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Lesson 10: Magnetic Habitability

What the MHI index measures, and what it doesn't

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🎯 Objectives

  • Know the four components of the MHI index and their weights
  • Compare Earth with Mars and with exoplanets in the habitable zone
  • Interpret an index without confusing it with 'possible life'

🧪 Exercise

  1. Simulate Proxima b for 4.5 Gyr and note the magnetopause radius.
  2. Repeat in Synthetic Mode raising the initial magnetic field: from what value does the shield become active?
  3. Write in two lines why a high MHI does not imply that there is life.

⚠️ Model limits

  • No exoplanet has a measured magnetic field: the engine uses typical values for its category.
  • The MHI measures only magnetic protection; it does not include temperature, water or atmospheric composition.
  • The 0.3 G threshold for 'active field' is an Earth reference, not a universal physical limit.

📚 References

  • Driscoll & Barnes (2015), Tidal heating of Earth-like exoplanets around M stars.
  • Vidotto et al. (2013), Effects of M dwarf magnetic fields on potentially habitable planets.
  • Jakosky et al. (2018), Loss of the Martian atmosphere to space (MAVEN).

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