Influence of heliospheric and geomagnetic activity on the dynamics of the relativistic electron fluxes in the Earth’s outer radiation belt around the minimum of the solar activity in 2008–2010

The relativistic electron flux in the Earth’s outer radiation belt generally decreased by almost three orders of magnitude during the minimum of cycle 23 in 2009. Such a behavior was possibly caused by very low geomagnetic activity during an extremely weak interplanetary field in that period. This decrease was replaced by an increase in the relativistic electron flux by two orders of magnitude during several months after the sunspot minimum at the beginning of 2010.     

The relation between solar activity and orientation of the solar wind electric field relative to the Earth’s magnetic moment

The relation of the Kp index of geomagnetic activity to the solar wind electric field (E _SW) and the projection of this field onto the geomagnetic dipole has been estimated. An analysis indicated that the southward component of the IMF vector (B _z < 0) is the main geoeffective parameter, as was repeatedly indicated by many researchers. The presence of this component in any combinations of the interplanetary medium parameters is responsible for a high correlation between such combinations and geomagnetic activity referred to by the authors of different studies. Precisely this field component also plays the main role in the relation between the Kp index and the relative orientation of E _SW and the Earth’ magnetic moment.     

Streamer belt in the solar corona and the Earth’s orbit

It has been indicated that the cross section of the streamer belt in the solar corona and its extension in the heliosphere—heliospheric plasma sheet (HPS)—have the form of two radially oriented closely located (at a distance of d ≈ 2.0–2.5° in the heliocentric coordinate system) rays with increased and generally different densities. The angular dimensions of the rays are ≈d. The neutral line of the magnetic field in the corona and the related sector boundary in the Earth’s orbit are located between the peaks of densities of these two rays. In the events, during which the true sector boundary coincides with the heliospheric current sheet, the transverse structure of the streamer belt in the heliosphere (or the HPS structure) is quasistationary; i.e., this structure slightly changes when the solar wind moves from the Sun to the Earth in, at least, 50% of cases. A hypothesis that a slow solar wind, flowing in the rays with increased density of the streamer belt, is probably generated on the Sun’s surface rather than at the top of the helmet, as was assumed in [Wang et al., 2000], is put forward.     

Deformation of the Earth’s crust in the Northern Tien Shan according to the earthquake focal data and satellite geodesy

For evaluating the deformations of the Earth’s crust in the Northern Tien Shan, we calculated the mode and intensity of the seismotectonic deformations (STD) for this region. The input for these calculations were the catalog data on the focal mechanisms of earthquakes, obtained by wave inversion of the signals recorded at the Kyrgyz seismic network (KNET) for the period 1994–2006. In the construction of STD maps, a modern approach to the classification of seismotectonic deformations was applied. This approach distinguishes eleven typical patterns of deformation. The areal distributions of the Lode-Nadai coefficient, as well as of the vertical component and the aspect angle of the deformed state were obtained. At the same time, based on the GPS measurements in the Northern Tien Shan during 1994–2006, the rates of dilatation and shear deformation of the Earth’s crust were estimated. A comparison between the directions of strain axes derived from the GPS data and from the earthquake focal data is carried out.     

Recent advances in radiation belt dynamics and wave-particle interactions in the Earth’s inner magnetosphere

<正>Radiation belt dynamics and the related wave-particle interactions in the Earth’s inner magnetosphere are a very important research field in space physics.Since the launch of Van Allen Probes on August 30,2012,many substantial advances have been achieved,and some of them are briefly reviewed in this paper.Using Van Allen Probes data soon after its launch,Baker et al.(2013)discovered a relativistic electron storage ring that was embedded in Earth’s outer Van Allen belt.The     

Prediction of relativistic electron flux in the Earth’s outer radiation belt at geostationary orbit by adaptive methods

The paper investigates the possibilities of the prediction of the time series of the flux of relativistic electrons in the Earth’s outer radiation belt by parameters of the solar wind and the interplanetary magnetic field measured at the libration point and by the values of the geomagnetic indices. Different adaptive methods are used (namely, artificial neural networks, group method of data handling, and projection to latent structures). The comparison of quality indicators of predictions with a horizon of 1–12 h between each other and with the trivial model prediction has shown that the best result is obtained for the average value of the responses of three neural networks that have been trained with different sets of initial weights. The prediction result of the group method of data handling is close to the result of neural networks, and the projection to latent structures is much worse. It is shown that an increase in the prediction horizon from 1 to 12 h reduces its quality but not dramatically, which makes it possible to use these methods for medium-term prediction.     

