Evolution of a Long-lived Sunspot Group and Its Associated Solar-terrestrial Events

A long-lived sunspot group (AR9604) on the south hemisphere that lasted five solar rotations and produced some strong bursts is analyzed. The focus is on its evolving features. Its whole life was successfully maintained by four Emerging Flux Regions (EFRs). Apart from the one that lasted only a short time and did not produce any bursts, the other three EFRs have the following common features: (1) A positive writhe of magnetic flux tubes and a twist of the field lines of the same sign, indicating kink instability. (2) A clockwise rotation and a high tilt because the writhe was right-handed. (3) A compact 'island δ' structure of the sunspot group indicating concentrated kink instability. Since magnetic reconnection easily occurs at the kinked point of a very kink-unstable flux tube, these features should be the inducement of the strong bursts.

Signature of high-order azimuthal MHD body modes in sunspot's low atmosphere

The five-minute oscillations inside sunspots appear to be the absorption of the solar p-mode. It is a potential tool to probe a sunspot＇s sub-structure. We studied the collective properties of five-minute oscillations in the power and phase distribution at the sunspot＇s umbra-penumbra boundary. The azimuthal distributions of the power and phase of five-minute oscillations enclosing a sunspot＇s umbra were obtained with images taken with the Solar Dynamics Observatory/Atmospheric Imaging Assembly （SDO/AIA）. The azimuthal modes were quantified with periodogram analysis and justified with significance tests. The azimuthal nodal structures in an approximately ax- ially symmetric sunspot AR 11131 （2010 Dec 08） were investigated. Mode numbers ra = 2, 3, 4, 7, 10 were obtained in both 1700 A and 1600A bandpasses. The 1600A channel also revealed an extra mode at m = 9. In the upper atmosphere （304 A）, fewer modes were detected at m = 3, 4, 7. The azimuthal modes in the sunspot＇s low atmo- sphere could be interpreted as high-order azimuthal MHD body modes. They were detected in the power and phase of the five-minute oscillations in sunspot AR 11131 with SDO/AIA data. Fewer modes were detected in the sunspot＇s upper atmosphere.

Multiple cycles of magnetic activity in the Sun and Sun-like stars and their evolution

The wavelet transform method for high-quality time-frequency analysis is applied to sets of observations of relative sunspot numbers and stellar chromosphere fluxes of 10 Sun-like stars. Wavelet analysis of solar data shows that in a certain interval of time there are several cycles of activity with pe- riods of duration which vary considerably from each other： from quasi-biennial cycles to lO0-yr cycles. Cyclic activity was detected in almost all Sun-like stars that we examined, even those that previously were not considered as stars with cyclic activity according to analysis using a Scargle periodogram. The durations of solar and stellar cycles significantly change during the observation period.

Support Vector Machine combined with K-Nearest Neighbors for Solar Flare Forecasting

A method combining the support vector machine （SVM） the K-Nearest Neighbors （KNN）, labelled the SVM-KNN method, is used to construct a solar flare forecasting model. Based on a proven relationship between SVM and KNN, the SVM-KNN method improves the SVM algorithm of classification by taking advantage of the KNN algorithm according to the distribution of test samples in a feature space. In our flare forecast study, sunspots and 10cm radio flux data observed during Solar Cycle 23 are taken as predictors, and whether an M class flare will occur for each active region within two days will be predicted. The SVM- KNN method is compared with the SVM and Neural networks-based method. The test results indicate that the rate of correct predictions from the SVM-KNN method is higher than that from the other two methods. This method shows promise as a practicable future forecasting model.

