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1.
A. Kilcik V. Yurchyshyn B. Donmez V. N. Obridko A. Ozguc J. P. Rozelot 《Solar physics》2018,293(4):63
We analyzed temporal and periodic variations of sunspot counts (SSCs) in flaring (C-, M-, or X-class flares), and non-flaring active regions (ARs) for nearly three solar cycles (1986 through 2016). Our main findings are as follows: i) temporal variations of monthly means of the daily total SSCs in flaring and non-flaring ARs behave differently during a solar cycle and the behavior varies from one cycle to another; during Solar Cycle 23 temporal SSC profiles of non-flaring ARs are wider than those of flaring ARs, while they are almost the same during Solar Cycle 22 and the current Cycle 24. The SSC profiles show a multi-peak structure and the second peak of flaring ARs dominates the current Cycle 24, while the difference between peaks is less pronounced during Solar Cycles 22 and 23. The first and second SSC peaks of non-flaring ARs have comparable magnitude in the current solar cycle, while the first peak is nearly absent in the case of the flaring ARs of the same cycle. ii) Periodic variations observed in the SSCs profiles of flaring and non-flaring ARs derived from the multi-taper method (MTM) spectrum and wavelet scalograms are quite different as well, and they vary from one solar cycle to another. The largest detected period in flaring ARs is \(113\pm 1.6~\mbox{days}\) while we detected much longer periodicities (\(327\pm 13\), \(312 \pm 11\), and \(256\pm 8~\mbox{days}\)) in the non-flaring AR profiles. No meaningful periodicities were detected in the MTM spectrum of flaring ARs exceeding \(55\pm 0.7~\mbox{days}\) during Solar Cycles 22 and 24, while a \(113\pm 1.3~\mbox{days}\) period was detected in flaring ARs of Solar Cycle 23. For the non-flaring ARs the largest detected period was only \(31\pm 0.2~\mbox{days}\) for Cycle 22 and \(72\pm 1.3~\mbox{days}\) for the current Cycle 24, while the largest measured period was \(327\pm 13~\mbox{days}\) during Solar Cycle 23. 相似文献
2.
We report on a prominence eruption as seen in H with the Crimean Lyot coronagraph, the global H network, and coronal images from the LASCO C2 instrument on board SOHO. We observed an H eruption at the northwest solar limb between 07:38:50 UT and 07:58:29 UT on 11 August 2000. The eruption originated in a quiet-Sun region and was not associated with an H filament. No flare was associated with the eruption, which may indicate that, in this case, a flux rope was formed prior to the eruption of the magnetic field. The H images and an H Dopplergram show a helical structure present in the erupted magnetic field. We suggest that the driving mechanism of the eruption may be magnetic flux emergence or magnetic flux injection. The limb H observations provide missing data on CME speed and acceleration in the lower corona. Our data show that the prominence accelerated impulsively at 5.5 km s–2 and reached a speed slightly greater than 800 km s–1 in a narrow region (h<0.14 R
) above the solar surface. The observations presented here also imply that, based only on a CME's speed and acceleration, it cannot be determined whether a CME is the result of a flare or an eruptive prominence. 相似文献
3.
In recent high-resolution observations of complex active regions, long-lasting and well-defined regions of strong flows were
identified in major flares and associated with bright kernels of visible, near-infrared, and X-ray radiation. These flows,
which occurred in the proximity of the magnetic neutral line, significantly contributed to the generation of magnetic shear.
Signatures of these shear flows are strongly curved penumbral filaments, which are almost tangential to sunspot umbrae rather
than exhibiting the typical radial filamentary structure. Solar active region NOAA 10756 was a moderately complex β
δ sunspot group, which provided an opportunity to extend previous studies of such shear flows to quieter settings. We conclude
that shear flows are a common phenomenon in complex active regions and δ spots. However, they are not necessarily a prerequisite condition for flaring. Indeed, in the present observations, the photospheric
shear flows along the magnetic neutral line are not related to any change of the local magnetic shear. We present high-resolution
observations of NOAA 10756 obtained with the 65-cm vacuum reflector at Big Bear Solar Observatory (BBSO). Time series of speckle-reconstructed
white-light images and two-dimensional spectroscopic data were combined to study the temporal evolution of the three-dimensional
vector flow field in the β
δ sunspot group. An hour-long data set of consistent high quality was obtained, which had a cadence of better than 30 seconds
and subarcsecond spatial resolution. 相似文献
4.
We study magnetic power spectra of active and quiet regions by using Big Bear Solar Observatory and SOHO/MDI measurements
of longitudinal magnetic fields. The MDI power spectra were corrected with Gaussian Modulation Transfer Function. We obtained
reliable magnetic power spectra in the high wave numbers range, up to k=4.6 Mm−1, which corresponds to a spatial scale l=1.4 Mm. We find that the occurrence of the spectral discontinuity at high wave numbers, k≥3 Mm−1, largely depends on the spatial resolution of the data and it appears at progressively higher wave numbers as the resolution
of the data improves. The spectral discontinuity in the raw spectra is located at wave numbers about 3 times smaller than
wave numbers, corresponding to the resolution of the data, and about 1.5–2.0 times smaller in the case of the noise- and-resolution
corrected spectra. The magnetic power spectra for active and quiet regions are different: active-region power spectra are
described as ∼k
−1.7, while in a quiet region the spectrum behaves as ∼k
−1.3. We suggest that the difference can be due to small-scale dynamo action in the quiet-Sun photosphere. Our estimations show
that the dynamo can generate more than 6% of the observed magnetic power. 相似文献
5.