Variations in solar radiation in the solar activity cycle: Response of Earth’s atmospheric parameters (numerical modeling and analysis of observational data)

The results of a three-dimensional numerical simulation of changes in the temperature and wind within a height range of up to 100 km caused by changes in fluxes in the solar ultraviolet (UV) radiation in the 23rd solar activity cycle (which was characterized by unusually low values of UV-radiation fluxes) and also of global changes in the ozone content are presented. The simulation results showed that the response of the temperature to variations in the UV radiation are substantially of a nonzonal character, which is caused by the presence in the model of sources of quasi-stationary waves corresponding to the observational data.     

Dynamic variation and the fast acceleration of particles in Earth’s radiation belt

We have quantitatively investigated the radiation belt’s dynamic variations of 1.5-6.0 MeV electrons during 54 CME (coronal mass ejection)-driven storms from 1993 to 2003 and 26 CIR (corotating interaction region)-driven recurrent storms in 1995 by utilizing case and statistical studies based on the data from the SAMPEX satellite. It is found that the boundaries determined by fitting an exponential to the flux as a function of L shell obtained in this study agree with the observed outer and inner boundaries of the outer radiation belt. Furthermore, we have constructed the Radiation Belt Content (RBC) index by integrating the number density of electrons between those inner and outer boundaries. According to the ratio of the maximum RBC index during the recovery phase to the pre-storm average RBC index, we conclude that CME-driven storms produce more relativistic electrons than CIR-driven storms in the entire outer radiation belt, although the relativistic electron fluxes during CIR-related storms are much higher than those during CME-related storms at geosynchronous orbit. The physical radiation belt model STEERB is based on the three-dimensional Fokker-Planck equation and includes the physical processes of local wave-particle interactions, radial diffusion, and adiabatic transport. Due to the limitation of numerical schemes, formal radiation belt models do not include the cross diffusion term of local wave-particle interactions. The numerical experiments of STEERB have shown that the energetic electron fluxes can be overestimated by a factor of 5 or even several orders (depending on the pitch angle) if the cross diffusion term is ignored. This implies that the cross diffusion term is indispensable for the evaluation of radiation belt electron fluxes. Formal radiation belt models often adopt dipole magnetic field; the time varying Hilmer-Voigt geomagnetic field was adopted by the STEERB model, which self-consistently included the adiabatic transport process. The test simulations clearly indicate that the adiabatic process can significantly affect the evolution of radiation belt electrons. The interactions between interplanetary shocks and magnetosphere can excite ULF waves in the inner magnetosphere; the excited polodial mode ULF wave can cause the fast acceleration of "killer electrons". The acceleration mechanism of energetic electrons by poloidal and toroidal mode ULF wave is different at different L shells. The acceleration of energetic electrons by the toroidal mode ULF waves becomes important in the region with a larger L shell (the outer magnetosphere); in smaller L shell regions (the inner magnetosphere), the poloidal mode ULF becomes responsible for the acceleration of energetic electrons.     

Variations in the polar precipitation equatorward boundary during the interaction between the Earth’s magnetosphere and solar wind streams from isolated solar sources

The position of the auroral luminosity equatorward boundary during the interaction between the Earth’s magnetosphere and isolated solar wind streams from different solar sources has been statistically studied based on the ground and satellite observations of auroras. These studies continue the series of the works performed in order to develop the technique for predicting auroras based on the characteristics of the interplanetary medium and auroral disturbances. The dependences of the minimal position of the auroral luminosity equatorward boundary (Φ′) on the values of the azimuthal component of the interplanetary electric field (E _y ) and AL indices of magnetic activity, averaged over 6 and 24 h, are presented. The distribution limits for each type of isolated solar wind streams on the Φ′-E _y and Φ′-AL planes have been determined.     

Impact of solar wind tangential discontinuities on the Earth’s magnetosphere

The collision of a solar wind tangential discontinuity with the bow shock and magnetopause is considered in the scope of an MHD approximation. Using MHD methods of trial calculations and generalized shock polars, it has been indicated that a fast shock refracted into the magnetosheath originates when density increases across a tangential discontinuity and a fast rarefaction wave is generated when density decreases at this discontinuity. It has been indicated that a shock front shift under the action of collisions with a tangential discontinuity is experimentally observed and a fast bow shock can be transformed into a slow shock. Using a specific event as an example, it has been demonstrated that solar wind tangential discontinuity affects the geomagnetic field behavior.     

