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If Venus in it is current state, started rotating at the same rate as Earths 24hrs rotation, would it develop a magnetic field of roughly the same strength as Earth's?

If so, would that help in any way to thin out the clouds on Venus?

UPDATE

The reason I even asked this question is because, Venus as hellish as it currently is, has one huge advantage over a planet like Mars, it’s size! But until I read Fred’s reply I didn’t know a plants core rotated faster then the plant itself. I thought the core rotated at the same speed as the rest of the planet.

So even if Venuses core was like Earths, it would need to me speeded to almost the speed of Earths core to generate a powerful enough magnetic field or even faster to account for it being closer to the sun?

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    $\begingroup$ I don’t see how increasing the magnetic field strength would have any particular effect on the clouds. (Or why “thinning out the clouds” is somehow desirable.) $\endgroup$
    – Peter Erwin
    Commented Mar 26, 2022 at 12:10
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    $\begingroup$ "spinning up" a planet is an unfeasibly energetic process. And any science fiction device that could change the rotation rate would probably accidentally melt the planet's surface. You'd make Venus an even more hellish place (if that's possible) $\endgroup$
    – James K
    Commented Mar 26, 2022 at 12:33
  • $\begingroup$ @JamesK luckily Stack Exchange wasn't around to tell him his train would melt if accelerated; Einstein's thought experiments $\endgroup$
    – uhoh
    Commented Mar 26, 2022 at 13:06
  • $\begingroup$ Aye, there's nowt wrong wi' thought experiments. But the second paragraph seems not to be couched in that context. Rather it seems to be a "would this be a practical step in terraforming Venus". That is a valid question, and just as interesting as interpreting it as a thought experiment. The consequence of the question, treated as real question, could make a good answer. My comment isn't a good answer, but it might prompt some further research: How much energy? Would it melt the surface? partially, fully? and so forth. Just saying "The OP was asking a thought experiment" is dismissive. $\endgroup$
    – James K
    Commented Mar 26, 2022 at 13:18

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Planetary magnetic fields are not produced by their rotation, they are produced by convection in the core. The rotation has an effect on the patterns of convection through Coriolis forces, but is not alone sufficient to produce a magnetic field. It is probably not even required, as Mercury has a magnetic field that is likely produced by a core dynamo despite its 58.6 day rotation period.

Aside from that, a magnetic field would do nothing to "thin out the clouds". It would reduce loss of hydrogen from the upper atmosphere, but any Venus terraforming program would require atmospheric modifications on such a scale that accounting for solar stripping of the atmosphere would be utterly trivial. And making those changes would be trivial in comparison to altering the rotation of the entire planet.

The only thing spinning the planet up would do is give a day/night period that Earth life could tolerate. That's important for full terraforming, but could far more easily be achieved by constructing orbital megastructures to provide shade or reflected sunlight, or by just constructing enclosed habitats with artificial light and regulated internal temperatures.

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Earth's magnetic field is more about the rotation of the Earth's core than the Earth itself. Earth's core rotates at a slightly higher rate than Earth itself. It's two-thirds of a second faster.

Increasing the rate of rotation of Venus, as a whole, will not produce a magnetic field. To get a magnetic field for Venus, the core would need to be spin at a much faster rate than it does and part of the core would need to be molten.

Scientists aren’t sure if the core of Venus is solid or liquid, but they have a few hints. That’s because Venus doesn’t have a planet wide magnetic field like the Earth. It’s believed that the Earth’s magnetic field is generated by the convection of liquid in the Earth’s core. Since Venus doesn’t have a planetary magnetic field, it’s possible that Venus’ core is made of solid metal, or maybe there isn’t enough of a temperature gradient between the inner and outer core to made this convection happen.

It’s believed that a global resurfacing event that occurred about 300-500 million years ago might have something to do with this. The entire surface of Venus was resurfaced, shutting down plate tectonics. This might have led to a reduced heat flux through the crust, trapping the heat inside the planet. Without the big heat difference, there’s little heat convection, and so no magnetic field coming from the core of Venus.

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