Under what circumstances would it be possible to harvest aurora for either energy or matter?
I would like to have a planet in which somehow it becomes necessary to harvest aurora for energy (and maybe matter if that's feasible).
The civilization of this planet is moderately advanced -- enough to have colonized other planets in its solar system, but not enough to have travel between stars.
Which of the following would improve the plausibility of harvesting aurora:
- A planet smaller or bigger than the earth
- A planet with a weaker or stronger magnetic field
- A planet closer or further away than the earth
- A sun smaller or bigger than our sun
- A higher rate of solar activity
- A planet with a smaller or bigger atmosphere (or no atmosphere)
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1 answer
I don't think we could directly harness the energy transferred to particles in auroras. However, we could probably captured the energy from the phenomena that caused auroras.
Wikipedia notes that the primary cause of auroras is an interaction between the Sun and the Earth's magnetosphere. Here are some ways we could exploit that:
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The solar wind. The solar wind is the primary cause of auroras. It's a continuous ejection of particles (e.g. electrons and protons) from the outer reaches of the Sun. When these particles interact with Earth's magnetosphere, they can cause and aurora.
The obvious use of the solar wind is to propel a solar sail, and push a spacecraft across vast distances. This makes travel to distant stars possible.
However, solar sails work off of the principle of radiation pressure - the idea that photons emitted by the Sun can exert a force against an object. The particles in the solar wind can also exert a force. In this answer, I calculated the force of a stellar wind on a spacecraft, and here, I calculated the force that a laser would exert on a comet. If you could take into account the force from particles of the stellar wind, you could calculate the force they would create if they pushed against a sort of "solar windmill".
Take a long rectangular object, and put it so that the longest side is bared against the Sun. Create a magnetic field emanating from a location 1/4 of the way from one edge that diverts the charged particles, so that only half of the rectangle is exposed to the solar wind. This means that the force will exert a torque on the rectangle, causing it to rotate. You might be able to harness the rotational energy of the rectangle.
(Replace "bounce" with "solar wind"!)
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Coronal mass ejection/Solar flade. Coronal mass ejections, or CMEs, often change the intensity of the solar wind. They can have some pretty bad effects on Earth! They're also related to solar flares, which can also have some negative effects.
Both of these events are related to the emission of additional X-rays from the Sun. These X-rays are very energetic, and are also damaging to Earth. However, if the X-ray flux were high enough, a large amount of energy could be obtained from a small area. In essence, a satellite might be able to harness a lot of solar power - if it was properly equipped to handle it!
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