Effects of coronal mass ejections on distant coronal streamers

The effects of a large coronal mass ejection (CME) on a solar coronal streamer located roughly 90° from the main direction of the CME propagation observed on January 2, 2012 by the SOHO/LASCO coronograph are analyzed. Radial coronal streamers undergo some bending when CMEs pass through the corona, even at large angular distances from the streamers. The phenomenon resembles a bending wave traveling along the streamer. Some researchers interpret these phenomena as the effects of traveling shocks generated by rapid CMEs, while others suggest they are waves excited inside the streamers by external impacts. The analysis presented here did not find convincing arguments in favor of either of these interpretations. It is concluded that the streamer behavior results from the effect of the magnetic field of a moving magnetic flux rope associated with the coronal ejection. The motion of the large-scale magnetic flux rope away from the Sun changes the surrounding magnetic field lines in the corona, and these changes resemble the half-period of a wave running along the streamer.     

The role of rising magnetic tubes in the formation of impulsive coronal mass ejections

Two impulsive limb coronal mass ejections (CMEs), one of which was accompanied by an active prominence and the other by a flare, are analyzed using AIA/SDO solar data. The analysis leads to the conclusion that, in both cases, the sources of the CME formation were magnetic tubes rising from beneath the photosphere at high velocity. One or more arch structures can be located in the path of the magnetic tube, which it influences and drags along with it. The arch structures may then participate in the formation of the future CME, whose main basis is the magnetic tube itself.     

Detecting the widths of shock fronts preceding coronal mass ejections

The perturbed zones and shocks preceding coronal mass ejections (CMEs) are studied using the data of the Mark 4, LASCO C2, and LASCO C3 coronagraphs. Detection of the perturbed zone indicating the presence or absence of the shock is most reliable in a frame moving with the frontal structure of the CME. The ability to correctly measure the width δ _F of the shock front using the Mark 4 and LASCO C2 data is established. The front width δ _F observed along the streamer belt at distances R < 5 R _⊙ from the center of the Sun is of the order of the mean free path of protons. This means that the energy dissipation in the shock front is collisional at such distances. At distances R ≥ (10 − 15) R _⊙, a new discontinuity with a front δ* _F ≪ δ _F is formed in the leading portion of the front. Within the errors, δ* _F ≈ (0.1–0.2) R _⊙ is independent of the distance R and is determined by the LASCO C3 spatial resolution. Initially, the discontinuity on the scale δ* _F is weak and coexists with the front with width δ _F . The relative amplitude of this discontinuity increases and the brightness profile behind it flattens as long as the distance R increases. This transformation of the brightness profile from a front of width δ F to a discontinuity of width δ* _F ≪ δ _F is explained as a transition from a collisional to a collisionless shock.     

Solar large-scale channeled dimmings produced by coronal mass ejections

A new type of dimmings, or transient coronal holes (i.e., regions of reduced soft-X-ray and EUV emission), is revealed in analyses of difference solar images obtained with the SOHO EIT ultraviolet telescope at 195 Å. Such features can be observed on the solar disk after halo-type coronal mass ejections (CMEs). If several active regions, filaments, and other structures are present on the disk during a major eruptive event, then strongly anisotropic, channel-shaped (“channeled”) dimmings coexist with relatively compact dimmings adjacent to the eruption center. The channeled dimmings are comparable to the compact dimmings in terms of their contrast; stretch along several narrow, extended features (channels); and can span nearly the entire visible disk. Coronal waves, which appear as fronts of enhanced brightness traveling ahead of the dimmings in some halo CME events, are also anisotropic. We argue that such transient phenomena are closely related to the strong disturbance and restructuring of large-scale magnetic fields involved in CMEs, and the channeled character of the dimmings reflects the complexity of the global solar magnetosphere, in particular, near the solar-activity maximum.     

