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Study of white-light flares observed by Hinode

Chinese Journal of Astronomy and Astrophysics 2009年第2期9卷 127-132页

作者： hai-min wang Space Weather Research Lab Center for Solar Terrestrial Research New Jersey Institute of Technology Newark NJ 07102 USA

White-light flares are considered to be the most energetic flaring events that are observable in the optical broad-band continuum of the solar spectrum. They have not been commonly observed. Observations of white-light flares with sub-arcsecond resolution have been very rare. The continuous high resolution observations of Hinode provide a unique opportunity to systematically study the white-light flares with a spatial resolution around 0.2 arcsec. We surveyed all the flares above GOES magnitude C5.0 since the launch of Hinode in 2006 October. 13 of these kinds of flares were covered by the Hinode G-band observations. We analyzed the peak contrasts and equivalent areas （calculated via integrated excess emission contrast） of these flares as a function of the GOES X-ray flux, and found that the cut-off visibility is likely around M1 flares under the observing limit of Hinode. Many other observational and physical factors should affect the visibility of white-light flares; as the observing conditions are improved, smaller flares are likely to have detectable white-light emissions. We are cautious that this limiting visibility is an overestimate, because G-band observations contain emissions from the upper atmosphere. Among the 13 events analyzed, only the M8.7 flare of 2007 June 4 had near-simultaneous observations in both the G-band and the blue continuum. The blue continuum had a peak contrast of 94% vs. 175% in G-band for this event. The equivalent area in the blue continuum is an order of magnitude lower than that in the G-band. Very recently, Jess et al. studied a C2.0 flare with a peak contrast of 300% in the blue continuum. Compared to the events presented in this letter, that event is probably an unusual white-light flare： a very small kernel with a large contrast that can be detected in high resolution observations.

关键词： Sun activity - Sun flares - Sun magnetic fields

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Magnetic field changes associated with three successive M-class solar flares on 2002 July 26

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Research in Astronomy and Astrophysics 2011年第6期11卷 692-700页

作者： Pu wang ming-De Ding hai-Sheng Ji hai-min wang epartment of Astronomy Nanjing UniversityNanjing 210093China Purple Mountain Observatory Chinese Academy of SciencesNanjing 210008China Space Weather Research Lab Center for Solar Terrestrial ResearchNew Jersey Institute of TechnologyNewarkNJ 07102US

With an extensive analysis,we study the temporal evolution of magnetic flux during three successive M-class flares in two adjacent active regions：NOAA 10039 and *** primary data are full disk longitudinal magnetograms observed by SOHO/*** three flares are observed to be accompanied by magnetic flux *** changes occurred immediately or within 1 ～ 10 minutes after the starting time of the flares,indicating that the changes are obvious consequences of the solar *** changes in many points are intrinsic in magnetic flux,for some sites,it is caused by a rapid expansion motion of magnetic *** the second flare,the associated change is more gradual compared with the ＇step-function＇ reported in ***,we use the data observed by the Imaging Vector Magnetograph（IVM） at Mees Solar Observatory to check possible line profile changes during the *** results from the IVM data confirm the flux changes obtained from the MDI data.A series of line profiles were obtained from the IVM＇s observations and analyzed for flux change *** find that the fluctuations in the width,depth and central wavelength of the lines are less than 5.0 even at the flare＇s *** line profile change is observed during or after the *** conclude that the magnetic field changes associated with the three solar flares are not caused by flare emission.

关键词： Sun:activity-Sun:magnetic field-Sun:flares

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Optical Design of Multilayer Achromatic Waveplate by Simulated Annealing Algorithm

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Chinese Journal of Astronomy and Astrophysics 2008年第3期8卷 349-361页

作者： Jun Ma Jing-Shan wang Carsten Denker hai-min wang Big Bear Solar Observatory 40386 North Shore Lane Big Bear City CA 92314 USA New Jersey Institute of Technology Center for Solar-Terrestrial Research 323 Martin Luther Kind Blvd. Newark NJ 07102 USA Astrophysikalisches Institut Potsdam An der Sternwarte 16 D- 14482 Potsdam Germany Currently working at Thorlabs Inc. 435 Route 206 Newton NJ 07860 USA

