Single Magnetic Field Component Research Articles

Improved and Interpretable Solar Flare Predictions With Spatial and Topological Features of the Polarity Inversion Line Masked Magnetograms

AbstractMany current research efforts undertake the solar flare classification task using the Space‐weather HMI Active Region Patch (SHARP) parameters as the predictors. The SHARP parameters are scalar quantities based on spatial average or integration of physical quantities derived from the vector magnetic field, which loses information of the two‐dimensional spatial distribution of the field and related quantities. In this paper, we construct two new sets of spatial features to expand the feature set used for the flare classification task. The first set uses the idea of topological data analysis to summarize the geometric information of the distributions of various SHARP quantities across active regions. The second set utilizes tools coming from spatial statistics to analyze the vertical magnetic field component Br and summarize its spatial variations and clustering patterns. All features are constructed within regions near the polarity inversion lines (PILs) and classification performances using the new features are compared against those using SHARP parameters (also along the PIL). We found that using the new features can improve the skill scores of the flare classification model and new features tend to have higher feature importance, especially the spatial statistics features. This potentially suggests that even using a single magnetic field component, Br, instead of all SHARP parameters, one can still derive strongly predictive features for flare classification.

Diffraction of Gauss beam by a resistive half-plane in an anisotropic plasma

The theoretical investigation of Gauss beam diffraction by a resistive half-plane surrounded by an anisotropic plasma is presented. For this purpose, an integral theory which yields the scattered fields in terms of the Fresnel function is considered. The kernel of the scattering integral is arranged, according to the relation between scattered geometric optics (GO) fields and the transition boundaries, to obtain the scattered fields. The magnetic line source illumination is considered since a single magnetic field component is affected by the anisotropy. Later, complex point source method is used for evaluation of Gauss beam diffraction. The resultant waves are plotted and discussed for the limiting cases of anisotropic medium and resistive half-plane.

Drift of the sensitive direction of Hall-effect devices in (1 0 0)-silicon caused by mechanical shear stress

Conventional Hall effect devices are designed to respond to a single magnetic field component in 3D space. However, if plastic encapsulated Hall effect devices in cubic crystals are exposed to poorly defined and unstable mechanical shear stress, small portions of unwanted, perpendicular magnetic field components will show up in the Hall output signals. Mathematically, any such crosstalk – may it originate from mechanical stress or not – can be expressed as a Taylor series in powers of the magnetic field. The even powers are the well known planar Hall effect at zero mechanical stress. In practice powers of even order are irrelevant, because they are eliminated by the widely used spinning current schemes. In this paper we address the odd powers of the magnetic crosstalk and their drift versus mechanical stress. The effect is small for Hall plates but large for Vertical Hall devices in (100)-silicon. It is fully described by piezo-resistance and piezo-Hall tensors. We present results of numerical simulations and measurements. Thin devices are less affected than thick devices. If magnetic angle sensors are made of Vertical Hall devices, in-plane shear stress leads to small orthogonality errors. This article lays the foundations for compensation circuits to eliminate such shear-stress induced orthogonality errors.

Prediction of magnetic field emissions by current source reconstruction using radial basis function network

Near-field measurement has been adopted in the prediction of emission levels for electromagnetic compatibility diagnosis and design purposes. A novel approach for effective reconstruction of the equivalent current source based on the near-field measurement data is presented, for the prediction of magnetic field emissions elsewhere. The approach consists of two steps: first, the distribution of the magnetic field component normal to the entire measurement plane is acquired by interpolation of the discrete measurement data using a radial basis function network; secondly, the magnetic emissions elsewhere are evaluated from the equivalent current source derived from the acquired magnetic field distribution. This approach requires the measurement of only one single magnetic field component. The accuracy of the proposed approach has been demonstrated by comparing the predicted field to that of the full-wave simulation; the robustness of the approach against measurement noise has also been verified.

