Metric Radio Emission Associated with X‐Ray Plasmoid Ejections

Kundu, M. R.; Nindos, A.; Vilmer, Nicole; Klein, Karl‐Ludwig; Shibata, Kazunari; Ohyama, M.

doi:10.1086/322301

Cited by 31 publications

(33 citation statements)

References 17 publications

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“…Usually, they slowly drift toward lower frequencies and are composed of many fast-drifting narrowband type III-like bursts. Observational details of these DPS were described by e.g., Kundu et al (2001), Khan et al (2002), Karlický, Fárník, and Mészárosová (2002), Karlický et al (2005), and Benz, Battaglia, and Vilmer (2011). The first theoretical model of DPS was proposed by Kliem, Karlický, and Benz (2000).…”

Section: Introductionmentioning

confidence: 99%

Fourier Analysis of Radio Bursts Observed with Very High Time Resolution

2014

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Numerous solar radio bursts were observed in 2000 -2001 using the Toruń radio spectrograph with its unique time resolution of 80 microseconds. This high time resolution enables an in-depth analysis of the time evolution of the power spectra and Fourier spectral indices of selected short radio bursts. We analyze the power-spectrum parameters and variability for two millisecond radio dm-spike events and one drifting pulsation structure (DPS) event, for which the structures of the recorded signals were analyzed with an effective time resolution of 0.0008 s in five adjacent frequency bands of their radio spectra.We found that Fourier spectral indices varied rapidly when radio fine structures were recorded. Otherwise they remained close to zero, indicating the presence of noise. For the 10 -40 Hz frequency interval of the power spectra the mean values of the Fourier spectral indices varied up to −1.51 for the dm-spikes and up to −1.53 for the DPS event. Crosscorrelation coefficients of radio fluxes in adjacent frequency bands varied between 0.12 and 0.60 for dm-spikes and between 0.77 and 0.94 for the DPS event. The shortest fine structure found in the studied events lasted 0.001 s.These results are entirely new for dm-radio spikes and confirm a single previous result found for the DPS events. On the basis of our results, we propose that dm-spikes and DPS events are physically similar and that both are signatures of cascades of interacting plasmoids of different sizes.

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Section: Introductionmentioning

confidence: 99%

Fourier Analysis of Radio Bursts Observed with Very High Time Resolution

2014

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“…Type IIIs are amongst various types of radio bursts generated by energetic electrons that are accelerated during both flares and small scale eruptions in the form of plasma jets (Aurass et al 1994;Kundu et al 1995;Nitta et al 2006;Klassen et al 2012;Chen et al 2013b). Sites of energetic electrons (radio sources) are also known to be closely associated with larger scale eruptions such as plasmoids and sigmoids (Kundu et al 2001;Khan et al 2002;Marqué et al 2002). Such eruptive activity often shows the sites of energetic electrons to be located close to the underlying active region or moving with the erupting structure itself (Pick et al 2005;Bain et al 2014), originally observed as flare continua and moving type IV bursts (Robinson & Smerd 1975;Pick 1986).…”

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confidence: 99%

Radio Diagnostics of Electron Acceleration Sites During the Eruption of a Flux Rope in the Solar Corona

Carley

Vilmer

Gallagher

2016

ApJ

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Electron acceleration in the solar corona is often associated with flares and the eruption of twisted magnetic structures known as flux ropes. However, the locations and mechanisms of such particle acceleration during the flare and eruption are still subject to much investigation. Observing the exact sites of particle acceleration can help confirm how the flare and eruption are initiated and how they evolve. Here we use the Atmospheric Imaging Assembly to analyse a flare and erupting flux rope on 2014-April-18, while observations from the Nançay Radio Astronomy Facility allows us to diagnose the sites of electron acceleration during the eruption. Our analysis shows evidence for a pre-formed flux rope which slowly rises and becomes destabilised at the time of a C-class flare, plasma jet and the escape of 75 keV electrons from rope center into the corona. As the eruption proceeds, continued acceleration of electrons with energies of ∼5 keV occurs above the flux rope for a period over 5 minutes. At flare peak, one site of electron acceleration is located close to the flare site while another is driven by the erupting flux rope into the corona at speeds of up to 400 km s −1 . Energetic electrons then fill the erupting volume, eventually allowing the flux rope legs to be clearly imaged from radio sources at 150-445 MHz. Following the analysis of Joshi et al. (2015), we conclude that the sites of energetic electrons are consistent with flux rope eruption via a tether-cutting or flux cancellation scenario inside a magnetic fan-spine structure. In total, our radio observations allow us to better understand the evolution of a flux rope eruption and its associated electron acceleration sites, from eruption initiation to propagation into the corona.

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“…Similarly, Kundu et al (2001) identified two moving "Yohkoh" soft X-ray ejecta associated with moving decimetric/metric radio sources observed by the Nancay radioheliograph.…”

Section: High-frequency Slowly Drifting Pulsating Structures Mapping mentioning

confidence: 88%

Diagnostics of solar flare reconnection

Karlický

Bárta

2004

Nonlin. Processes Geophys.

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Abstract. We present new diagnostics of the solar flare reconnection, mainly based on the plasma radio emission. We propose that the high-frequency (600-2000 MHz) slowly drifting pulsating structures map the flare magnetic field reconnection. These structures correspond to the radio emission from plasmoids which are formed in the extended current sheet due to tearing and coalescence processes. An increase of the frequency drift of the drifting structures is interpreted as an increase of the reconnection rate. Using this model, time scales of slowly drifting pulsating structure observed during the 12 April 2001 flare by the Trieste radiopolarimeter with high time resolution (1 ms) are interpreted as a radio manifestation of electron beams accelerated in the multi-scale reconnection process. For short periods Fourier spectra of the observed structure have a power-law form with power-law indices in the 1.3-1.6 range. For comparison the 2-D MHD numerical modeling of the multi-scale reconnection is made and it is shown that Fourier spectrum of the reconnection dissipation power has also a power-law form, but with power-law index 2. Furthermore, we compute a time evolution of plasma parameters (density, magnetic field etc) in the 2-D MHD model of the reconnection. Then assuming a plasma radio emission from locations, where the "doubleresonance" instability generates the upper-hybrid waves due to unstable distribution function of suprathermal electrons, we model radio spectra. Effects of the MHD turbulence are included. The resulting spectra are compared with those observed. It is found, that depending on model parameters the lace bursts and the decimetric spikes can be reproduced. Thus, it is shown that the model can be used for diagnostics of the flare reconnection process. We also point out possible radio signatures of reconnection outflow termination shocks. They are detected as type II-like herringbone structures in the 200-700 MHz frequency range. Finally, we mention Hα spectra of the 18 September 1995 eruptive prominence which indicate the bi-directional plasma flow as expected in the reconnection process.

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Metric Radio Emission Associated with X‐Ray Plasmoid Ejections

Cited by 31 publications

References 17 publications

Fourier Analysis of Radio Bursts Observed with Very High Time Resolution

Fourier Analysis of Radio Bursts Observed with Very High Time Resolution

Radio Diagnostics of Electron Acceleration Sites During the Eruption of a Flux Rope in the Solar Corona

Diagnostics of solar flare reconnection

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