顺铂处理的肺癌细胞NSUN 2 mRNA剪接异构体变化

目的:探讨顺铂(CDDP)处理肺癌细胞后NSUN 2 pre-mRNA的剪接变化。方法:在NSUN 2基因的pre-mRNA有选择性剪接的外显子两侧的外显子上设计检测引物,选取16例非小细胞肺癌患者的肿瘤组织及其癌旁正常组织,采用反转录聚合酶链式反应(RT-PCR)检测组织NSUN 2各mRNA剪接异构体的表达;取人肺癌细胞系A549细胞和H1299细胞分别用不同浓度CDDP处理,A549细胞分为0、8、16、24、32、40、48及56μmol/L组,H1299细胞分为0、12、24、36、48、60、72及84μmol/L组,采用RT-PCR检测各组细胞NSUN 2各mRNA剪接异构体的表达;RT-PCR产物胶回收后进行TA克隆测序并与NCBI网站数据库中NSUN 2的序列进行比对分析。结果:人肺癌细胞系A549细胞和H1299细胞及肺癌临床样本中NSUN 2基因可编码蛋白的mRNA剪接异构体表达量最高,占主导地位;随着CDDP浓度增加,NSUN 2可编码蛋白的异构体在H1299细胞的高浓度组中的表达下降(P<0.01),非编码蛋白的异构体在A549细胞和H1299细胞的高浓度组中表达均上升(P<0.05);检测到2种未见报道的mRNA剪接异构体。结论:CDDP处理后肺癌细胞中NSUN 2 pre-mRNA剪接会发生变化,NSUN 2基因的表达存在pre-mRNA选择性剪接调控。

Synthetic analysis of a two-ribbon microflare

High-resolution Stokes spectral data of Hα, Ca Ⅱ 8542A, and Fe 16302.5A lines for a two-ribbon microflare （TRMF） were simultaneously obtained by the THEMIS telescope on 2002 September 5. We derive the intensity, velocity, and longitudinal magnetic field maps. The hard X-ray emission observed by RHESSI provides evidence of nonthermal particle acceleration in the TRMF. Using Ha and Ca Ⅱ 8542A line profiles and a non-LTE calculation, we obtain semi-empirical atmospheric models for the two brightest kernels of the TRME Our result indicates that the temperature enhancement in the chromosphere is more than 2500 K. The kinetic and radiative energies at the kernels are also estimated, resulting in an estimate of the total energy of the TRMF of about 2.4×10^29 erg. Observations indicate that the TRMF results from the low coronal magnetic reconnection following the eruption of a small fila- ment. However, the local temperature ＂bump＂ in the chromosphere presents a puzzle for such a standard flare model. A possible solution to this is discussed.

The causality between the rapid rotation of a sunspot and an X3.4 flare

Using multi-wavelength data of Hinode, the rapid rotation of a sunspot in active region NOAA 10930 is studied in detail. We found extraordinary counterclockwise rotation of the sunspot with positive polarity before an X3.4 flare. From a series of vector magnetograms, it is found that magnetic force lines are highly sheared along the neutral line accompanying the sunspot rotation. Furthermore, it is also found that sheared loops and an inverse S-shaped magnetic loop in the corona formed gradually after the sunspot rotation. The X3.4 flare can be reasonably regarded as a result of this movement. A detailed analysis provides evidence that sunspot rotation leads to magnetic field lines twisting in the photosphere. The twist is then transported into the corona and triggers flares.

A comparison between magnetic shear and flare shear in a well-observed M-class flare

We give an extensive multi-wavelength analysis of an eruptive M1.0/1N class solar flare, which occurred in the active region NOAA 10044 on 2002 July 26. Our emphasis is on the relationship between magnetic shear and flare shear. Flare shear is defined as the angle formed between the line connecting the centroids of the two ribbons of the flare and the line perpendicular to the magnetic neutral line. The magnetic shear is computed from vector magnetograms observed at Big Bear Solar Observatory （BBSO）, while the flare shear is computed from Transition Region and Coronal Explorer （TRACE） 1700A images. By a detailed comparison, we find that; 1） The magnetic shear and the flare shear of this event are basically consistent, as judged from the directions of the transverse magnetic field and the line connecting the two ribbons＇ centroids. 2） During the period of the enhancement of magnetic shear, flare shear had a fast increase followed by a fluctuated decrease. 3） When the magnetic shear stopped its enhancement, the fluctuated decreasing behavior of the flare shear became very smooth. 4） Hard X-ray （HXR） spikes are well correlated with the unshearing peaks on the time profile of the rate of change of the flare shear. We give a discussion of the above phenomena.

