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.

A variation of the Davis‐Smith method for in‐flight determination of spacecraft magnetic fields

Abstract: A variation of a procedure developed by Davis and Smith (1968) is presented for the in-flight determination of spacecraft magnetic fields. Both methods take statistical advantage of the observation that fluctuations in the interplanetary magnetic field over short periods of time are primarily changes in direction rather than in magnitude. During typical solar wind conditions between 0.8 and 1.0 AU, a statistical analysis of 2-3 days of continuous interplanetary field measurements yields an estimate of a constant spacecraft field with an uncertainty of plus or minus 0.25 gamma in the direction radial to the sun and plus or minus 15 gammas in the directions transverse to the radial. The method is also of use in estimating variable spacecraft fields with gradients of the order of 0.1 gamma/day and less and in other special circumstances.

Mathematical models of the open magnetosphere - Application to dayside auroras.

Abstract: Two static mathematical models of the open or Dungey model of the magnetosphere are constructed. The process of construction is similar to that for early closed magnetosphere models, such as the Taylor-Hones model. The first model in fact is simply an addition of an interplanetary field in arbitrary direction to a Taylor-Hones image dipole model. In order to preserve the shape of the magnetosphere at high latitudes, and to partially exclude the exterior field, another model is constructed with the magnetopause approximated by a diamagnetic sphere. We find that there are some interplanetary field lines connected to the earth for all orientations of the interplanetary field other than strictly northward, and that the maximum number of connected field lines occurs with a due southward field. For an average spiral hose angle of the interplanetary field, the dayside neutral point occurs on the magnetopause at about 10 o'clock local time. Dayside auroras, convection patterns, and other phenomena may exhibit symmetry about this local time. For a positive (negative) interplanetary field sector, energetic, anisotropic particle fluxes should have direct access to the northern (southern) polar caps, as is supported by many recent observations.

Shear Alfvén waves on stretched magnetic field lines near midnight in Earth's magnetosphere

Abstract: The spectrum of toroidal standing shear Alfven waves (SAWs) is derived for a stretched magnetic field line geometry that is approximated by the Tsyganenko 96 magnetic field model. The model is applied to field lines near the midnight meridional plane. It is demonstrated that the fundamental mode frequency for typical ambient parameters of Earth's magnetosphere is in the 1–4 mHz range. This frequency is in agreement with the measured frequency of magnetospheric field line resonances, and is up to an order of magnitude smaller than for a dipolar magnetic field. We conclude that stretching of Earth's magnetic field offers a possible explanation for anomalously low frequency SAWs observed within diffuse auroral emission (Hβ) produced by energetic proton precipitation in the inner plasma sheet.

Line element for efficient computation of the magnetic field created by thin iron plates

Abstract: The problem of computing the magnetic anomaly created by iron ships in the Earth's field is considered. From a modeling point of view, one of the major characteristics of this problem is the external and uniform magnetic source (the Earth's field). A good way of taking this into account is to simulate infinity and to use the reduced scalar potential as the state function. The major difficulty in modeling ships is the presence of sophisticated 3-D geometries due to the disproportion between the global size of a ship and the thickness of the iron plates. The modeling of the thin iron plates is examined, and it is shown that an efficient method is to use line elements in 2-D and surface elements in 3-D. The authors present the finite-element formulations used, applied to scalar potentials (reduced or total). The formulations using line elements have been successfully applied, even to a magnetic region with small permeability values. Results in 2-D and comparisons with analytical solutions and actual measurements are presented. >