Are there spherical magnets

Answer 1

In high-energy physics, medical treatments, and space detections, quadrupole field distributions and sextupole field distributions are often required over a large spherical volume. Traditionally, these fields can be generated with cylindrical magnets. In comparison with cylindrical magnets, the spherical magnets have the advantages of smaller values of inductances, lower energy storage, and less magnetic flux leakage. The basic method derives from the target field approach that has been used to solve many of the inverse electromagnetic problems.

Calculation:

The geomagnetic poles or geocentric dipole, can be computed from the first three Gauss coefficients from a main field model, such as the WMM or IGRF. Based on the current WMM model, the 2005 location of the geomagnetic north pole is 79.74°N and 71.78°W and the geomagnetic south pole is 79.74°S and 108.22°E.

The magnetic poles or dip pole are computed from all the Gauss coefficients using an iterative method. Based on the current WMM model, the 2005 location of the north magnetic pole is 83.21°N and 118.32°W and the south magnetic pole is 64.53°S and 137.86°E.

The location of the center of the eccentric dipole, sometimes known as the magnetic center, computed using the first eight Gauss coefficients for 2005.0, is at approximately (r, φ´, λ) = (552 km, 22.2°N, 141.6°E).

The task of locating the principal magnetic pole by instrument is difficult for many reasons; the large area over which the dip or inclination (I) is nearly 90 degrees, the pole areas are not fixed points, but move tens to hundreds of kilometers because of daily variations and magnetic storms, and finally, the polar areas are relatively inaccessible to survey crews (map of North and South polar wander - courtesy of Dr. John Quinn, U.S. Geological Survey retired). The Geological Survey of Canada keeps track of the North Magnetic Pole, which is slowly drifting across the Canadian Arctic, by periodically carrying out magnetic surveys to redetermine the Pole's location. The most recent survey, completed in May, 2001, determined an updated position for the Pole and established that it is moving approximately northwest at 40 km per year.