Large-scale simulations of solar type III radio bursts: flux density, drift rate, duration, and bandwidth

Ratcliffe, Heather; Kontar, Eduard P.; Reid, Hamish

doi:10.1051/0004-6361/201423731

Cited by 63 publications

(51 citation statements)

References 61 publications

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“…Note that our simulation assumes instantaneous injection of the electron beam, whereas, in the corona, the electron acceleration time is finite and the beam will propagate out of the region of initial generation. The acceleration time also affects the actual duration of the bursts (28,29). The overall scenario is that coronal bursts produce nonthermal electrons that escape into space and produce interplanetary bursts (3) with accompanying waves.…”

Section: Discussionmentioning

confidence: 99%

How electron two-stream instability drives cyclic Langmuir collapse and continuous coherent emission

Che

Goldstein

Diamond

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Continuous plasma coherent emission is maintained by repetitive Langmuir collapse driven by the nonlinear evolution of a strong electron two-stream instability. The Langmuir waves are modulated by solitary waves in the linear stage and electrostatic whistler waves in the nonlinear stage. Modulational instability leads to Langmuir collapse and electron heating that fills in cavitons. The high pressure is released via excitation of a shortwavelength ion acoustic mode that is damped by electrons and reexcites small-scale Langmuir waves; this process closes a feedback loop that maintains the continuous coherent emission.electron beams | nonlinear wave interaction | Langmuir collapse | coherent emission | plasma turbulence E lectron beams accelerated by solar flares and nanoflares are believed to be responsible for several types of solar radio bursts observed in the corona and interplanetary medium, including flare-associated coronal type U and J and interplanetary type III radio bursts, and nanoflare-associated weak coronal type III bursts (1-4). In 1958, Ginzburg and Zhelezniakov first proposed a basic framework for such bursts, which was subsequently refined by others (refs. 5 and 6 and references therein). In essence, the scenario is one in which the electron two-stream instability (ETSI), driven by electron beams, generates Langmuir waves that are converted into plasma coherent emission via nonlinear three-wave coupling [e.g., two Langmuir waves and one ion acoustic wave (IAW)]. However, the mechanism whereby the nonlinear ETSI produces coherent emission with a duration of several orders of magnitude longer than the linear saturation time is not well understood (6-9). Nonlinear evolution of ETSI is a fundamental problem in nonlinear wave theory in which disparate three-wave couplings dominate the energy transport and dissipation (10). It has broad applications in plasma physics, planetary physics, and astrophysics, such as terahertz emission in laser beam experiments, radio bursts from Jupiter, pulsars, and the formation of exotic astrophysical objects.In the classical Kolmogorov turbulence scenario, the balance between energy input and its final absorption is controlled by a nonlinear cascade from large spatial scales (the region of external forcing) to viscosity-dominated short wavelengths. In plasmas, the source of instability is often beams of charged particles that generate Langmuir waves. At shorter wavelengths, the natural candidate to provide the sink of wave energy is Landau damping. However, nonlinear disparate wave interactions, it follows from direct calculation of basic three-wave coupling, can only lead to inverse cascades (to longer wavelengths) through modulational instability (11), and away from the Landau damping region of the spectrum. The eventual nonlinear process capable of overriding this inverse cascade was suggested by Zakharov, namely Langmuir collapse (LC), which is analogous to a selffocusing of the Langmuir waves packets, or cavitons (12, 13). LC has been discovered in both experimen...

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Section: Discussionmentioning

confidence: 99%

How electron two-stream instability drives cyclic Langmuir collapse and continuous coherent emission

Che

Goldstein

Diamond

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…wave mode conversion from Langmuir waves to ion acoustic and electromagnetic waves (Robinson 1992;Robinson et al 1994;Li et al 2012;Ratcliffe et al 2014).…”

Section: Discussionmentioning

confidence: 99%

Low frequency radio observations of bi-directional electron beams in the solar corona

