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I'm currently designing a world where the inhabitants see the Aurora Borealis on an almost nightly basis almost all the way to the equator. The lights are so strong they rarely see the stars beyond.

I've been wondering what could cause this, increased solar activity? Stronger magnetic poles? So far I've not found anything conclusive.

What could cause such an enhanced aurora?

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  • $\begingroup$ Not sure if this answer would be great but: how about "projected" northern lights? Like some very very big laser show a bit more pimped up? $\endgroup$ – Fulli Sep 26 '14 at 7:33
  • $\begingroup$ Just more energetic solar storms. For example during the XIX century Carrington event Auroras as low as France. Definitively magnetic storms will help $\endgroup$ – Barnaby Jan 29 '15 at 22:35
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Actually, and as also pointed out by Monica Cellio, auroras are sometimes seen in temperate latitudes on Earth, so are not restricted to high latitudes only (although they tend to be more common there).

Taking Wikipedia at face value, there are a few things that can impact the frequency of occurrence of aurora activity:

  • They are more common during periods of high solar activity (with our sun, this peaks in an 11-year cycle)
  • They are more common during the spring and autumn. The mechanism behind this is not fully known, but at those times of the year, the interplanetary magnetic field and the Earth's magnetic field lines up.
  • The solar wind is stronger from the Sun's poles than from its equator.

If we take these together, you'd want:

  • a magnetically very active sun
  • good alignment between the planet's and its sun's magnetic fields
  • a sun rotating at a strong angle relative to the planetary disk's plane; compare Uranus' rotation

I'm not sure if that would be sufficient to produce auroras as far as to the planet's equator, however.

It's quite worthwhile to also note what David Hammen wrote in an answer over on the Physics SE (my emphasis):

Regarding Mars, that's fairly simple. Mars is too small. Mars's core froze long ago, and if Mars ever did have plate tectonics, that process stopped long ago. The end of plate tectonics stops any outgassing that would otherwise have replenished the atmosphere. The freezing of Mars's core stopped Mars's magnetic field, if it ever had one. That Mars is small means it has a tenuous hold on its atmosphere. The loss of a magnetic field (if it ever had one) would most likely have exaggerated the atmospheric loss, particularly if this happened when the Sun was young and had a much greater solar wind than it has now. The combination of the above means that even if Mars was habitable long, long ago, that habitability was rather very short lived.

Also, as quite aptly noted by Monica in her answer, allowing for large amounts of aurora will probably cause problems with anything electrically sensitive. My guess is you'd be looking more at something along the lines of vacuum tube style technology or possibly space-hardened technology, and probably less reliance on electricity and electronics, than the highly minituarized electronics technology that we are used to depending so greatly on (because the latter fares very poorly with large induced voltages and currents, which you would see in such a scenario).

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  • $\begingroup$ Great job; you covered this way more thoroughly than I did. $\endgroup$ – Monica Cellio Sep 16 '14 at 19:42
  • $\begingroup$ @MonicaCellio I liked your answer as well, and upvoted it. Hope you don't mind that I borrowed a few points from it. $\endgroup$ – a CVn Sep 16 '14 at 19:45
  • $\begingroup$ Not at all; building on (cited) prior work is normal on Stack Exchange and I don't consider it in any way objectionable. $\endgroup$ – Monica Cellio Sep 16 '14 at 19:47
  • $\begingroup$ I don't even want to contemplate the potential downsides of a planet like that. :-) $\endgroup$ – Wesley Obenshain Sep 16 '14 at 20:42
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    $\begingroup$ Note that due to the basic principles of planetary formation, it would be extremely unlikely for a star to rotate in a significantly different plane compared to the orbiting planets. $\endgroup$ – Nzall Oct 27 '14 at 9:53
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On Earth, solar flares can lead to displays of the aurora that are both more spectacular and visible farther south. Flares in September 2014 led to the aurora being visible in Maine, which is around 45 degrees latitude, so that's halfway between the pole and the equator. (More typically you need to be closer to the arctic circle to see much.)

Solar flares can interfere with electro-magnetic systems, so if your world regularly has auroras visible over most of its surface, you should expect that to affect technological development. I don't know if more and bigger solar flares would, by itself, achieve this effect.

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Speak of the devil! I just answered a related question.

The relevant part of my answer is this:

Wikipedia talks briefly about creating a quadrupole field - that is, creating four poles. Two would be "North", and two would be "South". Here is a good visualization. Unfortunately, that one isn't loading here, so I'll go with this one instead: enter image description here
Image courtesy of Wikipedia user Geek3 under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Here is the caption:

Magnetic field lines of an idealized quadrupole field in the plane transverse to the nominal beam direction. The red arrows show the direction of the magnetic field while the blue arrows indicate the direction of the Lorentz force on a positive particle going into the image plane (away from the reader)

The caption for the other image is this (emphasis mine):

Example of a quadrupole field. This could also be constructed by moving two dipoles together. If this arrangement were placed at the center of the Earth, then a magnetic survey at the surface would find two magnetic north poles (at the geographic poles) and two south poles at the equator.

I doubt you'd see any electrical effects, but you might see an interesting aurora. An aurora is caused by the solar wind interacting with Earth's atmosphere, but the solar wind can also interact with Earth's magnetosphere to create some cool effects. A change in Earth's magnetic field means a change in the magnetosphere, which means some awesome aurora-like events.

So perhaps a planet with four magnetic poles could see auroras all over the globe.

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You could eliminate the magnetosphere entirely which would let the solar wind hit the atmosphere directly. Of course this would be on the day side, not the night side. To get it to hit the night side, you need to use the magnetosphere, and that will only pull the particles into rings near the magnetic poles.

You can probably move the magnetic poles around. They tend to align roughly with the rotation of the planet but Uranus is an example of a planet with significantly skewed magnetic poles, although it's obviously not a terrestrial planet. This could produce an aurora elsewhere, but it would still be a smallish ring around each magnetic pole, with some fluctuations. You'll never get an aurora near the magnetic equator.

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