The magnetic field of a current loop could sustain the magnetic dipole type magnetic field of the earth. Large-scale computer models are approaching a realistic simulation of such a geodynamo.
The basic dipole shape of Earth's magnetic field (bottom) and the teardrop shape of the magnetosphere created by the solar wind (top).
Roughly speaking it is the field of a magnetic dipole currently tilted at an angle of about 10 degrees with respect to Earth's rotational axis, as if there were a bar magnet placed at that angle at the center of the Earth.
The Earth has a substantial magnetic field, a fact of some historical importance because of the role of the magnetic compass in exploration of the planet.
Elevation is especially important when computing the magnetic field at aircraft or higher altitudes. If you are unsure of your elevation, and are interested in a location on the surface of Earth, the default of 0 is sufficient.
The magnetic field of Earth actually changes its polarity over time.
"At Cambridge, Massachusetts the magnitude of the earth's field is about 5.8 × 10-5 T and has an angle of dip that was 73 degrees." 58 µT. Worldbook Encyclopedia, vol. 13. 1995. "The Earth's magnetic field at the surface was about ½ gauss." 50 µT.
The magnetic field of earth is involved in a perturbation or morphing. This is taking place interdimensionally, and the net effect is incremental surges in amplitude or strength of the magnetic field.
The magnetic field of Earth is weakening more rapidly than many scientists thought it would, a sign that Earth’s magnetic poles might flip within a few hundred years as opposed to thousands of years.
Computer simulation of the Earth's field in a normal period between reversals. The tubes represent magnetic field lines, blue when the field points towards the center and yellow when away. The rotation axis of the Earth is centered and vertical.