Solar and heliospheric geoeffective disturbances

The past decade has brought advances in several areas of solar-terrestrial physics which, when combined, provide nearly all of the pieces necessary for predicting geomagnetic storms. Advances in techniques for observing the Sun in X-rays and white light allow identification of solar disturbances headed toward Earth. Advances in our understanding of how the resulting heliospheric disturbances reflect aspects of the Sun's magnetic field allow predictions of their magnetic topology and, hence, provide some measure of the geoeffective southward component which they carry. Advances in our understanding of the relationship between transient heliospheric disturbances and high-speed streams and how storm strength depends upon solar wind density and the magnetic polarity of streams allow substantial refinement for prediction schemes.     

Solar polar magnetic field

The solar polar magnetic field has attracted the attention of researchers since the polar magnetic field reversal was revealed in the middle of the last century (Babcock and Livingston, 1958). The polar magnetic field has regularly reversed because the magnetic flux is transported from the sunspot formation zone owing to differential rotation, meridional circulation, and turbulent diffusion. However, modeling of these processes leads to ambiguous conclusions, as a result of which it is sometimes unclear whether a transport model is actual. Thus, according to the last Hinode data, the problem of a standard transport model (Shiota et al., 2012) consists in that a decrease in the polar magnetic flux in the Southern Hemisphere lags behind such a decrease in the flux in the Northern Hemisphere (from 2008 to June 2012). On the other hand, Svalgaard and Kamide (2012) consider that the asymmetry in the sign reversal simply results from the asymmetry in the emerging flux in the sunspot formation region. A detailed study of the polar magnetic flux evolution according to the Solar Dynamics Observatory (SDO) data for May 2010–December 2012 is illustrated in the present work. Helioseismic & Magnetic Imager (HMI) magnetic data in the form of a magnetic field component along the line of sight (the time resolution is 720 s) are used here. The magnetic fluxes in sunspot formation regions and at high latitudes have been compared.     

Structural and dynamic features of geoeffective coronal ejections

The structure and physical conditions in 104 coronal mass ejections (CMEs) with a clear-cut leading shock front have been considered using satellite data for 1996–2008. In 99% of cases, the action of increased shock front dynamic pressure on the Earth’s magnetosphere resulted in the origination of geomagnetic storms with sudden commencement.     

Solar convection and magnetic fields

Mike Proctor looks at the interplay between convection and magnetism in the Sun's photosphere, using powerful numerical simulations.     

钢结构端板连接抗震设计方法

系统地总结了国内外钢结构端板连接研究成果以及相关设计规范的规定，提出了钢结构端板连接抗震设计具体方法，主要包括：节点标准构造、抗震承载力验算、极限承载力验算、延性设计，为我国钢结构抗震设计规范的相关内容提供了有益补充建议。     

半刚性连接钢框架结构弹性时程分析

用两端带转动弹簧的杆单元代替一般的杆单元,提出了一种新的平面杆系钢结构动力弹性时程分析计算模型。采用虚功原理,通过对单元转角-位移方程的修正,推导了这种计算模型的单元质量矩阵,并编制了相应的弹性时程分析计算程序,分析了连接的半刚性在不同地震动作用下对钢框架结构动力性能的影响,并与有限元结果进行了比较。算例结果表明:连接的半刚性对结构动力性能的影响非常大,结构的抗震性能优于刚性连接的情况。     

Solar magnetic field distribution and geomagnetic activity

Summary Regularities in the solar background magnetic field distribution are described and some of their specific patterns and their structures are studied. The influence of the solar differential rotation on the behaviour of Magnetic Active Longitudes is demonstrated. The origin of some specific details different in both polarities is discussed. The relation of this longitudinal solar magnetic field distribution to the longitudinal distribution of the daily geomagnetic character figures C9 is investigated. Some correlational characteristics are given. The specific Index of Geomagnetic Recurrence is estimated and the changes of its values in time are demonstrated.

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Solar magnetic activity: topology and prediction

We ascribe the solar magnetic activity to the interplay between the plasma flow and the magnetic field. Observations by SOHO, Hinode and upcoming SDO are discussed. We then discuss the understanding and modeling of solar magnetic activity based on mathematical topological concepts. We present predictions using neural networks. Further we describe the outcome of the cycle 24 prediction panel. Finally, recommendations are given for making improved predictions.     