Wavelet Analysis of Several Important Periodic Properties in the Relative Sunspot Numbers

We investigate the wavelet transform of yearly mean relative sunspot number series from 1700 to 2002. The curve of the global wavelet power spectrum peaks at 11-yr, 53-yr and 101-yr periods. The evolution of the amplitudes of the three periods is studied. The results show that around 1750 and 1800, the amplitude of the 53-yr period was much higher than that of the the 11-yr period, that the ca. 53-yr period was apparent only for the interval from 1725 to 1850, and was very low after 1850, that around 1750, 1800 and 1900, the amplitude of the 101-yr period was higher than that of the 11-yr period and that, from 1940 to 2000, the 11-yr period greatly dominates over the other two periods.

Low Dimensional Chaos from the Group Sunspot Numbers

We examine the nonlinear dynamical properties of the monthly smoothed group sunspot number Rg and find that the solar activity underlying the time series of Rg is globally governed by a low-dimensional chaotic attractor. This finding is consistent with the nonlinear study results of the monthly Wolf sunspot numbers. We estimate the maximal Lyaponuv exponent （MLE） for the Rg series to be positive and to equal approximately 0.0187 ± 0.0023 （month^- 1）. Thus, the Lyaponuv time or predictability time of the chaotic motion is obtained to be about 4.46 ± 0.5 years, which is slightly different with the predictability time obtained from Rz. However, they both indicate that solar activity forecast should be done only for a short to medium term due to the intrinsic complexity of the time behavior concerned.

Short-term solar flare prediction using multi-model integration method

A multi-model integration method is proposed to develop a multi-source and heterogeneous model for short-term solar flare prediction. Different prediction models are constructed on the basis of extracted predictors from a pool of observation databases. The outputs of the base models are normal- ized first because these established models extract predictors from many data resources using different prediction methods. Then weighted integration of the base models is used to develop a multi-model integrated model （MIM）. The weight set that single models assign is optimized by a genetic algorithm. Seven base models and data from Solar and Heliospheric Observatory/Michelson Doppler Imager lon- gitudinal magnetograms are used to construct the MIM, and then its performance is evaluated by cross validation. Experimental results showed that the MIM outperforms any individual model in nearly every data group, and the richer the diversity of the base models, the better the performance of the MIM. Thus, integrating more diversified models, such as an expert system, a statistical model and a physical model, will greatly improve the performance of the MIM.

A Multi-Wavelength Study of the 3B/X1.2 Flare Observed on 2003 October 26

We report results from a multi-wavelength study of the 3B/X1.2 tworibbon disk flare （S15E44）, which was well observed by both ground-based and space-borne instruments. Two pairs of conjugate kernels - K1 and K4, and K2 and K3 - in the Ha images are identified. These kernels are linked by two different systems of EUV loops. K1 and K4 correspond to the two 17 GHz and 34 GHz microwave sources observed by the Nobeyama Radioheliograph （NoRH）, while K2 and K3 have no corresponding microwave sources. Optical spectroscopic observations suggest that all the four kernels are possible precipitating sites of non-thermal electrons. Thus the energy of electron deposited in K2 and K3 should be less than 100keV. Two-dimensional distributions of the full widths at half maximum （FWHM） of the Ha profiles and the line-of-sight （LOS） velocities derived from the Ca n 8542 A profiles indicate that the largest FWHM and LOS velocity tends to be located near the outer edges of Hα kernels, which is consistent with the scenario of current two-ribbon flare models and previous results. When non-thermal electron bombardment is present, the observed Hα and Ca II 8542 A profiles are similar to previous observational and theoretical results, while the He I 10830 A profiles are different from the theoretical ones. This puts some constraints on future theoretical calculation of the He I 10830 A line.

Calibration of Vector Magnetogram with the Nonlinear Least-squares Fitting Technique

To acquire Stokes profiles from observations of a simple sunspot with the Video Vector Magnetograph at Huairou Solar Observing Station (HSOS), we scanned the FeI λ5324.19 A line over the wavelength interval from 150mA redward of the line center to 150mA blueward, in steps of 10mA. With the technique of analytic inversion of Stokes profiles via nonlinear least-squares, we present the calibration coefficients for the HSOS vector magnetic magnetogram. We obtained the theoretical calibration error with linear expressions derived from the Unno-Becker equation under weak-field approximation.

