Hyperbolic trajectory parametrization for spectral line broadening calculations

Poquérusse, A.; Alexiou, S.; Klodzh, E.

doi:10.1016/0022-4073(96)00022-2

Cited by 10 publications

(8 citation statements)

References 11 publications

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“…At different frequencies, the decay time has been found to be proportional to the duration of type III bursts, using the full-width, half-maximum of the flux profile. Later, Poquerusse (1977) found the same relation at a single frequency, around 169 MHz, insinuating that both quantities are linked to the electron beam dynamics at this frequency rather than the decay constant being linked to the ambient plasma, as previous expected. Whether this result holds true at lower frequencies, when the time profile is more asymmetrical, has not be researched.…”

Section: Introductionsupporting

confidence: 66%

“…The characteristic exponential decay time that was found from fits to radio bursts increases as a function of decreasing frequency (e.g. Aubier & Boischot 1972;Evans et al 1973;Alvarez & Haddock 1973a;Poquerusse 1977). This increase can be fit with a power-law over a wide range of frequencies (Alvarez & Haddock 1973a) finding a spectral index close to one.…”

Section: Introductionmentioning

confidence: 93%

“…The time profile of type III radio bursts has been studied by numerous authors (e.g. Hughes & Harkness 1963;Aubier & Boischot 1972;Evans et al 1973;Alvarez & Haddock 1973a;Poquerusse 1977;McLean & Labrum 1985;Tsybko 1989;Melnik et al 2011) to investigate electron beam and background plasma parameters. At a given frequency, it was suggested early on (see Aubier & Boischot 1972, for a complete explanation) that the type III burst could be made up of an exciter function followed by an exponential decay, as there is an observed asymmetry in the type III light-curve.…”

Section: Introductionmentioning

confidence: 99%

“…This has not been adequately researched in the literature. Poquerusse (1977) approximated the rise time at 169 MHz using the slope of the linear rise, finding it to scale with the slope of the decay, albeit with asymmetry.…”

Section: Introductionmentioning

confidence: 99%

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Solar type III radio burst time characteristics at LOFAR frequencies and the implications for electron beam transport

Reid

Kontar

2018

A&A

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Context. Solar type III radio bursts contain a wealth of information about the dynamics of electron beams in the solar corona and the inner heliosphere; currently unobtainable through other means. However, the motion of different regions of an electron beam (front, middle and back) have never been systematically analysed before. Aims. We characterise the type III burst frequency-time evolution using the enhanced resolution of LOFAR in the frequency range 30-70 MHz and use this to probe electron beam dynamics. Methods. The rise, peak and decay times with a ∼ 0.2 MHz spectral resolution were defined for a collection of 31 type III bursts. The frequency evolution is used to ascertain the apparent velocities of the front, middle and back of the type III sources and the trends are interpreted using theoretical and numerical treatments. Results. The type III time profile was better approximated by an asymmetric Gaussian profile, not an exponential as previously used. Rise and decay times increased with decreasing frequency and showed a strong correlation. Durations were smaller than previously observed. Drift rates from the rise times were faster than from the decay times, corresponding to inferred mean electron beam speeds for the front, middle and back of 0.2, 0.17, 0, 15 c, respectively. Faster beam speeds correlate with smaller type III durations. We also find type III frequency bandwidth decreases as frequency decreases. Conclusions. The different speeds naturally explain the elongation of an electron beam in space as it propagates through the heliosphere. The rate of expansion is proportional to the mean speed of the exciter; faster beams expand faster. Beam speeds are attributed to varying ensembles of electron energies at the front, middle and back of the beam.

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Section: Introductionsupporting

confidence: 66%

Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Solar type III radio burst time characteristics at LOFAR frequencies and the implications for electron beam transport

Reid

Kontar

2018

A&A

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“…Time profiles of type III bursts have been studied by various authors (Aubier & Boischot 1972;Alvarez & Haddock 1973;Evans et al 1973;Barrow & Achong 1975;Poquerusse 1977;Reid & Kontar 2018). They are characterized by an asymmetric profile, with a sharp rise and a slower, typically exponential, decay; the asymmetry becomes larger as the exponential decay time becomes larger.…”

Section: Introductionmentioning

confidence: 99%

A Fokker–Planck Framework for Studying the Diffusion of Radio Burst Waves in the Solar Corona

Bian

Emslie

Kontar

2019

ApJ

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Electromagnetic wave scattering off density inhomogeneities in the solar corona is an important process which determines both the apparent source size and the time profile of radio bursts observed at 1 AU. Here we model the scattering process using a Fokker-Planck equation and apply this formalism to several regimes of interest. In the first regime the density fluctuations are considered quasi-static and diffusion in wavevector space is dominated by angular diffusion on the surface of a constant energy sphere. In the small-angle ("pencil beam") approximation, this diffusion further occurs over a small solid angle in wavevector space. The second regime corresponds to a much later time, by which scattering has rendered the photon distribution near-isotropic resulting in a spatial diffusion of the radiation. The third regime involves time-dependent fluctuations and, therefore, Fermi acceleration of photons. Combined, these results provide a comprehensive theoretical framework within which to understand several important features of propagation of radio burst waves in the solar corona: emitted photons are accelerated in a relatively small inner region and then diffuse outwards to larger distances. En route, angular diffusion results both in source sizes which are substantially larger than the intrinsic source, and in observed intensity-versus-time profiles that are asymmetric, with a sharp rise and an exponential decay. Both of these features are consistent with observations of solar radio bursts.

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X-ray laser line narrowing: new developments

Alexiou¹

2001

Journal of Quantitative Spectroscopy and Radiative Transfer

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Hyperbolic trajectory parametrization for spectral line broadening calculations

Cited by 10 publications

References 11 publications

Solar type III radio burst time characteristics at LOFAR frequencies and the implications for electron beam transport

Solar type III radio burst time characteristics at LOFAR frequencies and the implications for electron beam transport

A Fokker–Planck Framework for Studying the Diffusion of Radio Burst Waves in the Solar Corona

X-ray laser line narrowing: new developments

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