Determine the three components of the magnetic field vector at a single point.
Usage
value = MakeMagGridPoint (cilm, lmax, a, r, lat, lon, dealloc)
Parameters
value: output, real(dp), dimension (3)- Vector components (r, theta, phi) of the magnetic field at (
r,lat,lon). cilm: input, real(dp), dimension (2,lmax+1,lmax+1)- The real Schmidt semi-normalized spherical harmonic coefficients of the magnetic potential. The coefficients
C1lmandC2lmrefer to the cosine (Clm) and sine (Slm) coefficients, respectively, withClm=cilm(1,l+1,m+1)andSlm=cilm(2,l+1,m+1). lmax: input, integer(int32)- The maximum spherical harmonic degree used in evaluating the function.
a: input, real(dp)- The reference radius of the spherical harmonic coefficients.
r: input, real(dp)- The radius to evaluate the magnetic field field.
lat: input, real(dp)- The latitude of the point in degrees.
lon: input, real(dp)- The longitude of the point in degrees.
dealloc: input, optional, integer(int32), default = 0- 0 (default) = Save variables used in the external Legendre function calls. (1) Deallocate this memory at the end of the funcion call.
Description
MakeMagGridPoint will compute the three components of the magnetic field vector at a single point. The input latitude and longitude are in degrees, and the output components are in spherical coordinates (r, theta, phi). The magnetic potential is given by
V = a Sum_{l=0}^lmax (a/r)^(l+1) Sum_{m=-l}^l C_{lm} Y_{lm},
and the vector magnetic field is
B = - Grad V.
The coefficients are referenced to a radius a, and the output values have the same units as the input spherical harmonic coefficients.