质子活动与太阳黑子群

本文对太阳活动第２１周、２２周（１９７６年—１９９２年间）９７个质子活动区进行统计分析，包括活动区的面积、型别、磁结构、半影纤维等，结果表明：７５％的质子耀斑产生于面积为５００≤Ｓｐ≤３０００单位的黑子群中；耀斑爆发前一天及后一天活动区面积有显著减少；质子活动区含δ复杂磁结构的占７０％；具有半影旋涡形态的质子活动区中，约７７％的耀斑发生在旋涡黑子出现以后。     

Common Characteristics of the Active Regions of Strong Proton Flares

Common characteristics of nine active regions with strong proton flares in the 22nd solar activity cycle have been presented. Results show that the typical morphology of these active regions is a -type sunspot with a single multiple structure, in which there are many umbras with different magnetic polarities, packed tightly by a single penumbra. In these active regions, the rotating directions of the sunspot groups are nearly independent of their position on the solar disk. When the angle of rotation approaches the positive or the negative maximum, proton flares may occur in these active regions. After proton flares, sunspot groups rotate in the inverse direction because of the slack in the flux rope.     

High energetic solar proton flares on the declining phase of solar cycle 22

The year 1991 is a part of the declining phase of the solar cycle 22, during which high energetic flares have been produced by active regions NOAA/USAF 6659 in June. The associated solar proton events have affected the Earth environment and their proton fluxes have been measured by GOES space craft. The evaluation of solar activity during the first half of June 1991, have been carried out by applying a method for high energetic solar flares prediction on the flares of June 1991. The method depends on cumulative summation curves according to observed H-alpha flares, X-ray bursts, in the active region 6659 during one rotation when the energetic solar flares of June 1991 have occurred. It has been found that the steep trend of increased activity sets on several tens of hours prior to the occurrence of the energetic flare, which can be used, together with other methods, for forecasts of major flares. All the used data at the present work are received from NOAA, Boulder, Colorado, USA.     

Magnetic Twist and Writhe of δ Active Regions

We have selected 104 active regions with a δ magnetic configuration from 1996 to 2002 to study how important a role the kink instability plays in such active regions. In this study, we employ the systematic tilt angle of each active region as a proxy for the writhe of a flux tube and the force-free parameter, α_best, as a proxy for the magnetic field twist in the flux tube. It is found that 65–67% of the active regions have the same sign of twist and writhe. About 34% (32%) of the active regions violate (follow) the Hale-Nicholson and Joy's Laws (HNJL) but follow (violate) the hemispheric helicity rule (HHR). Sixty-one (61) of the 104 active regions studied each produced more than five large flares. Active regions violating HNJL, but following HHR, have a much stronger tendency to produce X-class flares and/or strong proton events. Comparing with previous studies for active regions with well-defined (simpler) bipolar magnetic configuration, it is found that the numbers following both HNJL and HHR are significantly lower in the δ-configuration case, while numbers violating one of the laws and the rule significantly increase with the increase of the magnetic complexity of the active regions. These results support the prediction for the presence of a kink instability, that the twist and writhe of the magnetic fields exhibit the same sign for δ active regions (Linton et al., Astrophys. J. 507, 40, 1998, Astrophys. J. 522, 1205, 1999; Fan et al., Astrophys. J. 521, 460, 1999). Finally, we analyze possible origins of the twist and writhe of the magnetic fields for the active regions studied.     

Flare-Induced Excitation of Solar p modes

Solar flares release large amounts of energy at different layers of the solar atmosphere, including at the photosphere in the case of exceptionally major events. Therefore, it is expected that large flares would be able to excite acoustic waves on the solar surface, thereby affecting the p-mode oscillation characteristics. We have applied the ring-diagram analysis technique to 3-D power spectra obtained for different flare regions in order to study how flares affect the amplitude, frequency and width of the acoustic modes. Data from the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory (SOHO) has been used. We have used data obtained for several active regions of the current solar cycle that have produced flares. In most cases, during the period of high flare activity, power in p modes appears to be larger when compared to that in non-flaring regions of similar magnetic field strength.     

