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Based on SOHO/MDI, EIT, Yohkoh/SXT, Hα , and other relevant observations, we analyzed all the earth-directed halo coronal mass ejections (CMEs) in the interval from Mar. 1997 to Dec. 2003. A total of 288 earth-directed CMEs were studied and their associated surface activity events identified. Unlike the previous studies that often attributed a surface activity event or a given active region to a CME source region, this statistical analysis puts emphasis on the large-scale magnetic structures of CMEs, in which the CME-associated surface activity takes place. All the CMEs are found to be associated with large-scale source structures. The identified large-scale structures can be grouped into four different categories: extended bipolar regions (EBRs), transequatorial magnetic loops, transequatorial filaments and their associated magnetic structures, and long filaments along the boundaries of EBRs. The relative percentages of their associated CMEs are 36%, 40%, 13%, and 11%, respectively. The analysis indicates that CMEs are intrinsically associated with source magnetic structures on a large spatial scale.

Employing data recorded by the Michelson Doppler Imager (MDI) instrument on the Solar and Heliospheric Observatory (SOHO), we have identified 144 pairs of opposite magnetic polarity moving magnetic features (MMFs) in two active regions (NOAA ARs 8375 and 9236). The following results are obtained: (1) The majority of MMF pairs first appears at a distance of 1000 to 5000 km from the outer boundary of the sunspot, although MMF pairs appearing closer to the sunspot may be missed. (2) MMF bipoles are not randomly oriented. The member of an MMF pair further from the sunspot has the polarity of the parent sunspot in 85% of the cases. Furthermore, the orientations of MMF pairs are associated with the twist of the sunspot superpenumbra deduced from HIT images. (3) The mean lifetime of the studied MMFs is around 4 hours. (4) The separation between the two polarities of the MMFs falls in the range of 1100-1700 km. This separation remains almost unchanged, even decreases slightly as the MMF pairs move outwards. (5) MMFs are observed to cluster at particular azimuths around the parent sunspot, in particular in AR 8375. (6) MMF pairs move approximately radially outward from sunspots at an average speed of around 0.5 km s - 1 . Their motion is deflected towards large concentrations of magnetic flux of opposite polarity to that of the parent sunspot. A qualitative model based on these and other observations is presented. MMF pairs are proposed to be part of a U-loop emanating from the sunspot's magnetic canopy. Possible mechanisms leading to the formation of such a loop are discussed.

In this paper, we investigate the prospect of using previously occurring sunspot cycle signatures to determine future behavior in an ongoing cycle, with specific application to cycle 23, the current sunspot cycle. We find that the gross level of solar activity (i.e., the sum of the total number of sunspots over the course of a sunspot cycle) associated with cycle 23, based on a comparison of its first several years of activity against similar periods of preceding cycles, is such that cycle 23 best compares to cycle 2. Compared to cycles 2 and 22, respectively, cycle 23 appears 1.08 times larger and 0.75 times as large. Because cycle 2 was of shorter period, we infer that cycle 23 also might be of shorter length (period less than 11 years), ending sometime in late 2006 or early 2007.

In the present work, the dominant hemisphere of solar activity in each of solar cycles 12 to 22 has been clarified by calculating the actual probability of the hemispheric distribution of several solar activity phenomena using long-term observational records. An attempt is made to demonstrate that a long characteristic time scale, about 12-cycle length, is inferred to occur in solar activity.

Context. Balmer absorption is a rare phenomenon in active galactic nuclei (AGNs). So far, only seven Balmer-absorption AGNs have been reported in the literature. Aims. We here report the identification of SDSS J112611.63+425246 as a new Balmer-absorption AGN through our spectral analysis and study the kinematics of its narrow emission-line region (NLR). Methods. We modeled the continuum by a linear combination of a starlight component, a power law from the central AGN, and the emission from the FeII complex. After subtracting the modeled continuum, each emission or absorption line profile is a sum of multi-Gaussian functions. All the line shifts were determined with respect to the modeled starlight component. Results. By using the host starlight as a reference for the local system, both Hα and Hβ show AGN absorptions with a blueshift of ∼300 km s−1. We identify a strong anticorrelation between the inferred velocity shifts and the ionization potential for various narrow emission lines, which suggests a stratified NLR kinematics. A de-accelerated outflow is implied for the inner NLR gas, an accelerated inflow for the outer NLR gas. This complicated NLR kinematics additionally implies that AGN narrow emission lines, even for the low-ionized lines, might not be a reliable substitute for the velocity of the local system.

