Compute the power of the magnetic field for a single degree l given the Schmidt seminormalized magnetic potential spherical harmonic coefficients.

## Usage

power = SHMagPowerL (c, a, r, l)

## Parameters

power : output, real(dp)
The power at degree l
c : input, real(dp), dimension (2, l+1, l+1)
The Schmidt seminormalized spherical harmonic coefficients of the magnetic potential.
a : input, real(dp)
The reference radius of the magnetic potential spherical harmonic coefficients.
r : input, real(dp)
The radius to evaluate the magnetic field.
l : input, integer
The spherical harmonic degree for which the power will be calculated.

## Description

SHMagPowerL will calculate the power of the magnetic field at radius r for a single degree l given the magnetic potential Schmidt seminormalized spherical harmonic coefficients c evaluated at radius a. This is explicitly calculated as:

S(l) = (l+1) (a/r)**(2l+4) Sum_{m=0}^l [ c(1, l+1, m+1)**2 + c(2, l+1, m+1)**2 ].