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As of May 2024, Earth was just hit by a quite strong solar storm, lighting up the skies with auroras even in areas as far from the polar regions as Ushuaia, Coimbra or Northern California.

We often see discussed the potential for such episodes of strengthened solar winds, like Coronal Mass Ejections, to disrupt communications and the power-grids on Earth, perhaps even threatening civilization itself. The largest such event in recorded history was the Carrington Event. Back then human society didn't rely a lot on electronics, but yet there was reports of telegraph lines melting due to induced currents:

"In 1859, the first and most powerful solar flare ever observed occurred, known as the Carrington event. Within a couple of days of the flare, the Earth’s magnetic field oscillated wildly from the magnetized plasma thrown toward us. The magnetic field lines of the Earth bounced back and forth across telegraph wires, causing massive failures and even melted wires from the induced currents." - source

That begs the question, the same way solar plasma pushing against Earth's magnetic field can melt wires close to the surface, can it also induce or mess with currents down into the Earth core, that behaves like a giant conductor, whose currents generate this very magnetic field?

According to wikipedia, near the Earth's orbit at 1 astronomical unit (AU) the solar plasma flows at speeds ranging from 250 to 750 km/s with a density ranging between 3 and 10 particles (mostly hydrogen ions) per cubic centimeter. Earth's magnetic field is able to trap particles from the solar wind into Van Allen radiation belt that extends up to 60.000 km from Earth, so I believe the kinetic energy of plasma going through a circular section this wide gives sort of an upper bound to the amount of energy hypothetically available for exchange, that I tried to estimate as follows, taking mean values:

enter image description here

This estimate of 7 terawatts of mean solar wind power intercepted by Earth's magnetic field is quite large, despite the low average density of the solar wind, a few atoms per cubic centimeter. For comparison, the estimates for total geothermal power dissipated by the whole planet is about 47 terawatts, not that far, perhaps can be surpassed by a large storm like the one happening now.

So I wonder, even if Earth's core captures only a small amount of this energy flow as induced currents, if on timescales of billions of years this can have significant impact on Earth's geology.

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    $\begingroup$ Thank you, @uhoh , I added a bounty myself here. If it doesn't work here we can try in Earth Science. $\endgroup$
    – ksousa
    Commented May 13 at 22:33
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    $\begingroup$ Earth receives from Sun around 160.000TW of electrical energy in form of electromagnetic radiation - which also cause atmospheric ionization, induction of ring currents etc. Geology itself is not driven by the magnetic core, but by the heat and heat flux flux (I'm curious to learn otherwise). Thus while I expect a negative answer it's still difficult to dismiss and the devil might be in the details. $\endgroup$ Commented May 15 at 6:41
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    $\begingroup$ @planetmaker, I believe most of these 160.000TW are rerradiated back to space, from atmosphere and outer surface. $\endgroup$
    – ksousa
    Commented May 17 at 0:29
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    $\begingroup$ @ksousa your comment as written won't generate any notifications. The only reason I noticed it is that I clicked "Follow" under your post so I can see any activity. To get a message to the moderators, click "Flag" under your question, select "Another reason", then enter your same message as your comment. This will be brought to the moderators attention. $\endgroup$
    – uhoh
    Commented Jun 6 at 2:17
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    $\begingroup$ @ksousa Just fyi (though you probably already know this; if so, sorry!) the only way to get a notification to another user that you have replied in comments is to use the @replies feature. From the main SE meta FAQ see How do comment @replies work? And unless a moderator has commented here already, even the @ won't get a message to them because it would not be an actual reply to a previous comment. Flagging with a polite request usually works quite well! $\endgroup$
    – uhoh
    Commented Jun 6 at 2:18

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Based on the Lorentz force law yes there would be some interaction between the molten outer core and the particles of the solar wind. The magnitude of the interaction, for many of the particles, is going to be some small fraction of the particle's kinetic energy but the average is going to be around 50%. The intercept energy quoted in solar storm estimates is usually in terms of total particle energy, most of that being in the form of electromagnetic charge which makes estimating Lorentz energy transfer for individual storms hard to estimate. The steady (average) rate of transfer may be significant over geological time but large short-lived events are going to have little-to-no immediately notable impact.

80% of the particles in the solar wind are protons that have the potential to undergo a strong interaction with the earth's magnetic field. Of those approximately 50% are in plasma flows that present at a polarity at which they will interact strongly and that interaction will shed an average of 50% of their kinetic energy. Half of that is going to be transferred to the magnetic field and half is going to excite (read heat) the particle.

Time for some napkin math:

Intercept area is ~11.8x109km2
Average active particle density ~5.2cm-3
So the intercept rate is going to be ~6.1×1020Hz
Travelling at an average speed of 500000ms-1 the protons will have an individual kinetic energy of:
Ek=~2.1×10-15J

So the total interaction energy is on the order of ~319713.5Watts

Half of that energy will energise the interacting protons and half will be pumped into the geomagnetic field, about half of that will be constructive interaction (reinforcing the field), half destructive (weakening the local field) net effect minimal, and some (small) percentage of the total energy will be converted into waste heat in the outer core.

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  • $\begingroup$ Thank you. What equation did you use to arrive at that final value? $\endgroup$
    – ksousa
    Commented Jun 11 at 17:14
  • $\begingroup$ @ksousa This whole answer is a ballpark figure, the final is 1/4 of the total kinetic energy of the solar protons intercepted each second that being roughly the average amount of energy transferred. $\endgroup$
    – Ash
    Commented Jun 11 at 21:55

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