Relations estimated at shock discontinuities excited by coronal mass ejections

An analysis of SOHO/LASCO C₃ data shows that there are discontinuities in the radial profiles of the plasma density within limited regions in front of each of ten coronal mass ejections, which represent shocks. The shock velocities in various events reach V ≈ 800–2500 km/s. A comparison of the dependence of the AlfvenicMach numberM _A on the shock strength ρ ₂/ρ ₁ detected at distancesR > 10R⊙ from the center of the Sun with calculations carried out using ideal magnetic hydrodynamics shows that the effective ratio of specific heats γ describing processes inside the shock front varies from 2 to 5/3 (ρ ₁ and ρ ₂ are the densities in front of and behind the shock, and R⊙ is the solar radius). This corresponds to an effective number of degrees of freedom between two and three. A similar dependenceMA(ρ ₂ /ρ ₁) was found for near-Earth bow shocks and interplanetary collisionless shocks. These features support the hypothesis that the studied discontinuities preceding coronal mass ejections are collisionless shocks.     

Plasma motion in crossed fields and halo-type coronal mass ejections

Halo-type motions of plasma in the solar corona—so-called coronal mass ejections (CME)—are considered. This type of CME is relatively rare due to the requirement for a particular orientation of the magnetic-moment vector M (parallel to the line of sight). Variations in |M| may be due to the rapid motion of filaments with a characteristic time scale ?10³ s. The drifts in the crossed fields have speeds of ?200–1000 km/s and can account for the basic features of the CME geometry.     

The detection of coronal mass ejections in the interplanetary medium using scintillation observations

Daily observations of scintillating radio sources obtained from July 2011 through June 2012 on the Big Scanning Antenna of the P.N. Lebedev Physical Institute at 111 MHz using a 16 beams system are analyzed. Variations in the observed scintillation indices are compared with data on solar X-ray flares and geomagnetic disturbances. Comparison of the observed scintillation indices on successive days enables the detection of most propagating disturbances associated with coronal events of class M5.0 and higher.     

Evidence for shock generation in the solar corona in the absence of coronal mass ejections

The solar event SOL2012–10–23T03:13, which was associated with a X1.8 flare without an accompanying coronal mass ejection (CME) and with a Type II radio burst, is analyzed. A method for constructing the spatial and temporal profiles of the difference brightness detected in the AIA/SDOUVand EUV channels is used together with the analysis of the Type II radio burst. The formation and propagation of a region of compression preceded by a collisional shock detected at distances R < 1.3R _⊙ from the center of the Sun is observed in this event (R _⊙ is the solar radius). Comparison with a similar event studied earlier, SOL2011–02–28T07:34 [1], suggests that the region of compression and shock could be due to a transient (impulsive) action exerted on the surrounding plasma by an eruptive, high-temperature magnetic rope. The initial instability and eruption of this rope could be initiated by emerging magnetic flux, and its heating from magnetic reconnection. The cessation of the eruption of the rope could result from its interaction with surrounding magnetic structures (coronal loops).     

Magnetic-field variations in the active region NOAA 10486 and their relationship to X-ray flares and coronal mass ejections

SOHO/MDI magnetograms are used to analyze the time variations in the magnetic parameters of the active region (AR) NOAA 10486, which was part of a large activity complex that passed over the solar disk from October 26 to 31, 2003, during solar cycle 23. The results are compared with X-ray flares in the AR and the parameters of coronal mass ejections associated with the AR. The time variations in the distributions of themagnetic-field strengths associated with the total magnetic flux (Fa), the flux imbalance between the northern and southern polarities (Im), the complexity of the field, as a measure of the mutual overlapping of the opposite polarities (Co), and the tilt angle of the magnetic axis (An) are considered. The time variations in the free energy accumulated in current sheets of ARs were traced using a parameter introduced for this purpose (Sh). The following results were obtained. First, the parameters Fa, Im, Co, An, and Sh quantitatively describe the current state of the AR and can be used to trace and analyze the dynamical evolution of its magnetic field. Second, variations in the magnetic-field-strength distributions and the mean values of Fa, Im, Co, An, and Sh are associated with flares and coronal mass ejections, and the variations have considerable amplitudes. Third, the parameter Sh characterizing the degree to which the magnetic field is non-potential in regions adjacent to the main neutral line increases before eruptive events, and is thus particular interest for monitoring the states of ARs in real time. Fourth, the magnetic field of the AR manifests a sort of quasi-elasticity, so that the field structure is restored after active events, on average, within 1–3 h.     

