type III radio bursts for a relatively weak solar flare on 1981 August 6 at 10 : 32 UT. The hard X-ray observations were made at energies above 30 keV with the Hard X-Ray Burst Spectrometer on the Solar Maximum Mission and with a balloon-born coarse-imaging spectrometer from Frascati, Italy. The radio data were obtained in the frequency range from 100 to 1000 MHz with the analog and digital instruments from Ztirich, Switzerland. All the data sets have a time resolution of ~0.1 s or better. The dynamic radio spectrum shows many fast drift type III radio bursts with both normal and reverse slope, while the X-ray time profile contains many well resolved short spikes with durations of < 1 s. Some of the X-ray spikes appear to be associated in time with reverse-slope bursts suggesting either that the electron beams producing the radio bursts contain two or three orders of magnitude more fast electrons than has previously been assumed or that the electron beams can trigger or occur in coincidence with the acceleration of additional electrons. One case is presented in which a normal slope radio burst at ~ 600 MHz occurs in coincidence with the peak of an X-ray spike to within 0.1 s. If the coincidence is not merely accidental and if it is meaningful to compare peak times, then the short delay would indicate that the radio signal was at the harmonic and that the electrons producing the radio burst were accelerated at an altitude of ~ 4 x 10 9 cm. Such a short delay is inconsistent with models invoking cross-field drifts to produce the electron beams that generate type III bursts but it supports the model incorporating a MASER proposed by Sprangle and Vlahos (1983).

Section: Instrumentationmentioning

confidence: 99%

Section: The Radio Datamentioning

confidence: 99%

Decimetric type III radio bursts and associated hard X-ray spikes

Dennis

Benz

Ranieri³

et al. 1984

“…Type III bursts at metric wavelengths were discovered and analyzed at first by a number of researchers (Alvarez and Haddock, 1973;Benz et al, 1981;Benz, Jaeggi, and, Zlobec, 1982;Fu et al, 2004). In recent years, the observational characteristics of the type III bursts at different wavelengths, such as the frequency drift, time scale, frequency bandwidth and polarization, etc., have been understood in detail since radio telescopes with high sensitivity, high temporal resolution, and high spectral resolution were used for observations.…”

Section: Introductionmentioning

confidence: 98%

Statistical Analysis of Decimetric Type III Bursts

Xie

Wang

2006

Detailed statistics and analysis of 264 type III bursts observed with the 625-1500 MHz spectrograph during the 23rd solar cycle (from July 2000 to April 2003) are carried out in the present article. The main statistical results are similar to those of microwave type III bursts presented in the literature cited, such as the correlation between type III bursts and flares, polarization, duration, frequency drift rate (normal and reverse slopes), distribution of type III bursts and frequency bandwidth. At the same time, the statistical results also point out that the average values of the frequency drift rates and degrees of polarization increase with the increase in frequency and the average value of duration decreases with the increase in frequency. Other statistical results show that the starting frequencies of the type III bursts are mainly within the range from 650 to 800 MHz, and most type III bursts have an average bandwidth of 289 MHz. The distributions imply that the electron acceleration and the place of energy release are within a limited decimetric range. The characteristics of the narrow bandwidth possibly involve the magnetic configuration at decimetric wavelengths, the location of electron acceleration in the magnetic field nearto the main flare, the relevant runaway or trapped electrons, or the coherent radio emission produced by some secondary shock waves. In addition, the number of type III bursts with positive frequency drift rates is almost equal to that with negative frequency drift rates. This is probably explained by the hypothesis that an equal number of electron beams are accelerated upwards and downwards within the range of 625 to 1500 MHz. The radiation mechanism of type III bursts at decimetric wavelengths probably includes these microwave and metric mechanisms and the most likely cause of the coherent plasma radiation are the emission processes of the electron cyclotron maser.

“…Two peaks in the early main flare phase are indicated with a little red x, the main peak with a capital X. Also shown are nanoflares in quiet regions (Krucker and Benz, 2000), microflares in active regions (Benz et al, 1981;Fürst, Benz, and Hirth, 1982;Gary, Hartl, and Shimizu, 1997), impulsive and gradual flares (Benz and Güdel, 1994), quiescent BY Dra, dMe, and dKe stars , and a long-duration flare on the dMe star EQ Peg (Kundu et al, 1988). The dashed line presents the relation given in Equation 1.…”

Section: Preflares X X Xmentioning

confidence: 99%

Observations of a Radio-Quiet Solar Preflare

Benz¹,

Battaglia²,

Güdel³

2017

The preflare phase of the flare SOL2011-08-09T03:52 is unique in its long duration, its coverage by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the Nobeyama Radioheliograph, and the presence of three well-developed soft X-ray (SXR) peaks. No hard X-rays (HXR) are observed in the preflare phase. Here we report that also no associated radio emission at 17 GHz was found despite the higher sensitivity of the radio instrument. The ratio between the SXR peaks and the upper limit of the radio peaks is larger by more than one order of magnitude compared to regular flares. The result suggests that the ratio between acceleration and heating in the preflare phase was different than in regular flares. Acceleration to relativistic energies, if any, occurred with lower efficiency.