Manifestation of solar and geodynamic activity in the dynamics of the Earth’s rotation

The relationships between different manifestations of solar and geomagnetic activity and the structural peculiarities of the dynamics of the pole wobble and irregularities in the Earth??s rotation are studied using singular spectrum analysis. There are two close major peaks and several lower ones in the same frequency range (1.1?C1.3 years) in the Chandler wobble (CW) spectrum. Components in the geomagnetic activity were distinguished in the same frequency band (by the Dst and Ap indices). Six- to seven-year oscillations in the Earth??s rotation rate with a complex dynamics of amplitude variations are shown in variations in geomagnetic activity. It is revealed that secular (decade) variations in the Earth??s rotation rate on average repeat global variations in the secular trend of the Earth??s geomagnetic field with a delay of eight years during the whole observation period.     

Response of currents in Earth’s and Saturn’s dayside magnetopause to a sudden change in the solar wind density

When the effect of a solar wind dynamic pressure pulse on the magnetospheric and ionospheric dynamics is studied, it is usually difficult to detect the effect of a sudden change in the density against the background of the other varying solar wind parameters, which often play a most pronounced role. Cases in which the solar wind plasma density gradient dominated in the dynamics of the different parameters of an interplanetary medium and its magnetic field are considered in this work. Variations in the Earth’s dayside magnetopause current caused by a change in the solar wind ion density are presented for two such cases (February 11 and January 11, 1997) based on the method developed by us previously. Variations in the dayside magnetopause current for collisions of the magnetosphere with corotating interacting flows in January 2004, studied in detail by us previously, are also presented for Saturn. The estimates are comparable with the current values in the transitional three-dimensional current systems of Saturn that were previously calculated by us.     

Weak velocity anomaly in the Earth’s outer core from seismic data

Experimental data on the differential travel time t _BC–t _DF of seismic waves PKP_DF and PKP_BC in the Earth’s core under Africa and Australia are analyzed. The differential travel-time residuals beneath Africa in a narrow range of angles from 21° to 25° between the direction of the seismic ray in the core and the Earth’s rotation axis exhibit a scoop-shaped peculiarity not accounted for by cylindrical anisotropy in the inner core. A model with a 0.2–0.8% P-wave velocity anomaly with a radius of 1375 km in the cylindrical region in the outer core is proposed, which closely fits the experimental data. We suggest that the velocity anomaly is generated by the dynamical processes occurring in the outer core, namely, the growth of the inner core and the convection in the outer core, both leading to the formation of a low-density anomaly in the outer core.     

Sensitivity of the Earth’s middle atmosphere to short-term solar variability and its dependence on the choice of solar irradiance data set

We simulate the time evolution of the neutral and charged species in the terrestrial middle atmosphere using a 1-D radiative-convective model with interactive neutral and ion chemistry driven by four different sets of daily spectral solar irradiance (SSI) available in the literature for the year 2000. Obtained daily time series of ozone, hydroxyl and electron densities are used to calculate their sensitivity to the short-term SSI variability at 205 nm. All applied SSI data sets possess 27-day solar rotation cycle; however, its amplitude and phase as well as the correlation between considered SSI time series differ among data sets leading to the different behavior of the atmospheric response. Contrary, the ozone and hydroxyl sensitivities to the SSI changes during solar rotation cycle are almost identical for all applied SSI data sets in the stratosphere. In the mesosphere, the difference in correlation between SSI in Herzberg continuum and Lyman-α line in considered SSI data sets leads to substantial scatter of the sensitivity estimates based on 205 nm. Our results show that for the sensitivity analysis in the stratosphere based on the SSI at 205 nm any considered SSI data sets can be applied. For the mesosphere, where the sensitivity strongly varies among applied SSI data sets more robust results can be obtained using the sensitivity calculations based on the SSI in Lyman-α line.     

New approach to the construction of the Earth’s upper atmosphere model using the satellite local data on the atmosphere

The present-day models of the Earth’s upper atmosphere make it possible to construct the spatial-temporal pattern of variations in the atmospheric parameters on the planetary scale in essence in the averaged form. The set of data on the satellite deceleration in the atmosphere, probe measurements aboard geophysical rockets, and radiowave incoherent scatter measurements in the Earth’s atmosphere are used to construct these standard models. The current level of the space studies makes it possible to use a new method to study the Earth’s upper atmosphere: to study the upper atmosphere by measuring the absorption of the solar XUV radiation by the Earth’s atmosphere during the solar disk observations.     

