Fast-Track in-Stream Action to Enhance the Oxidative Capacity within Watershed

This work presents a non-conventional alternative for cleaning polluted agriculture drainage network within a certain watershed. In Egypt, a need for using marginal quality water in agriculture applications is becoming a great necessity due to water shortage. One important strategy to increase available water resources is to reuse agriculture drainage water for irrigation application. The water system, especially drainage network receives a remarkable amount of pollution (raw and partially treated wastewater). That results to an increase in organic load to an unacceptable level, accordingly, the water quality of the drainage water has been negatively affected and the "reuse" plan has been threatened. Fast-Track In-stream Action (FTIA) is an ongoing fast action suggested to control the pollution of drainage water within a certain watershed to make it more suitable for reuse practice. FTIA as a quick interfere will skip long-term processes of conventional water treatment stages to get satisfactory results in proper time. It presents a practical immediate solution to achieve acceptable level of water quality rather than waiting for full improvement through long-term and expensive conventional programs. In this study a biological maintenance solution was applied and tested in both bench and field scales to assess its efficiency in improving the water quality within selected watershed. An evaluation of this fast-track process was done by measuring a significant key water quality parameters (WQPs) at designed locations of the study area before, during and after application of material. For better explanation of overall water quality and proper comparison, a weighted arithmetic water quality index (AWQI) has been discussed based on eight selected WQPs. In addition to a bench-scale test, two other field investigations were adopted: the first one investigates the effects of fast-track resources when applying the bio-based material under high flow condition with intermediate shock flow (study area "1"), while the other one examine the application of material under low flow condition with intermediate shock pollution load (study area "2"). All indicators, including aesthetics showed improvements in selected WQPs and AWQI during the investigation period

Intermediate shock sub-structures within a slow-mode shock occurring in partially ionised plasma

Context. Slow-mode shocks are important in understanding fast magnetic reconnection, jet formation and heating in the solar atmosphere, and other astrophysical systems. The atmospheric conditions in the solar chromosphere allow both ionised and neutral particles to exist and interact. Under such conditions, fine sub-structures exist within slow-mode shocks due to the decoupling and recoupling of the plasma and neutral species. Aims. We study numerically the fine sub-structure within slow-mode shocks in a partially ionised plasma, in particular, analysing the formation of an intermediate transition within the slow-mode shock. Methods. High-resolution 1D numerical simulations were performed using the (PIP) code using a two-fluid approach. Results. We discover that long-lived intermediate (Alfvén) shocks can form within the slow-mode shock, where there is a shock transition from above to below the Alfvén speed and a reversal of the magnetic field across the shock front. The collisional coupling provides frictional heating to the neutral fluid, resulting in a Sedov-Taylor-like expansion with overshoots in the neutral velocity and neutral density. The increase in density results in a decrease of the Alfvén speed and with this the plasma inflow is accelerated to above the Alfvén speed within the finite width of the shock leading to the intermediate transition. This process occurs for a wide range of physical parameters and an intermediate shock is present for all investigated values of plasma-β, neutral fraction, and magnetic angle. As time advances the magnitude of the magnetic field reversal decreases since the neutral pressure cannot balance the Lorentz force. The intermediate shock is long-lived enough to be considered a physical structure, independent of the initial conditions. Conclusions. Intermediate shocks are a physical feature that can exist as shock sub-structure for long periods of time in partially ionised plasma due to collisional coupling between species.

Slow shock interactions in the heliosphere using an adaptive grid MHD model

A one-dimensional (1-D), time-dependent, adaptive-grid MHD model with solar wind structure has been used in the past to study the interaction of shocks. In the present study, we wish to study some fundamental processes that may be associated with slow shock genesis and their possible interactions with other discontinuities. This adaptive-grid model, suitable for appropriate spatial and temporal numerical simulations, is used for this purpose because its finer grid sizes in the vicinity of the steep gradients at shocks make it possible to delineate the physical parameters on both sides of the shocks. We found that a perturbation with deceleration of solar wind will generate an ensemble consisting of a forward slow shock, a fast forward wave and a reverse slow shock. On the other hand, a perturbation with an increase in acceleration of solar wind will generate both a slow shock and a fast shock. These two perturbations, although not unique, may be representative of momentum and pressure changes at the solar surface. During the transition of a fast shock overtaking a slow shock from behind, the slow shock might disappear temporarily. Also, during the process of the merging of two slow shocks, a slow shock-like structure is formed first; later, the slow shock-like structure evolves into an intermediate shock-like structure. This intermediate shock-like structure then evolves into an intermediate wave and a slow shock-like structure. Finally, the slow shock-like structure evolves into a slow shock, but the intermediate wave disappears by interacting with the non-uniform solar wind. This complex behavior demonstrates the non-unique nature of the formation of slow shocks, intermediate shocks and their derivative structures. We emphasize the main aim of this work to be both: (a) non-unique input physical parameters to explain the paucity of observed slow shocks, as well as (b) the impossibility of backward tracing to the history of input boundary conditions in view of the present inability to describe unambiguous inputs at the Sun.