Fluctuation analysis of solar radio bursts associated with geoeffective X-class flares

High temporal resolution solar observations in the decimetric range (1–3 GHz) can provide additional information on solar active regions dynamics and thus contribute to better understanding of solar geoeffective events as flares and coronal mass ejections. The June 6, 2000 flares are a set of remarkable geoeffective eruptive phenomena observed as solar radio bursts (SRB) by means of the 3 GHz Ondrejov Observatory radiometer. We have selected and analyzed, applying detrended fluctuation analysis (DFA), three decimetric bursts associated to X1.1, X1.2 and X2.3 flare-classes, respectively. The association with geomagnetic activity is also reported. DFA method is performed in the framework of a radio burst automatic monitoring system. Our results may characterize the SRB evolution, computing the DFA scaling exponent, scanning the SRB time series by a short windowing before the extreme event. For the first time, the importance of DFA in the context of SRB monitoring analysis is presented.     

板柱结构中柱节点抗震性能的试验研究

通过5个板柱结构中柱节点的水平低周反复荷载试验,研究了中柱节点的延性、滞回特性、耗能能力和破坏形态。实验结果表明,水平荷载作用下中柱节点主要有弯曲破坏和冲切破坏2种破坏形态,板中钢筋的配筋率是影响节点破坏形态的主要因素之一,板柱结构中柱节点的抗震性能要比框架结构的梁柱节点差。     

Role of wall panel connections on the seismic performance of precast structures

Past seismic events, including the 2009 L’Aquila earthquake and the 2012 Emilia earthquake, clearly demonstrated the inadequacy of the current design approach for the connection system of the cladding wall panels of precast buildings. To clarify this problem the present paper investigates the seismic behaviour of a traditional precast structural frame for industrial buildings with a new type of connection system of cladding panels. This system consists of a statically determined pendulum arrangement of panels, each supported with two hinges to the structure, one at the top and one at the bottom, so to have under seismic action a pure frame behaviour where the wall panels are masses without stiffness. Adding mutual connections between the panels, the wall cladding panels become part of the resisting structure, leading to a dual frame/wall system or to a wall system depending on the stiffness of the connections. The seismic behaviour of this structural assembly is investigated for different degrees of interaction between frame and panels, as well as for an enhanced solution with dissipative connections. The results of nonlinear static (pushover) analyses and nonlinear dynamic analyses under recorded and artificial earthquakes highlight the role of the wall panel connections on the seismic behaviour of the structural assembly and show the effectiveness of the dual frame/wall system with dissipative connections between panels.     

Spectral-temporal peculiarities of the microwave emission preceding geoeffective coronal mass ejections

Data on the complex of wave and spectral phenomena in the sporadic microwave emission that are associated with the formation and initial propagation of coronal mass ejections (CMEs) in the solar atmosphere are presented. Their characteristic time interval extends from 2–3 days preceding the event to the time of CME recording on coronagraphs.     

On geoeffective solar flares and variations of the seismic noise level

The work continues the study of interrelations between strong flare-induced magnetic storms and variations of seismicity. Using data on the time dependences of the parameters of seismic noise (average level and root mean squared (RMS)), recorded by stations of the KNET seismic network during monitoring of the territory of Bishkek geodynamic site (North Tien Shan). The presented results indicate the high sensitivity of the seismic noise in the frequency range of 10–20 Hz to external and, in particular, electromagnetic effects in comparison to the seismic activity. We noted the manifestations of the effects of magnetic storms that occurred after strong and super-strong solar flares in 2000–2006. These were short-term increases in the RMS of seismic noise, preceding changes in the accumulation rate of the number of events. The obtained results agree with conclusions about the interrelation between seismicity and magnetic storms. A model is suggested to describe one of the possible mechanisms by which the electromagnetic pulses and the currents induced by them in a medium devoid of piezoelectric properties influence the seismic process.     

Solar cyclic variation in magnetic elements of Moscow observatory

The data of Moscow observatory for the 1946-2006 interval of observations are analyzed in order to detect long-term geomagnetic variations related to solar activity against a background of the secular variations in the geomagnetic field.     

