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Welcome to fantasy earth: like Earth in all the same ways, with the exception that the sun you know has been replaced with a ring you don't.

What would the climate of Earth be if the sun was replaced with a ring ("magic", for however much it's functioning matters) with the following properties:

  • In geosynchronous (not geostationary!) orbit, at 35.800 km-ish height, and so taking 24 hours to orbit fantasy earth.

  • Orbiting at an inclination of 24 degrees.

  • Infinitely thin (like I said, magic). Imagine a string wrapped around the Earth and you'll get the idea. This infinitely thin part is flavor, more than anything else. It's a single magic loop of infinitely thin yarn outputting a magical amount of light around the planet.

  • Radiating light at about 0.007 the degree of brightness of the sun, with the same electromagnetic output of the sun, both in respect of what wavelengths are produced, as well as the irradiance that any individual area experiences, within the range of what's currently experienced by Earth.

Notes:

  • I'm assuming that from the perspective of the Earth's surface, the ring would move in a figure 8 pattern, with the net result being a ring weaving around it throughout the day

  • Half of the northern and southern hemispheres would likely experience night, and half day at the same time—what impact that would have on the climate, I don't know.

  • I'm assuming that some latitudes would experience a steady degree of irradiance, and so result in more static climate zones, but I'm not 100% certain regarding such things.

Addendum: a very rough estimate is fine, no extensive modeling is required, vibes will suffice.

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    $\begingroup$ I'm having some difficulty picturing it. What's meant by "infinitly thin?" Is this a ring shaped like Saturn's rings, and if so how big is it? $\endgroup$
    – BMF
    Nov 14, 2023 at 0:34
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    $\begingroup$ What is the diameter of the ring? If this is a planetary ring (like one of Saturn's rings), then the orbital period won't matter. You'll always have the same percentage of the ring over any longitude. If this is a ring like a Bishop ring, then it would be functionally identical to a spot-source of light. I'm not sure what the orbital stability would be for something in between. Could you specify? $\endgroup$ Nov 14, 2023 at 1:43
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    $\begingroup$ First off geosynchronous and geostationary both mean the same thing .. second off the length of time it takes to orbit is irrelevant, it's a ring, it will be over every point of it's orbit at all times no matter what the orbit speed is or isn't, or is it supposed to be flipping end to end around the planet? $\endgroup$
    – Pelinore
    Nov 14, 2023 at 8:47
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    $\begingroup$ @Pelinore: No, geosynchronous and geostationary do not mean the same thing. There are many geosynchronous orbits, but only one geostationary orbit. $\endgroup$
    – AlexP
    Nov 14, 2023 at 9:29
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    $\begingroup$ @Pelinore: No it won't. Seen from a point on the Equator, the ring will appear as a chord with fixed points east and west and the middle oscillating from 66° north to 66° south with a period of one day. From a point at 24° north, the ring will appear as a band stretching east to west through the zenith once per day, moving down to an east-to-west band culminating at 48° south and then rising up to the zenith again. From a point at 42° north, the ring will appear as a eastish-to-westish band culminating at 48° south once per day, then go down south until it sets completely before rising again. $\endgroup$
    – AlexP
    Nov 14, 2023 at 12:13

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There are numerous immediate and obvious differences that I can think of, mostly describing plant life, weather, and geology. I have to admit that my imagination only extends to things that such a model would eliminate from our current system.

I'm sure that everyone here can tell you about Hadley cells, and how the rotation of the earth creates high-altitude warm currents from the equator up to about 30 degrees. That would still happen, but to a lesser extent.

You won't see the massive heat pump of heat-expanded air driving wind currents around the planet, so there would be less overall wind. The plants would be more spindly because gusts that could knock them down would be once-in-a-lifetime events.

It occurs to me that, due to consistent heating, there would probably be places on the planet that it rained constantly due to prevailing winds running into mountains creating a watershed. These rainy areas would probably dig furrows through mountains the same way that rivers make oxbows in our world.

You won't see the day/night cycle raising temperatures in the day, then dumping water when the temperature drops below the dew point. Thus, much, much less precipitation, which means less erosion wearing mountains down into arable soil and fewer, narrower rivers. Maybe more of the plants would draw water from the air like tillandsia.

Right now, many plants will twist to follow the sun, getting the most out of the light. If it's always in the same direction (like in the temperate zones), then much of the vegetation would create a vertical wall of leaves pointing towards the equator. Equatorial plants might have a little phototropism, but that would be up to evolution.

Since you have consistent illumination, you will no longer have seasons. Most Earth plants use this to trigger their growth/reproduction cycles, so you'd have to think of something else.

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    $\begingroup$ "Constant illumination:" There will be always light between 66° latitude south and 66° latitude north, but far from constant. Above 66° latitude north and below 66° latitude south there will be a daily cycle of light and darkness. $\endgroup$
    – AlexP
    Nov 14, 2023 at 20:18
  • $\begingroup$ @AlexP, fair point, but you're talking about the area that, on Earth, is the Arctic Circle. I don't think that the ring-sun would change the effect that the high angle of incidence has on heat absorption. I'm sure that some plants would specialize up there, but I wouldn't expect them to dominate the ecosystem. If they actually depend on the day/night cycle, they wouldn't be able to survive in non-arctic climates. $\endgroup$ Nov 15, 2023 at 0:57
  • $\begingroup$ I'm going to wait for six hours before checking your response per guidelines $\endgroup$ Nov 15, 2023 at 15:08
  • $\begingroup$ Thank you! I thought of another one: No sun-tides, and you would have a hard time seeing a moon. $\endgroup$ Nov 16, 2023 at 0:36

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