Calculation by a Moment Technique of the Perturbation of the Geomagnetic Field by the Solar Wind
<p>An iterative method is developed by which one can calculate approximately the boundary of a magnetic field confined by a plasma. This method consists essentially of varying an assumed surface until the magnetic multipole moments of the currents, which would flow on that surface to bala...
| Summary: | <p>An iterative method is developed by which one can
calculate approximately the boundary of a magnetic field
confined by a plasma. This method consists essentially of
varying an assumed surface until the magnetic multipole
moments of the currents, which would flow on that surface
to balance the plasma pressure, cancel the corresponding
moments of the magnetic sources within the surface. The
method is applied to two problems.</p>
<p>For a dipole source of moment M emu in a plasma of
uniform pressure p dynes/cm^2 that does not penetrate the
magnetic field, the approximate equation of the surface
is r = 0.82615 M^(1/3) p^(-1/6)(1-0.120039α^2 - .004180α^4 - .001085α^6 + .000200α^8 - .000597α^(10) + .000326α^(12) - .000094α^(14)) cm, where α is the latitude in radians from the plane normal to M.</p>
<p>The surface formed by a cold plasma of density N_0 and pair mass velocity M_t moving past a dipole of moment Me_y with a velocity –U_oe_z extends to infinity downwind. In a coordinate system (x, y, z) centered at the dipole, neutral points, where the surface is parallel to the wind direction, occur at the points (0, ±R_n, .27R_n), and other points on the surface are (0, 0, 1.02R_n), (0, ±2R_n, -∞) and (±1.97R_n, 0, -∞). R_n = 1.0035 (M/(M_tN_oU^2_o)^(-1/2)^(1/3) is about 9 earth radii for the solar wind case.</p>
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