Multi-Waveband Emission Maps of Blazars

We are leading a comprehensive multi-waveband monitoring program of 34 γ-ray bright blazars designed to locate the emission regions of blazars from radio to γ-ray frequencies. The ‘maps’ are anchored by sequences of images in both total and polarized intensity obtained with the VLBA at an angular resolution of ～0.1 milliarcseconds. The time-variable linear polarization at radio to optical wavelengths and radio to γ-ray light curves allow us to specify the locations of flares relative to bright stationary features seen in the images and to infer the geometry of the magnetic field in different regions of the jet. Our data reveal that some flares occur simultaneously at different wavebands and others are only seen at some of the frequencies. The flares are often triggered by a superluminal knot passing through the stationary ‘core’ on the VLBA images. Other flares occur upstream or even parsecs downstream of the core.     

Determination of force-free factor α and forecast of proton flares

We evaluated the force-free factor α for 18 well-observed proton flare regions during 1967–1972 according to the degree of twist in their neutral line. We found that, on the day of the flare, α ≥ 0.34 for flares of Class 1 or greater and ≥ 0.50 for Class 2 or greater and that α always increased over the one or two days before the flare. We therefore suggest that α can be used in forecasting proton events. We also outline a squeezing force-free field model of large flares which can better explain certain observed facts.     

Characteristics of the surface distribution of the larger solar flares of the twenty-first cycle

A statistical analysis of the surface distribution of the larger solar flares of the 21st cycle is carried out in this paper. The results are as follows: (1) There exist two active longitude belts, 220°–140° and 340°–320°. (2) The distribution of flares is assymetric about the solar equator. (3) Active regions located in 50°–60° E and 10°–20° W are good producers of flares; those in 80°–90° E (i.e., near the East limb) and 60°–70° W are poor producers. (4) The autocorrelation function of the flare series shows that a flare active region has a large probability of producing another flare after one rotation and a small probability of so doing after more than one rotation, and that there is a high probability of a flare occurring in the region next to the one in which a flare has already occurred.     

Automatic Tracking of Active Regions and Detection of Solar Flares in Solar EUV Images

Solar catalogs are frequently handmade by experts using a manual approach or semi-automated approach. The appearance of new tools is very useful because the work is automated. Nowadays it is impossible to produce solar catalogs using these methods, because of the emergence of new spacecraft that provide a huge amount of information. In this article an automated system for detecting and tracking active regions and solar flares throughout their evolution using the Extreme UV Imaging Telescope (EIT) on the Solar and Heliospheric Observatory (SOHO) spacecraft is presented. The system is quite complex and consists of different phases: i) acquisition and preprocessing; ii) segmentation of regions of interest; iii) clustering of these regions to form candidate active regions which can become active regions; iv) tracking of active regions; v) detection of solar flares. This article describes all phases, but focuses on the phases of tracking and detection of active regions and solar flares. The system relies on consecutive solar images using a rotation law to track the active regions. Also, graphs of the evolution of a region and solar evolution are presented to detect solar flares. The procedure developed has been tested on 3500 full-disk solar images (corresponding to 35 days) taken from the spacecraft. More than 75 % of the active regions are tracked and more than 85 % of the solar flares are detected.     

The Association of Solar Flares with Coronal Mass Ejections During the Extended Solar Minimum

We study the association of solar flares with coronal mass ejections (CMEs) during the deep, extended solar minimum of 2007?–?2009, using extreme-ultraviolet (EUV) and white-light (coronagraph) images from the Solar Terrestrial Relations Observatory (STEREO). Although all of the fast (v>900 km?s^?1), wide (θ>100^°) CMEs are associated with a flare that is at least identified in GOES soft X-ray light curves, a majority of flares with relatively high X-ray intensity for the deep solar minimum (e.g. ?1×10^?6 W?m^?2 or C1) are not associated with CMEs. Intense flares tend to occur in active regions with a strong and complex photospheric magnetic field, but the active regions that produce CME-associated flares tend to be small, including those that have no sunspots and therefore no NOAA active-region numbers. Other factors on scales similar to and larger than active regions seem to exist that contribute to the association of flares with CMEs. We find the possible low coronal signatures of CMEs, namely eruptions, dimmings, EUV waves, and Type III bursts, in 91 %, 74 %, 57 %, and 74 %, respectively, of the 35 flares that we associate with CMEs. None of these observables can fully replace direct observations of CMEs by coronagraphs.     

