Does anything happen to our Solar System after we transit the Galactic plane? Is there one polarity "above" (artificially relatively speaking) the plane, and the opposite polarity "below"? When our entire Solar System transits the plane, what effects do the magnetism (or the change in polarity thereof) have on Earth's magnetosphere?
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1$\begingroup$ How do you define the plane? What indications do you have that anything changes when "the solar system transits the plane"? Are there any such indications e.g. from analogues like when the Moon crosses the ecliptic on its monthly orbit twice or any hints like in paleo-stratigraphic records? What's the ratio of magnetic fields you expect? Does astronomy.stackexchange.com/questions/42053/… answer your question? $\endgroup$– planetmakerCommented Jul 3 at 7:10
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2$\begingroup$ I can't see what problems people have with this question. It's asking about the relative strength and morphology of the Galactic magnetic field compared with that of the Earth. $\endgroup$– ProfRobCommented Jul 3 at 17:49
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$\begingroup$ Thanks for your responses. The earlier ones (since deleted) were pretty annoying. I am indeed asking about the strength and morphology, but I don't have this vocabulary natively. Earth has a N/S polarity, and a currently moving pole at that. I'm wondering about how the strength and polarity (morphology?) of the galactic field affects our own planet's polarity as we transit the galactic plane, particularly as we near, reach or pass the point where the galactic field bends back to the other pole. Forgive me my rudimentary language. $\endgroup$– JimCommented Jul 3 at 21:59
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$\begingroup$ @eshaya does the measurement of the galactic field strength ever fluctuate? I mean over time, was it ever lower or significantly higher than 6 μGauss near the Sun? And do we know what that strength is near Earth? (I'm not sure why it would be any different, but just wondering) $\endgroup$– JimCommented Jul 3 at 22:18
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$\begingroup$ Comments are not for answers. $\endgroup$– ProfRobCommented Jul 6 at 6:24
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2 Answers
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The galactic field strength is about 6 μGauss near the Sun. The Sun's magnetic field strength is 35 μGauss near the Earth but this varies a bit with the solar cycle. Earth's magnetic field is 0.2 - 0.6 Gauss. Therefore, the Earth's magnetic field is insignificantly perturbed by the galactic magnetic field.
The solar wind blows a bubble around the solar system called the heliosphere that keeps out the intergalactic medium along with its magnetic field. It ends at the heliopause (beyond Neptune). Exactly, where the heliopause is should be dependent on the strength of the intergalactic magnetic field, but also on the ISM density.
This illustration shows the position of NASA’s Voyager 1 and Voyager 2 probes, outside of the heliosphere, a protective bubble created by the Sun that extends well past the orbit of Pluto. Credits: NASA/JPL-Caltech
The position of the heliosphere has an influence on the amount of galactic cosmic radiation enters into the solar system and thus has an influence on the health and safety of astronauts venturing beyond the Earth's magnetopause.
The magnetic fields are stronger in the spiral arms, typically 10 - 15 μGauss. But, still insignificant except in the outer solar system. The Sun passes through spiral arms on a timescale of order 100 millions years.
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Absolutely nothing happen to planet Earth.
The majority of interstellar medium exist as hot ionized medium, the number density is $10^4 - 10^6 /m^3$, the average number density of Earth's atmosphere is around $10^{27} /m^3$. So it is very spread out. The closest star is $4.2ly$ away from us, the number density of stars is $1 /69pc^3$. So there is literally nothing than Earth can run into while crossing the galactic plane thus literally nothing can change the magnetic field of the solar system.
Yes, magnetic field does not need medium to spread out, but it is very hard to come across a object with a strong enough magnetic field to alter the magnetic field of planet Earth, and the galactic magnetic field can simply be ignored because it is just too small to even care about it (we are experiencing it every single day but nothing happened).
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$\begingroup$ I asked about magnetism. You seem to be trying to, exasperatingly, answer a different question. $\endgroup$– JimCommented Jul 3 at 1:47
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$\begingroup$ @Jim, I apologize for yesterday, I edited the answer and now it is about magnetism. $\endgroup$ Commented Jul 4 at 3:02