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The Energetics of White-light Flares Observed by SDO/HMI and RHESSI

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Research in Astronomy and Astrophysics 2016年第11期16卷 99-104页

作者： Neng-Yi Huang Yan Xu haimin wang Center for Solar-Terrestrial Research New Jersey Institute of Technology Newark NJ 07102-1982 USA Big Bear Solar Observatory Big Bear City CA 92314 USA

White-light （WL） flares have been observed and studied for more than a century since their first discovery. However, some fundamental physics behind the brilliant emission remains highly controversial. One of the important facts in addressing the flare energetics is the spatio-temporal correlation between the WL emission and the hard X-ray （HXR） radiation, presumably suggesting that energetic electrons are the energy sources. In this study, we present a statistical analysis of 25 strong flares （〉M5） observed simultaneously by the Helioseismic and Magnetic Imager （HMI）, on board the Solar Dynamics Observatory （SDO）, and the Reuven Ramaty High Energy Solar Spectroscopic lmager （RHESS1）. Among these events, WL emission was detected by SDO/HMI in 13 flares, associated with HXR emission. To quantitatively describe the strength of WL emission, equivalent area （EA） is defined as the integrated contrast enhancement over the entire flaring area. Our results show that the EA is inversely proportional to the HXR power-law index, indicating that stronger WL emission tends to be associated with a larger population of high energy electrons. However, no obvious correlation is found between WL emission and flux of non-thermal electrons at 50 keV. For the other group of 13 flares without detectable WL emission, the HXR spectra are softer （larger power-law index） than those flares with WL emission, especially for the X-class flares in this group.

关键词： Sun: flares - Sun: white-light - Sun: hard X-ray

Irreversible rapid changes of magnetic field associated with the 2012 October 23 circular near-limb X1.8 Flare

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Research in Astronomy and Astrophysics 2016年第6期16卷 99-104页

作者： Dan-Dan Ye Chang Liu haimin wang Space Weather Research Laboratory and Big Bear Solar Observatory New Jersey Institute of TechnologyUniversity Heights

It has been found that photospheric magnetic fields can change in accordance with restructuring of the three-dimensional magnetic field following solar eruptions. Previous studies mainly use vector mag- netic field data taken for events near the disk center. In this paper, we analyze the magnetic field evolution associated with the 2012 October 23 X1.8 flare in NOAA AR 11598 that is close to the solar limb, using both the 45 s cadence line-of-sight and 12 min cadence vector magnetograms from the Helioseismic and Magnetic Imager on board Solar Dynamics Observatory. This flare is classified as a circular-ribbon flare with spine-fan type magnetic topology containing a null point. In the line-of-sight magnetograms, there are two apparent polarity inversion lines （PILs）. The PIL closer to the limb is affected more by the projection effect. Between these two PILs there lie positive polarity magnetic fields, which are surrounded by negative polarity fields outside the PILs. We find that after the flare, both the apparent limb-ward and disk-ward negative fluxes decrease, while the positive flux in-between increases. We also find that the horizontal mag- netic fields have a significant increase along the disk-ward PIL, but in the surrounding area, they decrease. Synthesizing the observed field changes, we conclude that the magnetic fields collapse toward the surface above the disk-ward PIL as depicted in the coronal implosion scenario, while the peripheral field turns to a more vertical configuration after the flare. We also suggest that this event is an asymmetric circular-ribbon flare： a flux rope is likely present above the disk-ward PIL. Its eruption causes instability of the entire fan-spine structure and the implosion near that PIL.

关键词： Sun flares -- Sun magnetic field

The change of magnetic inclination angles associated with the X3.4 flare on December 13,2006

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Science China(Physics,Mechanics & Astronomy) 2009年第11期52卷 1702-1706页

作者： LI YiXuan JING Ju TAN ChangYi wang haimin Center for Solar-Terrestrial Research New Jersey Institute of TechnologyNewarkNJ 07102USA

Recent studies showed a consistent pattern of changes in the sunspot structure associated with major flares: part of the peripheral penumbral regions vanishes during flares, and meanwhile, the umbral cores and/or inner penumbral regions are darkened. To understand the underlying physics of these observations, we compare the magnetic inclination angle in the decayed peripheral and the enhanced inner penumbral regions before and after the 4B/X3.4 flare of 2006 December 13 by using the high-resolution vector magnetograms from Hinode. We find that the mean inclination angle in the decayed penumbra increases after the flare while that in the enhanced penumbra near flaring neutral line decreases. The result confirms the previous idea that two components of a δ sunspot become connected after flares. As a result of new connection, peripheral penumbral fields change from a more inclined to a more vertical configuration and transverse fields in umbral core and inner penumbral regions increase substantially (Liu et al. 2005). The flare-associated changes of Doppler width as well as other parameters (the transverse field strength, continuum intensity and filling factor) are also presented.

