# Are geostationary orbits impacted by changes to earths magnetic field?

Would geostationary satellites be pushed to different orbits by changes in the magnetic filed or even more so by shifting poles or even a reversal?

• I'd be really surprised if it made much difference. The force of gravity is many many times the force from the magnetic field. If they use magnetorquers for attitude control that might be a problem, but I don't know if those are used at geosync. – zeta-band Apr 15 at 19:08

I've never heard of a geostationary satellite having magnetic torquers. Since the magnetic field is very weak on such high orbits, wheel desaturation is carried out with thrusters.

Also, every geostationary satellite I'm aware of uses propulsion for station keeping, so even if any magnetic effect could cause orbit perturbations on them (as does solar radiation pressure, the Moon gravitational field and so on), their orbit would be corrected over time.

Last but not least, satellites are not magnetic monopoles, and the external magnetic field is basically constant over their volume, so the magnetic force acting on such a satellite if any, is negligible. Magnetic torque is usually negligible as well compared to other effects, such as gravity gradient.

Hence, even if the magnetic field changes, I don't expect it to cause any notable effect on the orbit of geostationary satellites.

However, changes in the magnetic field, or specially a decrease in its magnitude would affect the solar and deep space radiation hitting those satellites. That would surely disturb and possibly disable these satellites. This is sometimes happens and is called a geomagnetic storm.

Geostationary is approximately 35,786 km (22,236 mi) above mean sea level.

Earth's two main Van Allen Belts extend from an altitude of about 640 to 58,000 km (400 to 36,040 mi) above the surface.

Changes to the Earth's magnetic field will change its Van Allen Belts, which may have an impact on geostationary satellites. Particularly if the Inner Belt expands out to geostationary altitudes.

• That's a really interesting point! – uhoh Aug 27 at 15:12

$$\left(\frac{r}{R_{GEO}}\right)^3 \approx \left(\frac{6378}{42164}\right)^3 \approx 0.0034$$
That makes the field strength out there about $$0.0011$$ gauss, which is not going to have much impact at all.