Observational Characteristics of Radio Emission Related to Multi-polar Magnetic Configuration

We present a large complex radio burst and its associated fast time structures observed on 2001 April 10 in the frequency range of 0.65-7.6 GHz. The NoRH radio image observation shows very complex radio source structures which include preexisting, newly emerging, submerging/cancelling polarities and a bipolar, a tripolar （a ＇bipolar ＋ remote unipolar＇）, and a quadrupolar structure. This suggests that the radio burst is generated from a very complicated loop structure. According to the spectral and image observations, we assume that the beginning of this flare was caused by a single bipolar loop configuration with a ‘Y-type＇ re- connection structure. A composite of radio continuum and fast time structures is contained in this flare. The various fast radio emission phenomena include normal and reverse drifting type Ⅲ bursts, and slowly drifting and no-drift structures. The tripolar configurations may form a double-loop with a ＇three-legged＇ struc- ture, which is an important source of the various types of fast time structures. The two-loop reconnection model can lead simultaneously to electron acceleration and corona heating. We have also analyzed the behaviors of coronal magnetic polarities and the emission processes of different types radio emission qualitatively. Interactions of a bipolar or multi-polar loop are consistent with our observational results. Our observations favor the magnetic reconnection configurations of the ‘inverted Y-type＇ （bipolar） and the ‘three-legged＇ structures （tripolar or quadrupo- lar）.

Design and calibration of a high-sensitivity and high-accuracy polarimeter based on liquid crystal variable retarders

Polarimetry plays an important role in the measurement of solar magnetic fields. We devel- oped a high-sensitivity and high-accuracy polarimeter （HHP） based on nematic liquid crystal variable retarders （LCVRs）, which has a compact setup and no mechanical moving parts. The system design and calibration methods are discussed in detail. The azimuth error of the transmission axis of the polarizer as well as the fast axes of the two LCVRs and the quarter-wave plate were determined using dedicated procedures. Linearly and circularly polarized light were employed to evaluate the performance of the HHP. The experimental results indicate that a polarimetric sensitivity of better than 5.7 × 10-3 can be achieved by using a single short-exposure image, while an accuracy on the order of 10-5 can be reached by using a large number of short-exposure images. This makes the HHP a high-performance system that can be used with a ground-based solar telescope for high-precision solar magnetic field investigations.

Local sunspot oscillations and umbral dots

Data analysis of sunspot oscillations based on a 6-hr SDO run of an observation showed that low frequency （0.2 〈ω 〈 1 mHz） oscillations are locally similar to three and five minute oscillations. The oscillations in the sunspot are concentrated in cells of a few arcsec, each of which has its own oscillation spectrum. The analysis of two scenarios for sunspot oscillations leads to a conclusion that local sunspot oscillations occur due to a subphotospheric resonator for slow MHD waves. Empirical models of a sunspot atmosphere and the theory of slow waves in thin magnetic flux tubes are applied to modeling the subphotospheric resonator. The spectrum of local oscillations consists of a great number of lines. This kind of spectrum can occur only if the subphotospheric resonator is a magnetic tube with a rather weak magnetic field. Magnetic tubes of this sort are umbral dots that appear due to the convective tongues in monolithic sunspots. The interrelation of local oscillations with umbral dots and wavefronts of traveling waves in sunspots is discussed.

Application of a data-driven simulation method to the reconstruction of the coronal magnetic field

Ever since the magnetohydrodynamic （MHD） method for extrapolation of the solar coronal magnetic field was first developed to study the dynamic evolution of twisted magnetic flux tubes, it has proven to be efficient in the reconstruction of the solar coronal magnetic field. A recent example is the so-called data-driven simu- lation method （DDSM）, which has been demonstrated to be valid by an application to model analytic solutions such as a force-free equilibrium given by Low and Lou. We use DDSM for the observed magnetograms to reconstruct the magnetic field above an active region. To avoid an unnecessary sensitivity to boundary conditions, we use a classical total variation diminishing Lax-Friedrichs formulation to iteratively compute the full MHD equations. In order to incorporate a magnetogram consistently and sta- bly, the bottom boundary conditions are derived from the characteristic method. In our simulation, we change the tangential fields continually from an initial potential field to the vector magnetogram. In the relaxation, the initial potential field is changed to a nonlinear magnetic field until the MHD equilibrium state is reached. Such a stable equilibrium is expected to be able to represent the solar atmosphere at a specified time. By inputting the magnetograms before and after the X3.4 flare that occurred on 2006 December 13, we find a topological change after comparing the magnetic field before and after the flare. Some discussions are given regarding the change of magnetic con- figuration and current distribution. Furthermore, we compare the reconstructed field line configuration with the coronal loop observations by XRT onboard Hinode. The comparison shows a relatively good correlation.

