Millisecond time variations in hard X-ray solar flares

Kiplinger, A. L.; Dennis, B. R.; Frost, K. J.; Orwig, L. E.; Emslie, A. G.

doi:10.1086/183966

Cited by 153 publications

(74 citation statements)

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“…So emission at neither wavelength is periodic. This conclusion is consistent with the results by Kiplinger et al (1983Kiplinger et al ( , 1988 and Aschwanden et al (1993Aschwanden et al ( , 1998. But the same cannot be generalized to all flares, since Wang et al (2000) have found a dominant time scale of 0.3 -0.7 s. Therefore, for different flares, the mechanisms of elementary bursts may fundamentally differ.…”

Section: Hα and Hard X-rayssupporting

confidence: 90%

“…It was first discovered in high-resolution hard X-ray and microwave observations that flare bursts consist of fine structures on time scales from tens of milli-seconds to a few seconds de Jager, 1974, 1976;Hoyng, van Beek, and Brown, 1976;Kiplinger et al, 1983Kiplinger et al, , 1988Kaufmann et al, 1980Kaufmann et al, , 1984Kaufmann et al, , 2001Aschwanden, Benz, and Schwartz, 1993;Aschwanden, Schwartz, and Alt, 1995;Aschwanden et al, , 1998. These are called "elementary bursts" (de Jager and de Jonge, 1978).…”

Section: Introductionmentioning

confidence: 99%

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On the Temporal and Spatial Properties of Elementary Bursts

Qiu

Wang

2006

Sol Phys

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Abstract. "Elementary bursts" refer to fine time structures on scales of tens of milli-second to a few seconds in flare radiations. In this paper, we investigate temporal and spatial properties of elementary bursts by exploiting high-cadence Hα (100 ms) and hard X-ray (125 -500 ms) observations of an impulsive flare on March 16, 2000. We find that the time scale of 2 -3 s is likely an upper limit of the elementary bursts in this event, at which hard X-ray emissions observed by different instruments correlate, low energy (≤30 keV) hard X-rays and Hα flux correlate, and Hα emissions at conjugate flare kernels correlate. From our methods, and also largely limited by instrument resolutions, there is a weak indication of existence of sub-second structures. With the high-resolution Hα data, we also attempt to explore the spatial structure of "elementary bursts" by determining the average spatial displacement of Hα peak emission between successive "elementary bursts" defined from hard X-ray light curves. We find that, at the time scale of 3 s, the smallest spatial scale, as limited by the imaging resolution, is about 0.4 . We discuss these results with respect to mechanisms of fragmented magnetic energy release.

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Section: Hα and Hard X-rayssupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

On the Temporal and Spatial Properties of Elementary Bursts

Qiu

Wang

2006

Sol Phys

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“…The light curves of hard X-ray and microwave emission present temporal features with time scales of about one second or less on top of a gradual bulk emission (Kiplinger et al 1983;Kaufmann 1978;Correia & Kaufmann 1987). In the paper of Lin & Johns (1993), the importance of the inferred impulsive component above 40 keV electrons was 1/6 ( 17%) of the gradual component.…”

Section: Introductionmentioning

confidence: 98%

Microwave emission from the trapped and precipitated electrons in solar bursts

Costa¹,

Rosal²

2005

A&A

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Abstract.We analyzed the microwave spectra of a sample of 13 solar flares out of 40 events observed by the Nobeyama Radio Polarimeter in the period of August 8, 1998 through November 24, 2001. The solar burst time profiles were filtered to separate the slow component from the fast structures which were associated with the emission from trapped particles and to the emission from the minor precipitating population, respectively. The spectra of both components suggest a trap in a region with a mean magnetic field of about 600 G and a minor emission from the loop legs with a magnetic field of 1100 G, resulting in a mirror ratio of about two. The spectral indices of the optically thin emission from these two regions indicate pitch angle diffusion by Coulomb collisions.

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“…They are attributed to the Ðne structure in coronal magnetic Ðelds and related to the aggregation of photospheric magnetic Ðelds into small-scale magnetic elements. From a sample of nearly 3000 HXR solar Ñares as observed with the HXR burst spectrometer on the Solar Maximum Mission (SMM), Kiplinger et al (1983) found that a portion of the events has a subsecond temporal structure. More recent HXR observations from BATSE on board the Compton Gamma-Ray Observatory (CGRO) provide a much improved sensitivity and energy resolution, and a temporal resolution down to 64 ms. Aschwanden et al (1996) used the subsecond temporal structure to study the scales of magnetic loops in Ñares by applying the time-of-Ñight method.…”

Section: Introductionmentioning

confidence: 99%

High‐Cadence Observations of an Impulsive Flare

Wang¹,

Qiu²,

Denker³

et al. 2000

ApJ

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We analyzed high-cadence observations of a C5.7 Ñare on 1999 August 23 at Big Bear Solar Observatory (BBSO). The observing wavelength was 1.3 in the blue wing of Ha, with a cadence of 0.033 s. In A addition, the hard X-rayÏs time proÐle obtained by the Burst And Transient Source Experiment (BATSE) and BBSO high-resolution magnetograms was compared with our Ha observations to understand in detail the particle precipitation in this event. The important results are as follows :three Ñare kernels were observed in the early phase of the Ñare. The Ñare started in a A , nonmagnetic area at the magnetic neutral line. This suggests to us that the top of a low-lying loop is the initial energy release site, while the other two kernels are the footpoints of another overlying Ñare loop, formed after the magnetic reconnection.2. We analyzed the temporal behavior of the three Ñare kernels in the impulsive phase when hard X-ray (HXR) emission was signiÐcant. We found that during a 7 s period, the Ha[1.3 brightenings at A one of the footpoints showed a very good temporal correlation with the HXR Ñux variation. Therefore, from the spatially resolved Ha o †-band observations, we identiÐed this Ñare kernel as the source of HXR emission.3. From the footpoint which exhibits the best correlation with HXR emission, the Ha[1.3 emission A shows high-frequency Ñuctuations on a timescale of a few tenths of a second. The amplitude of the Ñuc-tuations is more than 3 times the noise. Such Ñuctuations are not evident in the other Ñare kernels which also do not show good correlation with HXR emission. For this reason, we suggest that the observed high-frequency Ñuctuations may be signatures of temporal Ðne structure related to the HXR elementary bursts.

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Millisecond time variations in hard X-ray solar flares

Cited by 153 publications

References 0 publications

On the Temporal and Spatial Properties of Elementary Bursts

On the Temporal and Spatial Properties of Elementary Bursts

Microwave emission from the trapped and precipitated electrons in solar bursts

High‐Cadence Observations of an Impulsive Flare

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