In this paper we study the evolution of magnetic fields of a 1F/2.4C solar flare and following magnetic flux cancellation. The data are Big Bear Solar Observatory and SOHO/MDI observations of active region NOAA 8375. The active region produced a multitude of subflares, many of them being clustered along the moat boundary in the area with mixed polarity magnetic fields. The study indicates a possible connection between the flare and the flux cancellation. The cancellation rate, defined from the data, was found to be 3×1019 Mx h–1. We observed strong upward directed plasma flows at the cancellation site. Suggesting that the cancellation is a result of reconnection process, we also found a reconnection rate of 0.5 km s–1, which is a significant fraction of Alfvén speed. The reconnection rate indicates a regime of fast photospheric reconnection happening during the cancellation. 相似文献
6.
Shuo Wang Yuanyong Deng Rajmal Jain Vasyl Yurchyshyn Haimin Wang Yuanyuan Liu Zhiliang Yang 《Journal of Astrophysics and Astronomy》2008,29(1-2):57-61
In this paper, we study the evolution of vector magnetic field of AR 10656 by using the observations of Huairou Solar Observing Station (HSOS, China) and Big Bear Solar Observatory (BBSO, USA). The magnetic flux emergence and cancellation, and thus, magnetic nonpotential changes, are associated with the major flares in this active region. Compared with some other super-active regions, the evolution of magnetic morphologies and non-potentialities are relatively gradual, and thus the energy transportation and release are relatively slow. This gradual process may result in the recurrent flares of AR 10656. 相似文献
7.
8.
Statistical Assessment of Photospheric Magnetic Features in Imminent Solar Flare Predictions 总被引：1，自引：0，他引：1
Hui Song Changyi Tan Ju Jing Haimin Wang Vasyl Yurchyshyn Valentyna Abramenko 《Solar physics》2009,254(1):101-125
In this study we use the ordinal logistic regression method to establish a prediction model, which estimates the probability
for each solar active region to produce X-, M-, or C-class flares during the next 1-day time period. The three predictive
parameters are (1) the total unsigned magnetic flux T
flux, which is a measure of an active region’s size, (2) the length of the strong-gradient neutral line L
gnl, which describes the global nonpotentiality of an active region, and (3) the total magnetic dissipation E
diss, which is another proxy of an active region’s nonpotentiality. These parameters are all derived from SOHO MDI magnetograms.
The ordinal response variable is the different level of solar flare magnitude. By analyzing 174 active regions, L
gnl is proven to be the most powerful predictor, if only one predictor is chosen. Compared with the current prediction methods
used by the Solar Monitor at the Solar Data Analysis Center (SDAC) and NOAA’s Space Weather Prediction Center (SWPC), the
ordinal logistic model using L
gnl, T
flux, and E
diss as predictors demonstrated its automatic functionality, simplicity, and fairly high prediction accuracy. To our knowledge,
this is the first time the ordinal logistic regression model has been used in solar physics to predict solar flares. 相似文献
9.
Kilcik Ali Sarp Volkan Yurchyshyn Vasyl Rozelot Jean-Pierre Ozguc Atila 《Solar physics》2020,295(4):1-23
Solar Physics - We study the features of the magnetic field variations within the 2011 June 7 eruptive event that includes a large filament eruption, a flare, and a CME formation. The magnetic... 相似文献
10.
We study the magnetic structure of five well-known active regions that produced great flares (X5 or larger). The six flares under investigation are the X12 flare on 1991 June 9 in AR 6659, the X5.7 flare on 2000 July 14 in AR 9077, the X5.6 flare on 2001 April 6 in AR 9415, the X5.3 flare on 2001 August 25 in AR 9591, the X17 flare on 2003 October 28 and the X10 flare on 2003 October 29, both in AR 10486. The last five events had corresponding LASCO observations and were all associated with Halo CMEs. We analyzed vector magne-tograms from Big Bear Solar Observatory, Huairou Solar Observing Station, Marshall Space Right Center and Mees Solar Observatory. In particular, we studied the magnetic gradient derived from line-of-sight magnetograms and magnetic shear derived from vector magne-tograms, and found an apparent correlation between these two parameters at a level of about 90%. We found that the magnetic gradient could be a better proxy than the shear for predicting where a major flare might occur: all six flares occurred in neutral lines with maximum gradient. The mean gradient of the flaring neutral lines ranges from 0.14 to 0.50 G km-1, 2.3 to 8 times the average value for all the neutral lines in the active regions. If we use magnetic shear as the proxy, the flaring neutral line in at least one, possibly two, of the six events would be mis-identified. 相似文献