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1

Empirical Scaling Relations for the Photospheric Magnetic Elements of the Flaring and Non-Flaring Active Regions

Moradhaseli M. A., Javaherian M., Fathalian N., Safari H.

Acta Astronomica

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2021

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Vol. 71, No. 2

163--188

EN

Here, we analyze magnetic elements of the solar active regions (ARs) observed in the line-of-sight magnetograms (the 6173 Å FeI line) recorded with the Solar Dynamics Observatory (SDO)/Hel\-ioseismic and Magnetic Imager (HMI). The Yet Another Feature Tracking Algorithm (YAFTA}) was employed to analyze the statistical properties of these features (e.g., filling factor, magnetic flux, and lifetime). Magnetic features were extracted from the areas of 180o×180o inside the flaring AR (NOAA 12443) for November 3-5, 2015 and non-flaring AR (NOAA 12446) for November 4-6, 2015. The mean filling factor of polarities was found to be about 0.49 for the flaring AR, while this value was 0.08 for the non-flaring AR. Time series of the filling factors of the negative and positive polarities for the flaring AR showed anti-correlated behavior (with the Pearson value of -0.80). However, there was a strong positive correlation (with the Pearson value of 0.95) for the non-flaring AR. A power-law function was fitted to the frequency distributions of flux (F), size (S), and lifetime ($T$). Power exponents of the distributions of flux, size, and lifetime for the flaring AR were found to be -2.36±0.27, -3.11±0.17, and -1.70±0.29, respectively, while for the non-flaring AR: -2.53±0.20, -3.42±0.21, and -1.61±0.19, respectively. The code detected a magnetic element with the maximum flux of 23.54×1020 Mx. The maximum size of detected patches was found to be about 300 Mm2. The most long-lived patch in the flaring AR belonged to an element with a lifetime of 2208 min. We showed that S, F, and T for patches in the flaring AR follow empirical scaling relations: S∼F0.66±0.01, F∼T0.48±0.04, and S∼T0.32±0.02, respectively. For patches in the non-flaring AR, we obtained S∼F0.64±0.02, F∼T0.37±0.06, and S∼T0.23±0.03, respectively. The comparisons indicated that correlations between parameters of F and T, and also, S and T for the flaring AR, are larger than those of the non-flaring AR. The scaling law relation between the flux growth rate of positive polarities and their size indicates a strong correlation of more than 0.7 in both ARs.

2

Propagational Aspects of Sunquake Waves

Mędrek M., Murawski K., Nakariakov V.

Acta Astronomica

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2000

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Vol. 50, No. 3

405--416

EN

We present the results of numerical simulations of impulsively generated seismic waves excited by a spatially localized impulse source which is connected with a nearby solar flare. The solar atmosphere is modeled as a two layer medium with constant temperature over the photosphere and linearly growing temperature below the photosphere. Effects of magnetic fields are neglected. Only two dimensional effects are considered. The source is localized slightly below the photosphere. The numerical results show that the initial pulse of enhanced pressure, which can be connected with the thermal energy release by interaction of flare-generated particles with the sub-photospheric medium in the flare-loop footpoint, generates an acoustic (seismic) wave. Interaction of the wave with the solar surface produces perturbations registered as sunquakes. Typical observationally registered features of the sunquakes, such as characteristic wave signatures and acceleration of the wave with the distance from the epicenter, are well reproduced with the model developed. It is found that the seismic waves are essentially dispersive and non-linear. The proposed model provides us with a theoretical basis for sunquake seismology of the solar interior.

3

Flaring Structures Observed in Deconvolved SXT Images

Sylwester B., Sylwester J.

Acta Astronomica

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1999

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Vol. 49, No. 1

85--102

EN

We present and discuss evolution of flaring structures morphology as observed in deconvolved soft X-ray images. The X-ray images have been obtained using the Soft X-ray Telescope (SXT) on Yohkoh. The deconvolution has been made using the iterative maximum likelihood algorithm Andril. In the reconstructed images it is possible to study the position of individual fine structures for the first time with the resolution superior to the SXT pixel size. We show example of the analysis of deconvolved images for one disc flare on July 11, 1992 at 15:25 UT. Corresponding figures and animations for two other flares are available at the address www.cbk.pan.wroc.pl and at the Acta Astronomica Archive (see second cover page for details). These flares occurred on November 19, 1991 and on January 13, 1992 and have been located near/at the limb. We conclude about the differences of physical conditions of the flaring plasma confined in compact bright regions (kernels) located in the footpoint and summit areas.