Numerical modeling of pedestal stability and broadband turbulence of wide-pedestal QH-mode plasmas on DIII-D

Wide pedestal Quiescent High confinement (QH) mode discovered on DIII-D in recent years is a stationary and quiescent H-mode with the pedestal width exceeding EPED prediction by at least 25%. Its characteristics, such as low rotation, high energy confinement and ELM-free operation, make it an attractive operation mode for future reactors. Linear and nonlinear simulations using BOUT++ reduced two fluid MHD model are carried out to investigate the bursty broadband turbulence often observed in the edge of wide-pedestal QH-mode plasmas. Two kinds of MHD-scale instabilities in different spatial locations within the pedestal were found in the simulations: one mild peeling-ballooning (PB) mode (γ_PB<0.04ω_A) located near the minimum in Er well propagating in ion diamagnetic drift direction; and one drift-Alfvén wave (DAW) locates at smaller radius compared to Er well propagating in the electron diamagnetic drift direction and unstable only when the parallel electron dynamics is included in the simulation. The coupling between drift wave and shear Alfvén wave provides a possible cause of the experimentally observed local profile flattening in the upper-pedestal. The rotation direction, mode location, as well as the wavenumber of these two modes from BOUT++ simulations agree reasonably well with the experimental measurements, while the lack of quantitatively agreement is likely due to the lack of trapped electron physics in current fluid model. This work presents improved physics understanding of the pedestal stability and turbulence dynamics for wide-pedestal QH-mode.

Neotectonics and geodynamics of the Streltsovsky ore region according to the analysis of digital elevation models

In the case of underground mining of mineral deposits under difficult mining and geological conditions and at great depths, one of the most urgent problems is the prevention of dangerous geodynamic events. The use of digital elevation models significantly expands the possibilities of preliminary assessment of the potential hazard of their manifestation. This article discusses the results of an assessment of the neotectonics and geodynamics of the Streltsovsky ore region carried out using digital elevation models. The interpretation of the obtained data is based on the concept of lateral tectonic flows adapted for the Far Eastern region of Russia. Digital elevation models based on the GTOPO30 made it possible to identify and evaluate the drift direction of three tectonic flows in the region. The direction determined by the relief coincides satisfactorily with the GPS direction.

Opportunistic evaluation of modelled sea ice drift using passively drifting telemetry collars in Hudson Bay, Canada

Sea ice drift plays a central role in the Arctic climate and ecology through its effects on the ice cover, thermodynamics, and energetics of northern marine ecosystems. Due to the challenges of accessing the Arctic, remote sensing has been used to obtain large-scale longitudinal data. These data are often associated with errors and biases that must be considered when incorporated into research. However, obtaining reference data for validation is often prohibitively expensive or practically unfeasible. We used the motion of 20 passively drifting high-accuracy GPS telemetry collars originally deployed on polar bears, Ursus maritimus, in western Hudson Bay, Canada, to validate a widely used sea ice drift dataset produced by the National Snow and Ice Data Center (NSIDC). Our results showed that the NSIDC model tended to underestimate the horizontal and vertical (i.e., u and v) components of drift. Consequently, the NSIDC model underestimated magnitude of drift, particularly at high ice speeds. Modelled drift direction was unbiased; however, it was less precise at lower drift speeds. Research using these drift data should consider integrating these biases into their analyses, particularly where absolute ground speed or direction is necessary. Further investigation is required into the sources of error, particularly in under-examined areas without in situ data.

Lower hybrid waves at the magnetosheath separatrix region

&lt;div&gt;Lower hybrid waves are investigated at the magnetosheath separatrix region in asymmetric guide-field reconnection at Earth&amp;#8217;s magnetopause by using MMS observations. These waves are found in a limited region, depending on the density gradient across the separatrix, and they are driven by the lower hybrid drift instability. Properties of these waves are presented: (1) the waves propagate towards the x-line due to the out-of-plane magnetic field, consistent with the electron drift direction; (2) the wave potential is about 20% of the electron temperature. These drift waves effectively produce cross-field particle diffusion, enabling the entry of magnetosheath electrons into the exhaust region.&lt;/div&gt;

Opportunistic evaluation of modelled sea ice drift using passively drifting telemetry collars in Hudson Bay, Canada

Sea ice drift plays a central role in the Arctic climate and ecology through its effects on the ice cover, thermodynamics, and energetics of northern marine ecosystems. Due to the challenges of accessing the Arctic, remote sensing has been used to obtain large-scale longitudinal data. These data are often associated with errors and biases that must be considered when incorporated into research. However, obtaining reference data for validation is often prohibitively expensive or practically unfeasible. We used the motion of 20 passively drifting high-accuracy GPS telemetry collars originally deployed on polar bears, Ursus maritimus, in western Hudson Bay, Canada to validate a widely used sea ice drift dataset produced by the National Snow and Ice Data Centre (NSIDC). Our results showed that the NSIDC model tended to underestimate the horizontal and vertical (i.e. u and v) components of drift. Consequently, the NSIDC model underestimated magnitude of drift, particularly at high ice speeds. Modelled drift direction was unbiased, however was less precise at lower drift speeds. Research using these drift data should consider integrating these biases into their analyses, particularly where absolute ground speed or direction is necessary. Further investigation is required into the sources of error, particularly in under-examined areas without in situ data.

A high resolution multi-turn TOF mass analyzer

An ion optical design of a high resolution multi-turn time-of-flight mass analyzer (MT-TOF MA) is presented. The analyzer has rotationally symmetric main electrodes with additional mirror symmetry about a mid-plane orthogonal to the axis of symmetry. Rotational symmetry allows a higher density of turns in the azimuthal (drift) direction compared to MT-TOF MAs that are linearly extended in the drift direction. Mirror symmetry about a mid-plane helps to achieve a high spatial isochronicity of the ions’ motion. The analyzer comprises a pair of polar-toroidal sectors S1 and S3, a pair of polar (trans-axial) lenses, and a pair of conical lenses for longitudinal and lateral focusing. A toroidal sector S2 located at the mid-plane of the analyzer has a set of embedded drift focusing segments providing focusing and spatial isochronicity in the drift direction. The ions’ drift in the azimuthal direction can be reversed by using dedicated reversing deflectors. This gives the possibility of several operational modes with different numbers of turns and passes in the drift direction. According to numerical simulations, the mass resolving power of the analyzer ranges from [Formula: see text]40 k (fwhm) at small (typically below ten) numbers of turns to [Formula: see text]450 k (fwhm) at 96 turns.