Large-scale dimmings produced by solar coronal mass ejections according to SOHO/EIT data in four EUV lines

SOHO/EIT data are used to analyze dimmings, or transient coronal holes (regions of reduced soft-X-ray and EUV emission), which are observed on the solar disk after halo-type coronal mass ejections (CMEs). Simultaneous observations in the 171 Å FeIX/X, 195 Å FeXII, and 284 Å FeIX coronal lines, which are sensitive to temperatures of T _e ≈1.2, 1.5, and 2.0 MK, respectively, are considered, together with the 304 Å HeII transition-region line (T _e ≈(0.02–0.08) MK). Difference images taken at intervals of six and twelve hours and compensated for solar rotation indicate that dimmings are normally strongly pronounced and have similar large-scale structures in the moderate-excitation-temperature 171 Å and 195 Å coronal lines, while the higher-temperature 284 Å line mainly display the deepest portions of the dimmings. In addition, clear dimmings with relatively small areas are visible in the 304 Å transition-region line during many CMEs, in particular, in regions adjacent to the source of the eruption. Moreover, dimmings in the transition region without coronal counterparts are observed during some events. These results suggest that the opening of magnetic-field lines and the resulting density reduction that occur during a CME can also involve cold plasma of the transition region. In addition, the effects of temperature variations cannot be ruled out for some dimming structures.     

Blast-wave and piston shocks connected with the formation and propagation of a coronal mass ejection

The solar coronal mass ejection observed on November 3, 2010 is analyzed using AIA/SDO data (images in the 193 and 211 Å channels) and white-corona images obtained with the SOHO LASCO C2 and C3 coronographs. We have succeeded in revealing both piston and blast-wave shocks attributed to the formation and propagation of a coronal mass ejection. Both of these types of shocks could be responsible for type II radio bursts propagating in front of each shock.     

Comparison between two types of multifractal modeling

The interrelationships between two previously developed multifractal models are discussed. These are the Evertsz-Mandelbrot model developed on the basis of the multifractal spectrum f(), and the Schertzer-Lovejoy model based on the codimension function C() where and represent Hölder exponent and field order, respectively. It is shown how these two models are interrelated: they are identical for values of within the range D–(0)D–_min. where D is the Euclidean dimension. For D–_maxD–(0), however, f() remains a continuous function of whereas C() assumes constant value. In this respect, the fractal spectrum f() can provide more information about the multifractal measure than the codimension function C(). The properties of the two models are illustrated by application to the binomial multiplicative cascade model.     

The formation of a perturbed zone and shock wave excited by a coronal mass ejection

The existence of perturbed zones ahead of coronal mass ejections (CMEs) has been confirmed, and their evolution with increasing CME velocity studied. At CME velocities that are close to or higher than the local Alfvén velocity, a discontinuity forms in the plasma density distribution ahead of the perturbed zone, which can be interpreted as a shock. Estimates testify that, at distances from the solar center of R < (15–20) R _⊙, the width of the observed shock front is probably of the order of the mean free path for proton-proton collisions.     

Star formation in extragalactic HII regions. Determination of parameters of the initial mass function

A method for using the colors of star-forming complexes to derive the slope and upper mass limit of the initial mass function (IMF) and the age of the complex is proposed in the framework of synthetic evolutionary models of star-cluster populations. The star-formation parameters of 105 complexes in 20 spiral and irregular galaxies are determined. The IMF slopes in different star-forming complexes differ appreciably, and their dependence on the luminosities and masses of the complexes is derived. The duration of the star-formation period increases with the luminosity of the complex, and complexes with longer star-formation periods are richer in metals. The slope of the integrated IMF in a Galaxy depends on the mass spectrum of its complexes, and the upper mass limit of the IMF is lower in early-type spirals.     

华南两种类型花岗岩成岩-成矿作用的差异

华南地区主要产出两种类型的花岗岩类，一是壳源的陆壳重熔型花岗岩类，二是壳-幔混源的钙碱型浅成花岗岩类。二者不仅在成因上有很大差别，在成矿作用上也明显不同。本文通过实例，探讨了这两种类型花岗岩在成岩-成矿关系上的差异。研究表明，陆壳重熔型花岗岩类的成岩与对应的成矿作用之间存在着明显的时间差，以南岭地区为例，在燕山中期第一阶段170~150 Ma达到高潮的陆壳重熔型花岗岩类，其相关的钨锡等稀有金属矿化多发生在燕山中期第二阶段150~139 Ma，成岩与成矿相差10~20 Ma，这一时间差反映了这类花岗岩成岩作用与成矿作用之间在物质来源和地质构造背景等方面的差异。而那些壳-幔混源的钙碱型浅成花岗岩类，由于其成岩时就具备这种条件，因此成岩-成矿基本同时，没有明显的时间差。由此可见，大规模金属成矿作用主要与拉张的动力学背景、壳-幔相互作用、高的热流值，以及深部流体的参与密切相关。     

