Sixteen-Second Periodic Pulsations Observed in the Correlated Microwave and Energetic X-Ray Emission from a Solar Flare

Parks, G. K.; Winckler, J. R.

doi:10.1086/180315

Cited by 166 publications

(87 citation statements)

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“…Perhaps the earliest observations of flaring QPP, at least in X-rays, were by Parks & Winckler (1969); see also Chiu (1970) for similar early work including in the radio band. Previous studies show that, in the majority of described cases, QPP are present in flaring lightcurves as short wave trains with varying periods and amplitudes (see, e.g.…”

Section: Introductionmentioning

confidence: 99%

Instrumental oscillations in RHESSI count rates during solar flares

Inglis

Zimovets

Dennis

et al. 2011

A&A

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Aims. We seek to illustrate the analysis problems posed by RHESSI spacecraft motion by studying persistent instrumental oscillations found in the lightcurves measured by RHESSI's X-ray detectors in the 6-12 keV and 12-25 keV energy range during the decay phase of the flares of 2004 November 4 and 6. Methods. The various motions of the RHESSI spacecraft which may contribute to the manifestation of oscillations are studied. The response of each detector in turn is also investigated. Results. We find that on 2004 November 6 the observed oscillations correspond to the nutation period of the RHESSI instrument. These oscillations are of greatest amplitude for detector 5, while in the lightcurves of many other detectors the oscillations are small or undetectable. We also find that the variation in detector pointing is much larger during this flare than the counterexample of 2004 November 4. Conclusions. Sufficiently large nutation motions of the RHESSI spacecraft lead to clearly observable oscillations in count rates, posing a significant hazard for data analysis. This issue is particularly problematic for detector 5 due to its design characteristics. Dynamic correction of the RHESSI counts, accounting for the livetime, data gaps, and the transmission of the bi-grid collimator of each detector, is required to overcome this issue. These corrections should be applied to all future oscillation studies.

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Section: Introductionmentioning

confidence: 99%

Instrumental oscillations in RHESSI count rates during solar flares

Inglis

Zimovets

Dennis

et al. 2011

A&A

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“…The first detection of a QPP pattern simultaneously in the x-ray and microwave emission of a solar flare was published almost fifty years ago in [5]. QPP are detected in different phases of flares, and in all observational bands, from radio to gamma-rays.…”

Section: Introductionmentioning

confidence: 99%

Non-stationary quasi-periodic pulsations in solar and stellar flares

Nakariakov

Kolotkov

Kupriyanova

et al. 2018

Plasma Phys. Control. Fusion

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Often the enhanced electromagnetic radiation generated in solar and stellar flares shows a pronounced (quasi)-oscillatory pattern-quasi-periodic pulsations (QPP), with characteristic periods ranging from a fraction of a second to several tens of minutes. We review recent advances in the empirical study of QPP in solar and stellar flares, addressing the intrinsic nonstationarity of the signal, i.e. the variation of its amplitude, period or phase with time. This nonstationarity could form a basis for a classification of QPP, necessary for revealing specific physical mechanisms responsible for their appearance. We could identify two possible classes of QPP, decaying harmonic oscillations, and trains of symmetric triangular pulsations. Apparent similarities between QPP and irregular geomagnetic pulsations Pi offer a promising avenue for the knowledge transfer in both analytical techniques and theory. Attention is also paid to the effect of the flare trend on the detection and analysis of QPP.

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“…This therefore allows for the detection of any source motion between the coronal looptop and chromospheric footpoints. During the rise phase of a typical flare, the flux of HXRs reaches a peak and the spectral index hardens (Parks & Winckler 1969;Benz 1977;Fletcher & Hudson 2002). Based on the theoretical derivations of nonthermal X-ray intensity with height in the coronal acceleration scenario (Brown & McClymont 1975), this is expected to result in a descent of the location of peak nonthermal emission in the time coming up to the HXR peak.…”

Section: Introductionmentioning

confidence: 99%

Solar flare X-ray source motion as a response to electron spectral hardening

O'Flannagain

Gallagher

Brown

et al. 2013

A&A

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Context. Solar flare hard X-rays (HXRs) are thought to be produced by nonthermal coronal electrons stopping in the chromosphere or remaining trapped in the corona. The collisional thick target model (CTTM) predicts that more energetic electrons penetrate to greater column depths along the flare loop. This requires that sources produced by harder power-law injection spectra should appear further down the legs or footpoints of a flareloop. Therefore, the frequently observed hardening of the injected power-law electron spectrum during flare onset should be concurrent with a descending hard X-ray source. Aims. We test this implication of the CTTM by comparing its predicted HXR source locations with those derived from observations of a solar flare which exhibits a nonthermally-dominated spectrum before the peak in HXRs, known as an early impulsive event.Methods. The HXR images and spectra of an early impulsive C-class flare were obtained using the Ramaty High-Energy Solar Spectroscopic Imager (RHESSI). Images were reconstructed to produce HXR source height evolutions for three energy bands. Spatially integrated spectral analysis was performed to isolate nonthermal emission and to determine the power-law index of the electron injection spectrum. The observed height-time evolutions were then fitted with CTTM-based simulated heights for each energy, using the electron spectral indices derived from the RHESSI spectra. Results. The flare emission was found to be dominantly nonthermal above ∼7 keV, with emission of thermal and nonthermal X-rays likely to be simultaneously observable below that energy. The density structure required for a good match between model and observed source heights agreed with previous studies of flare loop densities. Conclusions. The CTTM has been used to produce a descent of model HXR source heights that compares well with observations of this event. Based on this interpretation, downward motion of nonthermal sources should occur in any flare where there is spectral hardening in the electron distribution during a flare. However, this is often masked by thermal emission associated with flare plasma preheating. To date, flare models that predict transfer of energy from the corona to the chromosphere by means other than a flux of nonthermal electrons do not predict this observed source descent. Therefore, flares such as this will be key in explaining this elusive energy transfer process.

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Sixteen-Second Periodic Pulsations Observed in the Correlated Microwave and Energetic X-Ray Emission from a Solar Flare

Cited by 166 publications

References 0 publications

Instrumental oscillations in RHESSI count rates during solar flares

Instrumental oscillations in RHESSI count rates during solar flares

Non-stationary quasi-periodic pulsations in solar and stellar flares

Solar flare X-ray source motion as a response to electron spectral hardening

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