Geoeffectiveness of solar wind interplanetary magnetic structures

We address the geoeffectiveness of three interplanetary structures in the interplanetary space: magnetic clouds (MCs), interplanetary shocks (IPSs), and corotating interaction regions (CIRs). The geoeffectiveness is evaluated using the geomagnetic indices Kp, AE, and Dst. We find that MCs are more geoeffective than IPSs, or CIRs. The average values of magnetic indices are significantly enhanced during disturbed periods associated with MCs, IPSs and CIRs, compared to the whole interval. The highest effect is noted for MC disturbed periods.Results obtained for the three data sets are used to derive a theoretical (continuous) probability distribution function (PDF) by fitting the histograms representing the percentage of events against the intervals of magnetic index. PDFs allow estimation of the probability of a given level of geomagnetic activity to be reached after the detection, by in situ solar wind observations, of a given interplanetary structure approaching the Earth.     

Are there connections between the Earth's magnetic field and climate?

Understanding climate change is an active topic of research. Much of the observed increase in global surface temperature over the past 150 years occurred prior to the 1940s and after the 1980s. The main causes invoked are solar variability, changes in atmospheric greenhouse gas content or sulfur due to natural or anthropogenic action, or internal variability of the coupled ocean–atmosphere system. Magnetism has seldom been invoked, and evidence for connections between climate and magnetic field variations have received little attention. We review evidence for correlations which could suggest such (causal or non-causal) connections at various time scales (recent secular variation ∼ 10–100 yr, historical and archeomagnetic change ∼ 100–5000 yr, and excursions and reversals ∼ 10³–10⁶ yr), and attempt to suggest mechanisms. Evidence for correlations, which invoke Milankovic forcing in the core, either directly or through changes in ice distribution and moments of inertia of the Earth, is still tenuous. Correlation between decadal changes in amplitude of geomagnetic variations of external origin, solar irradiance and global temperature is stronger. It suggests that solar irradiance could have been a major forcing function of climate until the mid-1980s, when “anomalous” warming becomes apparent. The most intriguing feature may be the recently proposed archeomagnetic jerks, i.e. fairly abrupt (∼ 100 yr long) geomagnetic field variations found at irregular intervals over the past few millennia, using the archeological record from Europe to the Middle East. These seem to correlate with significant climatic events in the eastern North Atlantic region. A proposed mechanism involves variations in the geometry of the geomagnetic field (f.i. tilt of the dipole to lower latitudes), resulting in enhanced cosmic-ray induced nucleation of clouds. No forcing factor, be it changes in CO₂ concentration in the atmosphere or changes in cosmic ray flux modulated by solar activity and geomagnetism, or possibly other factors, can at present be neglected or shown to be the overwhelming single driver of climate change in past centuries. Intensive data acquisition is required to further probe indications that the Earth's and Sun's magnetic fields may have significant bearing on climate change at certain time scales.     

Solar magnetic cycle: Peculiarities of the photospheric field distribution

Synoptic maps for 1976–2003 obtained at the Kitt Peak National Solar Observatory are used to analyze the longitudinal distribution of the solar photospheric magnetic field. The superposition of synoptic maps gives different pictures for the rise-maximum phase and the decline-minimum phase. Two characteristic periods correspond to different situations in the 22-year solar magnetic cycle in the course of which both the global magnetic field and the magnetic field of the leading sunspot in a group change their sign.     

Detection and identification of north–south trending magnetic structures near the magnetic equator

Long, structurally undeformed north–south trending structures show no magnetic anomaly at the magnetic equator, except at the north and south truncations of the structure. However, folding, faulting, differential erosion or other structural deformation can produce detectable magnetic anomalies in a generally north–south trending equatorial structure. Spatial variation in magnetic susceptibility or remanent magnetization can also produce anomalies in equatorial north–south structures. These anomaly patterns are often more complicated than patterns produced by similar structures at high latitudes, but interpretational insight can be gained through numerical modelling of common structures. Reduction-to-pole and analytic signal filters can aid in interpretation of equatorial anomalies, but these must be applied carefully because of instabilities deriving from filter design and noise amplification.