The vector magnetic field characteristics of superactive regions (SARs) hold the key for understanding why SARs are extremely active and provide the guidance in space weather prediction. We aim to quantify the characteristics of SARs using the vector magnetograms taken by the Solar Magnetic Field Telescope at Huairou Solar Observatory Station. The vector magnetic field characteristics of 14 SARs in solar cycles 22 and 23 were analyzed using the following four parameters: 1) the magnetic flux imbalance between opposite polarities, 2) the total photospheric free magnetic energy, 3) the length of the magnetic neutral line with its steep horizontal magnetic gradient, and 4) the area with strong magnetic shear. Furthermore, we selected another eight large and inactive active regions (ARs), which are called fallow ARs (FARs), to compare them with the SARs. We found that most of the SARs have a net magnetic flux higher than 7.0\times10^21 Mx, a total photospheric free magnetic energy higher than 1.0\times10^24 erg/cm, a magnetic neutral line with a steep horizontal magnetic gradient (\geq 300 G/Mm) longer than 30 Mm, and an area with strong magnetic shear (shear angle \geq 80\degree) greater than 100 Mm^2. In contrast, the values of these parameters for the FARs are mostly very low. The Pearson \c{hi}2 test was used to examine the significance of the difference between the SARs and FARs, and the results indicate that these two types of ARs can be fairly distinguished by each of these parameters. The significance levels are 99.55%, 99.98%, 99.98%, and 99.96%, respectively. However, no single parameter can distinguish them perfectly. Therefore we propose a composite index based on these parameters, and find that the distinction between the two types of ARs is also significant with a significance level of 99.96%. These results are useful for a better physical understanding of the SAR and FAR, 9 pages, 3 figures, 2 tables

We investigate the coherence of the twin kilohertz quasi-periodic oscillations (kHz QPOs) in the low-mass X-ray binary (LMXB) theoretically. The profile of upper kHz QPO, interpreted as Keplerian frequency, is ascribed to the radial extent of the kHz QPO emission region associated with the transitional layer at the magnetosphere-disc boundary, which corresponds to the coherence of upper kHz QPO. The theoretical model for the Q-factor of upper kHz QPO is applied to the observational data of five Atoll and five Z sources, and the consistence is implied.

Context. Magnetic reconnection is a central concept for understanding solar activity, including filament eruptions, flares, and coronal mass ejections (CMEs). The existence of transverse and vertical current sheets, sites where reconnection takes place in the solar atmosphere, is frequently proposed as a precondition for flare/CME models, but is rarely identified in observations. Aims. We aim at identifying a transverse current sheet that existed in the pre-CME structure and persisted from the CME solar source to interplanetary space. Methods. STEREO A/B provide us a unique opportunity to calculate the interplanetary current sheets for the magnetic cloud. We analyze such a structure related to the fast halo CME of 2006 December 13 with assembled observations. A current sheet at the front of the magnetic cloud is analyzed to its origin in a transverse current sheet in the CME solar source, which can be revealed in the magnetic field extrapolations, XRT, and LASCO observations. Results. An interplanetary current sheet is identified as coming from the CME solar source by carefully mapping and examining multiple observations from the Sun to interplanetary space, along with nonlinear force-free magnetic field extrapolations of the active region NOAA 10930. Conclusions. The structure identified in the pre-flare state is a global transverse current sheet, which plays a role in the CME initiation, and propagates from the corona to interplanetary space.