Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 1409.6053

Optimal signals for spectral measurements at EKB SuperDARN radar: Theory and Experiment

Oleg I. Berngardt·A. L. Voronov·K. V. Grkovich
View original source ↗Read source document ↗Export metadata ↓

Abstract

The requirements for an optimal sequence for SuperDARN radar are stated. Obtained quasioptimal signals up to 26-pulse sequence are based on optimal and nearly optimal Golomb rulers. It is shown that standard 7-pulse SuperDARN sequence is one of the quasioptimal sounding signals, but 8-pulse kascan SuperDARN signal is not. The characteristics are calculated for quasioptimal sounding sequences up to 26-pulse one. It is shown that the most effective signals for the spectral measurements are 10, 12, 14, 18, 20, 24 and 26 pulse sequences. We present the results of the first spectral measurements at the EKB SuperDARN radar with quasioptimal 8- and 9-pulse sequences, as well as with the optimal 10-and 12-pulse sequences. A comparison with the results obtained with standard 7-pulse SuperDARN sequence were made. The continuity of results in amplitude and velocity is shown, the expected improvement in the spectral width are also demonstrated.

Explore related subjects

physics.geo-phphysics.space-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Oleg I. Berngardt, A. L. Voronov, K. V. Grkovich. 2014-09-21. Optimal signals for spectral measurements at EKB SuperDARN radar: Theory and Experiment. https://doi.org/10.1002/2014rs005589

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Three dimensional non-singular mollified elastic dislocation theory for extended width fault zones and inhomogeneous boundary element models

Classical elastic dislocation theory (CEDT) has two challenges when applied to faulting problems: 1) fictitious on-fault stresses not defined by ordinary integration and 2) the geometric unreality of infinitely thin fault zones. We show that both can be resolved by a mollified elastic dislocation theory (MEDT) built on Cortez blob (Cortez, 2001) mollified displacement discontinuity Green's functions, which represent deformation across spatially distributed fault zones of finite scale epsilon and produce singularity-free displacements and stresses everywhere. Analytical integration of the mollified source solution over arbitrary planar triangular elements is done with AI, and the resulting closed-form solutions allow for the calculation of non-singular stresses across geometrically complex fault systems. Further, we demonstrate the decoupling of the fault-zone width scale epsilon from the mesh length scale h, the elasticity analog of a result established for regularized viscous flow Stokeslets (Ferranti and Cortez, 2024). We use these mollified kernels to demonstrate numerically stable collocation boundary element models including spatially extended fault zones, material property variations and non-planar topography.

physics.geo-ph↗
arXiv2026

Identifying the approach of a major earthquake

By analyzing the seismicity in natural time and studying the evolution of the fluctuations of the entropy change of seismicity under time reversal for various scales of different length i (number of events), we can identify the approach of a major earthquake (EQ) occurrence. The current investigation is extended from 1984 until now for the seismicity in Japan.

physics.geo-ph↗
arXiv2026

ADEPTS: An auto-differentiable framework for time-dependent nonlinear thermo-chemical mantle convection inversion

Time-dependent mantle-dynamics inversion must address the high dimensionality of the initial state, nonlinear rheology, and gradient propagation through long-term thermo-mechanical evolution. We develop ADEPTS, a two-dimensional staggered-grid finite-difference framework for mantle-dynamics inversion based on automatic differentiation. The forward model solves incompressible Stokes flow, temperature advection-diffusion, and compositional advection with temperature- and strain-rate-dependent viscosity and plastic yielding. For the nonlinear Stokes system, we compare two gradient strategies: unrolled differentiation through a fixed number of Picard iterations and implicit differentiation of the converged discrete residual equations. Numerical experiments show that unrolled differentiation remains stable even when the nonlinear solve is not fully converged, whereas implicit differentiation requires sufficiently accurate nonlinear solutions; otherwise gradient consistency and optimization convergence deteriorate. With sufficiently converged solves, implicit differentiation recovers accurate gradients and reconstruction quality comparable to unrolled differentiation. Joint thermo-chemical twin experiments show that ADEPTS can simultaneously recover a high-dimensional initial temperature field and low-dimensional physical parameters, including compositional density, reference viscosity, and stress exponent, while fitting final-time temperature, surface horizontal velocity, and surface normal stress. These results demonstrate the feasibility of differentiable time-dependent mantle-dynamics inversion and clarify the different convergence requirements of unrolled and implicit differentiation.

physics.geo-ph↗