Dipole model of the Earth's magnetic field

About: Dipole model of the Earth's magnetic field is a research topic. Over the lifetime, 2756 publications have been published within this topic receiving 83021 citations.

Instability of a pseudo-relativistic model of matter with self-generated magnetic field

Abstract: For a pseudo-relativistic model of matter, based on the no-pair Hamiltonian, we prove that the inclusion of the interaction with the self-generated magnetic field leads to instability for all positive values of the fine structure constant This is true no matter whether this interaction is accounted for by the Breit potential, by an external magnetic field which is chosen to minimize the energy, or by the quantized radiation field

On the magnetic and thermodynamic consequences of the return-flux sunspot model

Abstract: The magnetic structure of sunspots from photosphere to low corona is considered on the basis of a new magnetohydrostatic theory of sunspots. The first numerical solutions of the basic nonlinear force-balance equation which takes into account returning magnetic flux are obtained using observational data for the maximum field, umbral, and penumbral size and for the veritical distribution of pressure on the sunspot axis and in the quiet Sun. Both vertical and horizontal distributions for the magnetic field were obtained as well as its vertical gradient. Further, the pressure and temperature distributions consistent with this field were also obtained. The dependence of the model on the Wilson depression, the maximum magnetic field of the sunspot, and the amount of return magnetic flux is investigated. A ''global'' force-balance relation is found to hold which relates the magnetic field gradient on the spot axis with the maximum magnetic field and the pressure deficit, or Wilson depression, in the spot photosphere.

The structure of the solar flare stream magnetic field

Abstract: The structure of the interplanetary magnetic field within the flare streams as well as associated variations of the geomagnetic disturbancy are considered. It is shown that in the main body of the flare stream the magnetic field is determined by the configuration of the large scale magnetic field on the Sun at the flare region. Within the head part of the flare stream the magnetic field represents by itself the compressed field of the background solar wind and hence is determined by the distribution of the super large scale solar magnetic field outside the flare region.

On the Resolution of the Azimuthal Ambiguity in Vector Magnetograms of Solar Active Regions

Abstract: We introduce a "structure minimization" technique to resolve the azimuthal ambiguity of 180°, intrinsic in solar vector magnetic field measurements. We resolve the 180° ambiguity by minimizing the inhomogeneities of the magnetic field strength perpendicular to the magnetic field vector. This relates to a minimization of the sheath currents that envelope the solar magnetic flux tubes, thus allowing for more space-filling and less complex magnetic fields. Structure minimization proceeds in two steps: First, it derives a local solution analytically, by means of a structure minimization function. Second, it reaches a global solution numerically, assuming smoothness of the magnetic field vector. Structure minimization (i) is disentangled from any use of potential or linear force-free extrapolations and (ii) eliminates pixel-to-pixel dependencies, thus reducing exponentially the required computations. We apply structure minimization to four active regions, located at various distances from disk center. The minimum structure solution for each case is compared with the "minimum energy" solution obtained by the slower simulated annealing algorithm. We find correlation coefficients ranging from significant to excellent. Moreover, structure minimization provides an ambiguity-free vertical gradient of the magnetic field strength that reveals the variation of the magnetic field with height. The simplicity and speed of the method allow a near real-time processing of solar vector magnetograms. This task was not possible in the past and may be of interest to both existing and future solar missions and ground-based magnetographs.

The Geometry of Turbulent Magnetic Fluctuations at High Heliograpahic Latitudes

Abstract: Although the orientation of wave vectors for interplanetary magnetic fluctuations is often discussed or assumed when modelling the solar wind turbulence, there were few if any direct measurements of the wave vector orientation until very recently. Indirect inferences abound. For instance, the transverse nature of magnetic fluctuations has often been used to infer a wave vector parallel to the mean magnetic field, but transverse fluctuations do not necessarily lead to parallel wave vectors — the fluctuations of two‐dimensional turbulence are fully tranverse, but their wave vectors are also transverse to the mean field. Bieber et al. [3] offer the first single‐point algorithm for separating field‐aligned wave vectors from perpendicular wave vectors using the component spectra. This method has since been used by others [5, 6, 8, 9] and is here applied to Ulysses measurements in a comparison of high latitude turbulence with the results of previous studies of near‐ecliptic observations.