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I'm conceiving of a world where humans can readily terraform worlds that were once considered "dead" due to the planet's magnetic field being long gone. In such a situation, what could humans do to recreate an artificial magnetic field to protect the planet.

I know it's relatively easy for us to create magnetic fields stronger than that of the earth in a lab, but it's unclear to me how this could be replicated on a planetary scale given an 1/r^2 strength of field over distance

My simplest idea would be a supercooled solenoid running around the planet to generate a magnetic field similar to that on earth. However, I'm not sure how to account for the planet in the center.

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  • $\begingroup$ Related answer here. $\endgroup$ – Cadence Sep 4 at 23:39
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    $\begingroup$ I don't understand why so many people believe that planetary magnetic fields are important on human historical time scales. Yes, they are important on geological time scales, but on such time scales the entire history of the human civilization is a negligible blip. The effects of a missing magnetic field won't be felt in a thousand years, or in thousand years, or even in a hundred thousand years. You need millions of years for the missing magnetic field to be felt. $\endgroup$ – AlexP Sep 5 at 3:32
  • $\begingroup$ @alexp but replacing the magnetic field WOULD be the first step in terraforming a "dead" planet. Otherwise, all your work would be undone the first time the planet caught a solar flare. $\endgroup$ – HA Harvey Sep 5 at 7:19
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    $\begingroup$ @Alexp it does all the time. Earth's magnetic field deflects and dissipates the lion's share of radiation that would otherwise strike the Earth. Losing our magnetic field (our molten iron core stops turning) would be an extinction level event. Only deep submarine life would have a chance to survive. $\endgroup$ – HA Harvey Sep 5 at 7:36
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    $\begingroup$ @HAHarvey: Earth has lost its magnetic field many many times in the past. Not only were those not extinction level events, they are not even noticeable at all in the history of life. And the bulk of the radiation which comes from the Sun is in the form of electromagnetic waves which do not interact with magnetic fields. $\endgroup$ – AlexP Sep 5 at 7:39
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Apparently, the amount of energy needed to shield Mars from the solar wind is less than one might think. There was a proposal to build a device that could project a magnetic field that would deflect the solar wind from Mars, potentially allowing a terraforming project to take place.

In a nutshell, the device would be placed in orbit at the L1 point between Mars and the Sun. It doesn't need an infeasible amount of energy to work - the magnetic field would be 1-2 Tesla, less than a MRI scanner. This could be provided through a superconducting magnet and powered by a PV array that could be constructed with today's technology.

https://phys.org/news/2017-03-nasa-magnetic-shield-mars-atmosphere.html

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  • $\begingroup$ The tough part being, getting the thing out there and then regular maintenance. $\endgroup$ – Spencer Sep 10 at 12:52

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