Acceleration of Pick-up Ions at the Solar Wind Termination Shock

It is generally accepted that pick-up ions act as a seed population for anomalous cosmic rays originating at the solar wind termination shock. We believe that the ion pre-acceleration process operating in the heliosphere up to the termination shock can be very important to inject the ions into the shock acceleration process. The pick-up ions pre-accelerated by solar wind turbulences have already a pronounced high energy tail when they reach the shock. Some fraction of these ions can experience further acceleration up to energies of anomalous cosmic rays by means of shock drift and diffusive acceleration. In the present paper the shock drift acceleration of pick-up ions suffering multiple reflection due to abrupt changes in both the strength and direction of the magnetic field through the shock is considered. The reflection process operates for high velocity particles different from the reflection by the electric cross-shock potential. During the first reflection the mean kinetic energy of pick-up ions increases by approximately a factor of 10. Reflected particles have highly anisotropic velocity distribution. Subsequent excursion of the particles in the turbulent upstream flow leads to diffusion in pitch-angle space and, as a result, the particles can return to the shock again suffering, thus, multiple encounters. In order to describe the motion of particles in the upstream and down streamparts of the flow we solve the Fokker-Plank transport equation for anisotropic velocity distribution function. This revised version was published online in July 2006 with corrections to the Cover Date.     

Signatures of the Interplanetary Helium Cone Reflected by Pick-up Ions

As known for a long time, interstellar wind neutral helium atoms deeply penetrate into the inner heliosphere and, when passing through the solar gravity field, form a strongly pronounced helium density cone in the downwind direction. Helium atoms are photoionized and picked-up by the solar wind magnetic field, but as pick-up ions they are not simply convected outwards with the solar wind in radial directions as assumed in earlier publications. Rather they undergo a complicated diffusion-convection process described here by an appropriate kinetic transport equation taking into account adiabatic cooling and focusing, pitch angle scattering and energy diffusion. In this paper, we solve this equation for He⁺pick-up ions which are injected into the solar wind mainly in the region of the helium cone. We show the resulting He⁺pick-up ion density profile along the orbit of the Earth in many respects differs from the density profile of the neutral helium cone: depending on solar-wind-entrained Alfvénic turbulence levels, the density maximum when looking from the Earth to the Sun is shifted towards the right side of the cone, the ratio of peak-densities to wing-densities varies and a left-to-right asymmetry of the He⁺-density profile is pronounced. Derivation of interstellar helium parameters from these He⁺-structures, such as the local interstellar medium (LISM) wind direction, LISM velocity and LISM temperature, are very much impeded. In addition, the pitch-angle spectrum of He⁺pick-up ions systematically becomes more anisotropic when passing from the left to the right wing of the cone structure. All effects mentioned are more strongly pronounced in high velocity solar wind compared to the low velocity solar wind.     

Geological factors governing ichthyofauna formation in rivers of Semlyachikskii volcanic region (Eastern Kamchatka)

The role of environmental factors is considered for the lower reaches of rivers and creeks originating from the slopes of volcanoes of the Semlyachikskaya group (East Kamchatka volcanic region). The hydrological and environmental conditions of rivers and creeks flowing into the Semlyachikskii Liman are described for the first time. The specific hydrological and geomorphological characteristics of the lower reaches of those streams and the relationship between abiotic characteristics and the specific features of the structure and abundance of fish communities are studied. The spawning intensity (density) of salmon Salmonidae and the complexity (balance) of the structure of young fish and resident fish communities depend on the stream size. The habitation density and the uniformity of young fish distribution are determined by channel slope and the morphology of channel relief forms. The temperature regime determines fish growth rate, and water chemistry determines the phonetic features of resident fish population.     

Instability of the structure of strong oblique MHD cosmic-ray shocks

A criterion of the instability of a flow of a thermal plasma and cosmic rays in front of an oblique MHD shock wave with respect to short-wavelength magnetosonic disturbances is derived. The dependence of a cosmic-ray diffusion tensor on a plasma density and a large-scale magnetic field is taken into account. The most unstable disturbances propagate at an angle to the magnetic field if diffusion is strongly anisotropic. In some cases the most strong instability connects with the off-diagonal terms of the diffusion tensor.     

Suspended sediment balance in Selenga delta at the late XX–early XXI century: Simulation by LANDSAT satellite images

Adaptation of the technology of water turbidity simulation by satellite image data for the delta of the Selenga R., the largest Baikal tributary is given. The results of processing a series of 82 Landsat images are used to assess the seasonal variability of suspended sediment balance in the Selenga delta in period from 1989 up to the present time. It is shown that, at higher water discharges (>1500 m³/s), suspended material will accumulate in the delta (on the average 15% of the total sediment transport at the delta head), governed by material precipitation within inundated floodplain area and lakes in the lower part of the delta. At lower water discharges (<1500 m³/s), a longitudinal increase in suspended sediment transport may take place, caused by setups from Baikal side and channel erosion in the branches.     

Influence of channel reconfigurations on the development of confluence nodes of rivers

Using the confluence nodes of broad-floodplain rivers as an example, we examine the different variants of effects of channel deformations (channel meandering of the main river and its tributary, formation of forks, and shift of meander bars) upon their configuration and reconfiguration across time. We demonstrate the diversity of these effects even where the deformations themselves are of the same type. Problems of further investigations are formulated.     

Parallel-branch braiding of river channels: Formation conditions,morphology, and dynamics

The conditions and mechanisms of the formation of parallel-branch braidings—the least studied and most complex variety of braided channels are analyzed. They are proved to be related with the appearance of a vertical interface between water masses in rivers with weakly stable, wide, spread channel; large runoff of channel-forming (tractable) sediments. Channels of this type in the Northern Dvina and the Upper Ob are described in detail.     

Intricately Braided River Channels of Lowland Rivers: Formation Conditions,Morphology, and Deformation

The types of braided channels of major rivers that show the most complex morphology and rearrangement are considered. The formation conditions of these channels are analyzed, and a relationship accounting for both the hydrological and morphological properties is proposed. The parameter of this relationship is demonstrated to distinguish each type of braiding.     

The suspended sediment discharge of the rivers running along territories of contemporary volcanism in Kamchatka

The sediment discharge of rivers for the territories of the Avachinskaya and Northern groups of volcanoes (the Klyuchevskaya group of volcanoes, and Shiveluch Volcano), constituting zones of active volcanism on the territory of Kamchatka Peninsula was analyzed. A special model based on the principle of multiple regression relationships between the amount of suspended sediment discharge and its formation factors has been employed. This has allowed us to obtain assessments of the sediment discharge into the Pacific Ocean for the eastern coast of Kamchatka.