The role of charge-exchange cross-section for pickup protons and neutrals in the inner heliosheath

The process of deceleration of the solar wind downstream of the termination shock is studied on the basis of a one-dimensional multi-component model. It is assumed that the solar wind consists of thermal protons, electrons and interstellar pickup protons. The protons interact with interstellar hydrogen atoms by charge-exchange. Two cases are considered. In the first one, the charge-exchange cross-section for thermal protons and hydrogen atoms is the same as for pickup protons and atoms. Under this condition, there is a strong dependence of the solar wind velocity on the downstream temperature of pickup protons. When the proton temperature is close to 10 keV, the change in the velocity with the distance from the termination shock is similar to that measured on the Voyager 1 spacecraft: linear velocity decrease is accompanied by an extended transition region with near-zero velocity. However, with a more careful approach to the choice of the charge-exchange cross-section, the situation changes dramatically. The strong dependence of the solar wind speed on the pickup proton temperature disappears and the transition region in the heliosheath disappears as well, at least at reasonable distances from the TS.     

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.     

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.     

Effects of placer mining on suspended sediment budget: case study of north of Russia’s Kamchatka Peninsula

Abstract

Placer mines are located in river valleys, along river benches, or along the pathways of ancient channels. Open-pit mining alters the stream hydrology and enhances sediment transport. The present study focuses on sediment transport in the area of the platinum placer mining located at the north of Russia’s Kamchatka Peninsula (Seynav-Galmoenan placer deposits). Based on hydrological field investigations, a conceptual model was derived to assess anthropogenic effects on the total sediment budget of rivers. The model illustrates key processes controlling sediment dynamics in the Vyvenka River basin. Field work included water-discharge and sediment-load measurements, assessment of annual channel change in rivers in mining site areas, and evaluation of the relative importance of sediment sources and transport processes. In this study, we estimated total sediment delivery from opencast placer mining of 60 t year^-1; the annual mass wasting rate ranges from 2 to 5.5 kg m^-2 year^-1, which is three orders of magnitude higher than from non-mined streams. Mass wasting dominates surface erosion on the hillslopes and produces significant wastewater effluents; however, erosion of the artificially stratified channel reaches is the primary contributor to the annual sediment yield of the mined rivers (21.4%).

Editor D. Koutsoyiannis

Citation Chalov, S.R., 2014. Effects of placer mining on suspended sediment budget: case study of north of Russia’s Kamchatka Peninsula. Hydrological Sciences Journal, 59 (5), 1081–1094.     

Sedimentation patterns in the Selenga River delta under changing hydroclimatic conditions

The Selenga River delta (Russia) is a large (>600 km²) fluvially dominated fresh water system that transfers water and sediment from an undammed drainage basin into Lake Baikal, a United Nations Educational, Scientific, and Cultural Organization World Heritage Site. Through sedimentation processes, the delta and its wetlands provide important environmental services, such as storage of sediment‐bound pollutants (e.g., metals), thereby reducing their input to Lake Baikal. However, in the Selenga River delta and many other deltas of the world, there is a lack of knowledge regarding impacts of potential shifts in the flow regime (e.g., due to climate change and other anthropogenic impacts) on sedimentation processes, including sediment exchanges between deltaic channels and adjacent wetlands. This study uses field measurements of water velocities and sediment characteristics in the Selenga River delta, investigating conditions of moderate discharge, which have become more frequent over the past decades (at the expense of peak flows, Q > 1,350 m³ s^?1). The aims are to determine if the river system under moderate flow conditions is capable of supporting sediment export from the main distributary channels of the delta to the adjacent wetlands. The results show that most of the deposited sediment outside of the deltaic channels is characterized by a large proportion of silt and clay material (i.e., <63 μm). For example, floodplain lakes function as sinks of very fine sediment (e.g., 97% of sediment by weight < 63 μm). Additionally, bed material sediment is found to be transported outside of the channel margins during conditions of moderate and high water discharge conditions (Q ≥ 1,000 m³ s^?1). Submerged banks and marshlands located in the backwater zone of the delta accumulate sediment during such discharges, supporting wetland development. Thus, these regions likely sequester various metals bound to Selenga River sediment.     

Reflection of pre-accelerated pick-up ions at the solar wind termination shock: The seed for anomalous cosmic rays

It has been hypothesized for quite some time that interplanetary pick-up ions due to energization taking place in the region close to the solar wind termination shock, at some fraction and as an outcome of a complicated chain of processes, eventually are converted into species of the anomalous cosmic-ray particles. For the actual conversion efficiency it is of great importance to know the energy distribution of these pick-up ions upon their arrival at the shock. It turns out that pre-acceleration of these ions during their passage through the heliosphere shall substantially increase their chances to become reflected at the shock into the upstream direction which is a prerequisite for a further climb-up in energy by virtue of Fermi-1 acceleration processes. In this paper we start out from stochastically pre-accelerated pick-up ions and investigate their behaviour at the shock. With the use of adiabatic approaches in the de Hoffman-Teller frame of the shock, we calculate the energy distribution function of the reflected part of pick-up ions. From the calculated distribution functions it turns out that the reflected ions in the average suffer an energy increase by about a factor of 10, still not enough to let them move off the shock by spatial diffusion in the upstream direction. Thus, since converted back into the shock, they can undergo repeated reflections and energy gains till the diffusion-convection limit is reached. As we show in addition, the reflection probability for pick-up ions is about a factor of 10 higher than expected from the present literature and strongly varies with the off-axis angle, pointing to the fact that the termination shock represents a surface with a three-dimensionally varying source strength for the production of anomalous cosmic rays. The ACR source pattern is also expected to vary during the solar cycle and the relevant injection energies are expected to be larger by factors of 10 to 100 than the canonically adopted 1 keV nucl^–1.Institute for Problems of Mechanics of the Russian Academy of Sciences, Prospect Vernadskogo 101, 117526, Moscow, Russia.     

Parameterization of channel processes for their forecast estimation and diagnostics of hazardous manifestations

The study considers parameterization principles of channel processes, which can be used to obtain quantitative or qualitative characteristics of various forms of channels and channel relief and hazardous manifestations of channel deformations. Channel parameters enable the development of hydromorphometric and hydrological–morphological relationships with the characteristics of channel process factors. The identification of measurable (direct) and integral (calculated and estimated) parameters is substantiated. The former parameters are taken to be the morphometric and morphologic characteristics of the channel and its forms (bends, bifurcations) and channel relief forms (ridges, riffles), the dynamic characteristics of the directions and rates of channel deformations.     

Assessing the morphodynamical complexity of a large river in planning hydroeconomic measures (as exemplified by the Ob’)

Along the entire length of a large river there is taking place a substantial change in the formation conditions and stability of the channel, the rate and character of channel deformations and, accordingly, in the possibilities of water resources utilization, transport and engineering development of the river. By parametrizing the channel processes, it is possible to rank the river sections according to the degree of complexity of the channel processes, forms of their manifestation, and to the regime of channel reconfiguration, which, in turn, determines the possibilities of planning the measures ensuring the water resources utilization. Using the Ob’ as an example, we provide a rationale for the criteria for singling out the river sections differing by the degree of complexity of the channel processes, on the basis of parameters characterizing the forms of their manifestation, the state of the channels, and the intensity of deformations. We have identified eight sections of a different length, sequentially alternating along the length of the river from the confluence of the Biya and Katun’ as far as the mouth. The ranking of the river sections permitted the future planning of the water resources utilization measures.