Courses › Computational astrophysics › Module 4: Magnetic field › Lesson 8
Lesson 8: Magnetospheres
The invisible shield, and how big it is
🎯 Objectives
- Explain the magnetopause as a balance of pressures
- Compare the model's magnetospheres with those measured by probes
- Calculate what field a planet would need for an effective shield
🧪 Exercise
- Using the rule R ∝ B^(1/3), calculate how much Earth's magnetopause would grow if the field were 8 times stronger.
- Check it in Synthetic Mode by raising the initial magnetic field.
- Explain why Jupiter's magnetosphere is larger than the simple model predicts.
⚠️ Model limits
- The model calculates the distance to the magnetopause on the star-facing side; it does not simulate its full shape (the equilibrium figure is a schematic).
- It does not include the internal plasma that inflates Jupiter's and Saturn's magnetospheres.
- The 5 and 20 G fields for Proxima b are hypothetical, and no exoplanet has had its field measured.
📚 References
- Bagenal (2013), Planetary Magnetospheres, in Planets, Stars and Stellar Systems, Springer.
- Winslow et al. (2013), Mercury's magnetopause and bow shock from MESSENGER observations, JGR 118.
- Vidotto et al. (2013), Effects of M dwarf magnetic fields on potentially habitable planets, A&A 557.
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