We applied a Monte Carlo method -- simulated annealing algorithm -- to carry out the design of multilayer achromatic waveplate. We present solutions for three-, six- and ten-layer achromatic waveplates. The optimized retardance settings are found to be 89°51′39″ ± 0°33′37″ and 89°54′46″ ± 0°22′4″ for the six- and ten-layer waveplates, respectively, for a wavelength range from 1000 nm to 1800 nm. The polarimetric properties of multilayer waveplates are investigated based on several numerical experiments. In contrast to previously proposed three-layer achromatic waveplate, the fast axes of the new six- and ten-layer achromatic waveplate remain at fixed angles, independent of the wavelength. Two applications of multilayer achromatic waveplate are discussed, the general-purpose phase shifter and the birefringent filter in the Infrared Imaging Magnetograph （IRIM） system of the Big Bear Solar Observatory （BBSO）. We also checked an experimental method to measure the retardance of waveplates.

关键词： instrumentation spectrographs -- methods numerical -- methods laboratory-- Sun infrared

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Determination of the Topology Skeleton of Magnetic Fields in a Solar Active Region

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Chinese Journal of Astronomy and Astrophysics 2008年第2期8卷 133-145页

作者： Hui Zhao Jing-Xiu wang Jun Zhang Chi-Jie Xiao hai-min wang National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 Big Bear Solar Observatory 40386 North Shore Lane Big Bear City CA 92314 USA

Magnetic topology has been a key to the understanding of magnetic energy release mechanism. Based on observed vector magnetograms, we have determined the threedimensional （3D） topology skeleton of the magnetic fields in the active region NOAA 10720. The skeleton consists of six 3D magnetic nulls and a network of corresponding spines, fans, and null-null lines. For the first time, we have identified a spiral magnetic null in Sun＇s corona. The magnetic lines of force twisted around the spine of the null, forming a ＇magnetic wreath＇ with excess of free magnetic energy and resembling observed brightening structures at extraultraviolet （EUV） wavebands. We found clear evidence of topology eruptions which are referred to as catastrophic changes of topology skeleton associated with a coronal mass ejection （CME） and an explosive X-ray flare. These results shed new lights on the structural complexity and its role in explosive magnetic activity. The concept of flux rope has been widely used in modelling explosive magnetic activity, although their observational identity is rather obscure or, at least, lacking of necessary details up to date. We suggest that the magnetic wreath associated with the 3D spiral null is likely an important class of the physical entity of flux ropes.

关键词： Sun: magnetic fields -- Sun: solar corona -- Sun: activity

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Observing the reconnection region in a transequatorial loop system

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Research in Astronomy and Astrophysics 2011年第10期11卷 1209-1228页

作者： Rui Liu Tong-Jiang wang Jeongwoo Lee Guillermo Stenborg Chang Liu Sung-Hong Park hai-min wang Space Weather Research Laboratory Center for Solar-Terrestrial Research NJIT Newark NJ 07102 USA Catholic University of America and NASA Goddard Space Flight Center Greenbelt MD 20771 USA Department of Physics NJIT Newark NJ 07102 USA Interferometrics Inc. Herndon VA 20171 USA Korea Astronomy and Space Science Institute Daejeon 305-348 Republic of Korea

