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I got inspired by a recently posted question dealing with an artificial magnetosphere to protect Martian atmosphere during and after terraforming.

Earth's magnetic field does funnel solar particles to the poles, creating the auroras when charged particles hit the atmosphere.

A similar system devised by NASA may be set up on the moon's surface and shield the moon from solar wind. My assumption is that like with earth's aurora, the system will attract charged particles to its poles. Particles with opposite charges moving perpendicular to a magnetic field will be deflected in opposite directions, so positioning the charge-collecting plates correctly is crucial.

My goal is to de-ionize the particles so that they are no longer charged, and some heavy elements like oxygen an nitrogen will bond with each other to create heavier still compounds that are less likely to be stripped away by the solar wind. At the same time, the charged particles hitting the plates (each with an opposite charge) will generate an electric current that keeps that device running. With time, heavy elements protected from solar winds will form an atmosphere and provide raw materials.

Here are my reality-check questions about that setup:

  • Is the stream of solar particles a mere jumble of positive and negative charges, or does it have a particular pattern which allows separating charges to generate electricity?
  • is the density of solar wind enough for reasonably fast accretion?
  • once atmosphere forms, the plates must be raised above the atmosphere to work properly but instead we may switch to solar or nuclear energy. Then we start mining the moon for materials. Does the moon provide enough of them?
  • Is gravity sufficient to hold the atmosphere if the solar wind issue has been resolved?
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  • $\begingroup$ I read that helium-3 already accumulates on the moon by virtue of the solar wind. So with this scheme you would still capture the solar wind particles by taking them in at the poles, but prevent the wind from stripping away the atmosphere you are accumulating. $\endgroup$ – Willk Aug 30 '17 at 18:52
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Several issues with this idea.

1) The vast majority of the solar wind is composed of electrons and protons, with small amounts of helium, oxygen, and other heavy elements depending on if the solar wind is coming from coronal holes or contains a solar flare/CME.

2) The particles coming to the poles (through the length process of day-side reconection, tail transport, lobe compression, and night side reconnection) are not moving perpendicular to the magnetic field, they are moving along the field (parallel) so the only difference between charged motion is the gyro-orbit, which you would be hard pressed to separate in a meaningful way.

3) Aurora are actually caused by the night side reconnection releasing large amounts of stored energy into the poles. This is not a continuous process but occurs in spurts. In addition, most of the charged particles coming into the poles are electrons, further limiting the amount of oxygen you are going to be able to collect.

Overall, even with only a small energy draw, there won't be enough charge separation to power a contraption such as this with just polar flux. You are also only going to collect a very small amount of oxygen and even less from other elements. Even if you removed the artificial magnetosphere and collected the solar wind directly there won't be enough to create an artificial atmosphere.

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  • $\begingroup$ I have searched for information on how the particles move once they leave te corona, but I have found no clear answer on the web. Do the particles move together and then protons and electrons recombine? Do they move together? In different directons or in different particle clouds? $\endgroup$ – Christmas Snow Aug 30 '17 at 19:26
  • $\begingroup$ They all move together. Essentially the solar wind is a near-constant outflow of electrons and protons (with a small amount of other elements). The exact composition depends on if it is a fast or slow solar wind (depending on if it is coming from coronal holes or not), and is also modified by solar flares and coronal mass ejections (which are essentially huge amounts of matter being ejected). The electrons and protons are too energetic to recombine. $\endgroup$ – Miles Engel Aug 30 '17 at 20:52

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