关键词： Sun:magnetic fields Sun:photosphere Sun:flares

DeepSun:machine-learning-as-a-service for solar flare prediction

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Research in Astronomy and Astrophysics 2021年第7期21卷 51-61页

作者： Yasser Abduallah Jason T.L.wang Yang Nie Chang Liu haimin wang Institute for Space Weather Sciences New Jersey Institute of TechnologyUniversity HeightsNewarkNJ 07102-1982USA Department of Computer Science New Jersey Institute of TechnologyUniversity HeightsNewarkNJ 07102-1982USA Big Bear Solar Observatory New Jersey Institute of Technology40386 North Shore LaneBig Bear CityCA 92314-9672USA Center for Solar-Terrestrial Research New Jersey Institute of TechnologyUniversity HeightsNewarkNJ 07102-1982USA

Solar flare prediction plays an important role in understanding and forecasting space *** main goal of the Helioseismic and Magnetic Imager(HMI), one of the instruments on NASA's Solar Dynamics Observatory, is to study the origin of solar variability and characterize the Sun's magnetic *** provides continuous full-disk observations of the solar vector magnetic field with high cadence data that lead to reliable predictive capability;yet, solar flare prediction effort utilizing these data is still limited. In this paper, we present a machine-learning-as-a-service(MLaa S) framework, called Deep Sun,for predicting solar flares on the web based on HMI's data products. Specifically, we construct training data by utilizing the physical parameters provided by the Space-weather HMI Active Region Patch(SHARP)and categorize solar flares into four classes, namely B, C, M and X, according to the X-ray flare catalogs available at the National Centers for Environmental Information(NCEI). Thus, the solar flare prediction problem at hand is essentially a multi-class(i.e., four-class) classification problem. The Deep Sun system employs several machine learning algorithms to tackle this multi-class prediction problem and provides an application programming interface(API) for remote programming users. To our knowledge, Deep Sun is the first MLaa S tool capable of predicting solar flares through the internet.

关键词： Sun:flares Sun:activity methods:data analysis

The correlation between expansion speed and magnetic field in solar flare ribbons

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Science China(Physics,Mechanics & Astronomy) 2009年第11期52卷 1754-1759页

作者： XIE WenBin wang haimin JING Ju BAO XingMing ZHANG HongQi Key Laboratory of Solar Activity National Astronomical Observatories of ChinaBeijing 100012China Physics Department New Jersey Institute of TechnologyNewarkNJ07102USA Jilin Normal University Jilin 136000China

In this paper, we study the correlation between the expansion speed of two-ribbon flares and the magnetic field measured in the ribbon location, and compare such correlation for two events with different magnetic configurations. These two events are: an M1.0 flare in the quiet sun on September 12, 2000 and an X2.3 flare in Active Region NOAA 9415 on April 10, 2001. The magnetic configuration of the M1.0 flare is simple, while that of X2.3 event is complex. We have derived a power-law correlation between the ribbon expansion speed (V r) and the longitudinal magnetic field (Bz) with an empirical relationship V r = A×Bz-δ, where A is a constant and δ is the index of the power-law correlation. We have found that δ for the M1.0 flare in the simple magnetic configuration is larger than that for the X2.3 flare in the complex magnetic configuration.

关键词： solar activity solar flares solar magnetic field

Attack on an Efficient Certificateless Aggregate Signature without Pairing

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Wuhan University Journal of Natural Sciences 2020年第2期25卷 139-145页

作者： LI Huimin LIANG Hongmei wang haimin ZHANG Jinhui School of Mathematics and Finance Putian UniversityPutian 351100FujianChina Key Laboratory of Applied Mathematics Fujian Province University(Putian University)Putian 351100FujianChina School of Mathematics and Statistics Minnan Normal UniversityZhangzhou 363000FujianChina

A Certificateless Aggregate Signature(CLAS) scheme was proposed by Qu and Mu recently, which was published in "Int J. Electronic Security and Digital Forensics, 2018, 10(2)". They used discrete logarithm to ensure the scheme's security. However,we show by formulating an attack that their CLAS scheme cannot defend against Type I adversary. Furthermore, we point out an error that exists in the signature simulation of their security *** that we give a correct signature simulation for the security proof. Finally, to resist the Type I attack, we present two methods for improving Qu et al's CLAS scheme. Moreover, the second improving method can elevate the trust level of Qu et al's CLAS scheme to the highest trust level: Level 3.

关键词： certificateless aggregate signature attack security random oracle model discrete logarithm problem

Algorithm Development of Cloud Removal from Solar Images Based on Pix2Pix Network

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Computers, Materials & Continua 2022年第5期71卷 3497-3512页

作者： Xian Wu Wei Song Xukun Zhang Ganghua Lin haimin wang Yuanyong Deng School of Information Engineering Minzu University of ChinaBeijing100081China Key Laboratory of Solar Activity Chinese Academy of Sciences(KLSACAS)Beijing100101China National Language Resource Monitoring and Research Center of Minority Languages Minzu University of ChinaBeijing100081China National Astronomical Observatories Chinese Academy of Sciences(NAOCCAS)Beijing100101China Center for Solar-Terrestrial Research New Jersey Institute of TechnologyUniversity HeightsNewark07102-1982USA Institute for Space Weather Sciences New Jersey Institute of TechnologyUniversity HeightsNewark07102-1982USA Big Bear Solar Observatory New Jersey Institute of Technology40386North Shore LaneBig Bear City92314-9672USA