A vertical current sheet is a crucial element in many flare/coronal mass ejection （CME） models. For the first time, Liu et al. reported a vertical current sheet directly imaged during the flare rising phase with the EUV Imaging Telescope （EIT） onboard the Solar and Heliospheric Observatory （SOHO）. As a follow-up study, here we present the comprehensive analysis and detailed physical interpretation of the observation. The current sheet formed due to the gradual rise of a transequatorial loop system. As the loop legs approached each other, plasma flew at - 6 km s^-1 into a local area where a cusp-shaped flare loop subsequently formed and the current sheet was seen as a bright, collimated structure of global length （_〉 0.25 RQ） and macroscopic width （（5-10）× 10^3 km）, extending from 50 Mm above the flaring loop to the border of the EIT field of view （FOV）. The reconnection rate in terms of the Alfven Mach number is estimated to be only 0.005-0.009, albeit a halo CME was accelerated from - 400 km s- 1 to - 1300 km s- 1 within the coronagraph FOV. Drifting pulsating structures at metric frequencies were recorded during the impulsive phase, implying tearing of the current sheet in the high corona. A radio Type III burst occurred when the current sheet was clearly seen in EUV, indicative of accelerated electrons beam- ing upward from the upper tip of the current sheet. A cusp-shaped dimming region was observed to be located above the post-flare arcade during the decay phase in EIT; both the arcade and the dimming expanded with time. With the Coronal Diagnostic Spectrometer （CDS） aboard SOHO, a clear signature of chromospheric evaporation was seen during the decay phase, i.e., the cusp-shaped dimming region was associ- ated with plasma upflows detected with EUV hot emission lines, while the post-flare loop was associated with downflows detected with cold lines. This event provides a comprehensive view of the reconnection geometry and dynamics in the solar corona.

关键词： Sun coronal mass ejections -- Sun flares -- Sun corona

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Real-time monitoring of DNAzyme cleavage process using fluorescent assay

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Chinese Chemical Letters 2009年第8期20卷 990-994页

作者： Xiang Xian Meng Xiao hai Yang Ke min wang Wei Hong Tan Qiu Ping Guo State Key Laboratory of Chemo/Biosensing and Chemometrics Engineering Center for BiomedicineKey Laboratory for Bio-Nanotechnology and Molecular Engineering of Hunan ProvinceCollege of Chemistry and Chemical Engineering Hunan University Changsha 410082 China

Detection of deoxyribozyme （DNAzyme） cleavage process usually needs complex and time-consuming radial labeling, gel electrophoresis and autoradiography. This paper reported an approach to detect DNAzyme cleavage process in real time using a fluorescence probe. The probe was employed as DNAzyme substrate to convert directly the cleavage information into fluorescence signal in real time. Compared with traditional approach, this non-isotope method not only brought a convenient means to monitor the DNAzyme cleavage reaction, but also offered abundant dynamic data for choosing potential gene therapeutic agents. It provides a new tool for DNAzyme research, as well as a new insight into research on human disease diagnosis. Based on this method, 8- 17deoxyribozyme （8-17DNAzyme） against hepatitis C virus RNA （HCV-RNA） was designed and the cleavage process was studied in real time. ？2009 Ke min wang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All fights reserved.

关键词： DNAzyme Cleavage Real time HCV-RNA

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The Relationship between Magnetic Gradient and Magnetic Shear in Five Super Active Regions Producing Great Flares

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Chinese Journal of Astronomy and Astrophysics 2006年第4期6卷 477-488页

作者： hai-min wang Hui Song Ju Jing Vasyl Yurchyshyn Yuan-Yong Deng Hong-Qi Zhang David Falconer Jing Li National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 Big Bear Solar Observatory New Jersey Institute of Technology Big Bear City CA 92314 USA Marshall Space Flight Center SD50 Huntsville AL 35812 USA Institute for Astronomy University of Hawaii 2680 Woodlawn Drive Honolulu HI 96822 USA

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 magnetograms from Big Bear Solar Observatory, Huairou Solar Observing Station, Marshall Space Flight Center and Mees Solar Observatory. In particular, we studied the magnetic gradient derived from line-of-sight magnetograms and magnetic shear derived from vector magnetograms, 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.

