Planetary Magnetic Field Strength Calculator Formula
Understand the math behind the planetary magnetic field strength calculator. Each variable explained with a worked example.
Formulas Used
Surface Magnetic Field (equator)
b_field = (1e-7) * dipole_moment / pow(planet_radius, 3)Field (Gauss)
b_field_gauss = (1e-7) * dipole_moment / pow(planet_radius, 3) * 1e4Polar Field
b_pole = 2 * (1e-7) * dipole_moment / pow(planet_radius, 3)Variables
| Variable | Description | Default |
|---|---|---|
dipole_moment | Magnetic Dipole Moment(A m2) | 7.94e+22 |
planet_radius | Planet Radius(m) | 6371000 |
How It Works
Planetary Magnetic Field
A planet's magnetic field can be approximated as a dipole near the surface.
Equatorial Field
B_eq = (mu0 / 4pi) * M / R cubed
where mu0/(4pi) = 1e-7 T m/A.
Polar Field
B_pole = 2 * B_eq
Earth's dipole moment is about 7.94 x 10^22 A m2, giving an equatorial field of roughly 3 x 10^-5 T (0.3 Gauss).
Worked Example
Earth: dipole moment = 7.94e22 A m2, radius = 6.371e6 m.
- 01B_eq = 1e-7 * M / R cubed
- 02R cubed = (6.371e6)^3 = 2.586e20
- 03B_eq = 1e-7 * 7.94e22 / 2.586e20
- 04B_eq = 3.07e-5 T = 0.307 Gauss
Frequently Asked Questions
What generates a planet's magnetic field?
Convective motion of electrically conducting fluid (molten iron in Earth's outer core) produces a self-sustaining dynamo.
Which planet has the strongest magnetic field?
Jupiter, with a dipole moment about 20 000 times Earth's, giving a surface field of about 4 Gauss.
Why is a magnetic field important for life?
It deflects the solar wind and cosmic rays, protecting the atmosphere from erosion and the surface from harmful radiation.
Ready to run the numbers?
Open Planetary Magnetic Field Strength Calculator