Vector projection of biomagnetic fields

Biomagnetic measurements are increasingly popular as functional imaging techniques for the non-invasive assessment of electrically active tissue. Although most currently available magnetometers utilise only one component of the vector magnetic field, some studies have suggested the possibility of obtaining additional information from recordings of the full magnetic field vector. Three projection techniques were applied to different biomagnetic signals for analysis of the three orthogonal components of the vector magnetic field. Vector magnetic fields obtained from fetal cardiac activity were projected into evenly spaced directions around a unit sphere. The vector magnetic field recorded from multiple intestinal current sources with independent temporal frequencies was then projected. Finally, an external reference signal from an invasive electrode was used to project the recorded vector magnetic fields due to gastric electrical activity. In each case, it was found that the information obtained by examination of the projected magnetic field vectors gave superior clinical insight to that obtained by analysis of any single magnetic field component.

An electromagnetic field algorithm for 2D implicit plasma simulation

A new, robust algorithm is presented for the implicit calculation of the electromagnetic fields used in the full-particle and hybrid modeling of 2D simulation plasmas. The algorithm allows for calculations at time steps Δt well in excess of the plasma period and for mesh scales Δξ far exceeding the Debye length-with electron inertial terms retained. The implicit fields suppress the numerical instability associated with plasma waves. Still, the At remain constrained by an electron Courant limit. The algorithm is considerably simpler than earlier implicit schemes, and more complete in its treatment of field errors. In its present form the algorithm is limited to plasmas moving and accelerating in a plane across a single component of magnetic field. An extension to include all the field components is suggested, however. In accordance with the implicit moment method, estimated electric and magnetic fields are obtained by solving Maxwell's equations self-consistently for a set of implicit sources, estimated with the aid of an auxiliary set of lower fluid moment equations (for component fluxes and density). The fluid pressure terms are treated explicitly, and the spatial differencing of the auxiliary moments is centered to facilitate the solution of the resultant field equations. Solution for the single magnetic field component is obtained by one elliptic equation .inversion, readily managed by a vectorized solver package. A subsequent irrotational old E-field correction is found to be crucial for the maintainence of anticipated quasi-neutrality. A concomitant rotational correction is needed for physical solutions in steep density gradient problems. We show that both corrections can be obtained simultaneously by referencing the deviations between the true currents flowing, and the currents predicted to flow in the plasma at the end of a cycle. The current correction is shown to be equivalent to the first (and usually sufficient) step of an iterative procedure leading to an exact solution for the fields. In addition, we demonstrate that electrostatic solutions can be obtained from the implicit algorithm by setting the speed of light to very large multiples of its physical value. Comparisons are made with earlier moment and direct method approaches, and the scheme is related to previous classical hybrid models. Demonstrative applications are discussed.

DIFFRACTION BY A CONDUCTING HALF-PLANE IN PLASM

The problem considered is that of a plane electromagnetic wave approaching from an arbitrary direction a perfectly conducting half-plane in an anisotropic plasma, characterized by a permittivity tensor. The system is such that the wave has a single magnetic field component, which is parallel both to the magneto-static field and the diffracting edge. The work is a simplification of previous work by Jull, involving the use of methods previously developed by the author.

DIFFRACTION BY A CONDUCTING HALF-PLANE IN AN ANISOTROPIC PLASMA

The diffraction of a plane electromagnetic wave by a perfectly conducting half-plane in an anisotropic plasma is considered. The plasma is characterized by a permittivity tensor and the wave is assumed to propagate in a direction normal to the magnetostatic field and the diffracting edge, but its angle of incidence is otherwise arbitrary. Only the H-polarized wave of the incident field, which has a single magnetic field component parallel to the edge, is affected by the anisotropy and the analysis is restricted accordingly. Representing the scattered field as an angular spectrum of plane waves leads to dual integral equations from which an expression for the scattered field is obtained. The total field is then reduced to Fresnel integrals and its far-field behavior is investigated. Agreement with Seshadri and Rajagopal's result for a wave normally incident on the conductor, which was obtained by using the Wiener–Hopf technique, is found. The differences between isotropic and anisotropic solutions to this problem, which arise from the differing boundary conditions on the tangential magnetic field, are examined.