Type Iii Radio Bursts Perturbed by Weak Coronal Shocks

Li, B.; Cairns, Iver H.

doi:10.1088/0004-637x/753/2/124

Cited by 13 publications

(18 citation statements)

References 80 publications

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“…Most of this block of emission has an intensity larger than 10 −18 W m −2 Hz −1 . These blocks of type III emission hide the probable type II burst related to the first CME in this time interval, as it is possible that these type III bursts are intensifying upstream and downstream of the CME shock, as predicted theoretically [ Li and Cairns , ] and sometimes inferred observationally [ Lacombe and Moller Pedersen , ].…”

Section: Observationssupporting

confidence: 54%

“…Thus, we do not make a stronger claim than that the fundamental type II emission predicted is not inconsistent with the available observations. One reason for the intensification of type III bursts in the observed domains of 1/ f ‐ t space may be the presence of the CME‐driven shock: theory [ Li and Cairns , ] and previous observations [ Lacombe and Moller Pedersen , ; MacDowall , ] show that type IIIs intensify at frequencies corresponding to locations upstream and downstream of the shock, thereby occurring at similar frequencies.…”

Section: Simulation Resultsmentioning

confidence: 98%

“…We see that the island structures and intensities of the predicted interplanetary burst are not inconsistent with the observations. There is clearly strong interference from type III emissions that are intensified near the predicted type II emission [e.g., Lacombe and Moller Pedersen , ; MacDowall , ; Li and Cairns , ]. The predicted fundamental type II emission forms a straight line in 1/ f ‐ t space that lies in the middle of the observed band formed by intensifications of type III bursts.…”

Section: Simulation Resultsmentioning

confidence: 99%

“…Our simulations predict interplanetary (kilometric) extensions of the coronal (hectometric) radio bursts with island structures and intensities not inconsistent with the observations. The first 250 min of the first type II radio burst and the interplanetary bursts are obscured by type III radio emission in the observations, which can intensify in the vicinity of the shock front [ Lacombe and Moller Pedersen , ; MacDowall , ; Li and Cairns , ]. We cannot address the origin of these type III disturbances or their radio emission with our simulations, which have a different mechanism for formation of electron beams that is not included in our theory and simulations for type II bursts.…”

Section: Discussionmentioning

confidence: 98%

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The solar type II radio bursts of 7 March 2012: Detailed simulation analyses

2014

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Type II solar radio bursts are often indicators for impending space weather events at Earth.They are consequences of shock waves driven by coronal mass ejections (CMEs) that move outward from the Sun. We simulate such type II radio bursts by combining elaborate three-dimensional (3-D) magnetohydrodynamic (MHD) predictions of realistic CMEs near the Sun with an analytic kinetic radiation theory developed recently. The simulation approach includes the reconstruction of initial solar magnetic fields, the dimensioning of the initial flux rope of the CME with STEREO spacecraft data, and the launch of the CME into an empirical data-driven corona and solar wind. In this paper, we simulate a complicated double CME event (a very fast CME followed by a slower CME without interaction) and the related coronal and interplanetary type II radio bursts that occurred on 7 March 2012. We extend our previous work to show harmonic and interplanetary emission as well as the simulation's surprising ability (for these events at least) for predicting emission for two closely spaced CMEs leaving the same active region. We demonstrate that the theory predicts well the observed fundamental and harmonic emission from ∼20 MHz to 50 kHz or from the high corona to near 1 AU. Specifically, the theory predicts flux, frequency, and time variations that are consistent with the presence or absence of observed type II emissions when interfering emissions are absent and are not inconsistent with observations when interfering type III bursts are present. The predicted and observed type II emission is predominantly fundamental for these two events. Harmonic emission occurs for the second CME only for a short time interval, when an extended shock has developed that can drive flank emission. The coronal and interplanetary emission follow closely hyperbolic lines in frequency-time space, consisting of a succession of islands of emission with varying intensity. The islands develop due to competition between the shock moving through varying coronal and solar wind magnetic field structures (e.g., loops and streamers), growth of the driven radio source due to the spherical expansion of the shock, and movement of the active radio sources from the shock's nose to its flanks.

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Section: Observationssupporting

confidence: 54%

Section: Simulation Resultsmentioning

confidence: 98%

Section: Simulation Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 98%

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The solar type II radio bursts of 7 March 2012: Detailed simulation analyses

2014

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“…This event also had local harmonic radio emission, Langmuir waves, and accelerated electrons observed upstream of the shock crossing at STEREO A [Graham and Cairns, 2015]. Produced by electron beams accelerated in solar flares, type IIIs can intensify as the beams cross the shock [Lacombe and Moller Pedersen, 1971;MacDowall, 1989;Li and Cairns, 2012], based on radio telescope triangulation measurements and theory. Interference from type III bursts, the almost vertical frequency-time signals in Figure 1, is apparent.…”

Section: Radio Theory and Observationsmentioning

confidence: 99%

Quantitative prediction of type II solar radio emission from the Sun to 1 AU

Schmidt

Cairns

2016

Geophysical Research Letters

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Coronal mass ejections (CMEs) are frequently associated with shocks and type II solar radio bursts. Despite involving fundamental plasma physics and being the archetype for collective radio emission from shocks, type II bursts have resisted detailed explanation for over 60 years. Between 29 November and 1 December 2013 the two widely separated spacecraft STEREO A and B observed a long lasting, intermittent, type II radio burst from ≈4 MHz to 30 kHz (harmonic), including an intensification when the CME‐driven shock reached STEREO A. We demonstrate the first accurate and quantitative simulation of a type II burst from the high corona (near 11 solar radii) to 1 AU for this event with a combination of a data‐driven three‐dimensional magnetohydrodynamic simulation for the CME and plasma background and an analytic quantitative kinetic model for the radio emission.

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Type III bursts produced by power law injected electrons in Maxwellian background coronal plasmas

Cairns

2013

JGR Space Physics

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[1] Simulations are presented for coronal type III bursts produced by injection of energetic electrons with power law speed spectra onto open magnetic field lines embedded in an otherwise unmagnetized Maxwellian background coronal plasma, including quasi-linear wave-particle interactions and nonlinear wave-wave processes. The simulations show that although fast electrons with speeds > 0.3c are injected, they are important only to the onset and not to the peak of f p emission, where f p is the local electron plasma frequency. Instead, slower beam electrons are the major drivers of the peak f p emission. Therefore, the type III beam speeds derived from the drift rates of peak f p emission are less than the typical speeds of c/3 observed for coronal type III bursts. This occurs mainly because the number of fast beam electrons with speeds > 0.3c is much less than the slower ones, causing weaker f p emission from these fast beam electrons. Comparisons are made with injected electrons having Maxwellian spectra. We find that type III beams are faster when the injection has power law spectra, since there are more fast electrons injected than for Maxwellian spectra. These results suggest that type III beams produced in the corona with Maxwellian background particle distributions and either power law or Maxwellian spectra can account only for the lower half of the observed range 0.1-0.6c of type III beam speeds but not for the upper half.Citation: Li, B., and I. H. Cairns (2013), Type III bursts produced by power law injected electrons in Maxwellian background coronal plasmas,

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Type Iii Radio Bursts Perturbed by Weak Coronal Shocks

Cited by 13 publications

References 80 publications

The solar type II radio bursts of 7 March 2012: Detailed simulation analyses

The solar type II radio bursts of 7 March 2012: Detailed simulation analyses

Quantitative prediction of type II solar radio emission from the Sun to 1 AU

Type III bursts produced by power law injected electrons in Maxwellian background coronal plasmas

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