A Tilt-correction Adaptive Optical System for the Solar Telescope of Nanjing University

A tilt-correction adaptive optical system installed on the 430 mm Solar Telescope of Nanjing University has been put in operation. It consists of a tip-tilt mirror, a correlation tracker and an imaging CCD camera. An absolute difference algorithm is used for detecting image motion in the correlation tracker. The sampling frequency of the system is 419 Hz. We give a description of the system's configuration, an analysis of its performance and a report of our observational results. A residual jitter of 0.14 arcsec has been achieved. The error rejection bandwidth of the system can be adjusted in the range 5-28 Hz according to the beacon size and the strength of atmospheric turbulence.

LRG1 promotes corneal angiogenesis and lymphangiogenesis in a corneal alkali burn mouse model

AIM:To investigate the potential effect and mechanism of leucine-richα-2-glycoprotein-1(LRG1)on corneal angiogenesis and lymphangiogenesis.METHODS:Corneal neovascularization and lymphatics were induced by establishing alkali burn mouse model.Immunofluorescence staining was performed to detect the location of LRG1 in cornea tissues and to verify the source of LRG1-positive cells.Corneal whole-mount staining for CD31(a panendothelial cell marker)and lymphatic endothelial hyluronan receptor-1(LYVE-1;lymphatic marker)was performed to detect the growth of blood and lymphatic vessels after local application of exogenous LRG1 protein or LRG1 si RNA.In addition,expressions of the proangiogenic vascular endothelial growth factor(VEGF)related proteins were detected using Western blot analysis.RESULTS:LRG1 was dramatically increased in alkali burned corneal stroma in both the limbal and central areas.LRG1-positive cells in the corneal stroma were mainly derived from Vimentin-positive cells.Local application ofexogenous LRG1 protein not only aggravated angiogenesis but also lymphangiogenesis significantly(P<0.01).LRG1 group upregulated the levels of VEGF and the vascular endothelial growth factor receptor(VEGFR)family when compared with the phosphate-buffered saline(PBS)control group.We also found that LRG1-specific si RNA could suppress corneal angiogenesis and lymphangiogenesis when compared with the scramble si RNA-treated group(P<0.01).CONCLUSION:LRG1 can facilitate corneal angiogenesis and lymphangiogenesis through heightening the stromal expression of VEGF-A,B,C,D and VEGFR-1,2,3;LRG1-specific si RNA can suppress corneal angiogenesis and lymphangiogenesis in corneal alkali burn mice.

Preprocessing photospheric vector magnetograms for nonlinear force-free field extrapolation of the global corona

Nonlinear force-free magnetic field （NLFFF） extrapolation based on the observed photo- spheric magnetic field is the most important method to obtain the coronal magnetic field nowadays. However, raw photospheric magnetograms contain magnetic forces and small-scale noises, and fail to be consistent with the force-free assumption of NLFFF models. The procedure for removing the forces and noises in observed data is called preprocessing. In this paper, we extend the preprocessing code of Jiang ＆ Feng to spherical coordinates for a full sphere. We first smooth the observed data with Gaussian smoothing, and then split the smoothed magnetic field into a potential field and a non-potential field. The potential part is computed by a numerical potential field model, and the non-potential part is prepro- cessed using an optimization method to minimize the magnetic forces and magnetic torques. Applying the code to synoptic charts of the vector magnetic field from SDO/HMI, we find it can effectively reduce the noises and forces, and improve the quality of data for a better input which will be used for NLFFF extrapolations applied to the global corona.