Location of narrowband spikes in solar flares

Benz, A. O.; Saint-Hilaire, Pascal; Vilmer, Nicole

doi:10.1051/0004-6361:20011774

Cited by 40 publications

(35 citation statements)

References 29 publications

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“…Effect (i): Benz et al (2002) reported the location of decimetric spike sources some 20 to 400 away from the HXR source. Their observations corresponded to a frequency of 420 MHz and 432 MHz.…”

Section: Origin Of Delaysmentioning

confidence: 99%

Correlation between decimetric radio emission and hard X-rays in solar flares

Dąbrowski

Benz²

2009

A&A

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Aims. The emission of decimetric flare radiation, in particular narrowband spikes and pulsations, is generally considered to originate in accelerated, non-thermal particles. On the other hand, non-thermal hard X-rays are also understood to be products of this acceleration. Do radio emission and hard X-ray signatures originate from the same acceleration process? A strong correlation between the light curves in the radio and HXR ranges may help answer this question. Methods. The delay between the radio and hard X-ray emission was determined by cross-correlation. The time profiles of X-ray and radio emission include a wide range of energies and frequencies. Thus, correlation is not simply a yes/no question, but must be systematically searched for in various ranges. The high spectral resolution of RHESSI ensured that it was possible to carefully choose the energy range, excluding thermal emission. The broad bandwidth of Phoenix-2 allowed the selection of any emission in the full decimetre range. The energy range and duration in hard X-rays, and the frequency range in radio spectrograms were chosen to optimize the correlation. The cross-correlation coefficient was then analyzed by a Gaussian fitting method. Results. The measured delays have a distribution of FWHM 4.9 s and 4.7 s for pulsations and spikes, respectively, evaluated from such a Gaussian fitting method. The mean delay for pulsations was found to be −1.4 ± 0.9 s (minus indicates that hard X-ray emission comes first), and for narrowband spikes to −2.5 ± 2.5 s. There are broad wings in the distribution, which we interpret as chance coincidences. The delays do not depend on centre frequency, cross-correlation coefficient, duration of the correlating sequence, and position on the disk. However, we find an increase in the delay for the spikes with GOES magnitude (peak soft X-ray emission) of the flare and with peak hard X-ray flux. This was not the case for pulsations. Conclusions. In contrast to previous reports, the average delays for all pulsations and all spike groups are consistent with zero. Thus, correlated decimetric pulsations and spikes are, on average, concomitant with non-thermal X-rays.

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Section: Origin Of Delaysmentioning

confidence: 99%

Correlation between decimetric radio emission and hard X-rays in solar flares

Dąbrowski

Benz²

2009

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“…In a flare scenario as described above where the acceleration is thought to be strongly related to the coronal X-ray Article published by EDP Sciences source, the location of the spikes would then be expected to be at or close to the position of coronal hard X-ray sources. Benz et al (2002) studied a number of solar flares with associated hard X-ray sources and spikes, finding the location of the spikes to be offset by up to 400 from the flaring site as observed in hard X-ray footpoints, soft X-rays, and EUV. Since their events were observed on the solar disk, the complete geometry of the events could not be determined.…”

Section: Introductionmentioning

confidence: 99%

Do solar decimetric spikes originate in coronal X-ray sources?

Battaglia¹,

Benz²

2009

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Context. In the standard solar flare scenario, a large number of particles are accelerated in the corona. Nonthermal electrons emit both X-rays and radio waves. Thus, correlated signatures of the acceleration process are predicted at both wavelengths, coinciding either close to the footpoints of a magnetic loop or near the coronal X-ray source. Aims. We attempt to study the spatial connection between coronal X-ray emission and decimetric radio spikes to determine the site and geometry of the acceleration process. Methods. The positions of radio-spike sources and coronal X-ray sources are determined and analyzed in a well-observed limb event. Radio spikes are identified in observations from the Phoenix-2 spectrometer. Data from the Nançay radioheliograph are used to determine the position of the radio spikes. RHESSI images in soft and hard X-ray wavelengths are used to determine the X-ray flare geometry. Those observations are complemented by images from GOES/SXI. Results. We find that the radio emission originates at altitudes much higher than the coronal X-ray source, having an offset from the coronal X-ray source amounting to 90 and to 113 and 131 from the two footpoints, averaged over time and frequency. Conclusions. Decimetric spikes do not originate from coronal X-ray flare sources contrary to previous expectations. However, the observations suggest a causal link between the coronal X-ray source, related to the major energy release site, and simultaneous activity in the higher corona.

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“…Earlier work by Krucker et al (1997) and Paesold et al (2001) presented images of radio spike burst sources in relation to soft X-ray emission, while Benz et al (2002) showed the first reported example of images of radio spike bursts in relation to hard X-ray sources. These earlier works provided essentially snapshots of contextual information associated with the radio spike burst emission.…”

Section: Discussionmentioning

confidence: 99%

“…The source locations of radio spike bursts have already been determined and examined in a few cases (e.g., Heyvaerts et al 1978;Krucker et al 1995Krucker et al , 1997Paesold et al 2001;Benz et al 2002). However adequately detailed comparisons with coronal structures and hard X-ray sources have not yet been reported.…”

Section: Introductionmentioning

confidence: 99%

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

Khan

Auraß

2006

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We present the results of an analysis of multi-wavelength data for a solar radio spike burst event which was observed on 1997 November 14 by the Solar Radio Spectrometers of the Astrophysikalisches Institut Potsdam (AIP). Using radio imaging data from the Nançay Radioheliograph we are able to determine the location of the spike burst emission sites in relation to the associated flare and its coronal environment as seen in images from the Yohkoh Soft X-ray Telescope (SXT), Hard X-ray Telescope (HXT) and the Solar and Heliospheric Observatory (SOHO) Extreme ultraviolet Imaging Telescope (EIT). For this event we find that the spike burst emission originated high in the corona, ∼122 Mm above the soft X-ray and hard X-ray emitting regions of the associated (near-limb) flaring region. Using imaging data from SXT, HXT, and EIT we are also able to show, for the first time, the location of a solar radio spike burst in relation to the dynamics of coronal structures. We find that as an earlier flare-associated coronal mass ejection (CME) in the vicinity expanded outwards it appeared to compress the magnetic field structures at its flanks (associated with highly inclined coronal loops at the periphery of the active region). The radio spike bursts appeared at the time and in the vicinity of the compression of the coronal field. The compression presumably led to reconnection of the coronal magnetic field structures, particle acceleration and the radio spike burst emission signatures. For the specific event we analyse we find that the spike burst emission is associated with secondary flare energy release induced by an earlier flare-associated CME. These observations also provide evidence for a new category of sympathetic flaring where a large flare-associated coronal mass ejection compresses adjacent magnetic structures leading to nearby, but remote, small-scale flaring.

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Location of narrowband spikes in solar flares

Cited by 40 publications

References 29 publications

Correlation between decimetric radio emission and hard X-rays in solar flares

Correlation between decimetric radio emission and hard X-rays in solar flares

Do solar decimetric spikes originate in coronal X-ray sources?

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

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