Topic
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.
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TL;DR: In this article, the structure and dynamics of neutral sheets in the solar wind are examined, and the internal magnetic topology of the sheet is argued to be that of thin magnetic tongues greatly distended outward by the expansion inside the sheet.
Abstract: The structure and dynamics of neutral sheets in the solar wind is examined. The internal magnetic topology of the sheet is argued to be that of thin magnetic tongues greatly distended outward by the expansion inside the sheet. Due to finite conductivity effects, outward flow takes place across field lines but is retarded relative to the ambient solar wind by the reverse J×B force. The sheet thickness as well as the internal transverse magnetic field are found to be proportional to the electrical conductivity to the inverse one third power. Estimating a conductivity appropriate for a current carried largely by the ions perpendicular to the magnetic field, we find sheet dimensions of the order of 500km representative for the inner solar corona. For a radial field of strength 1/2G at 2R⊙, the transverse field there is about 2 × 10−3G and decreases outward rapidly.
26 citations
TL;DR: In this paper, the main phase evolution of magnetic storms associated with the passage of different interplanetary magnetic structures is discussed, and it is shown that their evolution, driven by intense magnetic fields in the sheath region just behind inter-planetary shocks, evolves faster (implying physically different magnetospheric configurations) than that associated with intense magnetic forces in the ejecta itself and in corotating streams.
Abstract: In this paper we discuss the main-phase evolution of intense magnetic storms, associated with the passage of different interplanetary magnetic structures. It is shown that their evolution, driven by intense magnetic fields in the sheath region just behind interplanetary shocks, evolves faster (implying physically different magnetospheric configurations) than that associated with intense magnetic fields in the ejecta itself and in corotating streams. The estimated ring-current injection rate for the main phase of intense magnetic storms caused by sheath fields is ∼10 times greater than the estimated injection rate for N–S magnetic clouds. Based on these results, we propose storm-intensity criteria for several classes of the driving interplanetary structures. The time necessary to reach a Dst/SYM index threshold level is an important parameter for a space weather forecast.
26 citations
TL;DR: In this article, the interior magnetohydrodynamic structure of a rotating stationary axisymmetric neutron star was studied and it was shown that the magnetic field must be uniform in the interior in accordance with the Deutsch model.
Abstract: We study the interior magnetohydrodynamic structure of a rotating stationary axisymmetric neutron star. We assume the fluid is ideal, infinitely conducting, and flows only azimuthaly. We justify this assumption by considering in detail the superfluid physics in the interior. We obtain some of our results by taking a certain limit of previously discovered magnetohydrodynamic conservation laws. We show that the angular velocity, electric and magnetic potentials, and the red-shifted chemical potential are constant on magnetic surfaces. We demonstrate that the absence of meridional circulation implies the vanishing of the toriodal magnetic field. This clashes with previous arguments from the probable evolution of the magnetic field during the collapse to the neutron star. We solve completely Maxwell's equations for the distribution of magnetic field strength, and we show that the magnetic surfaces are the equipotentials of a simple geometrical invariant. With neglect of gravitational effects the magnetic field must be uniform in the interior in accordance with the Deutsch model, but at variance with numerous other models which have been proposed for ordinary stars. Gravitation causes the magnetic surfaces to flare out toward the polar regions and enhances the central field as compared to the polar field. The star must bemore » charged; the charge distribution depends on the magnetic field strength and on the angular velocity relative to the local inertial frames.« less
26 citations
TL;DR: In this paper, the average strength of the magnetic field B = Bp + BT in the Earth's core is estimated using indirect methods, arguing that B is probably about 10−2 T (100 Γ), but might be as low as 10−3 T (10 Γ) or as high as 5 × 10− 2 T (500 Γ).
26 citations
TL;DR: In this article, a weak interplanetary magnetic field is shown to be compressed into a boundary layer of high magnetic-field intensity several earth radii deep at the surface of the magnetosphere.
Abstract: A weak interplanetary magnetic field is shown to be compressed into a boundary layer of high magnetic-field intensity several earth radii deep at the surface of the magnetosphere. Thus, if the solar wind consisted of streams of plasma interspersed with an interplanetary magnetic field, magnetic intensity beyond the magnetopause would be expected to fluctuate for several earth radii from zero to as high as the value at the boundary of the magnetosphere. The compressed field is tangential to the boundary and, in general, unrelated in direction to the field inside the boundary. Both conclusions are in agreement with satellite measurements. Particles in the solar wind travel smoothly around to the dark side of the earth where their pressure and the compressed interplanetary magnetic pressure may be expected to close the hollow the geomagnetic field creates in the solar wind.
26 citations