Decay of activity complexes and the formation of coronal holes

Analysis of long-term measurements of solar magnetic fields and the flux of UV radiation from the Sun indicates a cause-effect relationship between activity complexs, their residual magnetic fields, and coronal holes. A comparison of the background magnetic fields of the Sun and the evolution of former activity complexes reveals unipolar magnetic regions that form after the decay of these complexes. The latitude and time evolution of unipolar magnetic regions in solar cycles 21–24 is studied. A North-South asymmetry in solar activity is manifest in the distribution of unipolar regions migrating toward higher latitudes. It is shown that, when residual magnetic fields of the opposite polarity reach the polar regions, this leads to a sign change of the polar magnetic field and a decrease in the area of polar coronal holes, or even their complete disappearance. These interactions can explain the triple sign change of the polar magnetic field of the Sun in cycle 21 and the short-term polarity reversals observed in 2010 and 2011.     

下沉式抗滑桩与普通抗滑桩内力分析比较

通过将一组下沉式模型实验数据按照比例扩大到实际大小,建立计算模型,再利用地基系数法计算出桩身上的最大剪应力和最大弯矩。然后把模型中的下沉式抗滑桩换成普通抗滑桩,重新计算。通过比较计算结果,可以发现下沉式抗滑桩所独有的优越性,同时就这种特殊抗滑桩的适用性提出一些看法。     

东天山地区两类钒钛磁铁矿型矿床含矿岩石对比

新疆东天山地区产出有两类岩浆型钒钛磁铁矿矿床，分别以尾亚和香山西矿床为代表。尾亚是以铁钛为主的中型钒钛磁铁矿矿床，香山西则是以钛为主的大型钛铁矿矿床，与铜镍矿床共生。尾亚矿床含矿岩石的岩石学、岩石化学、稀土及微量元素特征与典型的钒钛磁铁矿矿床相似。而香山西矿床含矿岩石的碱度、镁铁指数（FeO^＊／MgO）、岩浆酸度（αsi）、钙碱富集指数（calk／m）等地球化学参数，氧逸度和硫逸度等物理化学参数均介于独立的典型铜镍硫化物和典型钒钛磁铁矿矿床之间。两类矿床含矿岩石特征的差异可能在于其产出的构造背景不同，导致其含矿岩浆演化过程中处于不同的物理化学条件。     

Some properties of the development of the perturbed zone and shock preceding a coronal mass ejection

SOHO/LASCO C2 and C3 data have been used to carry out a detailed study of the perturbed zone and shock that form as a coronal mass ejection (CME) moves away from the Sun, as a result of its interaction with the ambient solar wind. The event of January 4, 2002 is used as an example. The perturbed zone is most extensive along the direction of propagation of the CME, decreases away from this direction, and reaches its minimum values perpendicular to this direction. The mass of the perturbed zone is ≥0.1 of the total mass of the CME. The condition for the formation of a shock preceding the CME (in the direction of propagation of the CME) is V − V _SW > V _A , where V, V _SW , and V _A are the CME, solar wind, and Alfvén velocities, respectively. Perpendicular to the CME axis, at distances of ≈4–6R _⊙ fromthe center of the Sun, the condition for the formation of shock is V/2 > V _A .     

First experimental studies of a perturbed zone preceding the front of a coronal mass ejection

The first experimental evidence for a perturbed zone that is likely filled with fast magnetoacoustic oscillations and precedes a coronal mass ejection is presented. When the speed of the coronal mass ejection exceeds the Alfven speed, an outward-moving discontinuity of the plasma density is observed in front of the perturbed zone, on scales comparable to the mean-free path for proton-proton collisions. This suggests that this discontinuity should be interpreted as a collisional shock at distances of R < 30 R _⊙ (where R _⊙ is the solar radius).