Carley

Reid

Vilmer

et al. 2015

A&A

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The radio signature of a shock travelling through the solar corona is known as a type II solar radio burst. In rare cases these bursts can exhibit a fine structure known as "herringbones", which are a direct indicator of particle acceleration occurring at the shock front. However, few studies have been performed on herringbones and the details of the underlying particle acceleration processes are unknown. Here, we use an image processing technique known as the Hough transform to statistically analyse the herringbone fine structure in a radio burst at ∼20-90 MHz observed from the Rosse Solar-Terrestrial Observatory on 2011 September 22. We identify 188 individual bursts which are signatures of bi-directional electron beams continuously accelerated to speeds of 0.16−0.10 c. This occurs at a shock acceleration site initially at a constant altitude of ∼0.6 R in the corona, followed by a shift to ∼0.5 R . The anti-sunward beams travel a distance of 170 +174 −97 Mm (and possibly further) away from the acceleration site, while those travelling toward the Sun come to a stop sooner, reaching a smaller distance of 112 +84 −76 Mm. We show that the stopping distance for the sunward beams may depend on the total number density and the velocity of the beam. Our study concludes that a detailed statistical analysis of herringbone fine structure can provide information on the physical properties of the corona which lead to these relatively rare radio bursts.

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“…Non-linear wave-wave interaction then converts some of the energy contained in the Langmuir waves A&A 597, A77 (2017) into electromagnetic emission near the local plasma frequency or at its harmonic (e.g. Melrose 1980;Li & Cairns 2014;Ratcliffe et al 2014), producing radio emission that drifts from high to low frequencies as the electrons propagate through the corona and into interplanetary space. In recent years, several numerical simulations have been performed to simulate the radio coronal type III emissions from energetic electrons and investigate the effects of beam and coronal parameters on the emission (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…In recent years, several numerical simulations have been performed to simulate the radio coronal type III emissions from energetic electrons and investigate the effects of beam and coronal parameters on the emission (e.g. Li et al 2008bLi et al , 2009Li et al , 2011Tsiklauri 2011;Li & Cairns 2014;Ratcliffe et al 2014) Since the discovery of type III bursts and the advent of continuous and regular HXR observations, many studies have analysed the relationship between type III bursts and hard X-ray emissions. The first studies of the temporal correlations between metric (coronal) type III bursts and HXRs above 10 keV were achieved by Kane (1972Kane ( , 1981.…”

Section: Introductionmentioning

confidence: 99%

Coronal type III radio bursts and their X-ray flare and interplanetary type III counterparts

Reid

Vilmer

2017

A&A

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Context. Type III bursts and hard X-rays are both produced by flare energetic electron beams. The link between both emissions has been investigated in many previous studies, but no statistical studies have compared both coronal and interplanetary type III bursts with X-ray flares. Aims. Using events where the coronal radio emission above 100 MHz is exclusively from type III bursts, we revisited some longstanding questions regarding the relation between type III bursts and X-ray flares: Do all coronal type III bursts have X-ray counterparts? What correlation, if any, occurs between radio and X-ray intensities? What X-ray and radio signatures above 100 MHz occur in connection with interplanetary type III bursts below 14 MHz? Methods. We analysed ten years of data from 2002 to 2011 starting with a selection of coronal type III bursts above 100 MHz. We used X-ray flare information from RHESSI >6 keV to make a list of 321 events that have associated type III bursts and X-ray flares, encompassing at least 28% of the initial sample of type III events. We then examined the timings, intensities, associated GOES class, and whether there was an associated interplanetary radio signature in both radio and X-rays. Results. For our 321 events with radio and X-ray signatures, the X-ray emission at 6 keV usually lasted much longer than the groups of type III bursts at frequencies >100 MHz. The selected events were mostly associated with GOES B and C class flares. A weak correlation was found between the type III radio flux at frequencies below 327 MHz and the X-ray intensity at 25-50 keV, with an absence of events at high X-ray intensity and low type III radio flux. The weakness of the correlation is related to the coherent emission mechanism of radio type IIIs which can produce high radio fluxes by low density electron beams. Interplanetary type III bursts (<4 MHz) were observed for 54% of the events. The percentage of association increased when events were observed with 25-50 keV X-rays. A stronger interplanetary association was present when 25-50 keV RHESSI count rates were above 250 counts/s or radio fluxes of around 170 MHz were large (>10 3 SFU), relating to electron beams with more energetic electrons above 25 keV and events where magnetic flux tubes extend into the high corona. We also find that whilst on average type III bursts increase in flux with decreasing frequency, the rate of this increase varies from event to event.

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Large-scale simulations of solar type III radio bursts: flux density, drift rate, duration, and bandwidth

Cited by 63 publications

References 61 publications

How electron two-stream instability drives cyclic Langmuir collapse and continuous coherent emission

How electron two-stream instability drives cyclic Langmuir collapse and continuous coherent emission

Low frequency radio observations of bi-directional electron beams in the solar corona

Coronal type III radio bursts and their X-ray flare and interplanetary type III counterparts

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