Frequency distributions and correlations of solar X-ray flare parameters

Crosby, Norma; Aschwanden, Markus J.; Dennis, B. R.

doi:10.1007/bf00646488

Cited by 485 publications

(434 citation statements)

References 19 publications

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“…of all sizes that follow a well defined statistical law [30,31,32], which agrees remarkably well with the observed flare statistics [33]. We can then conclude, after many years of studies, that a possible model for the dynamic evolution of the AR is the following: The 3D magnetic field is stressed from the photospheric motions, forms continuously UCS which relax, re-arranging the local magnetic field and causing flares of all sizes (Fig.…”

Section: Energy Release and Particle Acceleration In Complex Magneticsupporting

confidence: 81%

Magnetic Complexity, Fragmentation, Particle Acceleration and Radio Emission from the Sun

Vlahos

2007

The High Energy Solar Corona: Waves, Eruptions, Particles

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Abstract. The most popular flare model used to explain the energy release, particle acceleration and radio emission is based on the following assumptions: (1) The formation of a current sheet above a magnetic loop, (2) The stochastic acceleration of particles in the current sheet at the helmet of the loop, (3) the transport and trapping of particles inside the flaring loop. We review the observational consequences of the above model and try to generalize by putting forward a new suggestion, namely assuming that a complex active region driven by the photospheric motions forms naturally a large number of stochastic current sheets that accelerate particles, which in turn can be trapped or move along complex field line structures. The emphasis will be placed on the efficiency and the observational tests of the different models proposed for a flare

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Section: Energy Release and Particle Acceleration In Complex Magneticsupporting

confidence: 81%

Magnetic Complexity, Fragmentation, Particle Acceleration and Radio Emission from the Sun

Vlahos

2007

The High Energy Solar Corona: Waves, Eruptions, Particles

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“…Furthermore, the blue and green curves in Fig. 1 represent the differential energy frequency distribution with α E = 1.65 ± 0.02 for Ramaty High Energy Solar Spectroscopic Imager (RHESSI) solar flares 20 , and α E = 1.53 ± 0.02 for Hard X-ray Burst Spectrometer (HXRBS) solar flares 21 , respectively. The energy of a solar flare is the non-thermal energy in electrons above 25 keV.…”

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confidence: 99%

Self-organized criticality in X-ray flares of gamma-ray-burst afterglows

2013

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X-ray flares detected in nearly half of gamma-ray-burst (GRB) afterglows are one of the most intriguing phenomena in highenergy astrophysics 1-8 . All of the observations indicate that the central engines of bursts, after the gamma-ray emission has ended, still have long periods of activity, during which energetic explosions eject relativistic materials, leading to late-time X-ray emission 2,9,10 . It is thus expected that X-ray flares provide important clues as to the nature of the central engines of GRBs, and more importantly, unveil the physical mechanism of the flares themselves, which has so far remained mysterious. Here we report statistical results of X-ray flares of GRBs with known redshifts, and show that X-ray flares and solar flares share three statistical properties: power-law frequency distributions for energies, durations and waiting times. All of the distributions can be well understood within the physical framework of a self-organized criticality (SOC) system. The statistical properties of X-ray flares of GRBs are similar to solar flares, and thus both can be attributed to a SOC process. Both types of flares may be driven by a magnetic reconnection process, but X-ray flares of GRBs are produced in ultra-strongly magnetized millisecond pulsars 11,12 or long-term hyperaccreting disks around stellar-mass black holes 13 .GRBs are flashes of gamma-rays occurring at cosmological distances with an isotropic-equivalent energy release from 10 51 to 10 54 ergs 9,10,14,15 . They can be sorted into two classes: shortduration hard-spectrum bursts (< 2 s) and long-duration softspectrum bursts 16 . Thanks to the rapid-response capability and high sensitivity of the Swift satellite 17 , numerous unforeseen features have been discovered, one of which is that about half of the bursts have large, late-time X-ray flares with short rise and decay times 4,5 . Unexpected X-ray flares with an isotropicequivalent energy from 10 48 to 10 52 ergs have been detected for both long and short bursts 4,6,7 . The occurrence times of X-ray flares range from a few seconds to 10 6 seconds after the GRB trigger 8 . Until now, the physical mechanism of X-ray flares has remained mysterious, although some models have been proposed 9,10 . Due to the 8-year observations of Swift, plentiful X-ray flare data have been collected. Here we investigate the frequency distributions of energies, durations and waiting times of GRB X-ray flares for the first time. On the other hand, it is well known that solar flares with a timescale of hours are explosive phenomena in the solar atmosphere with an energy release of about 10 28 -10 32 ergs, which are widely believed to be triggered by a magnetic reconnection process 18 . They have been observed in broadband electromagnetic waves, but we focus here on solar hard X-ray flares.Although X-ray flares are common phenomena in GRBs and the Sun, the flare energy spans about 20 orders of magnitude and an outstanding question appears, namely, do GRB X-ray flares and solar flares have a similar physical mechani...

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“…Originally referring solely to energy release through magnetic reconnection, the term nanoflare now encompasses any impulsive mechanism that delivers energy in that range, for example, heating by Alfvén waves (Moriyasu et al, 2004). The latter has yet to be confirmed despite studies of the frequency distribution of thermal energies for hard X-ray flares (Crosby, Aschwanden, and Dennis, 1993), active region transient brightenings (Shimizu, 1995), and quiet-Sun nanoflares and microflares (Krucker and Benz, 1998;Parnell and Jupp, 2000;Aschwanden et al, 2000;Benz and Krucker, 2002;Aschwanden and Parnell, 2002;Taroyan, Erdélyi, and Bradshaw, 2011). However, it remains an open avenue of investigation.…”

Section: Introductionmentioning

confidence: 99%

Forward Modelling of a Brightening Observed by AIA

et al. 2015

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A comprehensive understanding of the different transient events is necessary for any eventual solution of the coronal heating problem. We present a cold loop whose heating caused a short-lived small-scale brightening that was observed by AIA. The loop was simulated using an adaptive hydrodynamic radiation code that considers the ions to be in a state of non-equilibrium. Forward modelling was used to create synthetic AIA intensity plots, which were tested against the observational data to confirm the simulated properties of the event. The hydrodynamic properties of the loop were determined. We found that the energy released by the heating event is within the canonical energy range of a nanoflare.

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Frequency distributions and correlations of solar X-ray flare parameters

Cited by 485 publications

References 19 publications

Magnetic Complexity, Fragmentation, Particle Acceleration and Radio Emission from the Sun

Magnetic Complexity, Fragmentation, Particle Acceleration and Radio Emission from the Sun

Self-organized criticality in X-ray flares of gamma-ray-burst afterglows

Forward Modelling of a Brightening Observed by AIA

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