Sky clouds affect solar observations *** shadows obscure the details of solar features in observed ***-covered solar images are difficult to be used for further research without *** this paper,the solar image cloud removing problem is converted to an image-to-image translation problem,with a used algorithm of the Pixel to Pixel Network(Pix2Pix),which generates a cloudless solar image without relying on the physical scattering ***2Pix is consists of a generator and a *** generator is a well-designed *** discriminator uses PatchGAN structure to improve the details of the generated solar image,which guides the generator to create a pseudo realistic solar *** image generation model and the training process are optimized,and the generator is jointly trained with the *** the generation model which can stably generate cloudless solar image is *** experiment results on Huairou Solar Observing Station,National Astronomical Observatories,and Chinese Academy of Sciences(HSOS,NAOC and CAS)datasets show that Pix2Pix is superior to the traditional methods based on physical prior knowledge in peak signal-to-noise ratio,structural similarity,perceptual index,and subjective visual *** result of the PSNR,SSIM and PI are 27.2121 dB,0.8601 and 3.3341.

关键词： Pix2Pix solar image cloud removal

Comparison between the eruptive X2.2 flare on 2011 February15 and confined X3.1 flare on 2014 October 24

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Research in Astronomy and Astrophysics 2015年第9期15卷 1537-1546页

作者： Ju Jing Yan Xu Jeongwoo Lee Nariaki V.Nitta Chang Liu Sung-Hong Park Thomas Wiegelmann haimin wang Center for Solar-Terrestrial Research New Jersey Institute of Technology Big Bear Solar Observatory Astronomy Program Department of Physics and Astronomy Seoul National University Lockheed Martin Solar and Astrophysics Laboratory Institute for Astronomy Astrophysics Space Applications and Remote Sensing (IAASARS)National Observatory of Athens Max-Planck-Institut fuer Sonnensystemforschung

We compare two contrasting X-class flares in terms of magnetic free energy, relative magnetic helicity and decay index of the active regions （ARs） in which they occurred. The events in question are the eruptive X2.2 flare from AR 11158 accompanied by a halo coronal mass ejection （CME） and the confined X3.1 flare from AR 12192 with no associated CME. These two flares exhibit similar behavior of free magnetic energy and helicity buildup for a few days preceding them. A major difference between the two flares is found to lie in the time-dependent change of magnetic helicity of the ARs that hosted them. AR 11158 shows a significant decrease in magnetic helicity starting -4 hours prior to the flare, but no apparent decrease in helicity is observed in AR 12192. By examining the magnetic helicity injection rates in terms of sign, we confirmed that the drastic decrease in magnetic helicity before the eruptive X2.2 flare was not caused by the injection of reversed helicity through the photosphere but rather the CME-related change in the coronal magnetic field. Another major difference we find is that AR 11158 had a significantly larger decay index and therefore weaker overlying field than AR 12192. These results suggest that the coronal magnetic helicity and the decay index of the overlying field can provide a clue about the occurrence of CMEs.

关键词： Sun: magnetic topology -- Sun: evolution -- Sun: flares -- Sun: coronal mass ejections (CMEs)

Development of technique to detect and classify small-scale magnetic flux cancellation and rapid blue-shifted excursions

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Research in Astronomy and Astrophysics 2015年第7期15卷 1012-1026页

作者： Xin Chen Na Deng Derek A.Lamb Ju Jing Chang Liu Rui Liu Sung-Hong Park haimin wang Space Weather Research Laboratory New Jersey Institute of Technology University Heights Southwest Research Institute CAS Key Laboratory of Geospace Environment Department of Geophysics and Planetary Sciences University of Science and Technology of China Institute for Astronomy Astrophysics Space Applications and Remote Sensing National Observatory of Athens Korea Astronomy and Space Science Institute

We present a set of tools for detecting small-scale solar magnetic cancellations and the disk counterpart of type II spicules（the so-called Rapid Blueshifted Excursions（RBEs））, using line-of-sight photospheric magnetograms and chromospheric spectroscopic observations, respectively. For tracking magnetic cancellation,we improve the Southwest Automatic Magnetic Identification Suite（SWAMIS） so that it is able to detect certain obscure cancellations that can be easily missed. For detecting RBEs, we use a normalized reference profile to reduce false-positive detections caused by the non-uniform background and seeing condition. Similar to the magnetic feature tracking in SWAMIS, we apply a dual-threshold method to enhance the accuracy of RBE detection. These tools are employed to analyze our coordinated observations using the Interferometric BIdimensional Spectrometer at the Dunn Solar Telescope of the National Solar Observatory and Hinode. We present the statistical properties of magnetic cancellations and RBEs, and explore their correlation using this data set.

关键词： Sun: chromosphere -- Sun: magnetic fields