ANALYSES OF VECTOR MAGNETOGRAMS IN FLARE-PRODUCTIVE ACTIVE REGIONS

This paper reviews studies of the relationship between the evolution of vector magnetic fields and the occurrence of major solar flares. Most of the data were obtained by the video magnetograph systems at Big Bear Solar Observatory (BBSO) and Huairou Solar Observatory (HSO). Due to the favorable weather and seeing conditions at both stations, high-resolution vector magnetograph sequences of many active regions that produced major flares during last solar maximum (1989–1993) have been recorded. We have analyzed several sequences of magnetograms to study the evolution of vector magnetic fields of flare productive active regions. The studies have focused on the following three aspects: (1) processes which build up magnetic shear in active regions; (2) the pre-flare magnetic structure of active regions; and (3) changes of magnetic shear immediately preceding and following major flares. We obtained the following results based on above studies: (1) Emerging flux regions (EFRs) play very important roles in the production of complicated photospheric flow patterns, magnetic shear and flares. (2) Although the majority of flares prefer to occur in magnetically sheared regions, many flares occurred in regions without strong photospheric magnetic shear. (3) We found that photospheric magnetic shear increased after all the 6 X-class flares studied by us. We want to emphasize that this discovery is not contradictory to the energy conservation principle, because a flare is a three-dimensional process, and the photosphere only provides a two-dimensional boundary condition. This argument is supported by the fact that if two initial ribbons of a flare are widely separated (which may correspond to a higher-altitude flare), the correlation of the flare with strong magnetic shear is weak; if the two ribbons of a flare are close (which may correspond to a lower-altitude flare), its correlation with the strong shear is strong. (4) We have analyzed 18 additional M-class flares observed by HSO in 1989 and 1990. No detectable shear change was found for all the cases. It is likely that only the most energetic flares can affect the photospheric magnetic topology.     

太阳黑子运动引起的耀斑与活动区的耦合

利用紫台赣榆站太阳精细结构望远镜拍摄的色球和光球照片，研究了1990年11月6日至13日NOAA6361活动区的磁位形演化和耀斑产生区域，发现该活动区的活动主要集中在11日和12日两天还观测到新老活动区的碰撞耦合及耦合界面处小纤维（fibril）的快速变化，这些现象是由于前导黑子之一的p1黑子的连续几天的运动造成的．所有的活动也主要集中在P1黑子的周围．     

太阳质子事件预报研究进展

就太阳质子事件预报研究的重要意义,产生太阳质子事件的太阳活动区的一般特征,质子耀斑的辐射特征,质子事件几个重要参数预报方法简述了目前的研究进展。还给出了当前为满足用户需要改进预报应着重研究的方面。     

Solar plasma temperature diagnostics in flares and active regions from spectral lines in the range 280–330 Å in the SPIRIT/CORONAS-F experiment

Plasma temperature diagnostics in solar flares and active regions has been carried out using data from the SPIRIT spectroheliograph onboard the CORONAS-F satellite. The temperature distribution of the differential emission measure (DEM) has been determined from the relative intensities of spectral lines recorded in the spectral range 280–330 Å in the period from 2001 to 2005. Analysis of these distributions has led to the conclusion about the existence of active regions with various “characteristic” temperature compositions. The presence of a hot plasma with temperatures logT = 6.8?7.2 in active regions has been established for the first time from XUV spectroscopic data and monochromatic X-ray line images. The DEM distribution for intense long-decay flares has also been obtained for the first time and a similarity of the temperature compositions for flares of different classes at the decay phase has been found. The spectra have been modeled on the basis of the calculated DEMs. The systematic discrepancies between the calculated and measured line intensities are discussed.     

The imaging vector magnetograph at Haleakala

We describe an instrument we have built and installed at Mees Solar Observatory on Haleakala, Maui, to measure polarization in narrow-band solar images. Observations in Zeemansensitive photospheric lines have been made for nearly all solar active regions since the instrument began operations in 1992. The magnetograph includes a 28-cm aperture telescope, a polarization modulator, a tunable Fabry-Pérot filter, CCD cameras and control electronics. Stokes spectra of a photospheric line are obtained with 7 pm spectral resolution, 1 arc sec spatial resolution over a field 4.7 arc min square, and polarimetric precision of 0.1%. A complete vector magnetogram observation can be made every eight minutes. The flexibility of the instrument encourages diverse observations: besides active region magnetograms we have made, for example, composite vector magnetograms of the full solar disk, and H polarization movies of flaring regions.     

