Observations of the coronal dynamics associated with solar radio spike burst emission

Khan, J. I.; Auraß, H.

doi:10.1051/0004-6361:20054034

Cited by 19 publications

(15 citation statements)

References 34 publications

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“…Furthermore, the finding by Aschwanden and Güdel (1992) that the integrated spike flux is delayed by 2 -5 s with respect to the associated HXR peaks is also inconsistent with the interpretation of the spikes as tracers of the primary energy release. Khan and Aurass (2006) found one case where narrowband radio spike bursts are seen as a side phenomenon just during the liftoff of a structure related with a CME. Figure 5 shows a composed overlay of Yohkoh SXT and HXT images with isolines of the spike cloud emission at 327 and 410 MHz from simultaneous NRH data.…”

Section: Narrowband Spikesmentioning

confidence: 97%

Radio Emission of Flares and Coronal Mass Ejections

et al. 2008

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We review recent progress on our understanding of radio emission from solar flares and coronal mass ejections (CMEs) with emphasis on those aspects of the subject that help us address questions about energy release and its properties, the configuration of flare -CME source regions, coronal shocks, particle acceleration and transport, and the origin of solar energetic particle (SEP) events. Radio emission from electron beams can provide information about the electron acceleration process, the location of injection of electrons in the corona, and the properties of the ambient coronal structures. Mildly relativistic electrons gyrating in the magnetic fields of flaring loops produce radio emission via the gyrosynchrotron mechanism, which provides constraints on the magnetic field and the properties of energetic electrons. CME detection at radio wavelengths tracks the eruption from its early phase and reveals the participation of a multitude of loops of widely differing scale. Both flares and CMEs can ignite shock waves and radio observations offer the most robust tool to study them. The incorporation of radio data into the study of SEP events reveals that a clear-cut distinction between flare-related and CME-related SEP events is difficult to establish.

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Section: Narrowband Spikesmentioning

confidence: 97%

Radio Emission of Flares and Coronal Mass Ejections

et al. 2008

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“…There are reports about large spatial distances between decimetric radio sources and radio flux-correlated HXR sources (Khan & Aurass 2006;Battaglia & Benz 2009). However, these authors studied clouds of spike burst emission, a phenomenon with a patchy broadband morphology in the dynamic spectrum.…”

Section: Where Is the Flare Current Sheet?mentioning

confidence: 99%

“…They occur as a consequence of secondary processes in the continuum source volume, e.g. loop collisions (Khan & Aurass 2006), whistler wave propagation (Benz & Mann 1998), double-plasma-resonance of bouncing electrons (Zlotnik et al 2003), or simply injection of a new electron ensemble ).…”

Section: Introductionmentioning

confidence: 99%

A microflare with hard X-ray-correlated gyroresonance line emission at 314 MHz

Auraß

Rausche

Berkebile-Stoiser

et al. 2010

A&A

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Context. Small energy release events in the solar corona can give insights into the flare process which are regularly hidden in the complex morphology of larger events. For one case we find a narrowband radio signal well correlated with the hard X-ray flare. We investigate wether these signals are probes for the flare current sheet. Aims. We aim to establish the relation between narrowband and short-duration features (<1% of the observing frequency in the spectral range 250-340 MHz, and some 5 s until 2 min, respectively) in dynamic radio spectral diagrams and simultaneously occuring HXR bursts. Methods. We use dynamic radio spectra from the Astrophysical Institute Potsdam, HXR images of RHESSI, TRACE coronal and chromospheric images, SOHO-MDI high resolution magnetogram data, and its potential field extrapolation for the analysis of one small flare event in AR10465 on September 26, 2003. We point to similar effects in e.g. the X-class flare on November 03, 2003 to demonstrate that we are not dealing with a singular phenomenon. Results. We confirm the solar origin of the extremely narrowband radio emission. From RHESSI images and the magnetic field data we identify the probable site of the radio source as well as the HXR footpoint and the SXR flare loop emission. The flare loop is included in an ongoing change of magnetic connectivity as confirmed by TRACE images of hot coronal loops. The flare energy is stored in the nonpotential magnetic field substructure around the microflare site which is relaxed to a potential one. Conclusions. We conclude that the correlated HXR footpoint/narrowband radio emission, and the transition to a second energy release in HXR without associated radio emission are direct probes of changing magnetic connectivity during the flare. We suppose that the narrowband radio emission is due to gyroresonance radiation at the second harmonic of the local electron cyclotron frequency. It follows an upper limit of the magnetic field in the radio source volume of less than 50% of the mean potential field in the same height range. This supports the idea that the narrowband radio source is situated in the immediate surroundings of the flare current sheet.

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“…Eventually, sudden changes or interruptions of ongoing radio emission 4 , point to large-scale dynamics in the corona associated with the CME motion (comp. Khan & Aurass 2006). …”

Section: Radio and X-ray Observationsmentioning

confidence: 99%

Coronal current sheet signatures during the 17 May 2002 CME-flare

Auraß

Landini

Poletto

2009

A&A

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Context. The relation between current sheets (CSs) associated with flares, revealed by characteristic radio signatures, and current sheets associated with coronal mass ejections (CMEs), detected in coronal ultraviolet (UV) and white light data, has not been analyzed, yet. Aims. We aim at establishing the relationship between CSs associated with a limb flare and CSs associated with the CME that apparently develops after the flare. We use a unique data set, acquired on May 17, 2002, which includes radio and extreme ultraviolet (XUV) observations. Methods. Spectral radio diagnostics, UV spectroscopic techniques, white light coronograph imaging, and (partly) radio imaging are used to illustrate the relation between the CSs and to infer the physical parameters of the radially aligned features that develop in the aftermath of the CME. Results. During the flare, several phenomena are interpreted in accordance with earlier work and with reference to the common eruptive flare scenario as evidence of flare CSs in the low corona. These are drifting pulsating structures in dynamic radio spectra, an erupting filament, expanding coronal loops morphologically recalling the later white light CME, and associated with earlier reported hard X-ray source sites. In the aftermath of the CME, UV spectra allowed us to estimate the CS temperature and density, over the 1.5-2.1 R interval of heliocentric altitudes. The UV detected CS, however, appears to be only one of many current sheets that exist underneath the erupting flux rope. A type II burst following the CME radio continuum in time at lower frequencies is considered as the radio signature of a coronal shock excited at the flank of the CME. Conclusions. The results show that we can build an overall scenario where the CME is interpreted in terms of an erupting arcade crossing the limb of the Sun and connected to underlying structures via multiple CSs. Eventually, the observed limb flare seems to be a consequence of the ongoing CME.

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Observations of the coronal dynamics associated with solar radio spike burst emission

Cited by 19 publications

References 34 publications

Radio Emission of Flares and Coronal Mass Ejections

Radio Emission of Flares and Coronal Mass Ejections

A microflare with hard X-ray-correlated gyroresonance line emission at 314 MHz

Coronal current sheet signatures during the 17 May 2002 CME-flare

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