Joy’s law and its features according to the data of three sunspot catalogs

This paper investigates the trend towards an increase in the tilt of sunspot groups with increasing latitude (Joy??s law) and the relationship between the features of this law and solar activity parameters. In addition to the known data of the Mount Wilson and Kodaikanal observatories, the analysis uses the Pulkovo database of solar activity, which allows for the estimation of the reliability of the conclusions obtained by other authors from the first two catalogs. It is shown that Joy??s law is manifested in all three data series and has many features in common. In particular at latitudes above 25?C30°, the tilt of sunspot groups is not linearly dependent on latitude and displays a slight decrease. However, some features of this law found previously in the data of the first two observatories (e.g., a decrease in its strength with an increase in the strength of the solar cycle) are not confirmed by our analysis.     

Some sources of plasma inhomogeneities in the solar wind in front of the Earth’s magnetosphere

The origination of various plasma inhomogeneities in the magnetosheath in front of the Earth’s magnetosphere is analyzed within classical magnetohydrodynamics. The effect of directional discontinuities or tangential and rotational discontinuities of the solar wind on plasma is studied. The origination of inhomogeneities of the type of secondary MHD waves in the magnetosheath is shown; the former equalize plasma parameters when restoring the stationary state. The effect of a rotational discontinuity on the bow shock–Earth’s magnetosphere system is of special interest, with distinguishing of plasma inhomogeneities of the plateau type observed in the near-Earth space.     

Nonlinear phenomena related to the solar shock motion in the Earth’s magnetosphere

The motion of the MHD nonlinear shock in the Earth’s magnetosphere is considered in the scope of magnetic hydrodynamics. This wave comes from the solar wind and is refracted into the magnetosphere, generating a fast return rarefaction wave. It has been indicated that a wave refracted into the magnetosphere is a weak fast dissipative shock, propagating in magnetospheric plasma at a velocity higher than its propagation velocity in a solar wind stream. The wave motion near the Earth-Sun line with regard to the effect of the geomagnetic field transverse component is described. In this case, shock damping follows the generalized Crussard-Landau law and a wave retains its shock character up to the plasmapause, interacting with this region when an arbitrary MHD discontinuity is disintegrated. It is stated that an MHD shock loses its shock character when moving in a strongly inhomogeneous plasma within the plasmasphere and a weak shock reflected from the plasmapause can combine with a return secondary shock in the magnetosheath, promoting the experimentally observed backward motion of the bow shock front.     

Lunar–solar tide effects in the Earth’s crust and atmosphere

The gravitational interaction in the Earth–Moon–Sun system is considered from the standpoint of influencing the formation of time variations in the geophysical fields and some natural processes. The analysis of the results of instrumental observations revealed the main periodicities and cycles in the time variations of subsoil radon volumetric activity with the same periods as the vertical component of the variations of the tidal force. The amplitude modulation of seismic noise by the lunar-solar tide is demonstrated. It is shown that the intensity of relaxation processes in the Earth’s crust has a near-diurnal periodicity, whereas the spectrum of groundwater level fluctuations includes clearly expressed tidal waves. Based on the data on the tilts of the Earth’s surface, the role of tidal deformation in the formation of the block motions in the Earth’s crust is analyzed. A new approach is suggested for identifying tidal waves in the atmosphere by analyzing micropulsations of the atmospheric pressure with the use of adaptive rejection filters.     

On mechanical Q parameters of the lower mantle inferred from data on the Earth’s free oscillations and nutation

A new method for the interpretation of recent tidal and astrometry data based on integral relations connecting the mantle Q parameters to variations in frequencies of the main Earth’s spheroidal oscillation, nearly diurnal free nutation, Chandler wobble, and Love numbers is proposed in this paper. The normalized weighting functions in the aforementioned integral relations are shown to be very close to each other in a wide range of oscillation periods (from 54 minutes to 14 months) for the actual Earth’s model and therefore the detection of the dependence of the mantle Q parameters averaged with these weighting functions on frequency does not need to be solved for the inverse problem of the Q parameters as a function of the oscillation frequency and depth: instead, it is sufficient to determine the dependence of the adequate integral characteristics of the mantle’s inelasticity only on frequency. This makes it possible to significantly simplify the solution of the inverse problem and improve the rheologic models of the lower mantle.