BEARALERTS: A successful flare prediction system

We describe our BEARALERT program of predicting solar flares or rapid development of activity in certain sunspot groups. The purpose of the program is to test our understanding of the flare process by making public predictions via electronic mail. Neither the exact timing of the flare nor the possibility of emergence of new active regions can be predicted. But high-resolution observations of the magnetic configuration, Ha brightness and structure and other properties of a region enabled us to announce the onset of 15 of 23 major active regions over a two-year period, and 15 of 32 BEARALERTS were followed by this activity. We used high-resolution real-time data available at the Big Bear Solar Observatory (BBSO). The criteria for prediction are given and discussed, along with those for filament eruption.The success fo the BEARALERT is evaluated by counting the M- and X-class flares in six days following the alert and comparing these results with those of a number of other predictive schemes. We find the single regions chosen had about 30% more flares than the whole disk on random days, or several times more than individual regions chosen at random. There was a gain of 1.5 to 2.0 times in flare frequency compared to regions selected by spot size or complexity. We also find an improvement of 20–40% over large or complex regions that have had some flares already. The ratio of improvement has increased with time as we gained experience. In the 24-hr period following each alert, one or more M-class or greater flares occurred 72% of the time.We also checked the possibility of prediction by the 152-day interval which some workers have claimed, but found those results slightly worse than random and considerably inferior to the BEARALERTS. All of the particularly active regions that were missed either occurred during bad weather at BBSO or were missed because we only issued alerts for one region at a time.     

Analysis of the Properties of Super Solar Proton Events and Associated Phenomena

The solar flares, the speeds of shocks propagated in the solar-terrestrial space and driven by coronal mass ejections (CMEs), the heliographic longitudes and Carrington longitudes of source regions, and the geomagnetic storms, which are accompanied by the super solar proton events with a peak ?ux equal to or exceeding 10 000 pfu, have been studied by using the data of ground-based and space observations. The results show that the heliographic longitudes of source regions of super solar proton events distributed in the range from E30? to W75°. The Carrington longitudes of source regions of super solar proton events distributed in the two longitudinal belts, 130°∼220° and 260°∼320°, respectively. All super solar proton events were accompanied by major solar flares and fast CMEs. The averaged speeds of shocks propagated from the sun to the Earth were greater than 1 200 km/s. Eight super solar proton events were followed by major geomagnetic storms (Dst≤−100 nT), except that one super solar proton event was followed by a geomagnetic storm with the geomagnetic activity index Dst=−96 nT, a little smaller than that of major geomagnetic storms.     

Observation of Hα line impact polarization in solar flares

We present the results of studying the impact linear polarization of 32 solar flares of X-ray classes C, M, and X (two flares) observed with the Large Solar Vacuum Telescope. It has turned out that there is evidence for impact polarization only in 13 of them. The newly obtained data have confirmed that the linear Stokes parameters are predominantly 2–7%, while the spatial sizes of flaring points with nonzero Stokes parameters are small (1″-2″). Two features of the manifestation of impact polarization in flares revealed by these studies are of greatest interest: (1) at the two foot points of a single flare loop or an arcade of loops, both the Hα intensity profiles and the Stokes profiles differ in behavior; (2) based on the Hα line, we have found for the first time that the sign of the Stokes parameters changes not only across the flare ribbon but also with depth of the chromosphere.     

太阳质子事件耀斑的短期预报

回顾产生太阳质子事件耀斑的短期预报,讨论短期预报在近期应做的研究．给出以下结论：（１）在６０年代和７０年代,质子事件耀斑的预报有相当大的进展;（２）新预报方法的探索和质子流在日冕与行星际的传播问题,是当前改进短期预报的关键;（３）对实际应用的短期预报工作的改进,可能需要从空间天气预报的角度,研究太阳活动区的分类．     

On the role of the magnetic configuration of flares for production of type III solar radio bursts

This paper investigates the possibility that the particular location of flare production sites in an active region is intimately connected to the production of type III radio bursts as well as centimetric and hard X-ray events. For the few active regions analysed (viz. McMath 8863, 8905, 8907 and 8921) it is shown that even a crude statistical test is sufficient in revealing significant differences concerning the emissions of these radiations by flares located in various flare production sites. In particular, flares located outside the general bipolar pattern of the active region are characterized by a higher type III flare association rate (? 50 %) than those taking place inside of it (? 20 %). Centimetric and hard X-ray events are more likely to be expected in connection with flares located inside strong magnetic fields arising from well developed sunspots. Such results are pointing out that the concept of ‘flare production sites’ is important not only in relation with the Hα flare activity but also in relation with the non-thermal emissions accompanying the flares. Probably this is due to changing magnetic configuration from one flare site to the other.