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A planet the size of earth around a pretty active M7 red dwarf (think of M to X level flares almost every day) has a decent magnetic field of 0.5-0.8 Gauss, orbiting at a distance of 0.0443AU, with a 1.1 atm Nitrogen and Oxygen dominated atmosphere. How far south would auroras be visible in a situation like that? I would have thought that a strong magnetic field will result in weaker and smaller auroras, however the red dwarf is pretty active so it could compensate for that and still produce pretty bright auroras?

Planet inclination: 13º

Magnetic field alignment vs rotation alignment offset: 15º

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  • $\begingroup$ What is your planet's magnetic field alignment vs its rotation axis? Also its inclination. Also do you want to check daytime visibility of auroras or not? $\endgroup$
    – Vesper
    Commented Oct 12, 2023 at 7:49
  • $\begingroup$ @Vesper About 15º difference from the rotation axis. The inclination of the planet is about 13º. And sure i don’t mind checking for daytime visibility $\endgroup$ Commented Oct 12, 2023 at 7:52
  • $\begingroup$ Hmm, hmmm. Been reading this swpc.noaa.gov/content/aurora-tutorial a dependency is depicted from solar magnetic events interfering with geomagnetism in form of a K[sub]p[/sub] and location of aurorae. Perhaps calculating Kp for your planet and a given solar activity would give you some answers. Also with 15 degrees offset, the areas at the same longitude as the magnetic pole would get aurora at lower latitudes than those sideward, by roughly this offset, give or take local field anomalies. $\endgroup$
    – Vesper
    Commented Oct 12, 2023 at 8:00
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    $\begingroup$ @FoxStudios In the future, please note that we recommend querents waiting 24-48 hours before awarding the coveted green check mark. We have users around the world and human nature is to stop looking at questions that have been "officially answered." You might find a better answer, but even if you don't, future users might find excellent insight when reviewing your question due to the greater number of answers - and you might read an answer that changes your view of why you were asking the question. $\endgroup$
    – JBH
    Commented Oct 12, 2023 at 15:35
  • $\begingroup$ I guess such planet could have fantastic and frequent auroras wherever on the globe and also strong zodiacal light due to the close orbit to star. I've noticed half a Gauss must be very strong value while all orbital parameters are "rescaled" in comparison to it. I didn't simulate such a thing below M4 star, so you honestly could call your planet Aurora Intrappolato. $\endgroup$
    – Peter.k
    Commented Oct 19, 2023 at 20:35

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Apparently, magnetic poles and geomagnetic poles do not necessarily coincide, as deep-core geophysics is complicated enough causing several magnetic pole areas to sometimes appear on the surface. With space-based events, only geomagnetic poles matter.

The auroras on Earth have been detected as far as southern Europe in 1938, or northern Texas in 2023. So, assuming you have given the geomagnetic pole offset of 15 degrees from north pole, and assuming longitude zero at the geomagnetic pole closer to the north pole (this moves over time, but for estimation such a cooordinate system will do), and the equal magnetic storm on your planet with Earth's Kp=9, this corresponds to having visible aurorae at about 6 degrees closer to equator at zero longitude (according to this Japanese map of geomagnetic pole location, the Earth's north geomagnetic pole has latitude of about 81 degrees, 6 degrees more than your planet's), or 29.5 degrees north. According to auroral maps on Wiki the sideward (90E, 90W) areas would get auroras at about 50 degrees northern latitude, and backward (180E) areas would have the hardest with aurorae, with about 61 degrees north at the highest levels of solar activity.

But, feel free to balance auroral regions with the planet's magnetic field strength, the lower it is, the stronger and the wider would be the area where aurorae would be seen. After all, Kp is an arbitrary coefficient made for general public, at your planet it could reach higher values if compared to Earth's levels of magnetic storms.

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Auroras are basically solarwinds plasma ignigting a atmosphere. Now it will be lesser acitve around a red dwarf, due to it being more longtime stable, less energetic. But if you had other objects in the system, which have a strong magnetic influence. Neutron stars comes to min, they can channel, bend and deform any solarwind ejected. In theory, with enough of them around, you could build a solar sized cyclotron, which could produce really strange effects if the particles leak or collide.

https://en.wikipedia.org/wiki/Magnetar

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