Shape Of Magnetopause Research Articles

The ratio between magnetotail height and neutral point height

The ratio between the magnetotail height and the neutral point height is exactly 2 in the classical calculation of the shape of the magnetopause following Chapman and Ferraro. This ratio is useful in assessing the results of calculations. There exist possibilities for improvement of magnetopause shape calculations, especially in the tail region or in the neutral point region for “tilted” cases.

The influence of the interplanetary magnetic field and thermal pressure on the position and shape of the magnetopause

An ellipsoidal model is used to represent the location of the dayside magnetopause and to study the influences of the interplanetary magnetic field and thermal pressure on its location. The position and shape of the dayside magnetopause in an unmagnetized cold solar wind can be approximately represented by an ellipsoid of revolution with a constant eccentricity. The size of the ellipsoid, its semilatus rectum l0, is inversely proportional to the sixth root of the stream pressure of the solar wind. The effects of the IMF and thermal pressure on the location of magnetopause are calculated analytically by using the Chapman‐Ferraro theory. When the IMF B0 is included in the boundary calculation, the changes in the magnetopause size, shape, and orientation are inversely proportional to the square of the Alfven Mach number of the solar wind (MA²) and depend on the direction of B0. For B0 directed along an Archimedian spiral and MA=7.3, the symmetry axis of the ellipsoid will deflect 0.6° from the sun‐earth line to the east of the sun. The changes in the magnetopause size, shape, and orientation caused by including the thermal pressure are inversely proportional to the square of the sonic Mach number of the solar wind (MS²). These effects are sufficient to explain the observed slight departure of the magnetotail from the expected aberration due to the earth's orbital motion. There is no requirement, based on the tail observations to invoke a nonradial solar wind component. Hence our results suggest that little angular momentum is presently being carried away from the Sun by the solar wind.

A mathematical magnetospheric field model with independent physical parameters

A quantitative magnetospheric magnetic field model has been calculated in three dimensions. The model is based on an analytical solution of the Chapman-Ferraro problem. For this solution, the magnetopause was assumed to be an infinitesimally thin discontinuity with given geometry. The shape of the dayside magnetopause is in agreement with measurements derived from spacecraft boundary crossings. The magnetic field of the magnetopause currents can be derived from scalar potentials. The scalar potentials result from solutions of Laplace's equation with Neumann's boundary conditions. The boundary values and the magnetic flux through the magnetopause are determined by all magnetic sources which are located inside and outside the magnetospheric cavity. They include the Earth's dipole field, the fields of the equatorial ring current and tail current systems, and the homogeneous interplanetary magnetic field. In addition, the flux through the magnetopause depends on two constants of interconnection which provide the possibility of calculating static interconnection between magnetospheric and interplanetary field lines. Realistic numerical values for both constants have been derived empirically from observed displacements of the polar cusps which are due to changes in the orientation of the interplanetary field. The transition from a closed to an open magnetosphere and vice versa can be computed in terms of a change of the magnetic boundary conditions on the magnetopause. The magnetic field configuration of the closed magnetosphere is independent of the amount and orientation of the interplanetary field. In contrast, the configuration of the open magnetosphere confirms the observational finding that field line interconnection occurs primarily in the polar cusp and high latitude tail regions. The tail current system reflects explicitly the effect of dayside magnetospheric compression which is caused by the solar wind. In addition, the position of the plasma sheet relative to the ecliptic plane depends explicitly on the tilt angle of the Earth's dipole. Near the tail axis, the tail field is approximately in a self-consistent equilibrium with the tail currents and the isotropic thermal plasma. The models for the equatorial ring current depend on the D st -parameter. They are self-consistent with respect to measured energy distributions of ring current protons and the axially symmetric part of the magnetospheric field.

Magnetopause shapes: General solutions

The problem of determining the shape of a magnetopause, namely, the tangential discontinuity separating (typically) the magnetic field of a source from external plasma, is reduced to solving an integral equation. No symmetry assumptions whatsoever are used in the derivation, consequently, realistic problems such as model shapes for the earth's magnetosphere (tilted dipole, flowing plasma, etc.) can in principle be treated. Moreover, the magnetic field source itself need not be a simple dipole. A variational method is suggested whereby the optimum parameters for any finite term trial shape are obtained.

Accretion magnetospheres - General solutions

view Abstract Citations (26) References (5) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Accretion magnetospheres: general solutions. Michel, F. C. Abstract A method is presented for dealing with problems of magnetic-field confinement by external plasmas. This method reduces the problem of finding the magnetopause shape, given the surface pressure conditions (or vice versa), to that of solving an integral equation constituting a nonlinear Fredholm equation of the first kind. The trivial case of spherical confinement is treated analytically along with nontrivial cases of general multipole surfaces up to the K = 6 magnetopause. Numerical solutions are obtained and compared for K in the range from zero to 6.0. It is noted that the proposed method can apparently be generalized to problems where the magnetopause is not symmetric about the equator (although the integral equation as written requires axial symmetry) and where the confined-field source is a sum of multipoles. Publication: The Astrophysical Journal Pub Date: May 1977 DOI: 10.1086/155215 Bibcode: 1977ApJ...213..836M Keywords: Magnetic Stars; Neutron Stars; Stellar Atmospheres; Stellar Magnetic Fields; Stellar Magnetospheres; Stellar Mass Accretion; Companion Stars; Integral Equations; Magnetic Dipoles; Magnetopause; Numerical Analysis; X Ray Sources; Astrophysics full text sources ADS |

The magnetopause at 5.2REon August 4, 1972: Magnetopause shape and structure

The relatively large magnitude magnetopause field observed in several crossings associated with the ATS 5 and Explorer 45 satellites on August 4, 1972, is used to examine the structure of the magnetopause. The discussion covers magnetopause normals and their intepretation with respect to the shape of the magnetopause and to waves propagating in the magnetopause; magnetopause structure in terms of the field changes observed during magnetopause passages and of the associated magnetopause electric currents interred from the observations; and comparison of the observations with theoretical properties of open and close magnetopause models. Features necessary for comparison of magnetometer observations with pertinent theories are highlighted.

Perturbation of the geomagnetic field-A spherical harmonic expansion

The spherical harmonic expansion of the perturbation of the geomagnetic field is calculated, using the magnetopause shape and current system determined previously by the moment technique. The expansion coefficients are compared with those determined by another method by Mead.