Weak turbulence theory of the non-linear evolution of the ion ring distribution

The nonlinear evolution of an ion ring instability in a low-beta magnetospheric plasma is considered. The evolution of the two-dimensional ring distribution is essentially quasilinear. Ignoring nonlinear processes the time-scale for the quasilinear evolution is the same as for the linear instability 1/t_ql gamma_l. However, when nonlinear processes become important, a new time scale becomes relevant to the wave saturation mechanism. Induced nonlinear scattering of the lower-hybrid waves by plasma electrons is the dominant nonlinearity relevant for plasmas in the inner magnetosphere and typically occurs on the timescale 1/t_ql w(M/m)W/nT, where W is the wave energy density, nT is the thermal energy density of the background plasma, and M/m is the ion to electron mass ratio, which has the consequence that the wave amplitude saturates at a low level, and the timescale for quasilinear relaxation is extended by orders of magnitude

Quasilinear Evolution of Kinetic Alfven Wave Turbulence and Perpendicular Ion Heating in the Solar Wind

The measured spectrum of kinetic Alfven wave fluctuations in the turbulent solar wind plasma is used to calculate the electron and ion distribution functions resulting from quasi-linear diffusion. The modified ion distribution function is found to be unstable to long wavelength electromagnetic ion cyclotron waves. These waves pitch angle scatter the parallel ion velocity into perpendicular velocity which effectively increases the perpendicular ion temperature.Comment: 14 pages, 3 figure

Application of activated sludge model (ASM3) and anaerobic digestion model (ADM1) on wastewater treatment plant Anjana in Surat : India

Mathematical modelling becomes more and more an integral part of the design, operation and performance assessment of wastewater treatment plant (WWTP). A better understanding in terms of process dynamics is required to improve plants operational performance and achieve effective control. This could be achieved by mean of simulations by a comprehensive mathematical model.A combined Activated Sludge Model (ASM3) and Anaerobic Digestion Model (ADM1) were used in this study to describe organic matter and nitrogen removal as well as sludge stabilization, in a full-scale wastewater treatment plant (WWTP) Anjana in Surat-India.The WWTP Anjana started in the year 1995 and the original design was based on organic removal only. It is conventional activated sludge process with anaerobic sludge digestion. An extensive sampling program and analysis for 16 days was carried out during the period of October-November 2004 at the Anjana WWTP. The sampling program results showed that the WWTP Anjana was performing well regarding the organic matter removal. The performance of primary settling tank was excellent while limiting digester performance for COD stabilization was found.The modelling exercise was not only carried out to get more knowledge about the models and to apply it on full scale WWTP, but also to understand the WWTP behaviour under different conditions and to further optimise the plant performance. The ASM3, ADM1 and the coupled model (ASM3+ADM1) were applied for the first time under Indian condition. Both models were calibrated based on the results obtained during sampling program. They were calibrated separately before theirs coupling.The ASM3 was successfully applied to wastewater line at Anjana WWTP and proved capable of defining performance of the wastewater line with the calibration of only three parameters; (1) autotrophic growth rate, (2) aerobic endogenous respiration rate of autotrophs and (3) anoxic reduction factor of endogenous respiration of autotrophs. The STOWA guidelines were used for wastewater characterisation for the first time in India and proved applicable. The ADM1 was applied to anaerobic sludge digesters and proved capable of defining performance of the sludge line. Only particulate and inert fraction produced during disintegration step were changed to calibrate model successfully without calibrating any other default parameter. The sludge characterisation for ADM1 was carried out on the basis of COD degradation data of digester from the sampling program. These models were coupled using simplified approach of ASM to ADM unit conversion duly introducing virtual compartments. The two models were applied in combination to the full-scale WWTP to study the plant behaviour in different conditions. In total successful application of modelling on WWTP Anjana was achieved with change of five model parameters only.The coupled model was used simulate three different scenarios. The model simulation showed the improvement in plant performance with the simple set of operational changes for present as well as for future conditions. The coupled model was also used to simulate optimisation and upgrade of the plant by N-removal as well as to optimise the methane production. The simulation results showed that sludge retention time was influencing the plant performance, which needed to be increased. The simulation with the creation of anoxic zone showed remarkable influence on Nitrogen removal. However, the N-removal upgrade showed marginal negative influence on methane production. Although, the primary settling tank was not part of the model, its COD removal efficiency influence the performance of the activated sludge process and anaerobic sludge digestion, showed that it need attention towards its efficient operation, in future with more flow and load. The more primary sludge would help in getting more methane production.Overall, it was observed that the plant could be upgraded to N-removal with the creation of anoxic zone and simple operational modification, without disturbing much the methane production for present as well as future flow. The model has certainly the capacity to be used as an effective tool in decision-making for other WWTPs in India