Schematic drawing of a rectangular solenoid with definition of dimensions (az, ay, az) and the direction of current I, positioned along the axis z, as defined in the paper by Hampton et al.
See also: Magnetic field of cuboid magnet or rectangular solenoid at arbitrary point in space
This image is copied from:
hampton_et_al_rectangular_solenoid.png
You are permitted to use this image freely, for any legal purpose including commercial (the permission is given, so there is no need to ask for it explicitly again), but you must always include the following credits:
S. Hampton, R. A. Lane, R. M. Hedlof, R. E. Phillips, C. A. Ordonez, AIP Advances, CC-BY-SA-4.0