The state of stress in the Earth's crust as based on measurements in mines and on geophysical data

Measurements of stress carried out in mines suggest that much of the Earth's crust is in a state of horizontal compression. The average of the two principal horizontal stresses usually exceeds the hydrostatic (geostatic) pressure and fits N. Hast's empirical relationship of increasing excess compressive stress with depth. High compressive stresses are usually aligned perpendicular to the trends of young, folded mountain ranges and to axes of positive and negative gravity anomalies.     

Eurasia as a composite continent

The orogenetic history of the Eurasian continent is outlined. Geological and geophysical — mainly paleomagnetical — evidence points to a history of crustal tension and compression, in accordance with the hypothesis of continental drift.     

On interplanetary electric and magnetic fields

A kinematic model of the stationary electromagnetic fields in interplanetary space with finite conductivity is considered. The electrodynamic problem is solved for a medium with uniform conductivity and radial plasma outflow from a spherical source. Simple analytical formulae are obtained for electric and magnetic fields, currents and charges in the case of a uniformly-magnetized rotating sphere.     

Dynamics of equilibrium upset and electromagnetic energy transformation in the geomagnetotail: A theory and simulation using particles. 1. Evolution of configurations in an MHD approximation

The process of equilibrium disruption in the system with a current sheet (CS) under the conditions of small magnetic field component normal to CS, which is induced by an external disturbance, has been theoretically studied within the scope of MHD. In the geomagnetotail, this disturbance can be caused by a tearing instability developing in the more distant tail section, or by a ballooning instability in the tail nearest section, or by a rapid reconfiguration at the magnetopause during the disturbance passage in the solar wind. Locally, in a limited CS section, a longitudinal momentum balance is rapidly (on the Alfvén time scale) upset when a fast MHD disturbance, the form of which depends on the presence of CS, passes along the tail. The nonequilibrium temperature, which subsequently evolves through splitting of CS into several current structures, originates on a substantially larger (due to the smallness of the normal field component) time scale. Such a reconfiguration SPONTANEOUSLY develops after the initial equilibrium upset under the action of an external (weak) disturbance. During an analysis within the scope of MHD, this reconfiguration can be described as the well-known process with two pairs of nonlinear waves propagating in both directions from the central sheet plane at constant velocities: these are fast rarefaction waves and the following slow “switching-off” shocks. However, the kinetic theory reveals substantially different relaxation channels. These channels are studied in the second and third work sections, where the kinetic numerical simulation of the problem is presented and the results of this simulation are analyzed.     

Dynamics of equilibrium upset and electromagnetic energy transformation in the geomagnetotail: A theory and simulation using particles. 2. Numerical simulation using particles

The process of rapid geomagnetotail reconfiguration after the equilibrium upset (substorm activation) has been studied using the numerical simulation. The decisive reconfiguration feature consists in the spontaneous formation of nonlinear kinetic small-scale structures in the position of the initial current sheet (CS). Substantially different reconfiguration channels are possible depending on the value of the magnetic field component normal to CS: the dominating process can be the formation of a collisionless slow magnetosonic shock or a forced kinetic current sheet (FKCS). The first option is presented in this part of the work. During the late stages, the process is independent of the type of an initial disturbance; the disturbance intensity is spontaneously formed at a certain final level. Far from CS, the disturbance has the form of a rarefaction wave propagating from CS in background plasma. The reconfiguration results in a large-scale transformation of electromagnetic energy into the energy of plasma flows and heat.     

The generation of magnetic field via convective motions in the photosphere,Alvén waves,and the origin of chromospheric spicules

The basis is laid out for a theory relating various phenomena in the solar atmosphere, including localized concentrations of magnetic field at the bases of coronal magnetic arches, chromospheric spicules, twisted coronal magnetic flux tubes, and flows of energy carried by Alfvén waves propagating upward into the corona. The structure of photospheric currents localized in the vicinity of supergranule boundaries and excited by convective motions is studied. These currents exist primarily in a “dynamo layer” of sharply enhanced transverse conductivity, which forms in the weakly ionized thermal photospheric plasma located in the solar gravitational field. The motions of the electrons and ions in this layer have appreciably different characters: the ions are collisionly driven by the flows of neutral atoms, while the electrons drift in the crossed electric and magnetic fields. The electric field supporting the current arises due to the polarization of the electrons and ions. This field also gives rise to Alfvén perturbations that propagate upward into the corona, together with their associated longitudinal currents. The character of this “loading” makes the system of fields and currents uniquely defined. Moreover, the momentum flux carried by these Alfvén waves should be transferred to the cool chromospheric gas, facilitating the vertical ejection of this gas in the form of spicules, as was first proposed in 1992 by Haerendel.     

The Acceleration of Outer-Belt Electrons by Localized Electric Fields

Geomagnetism and Aeronomy - To explain the populations of the outer-belt energetic electrons, including relativistic electrons, that sporadically appear in the magnetosphere, a mechanism was...     

Energy conversion and magnetic reconnection in space plasmas: Role of nonlinear kinetic processes and structures

Dynamics of plasma systems in space involves processes of large-scale energy conversion. Like in conventional gas dynamics, the conversion can occur on shocks. However, in collisionless magnetized plasma systems, quite different nonlinear structures may be responsible for energy conversion. Those are anisotropic kinetic current sheets. It is demonstrated that observations at the Earth’s magnetopause provide evidence of long-term existence of such structures.     

Dipolarization Flux Bundles

Geomagnetism and Aeronomy - Localized fast plasma flows in the geomagnetic tail (bursty bulk flows, BBF, and dipolarizing flux bundles, DFB, having smaller spatial scale) which have been observed...     

Variations of Electron Fluxes in the Outer Radiation Belt: Influence of High-Latitude Traps in the Dayside Cusps

Geomagnetism and Aeronomy - Bifurcation of the drift trajectory of an energetic particle, which occurs near the daytime magnetopause, transfers it from the equatorial region to high-latitude zones...