A new functional form to study the solar wind control of the magnetopause size and shape
Abstract
In this study a new functional form, r=r_{0}[2/(1+cosθ)]^{α}, is used to fit the size and shape of the magnetopause using crossings from ISEE 1 and 2, Active Magnetospheric Particle Tracer Explorers/Ion Release Module (AMPTE/IRM), and IMP 8 satellites. This functional form has two parameters, r_{0} and α, representing the standoff distance and the level of tail flaring. The value r is the radial distance at an angle (θ) between the SunEarth line and the direction of r. It is found that r_{0} varies with the interplanetary magnetic field (IMF) B_{z} component and has a break in the slope at B_{z}=0nT. The bestfit value of r_{0} decreases with increasing southward IMF B_{z}. For northward IMF B_{z}, the bestfit value of r_{0} increases slightly with increasing B_{z}. The bestfit value of α increases monotonically with decreasing IMF B_{z}. The dynamic pressure (D_{p}) also changes r_{0} and α. The parameters D_{p} and r_{0} are related by a power law of 1/(6.6+/0.8). The bestfit value of α is slightly larger for larger dynamic pressure, which implies that D_{p} also has a role in flux transfer from the dayside to the nightside, but the size of this effect is small. An explicit function for the size and shape of the magnetopause, in terms of D_{p} and B_{z}, is obtained by using multiple parameter fitting in a form that is useful for operational space applications such as predicting when satellites at geosynchronous orbit will be found in the magnetosheath.
 Publication:

Journal of Geophysical Research
 Pub Date:
 May 1997
 DOI:
 10.1029/97JA00196
 Bibcode:
 1997JGR...102.9497S
 Keywords:

 Magnetospheric Physics: Solar wind/magnetosphere interactions;
 Magnetospheric Physics: Magnetospheric configuration and dynamics;
 Magnetospheric Physics: Magnetopause;
 cusp;
 and boundary layers;
 Magnetospheric Physics: Numerical modeling