关键词： Sun: activity -- Sun: flares -- Sun: magnetic fields -- Sun: coronal mass ejections (CMEs)

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A Statistical Study of Rapid Sunspot Structure Change Associated with Flares

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Chinese Journal of Astronomy and Astrophysics 2007年第5期7卷 733-742页

作者： Wei-Zhong Chen Chang Liu Hui Song Na Deng Chang-Yi Tan hai-min wang Center for Solar-Terrestrial Research New Jersey Institute of Technology University Heights Newark N J 07102-1982 USA

We reported recently some rapid changes of sunspot structure in white-light （WL） associated with major flares. We extend the study to smaller events and present here results of a statistical study of this phenomenon. In total, we investigate 403 events from 1998 May 9 to 2004 July 17, including 40 X-class, 174 M-class, and 189 C-class flares. By monitoring the structure of the flaring active regions using the WL observations from the Transition Region and Coronal Explorer （TRACE）, we find that segments in the outer sunspot structure decayed rapidly right after many flares; and that, on the other hand, the central part of sunspots near the flare-associated magnetic neutral line became darkened. These rapid and permanent changes are evidenced in the time profiles of WL mean intensity and are not likely resulted from the flare emissions. Our study further shows that the outer sunspot structure decay as well as the central structure darkening are more likely to be detected in larger solar flares. For X-class flares, over 40% events show distinct sunspot structure change. For M- and C-class flares, this percentage drops to 17% and 10%, respectively. The results of this statistical study support our previously proposed reconnection picture, i.e., the flare-related magnetic fields evolve from a highly inclined to a more vertical configuration.

关键词： Sun activity -- Sun flares -- Sun magnetic fields -- sunspots

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Automated lfare forecasting using a statistical learning technique

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Research in Astronomy and Astrophysics 2010年第8期10卷 785-796页

作者： Yuan Yuan Frank Y. Shih Ju Jing hai-min wang Computer Vision Laboratory Department of Computer Science New Jersey Institute of Technology Newark NJ 07102 USA Space Weather Research Laboratory Physics Department New Jersey Institute of Technology Newark NJ 07102 USA

We present a new method for automatically forecasting the occurrence of solar flares based on photospheric magnetic measurements. The method is a cascading combination of an ordinal logistic regression model and a support vector machine classifier. The predictive variables are three photospheric magnetic parameters, i.e., the total unsigned magnetic flux, length of the strong-gradient magnetic polarity inversion line, and total magnetic energy dissipation. The output is true or false for the occurrence of a certain level of flares within 24 hours. Experimental results, from a sample of 230 active regions between 1996 and 2005, show the accuracies of a 24- hour flare forecast to be 0.86, 0.72, 0.65 and 0.84 respectively for the four different levels. Comparison shows an improvement in the accuracy of X-class flare forecasting.

关键词： Sun flares -- Sun magnetic fields

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GATA3 siRNA inhibits the binding of NFAT1 to interleukin-13 promoter in human T cells

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Chinese Medical Journal 2010年第6期123卷 739-744页

作者： YAO Xin YANG Yan HE hai-yan wang min YIN Kai-sheng HUANG Mao Department of Respiratory Disease First Affiliated Hospital of Nanjing Medical UniversityNanjingJiangsu 210029China

Background Intedeukin-13 （IL-13） is recognized to be a key modulator in the pathogenesis of Th2-induced allergic inflammation. Transcription factors GATA3 and NFAT1 have been both implicated in the regulation of Th2 cytokines. We previously demonstrated the GATA3-NFAT1 association during human T cell activation. However, the function of the GATA3-NFAT1 complex in Th2 cytokines regulation is still unknown. Small interference RNA （siRNA） was constructed to knock down GATA3 expression in Hut-78 cells to investigate the possible role of GATA3-NFAT1 complex in IL-13 *** Cells were stimulated with anti-CD3 plus anti-CD28 antibodies to mimic in vivo antigen-mediated co-stimulation; the expression of IL-13 mRNA was determined by real-time PCR; chromation immunoprecipitation （CHIP） assay was employed to investigate the NFAT1 binding to IL-13 promoter. Results GATA3 siRNA suppressed the expression of GATA3 both in mRNA and protein levels in Hut-78 cells. The binding of NFAT1 to IL-13 promoter was inhibited by GATA3 siRNA in activated T cells, which was followed by the reduction of IL-13 *** GATA3-NFAT1 complex may play an important role in the regulation of IL-13 transcription in human T cells.

关键词： interleukin-13 asthma GATA3 NFAT1

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