Indirect estimation of turbulent mixing in western route of Indonesian throughflow

The Indonesian Throughflow (ITF) via its western path conveys mainly North Pacific water origin with Smax thermocline water and Smin intermediate water from its entry portal in Sangihe-Talaud arcs to the main outflow straits in Lombok, Ombai and Timor passage. Along its route, the throughflow water characteristics transforms significantly due to strong diapycnal mixing forced by internal tidal waves interaction along complex topography such as passages, sill, straits, and shallow islands chains. This paper reports a brief estimate of turbulent mixing profiles in Sangihe chains, and Makassar Strait. The CTD dataset are obtained from the year of maritime continent (YMC) Cruise in August 2019 on board the R.V. Baruna Jaya I. The Thorpe method is used to analysis dissipation energy ( ε ) and vertical diffusivity (Kz ) from CTD dataset. It is shown that the highest ε epsilon 5.87 × 10−7 Wkg −1 and Kz 4.42 × 10−3 m2s 1 are found in the Sangihe area. In Labani Channel and Dewakang Sill the averaged vertical diffusivity is much weaker at the order of 10−4 m 2s1. Thus, Sangihe Chains station have the highest values compared to other stations at depth 950-1000 meters.

Inward and outward dust acoustic cylindrical and spherical waves interaction in four-component dusty plasma with nonthermal ions

A theoretical investigation by an all-inclusive adaptation of the PLK strategy is carried out in order to study the inward and outward interaction between two cylindrical and spherical dust acoustic solitary waves (DASWs) in an unmagnetized dusty plasma consisting of nonthermal distributed ions, negatively and positively charged dust grains along with electrons featuring Boltzmann’s distribution. The interactions and collisions between two cylindrical and spherical geometries at different time scales are studied. Also the combined effects of the nonthermality of ions, ion to electron temperature ratio as well as mass ratio of positive to negative dust grains have been studied in detail on the phase shifts raised due to collision. It has been seen that the properties of the cooperation of DASWs in cylindrical and spherical shaped are distinct.

A new approach of implementation of Wave Boundary Layer in OpenIFS

<p>Despite of significant improvement in modelling of the atmosphere after years of research, the accuracy of predicting cyclone/typhoon waves still remains highly challenging. Evidence shows that the air-sea-waves interaction over the ocean surface can significantly impact on the coupled atmosphere-ocean systems, through momentum, mass, and energy exchanges. In particular, the momentum exchanges have been found to affect both the structure of the wave boundary layer and the sea state, through the wave dissipation and wave breaking. For many decades, studies suggested different parameterizations of the momentum fluxes, through drag coefficient (C<sub>d</sub>) and the roughness length (z<sub>0</sub>). In recent years, research has been focused on the theoretical approaches of the momentum parameterization within the Wave Boundary Layer (WBL) in order to obtain the best C<sub>d</sub> and z<sub>0</sub> (Hara and Belcher 2002,2004; Moon et al. 2004; Du et al. 2017,2019). In this study, based on the works of Du et al. (2017, 2019), we introduce a new approach of the parameterization of the momentum flux using the roughness length. The potential of the scheme is analysed with extreme wind and wave events and the results are validated against buoy observations.</p>

Electron beaming instabilities as sources of CME radio emissions

<p>Radio emissions accompanying coronal mass ejections (CMEs) from their flaring sources (type III bursts) to interplanetary shocks (type II bursts) are believed to originate in the electrostatic (ES) wave instabilities, which are excited by the electrons beaming along the intense magnetic fields. Theoretically, radio emissions of fundamental (plasma) frequency $\omega_{p}$ or the second harmonic $2 \omega_{p}$ may result from non-linear three waves interaction of electrostatic Langmuir and ion sound fluctuations. However, it is not clear yet what kind of electron beams and specific CME plasma conditions can determine destabilization of Langmuir waves (ion sound waves may result from non-linear decay). Recent attempts to identify and characterize these unstable regimes suggest very critical and limited conditions for Langmuir instabilities to develop, which may undermine our current understanding of their implication in nonlinear generation of radio waves. Thus, even for a dominance of ES instabilities, conditioned by high beaming velocities, Langmuir waves appear to be in close competition with other ES growing modes (such as electron acoustic instabilities), while for less energetic beams the theory predicts a strong interplay with instabilities of different nature (electromagnetic or hybrid, and propagating obliquely to the magnetic field). </p>

Estimating energy dissipation in internal solitary waves breaking on slopes

<p>The shoaling mechanisms of internal solitary waves that propagate horizontally are an important source of mixing and transport in the coastal zones. Numerical modelling, llaboratory experiments and observations are needed for understanding wave energetics, especially energy transformation during waves interaction with the slopes. Two shoaling mechanisms are important during interaction with the slope: (i) wave breaking that results in mixing and dissipation, (ii) changing of the polarity of the initial wave of depression on the slope. Classification based on regimes of interaction with the slope was presented in [1]. Four zones were separated in αβγ (γ - is slope angle, α-  is the non-dimensional wave amplitude (wave amplitude normalized on the thermocline thickness) and β – is the blocking parameter that is the ratio of the height of the bottom layer on the shelf to the incident wave amplitude) classification diagram: (I) without changing polarity and wave breaking, (II) changing polarity without breaking; (III) wave breaking without changing polarity; (IV) wave breaking with changing polarity. It was shown that results of field, laboratory and numerical experiments are in good agreement with proposed classification.  In the present study we estimate energy dissipation for all the types of interaction and present the algorithm for building a zone map with a ‘hot spot’ of energy dissipation for real slopes in the ocean.</p><p> </p><p>[1] K Terletska, BH Choi, V Maderich, T Talipova  Classification of internal waves shoaling over slope-shelf topography RUSSIAN JOURNAL OF EARTH SCIENCES vol. 20, 4, 2020, doi: 10.2205/2020ES000730</p>