Fine Structure of Solar Radio Bursts

Chernov, G. P.

doi:10.1007/978-3-642-20015-1

Cited by 68 publications

(63 citation statements)

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“…5, the drifting emission feature shows narrow-band spikes or zebra pattern structures above about 340 MHz (upper panel) and time-extended fibre bursts with negative frequency drift below 360 MHz. Chernov (2011) gives a detailed review of fine structures in solar radio bursts. All spectral features of the slowly drifting lane of dm-m wave emission that accompanied the second relativistic proton release were typical of a burst of Type IV, also called a flare continuum.…”

Section: Relativistic Proton Release and Electromagnetic Emissionsmentioning

confidence: 99%

The relativistic solar particle event of 2005 January 20: origin of delayed particle acceleration

Klein

Masson

Bouratzis

et al. 2014

A&A

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Context. The highest energies of solar energetic nucleons detected in space or through gamma-ray emission in the solar atmosphere are in the GeV range. Where and how the particles are accelerated is still controversial. Aims. We search for observational information on the location and nature of the acceleration region(s) by comparing the timing of relativistic protons detected on Earth and radiative signatures in the solar atmosphere during the particularly well-observed 2005 Jan. 20 event.Methods. This investigation focusses on the post-impulsive flare phase, where a second peak was observed in the relativistic proton time profile by neutron monitors. This time profile is compared in detail with UV imaging and radio spectrography over a broad frequency band from the low corona to interplanetary space. Results. It is shown that the late relativistic proton release to interplanetary space was accompanied by a distinct new episode of energy release and electron acceleration in the corona traced by the radio emission and by brightenings of UV kernels. These signatures are interpreted in terms of magnetic restructuring in the corona after the coronal mass ejection passage. Conclusions. We attribute the delayed relativistic proton acceleration to magnetic reconnection and possibly to turbulence in largescale coronal loops. While Type II radio emission was observed in the high corona, no evidence of a temporal relationship with the relativistic proton acceleration was found.

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Section: Relativistic Proton Release and Electromagnetic Emissionsmentioning

confidence: 99%

The relativistic solar particle event of 2005 January 20: origin of delayed particle acceleration

Klein

Masson

Bouratzis

et al. 2014

A&A

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“…Spikes drifting toward lower frequencies (negative drift rate) are considered signatures of an outwardly moving exciter and are called direct (d). Spikes with positive drift are named reverse (r), while those without measurable drift rate are called stable (s) (see Chernov 2011). Spikes may appearing isolated, in loose clusters, or organized chains.…”

Section: Introductionmentioning

confidence: 99%

High resolution observations with Artemis-IV and the NRH

Bouratzis

Hillaris

Alissandrakis

et al. 2016

A&A

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Context. Narrow-band bursts appear on dynamic spectra from microwave to decametric frequencies as fine structures with very small duration and bandwidth. They are believed to be manifestations of small scale energy release through magnetic reconnection. Aims. We analyzed 27 metric type IV events with embedded narrow-band bursts, which were observed by the ARTEMIS-IV radio spectrograph from 30 June 1999 to 1 August 2010. We examined the morphological characteristics of isolated narrow-band structures (mostly spikes) and groups or chains of structures. Methods. The events were recorded with the SAO high resolution (10 ms cadence) receiver of ARTEMIS-IV in the 270-450 MHz range. We measured the duration, spectral width, and frequency drift of ∼12 000 individual narrow-band bursts, groups, and chains. Spike sources were imaged with the Nançay radioheliograph (NRH) for the event of 21 April 2003. Results. The mean duration of individual bursts at fixed frequency was ∼100 ms, while the instantaneous relative bandwidth was ∼2%. Some bursts had measurable frequency drift, either positive or negative. Quite often spikes appeared in chains, which were closely spaced in time (column chains) or in frequency (row chains). Column chains had frequency drifts similar to type-IIId bursts, while most of the row chains exhibited negative frequently drifts with a rate close to that of fiber bursts. From the analysis of NRH data, we found that spikes were superimposed on a larger, slowly varying, background component. They were polarized in the same sense as the background source, with a slightly higher degree of polarization of ∼65%, and their size was about 60% of their size in total intensity. Conclusions. The duration and bandwidth distributions did not show any clear separation in groups. Some chains tended to assume the form of zebra, lace stripes, fiber bursts, or bursts of the type-III family, suggesting that such bursts might be resolved in spikes when viewed with high resolution. The NRH data indicate that the spikes are not fluctuations of the background, but represent additional emission such as what would be expected from small-scale reconnection.

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“…Moreover, it is still debated whether all zebras are of the same physical origin or if zebras are generated by several different mechanisms (Tan et al 2014). For a review and comparison of zebra models, see Chernov (2011).…”

Section: Introductionmentioning

confidence: 99%

Determination of plasma parameters in solar zebra radio sources

Karlický

Yasnov

2015

A&A

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Aims. We present a new method for determining the magnetic field strength and plasma density in the solar zebra radio sources. Methods. Using the double plasma resonance (DPR) model of the zebra emission, we analytically derived the equations for computing the gyroharmonic number s of selected zebra lines and then solved these equations numerically. Results. The method was successfully tested on artificially generated zebras and then applied to observed ones. The magnetic field strength and plasma density in the radio sources were determined. Simultaneously, we evaluated the parameterwhere L n and L b are the characteristic scale-heights of the plasma density and magnetic field strength in the zebra source, respectively. Computations show that the maximum frequency of the low-polarized zebras is about 8 GHz, in very good agreement with observations. For the high-polarized zebras, this limit is about four times lower. Microwave zebras are preferentially generated in the regions with steep gradients of the plasma density, such as in the transition region. In models with smaller density gradients, such as those with a barometric density profile, the microwave zebras cannot be produced owing to the strong bremsstrahlung and cyclotron absorptions. We also show that our DPR model is able to explain the zebras with frequency-equidistant zebra lines.

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Fine Structure of Solar Radio Bursts

Cited by 68 publications

References 0 publications

The relativistic solar particle event of 2005 January 20: origin of delayed particle acceleration

The relativistic solar particle event of 2005 January 20: origin of delayed particle acceleration

High resolution observations with Artemis-IV and the NRH

Determination of plasma parameters in solar zebra radio sources

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