How far away would you need to be to survive a jet of stellar plasma on the surface of a "planet" built around a sun?

Question

So, I'm considering writing a story, and one of the settings is a world created by a powerful wizard millions of years ago, by opening a thousand portals to gate in a thousand Earth-like worlds that were then magically disassembled to form an Earth-like shell around a sun, and which was prevented from collapsing inwards by the pressure of the magic and solar energy the sun radiated (which also allows for an apparent Earth-like surface gravity); the surface was then maintained at a habitable temperature by the radiation of the now-covered sun's binary partner, which was within the habitable zone of the new Sun-sized "planet"; the atmosphere and oceans for this new "planet" were provided by thousands upon thousands of comets that were then teleported in.

However, over the millions of years that have passed since the world's creation, the network of magical infrastructure that allowed this world to function has begun degrading due to continental drift, and some areas of the surface of this "planet" (12,000 times the surface area of Earth) have collapsed into the sun, and as a result, the surface of the star beneath was exposed, and solar prominences have emerged from them, jetting up above the surface of the new planet.

Obviously, the area around such hole in the surface would be quite uninhabitable, but how far away would you need to travel from such a hole before the surface once more returned to a more Earth-like level of habitability? If the size of the hole matters, perhaps a hole roughly Earth-sized.

Answer 1

i'm working under the assumption that you are referring to our sun.

A strong solar flare produces about 10^25 watts of radiative energy of differant sorts at peak(CME's and other massive events notwithstanding. the surface of earth, on the other hand, is only hit with a mere 1500 watts. in order to dissipate to that scale it is necessary to be about 75 million kilometers away, or half an AU, which is not what you wanted. [this assumes you have a hole the size of one square meter that at it's peak blows off only solar flares and they spread out in a perfect hemisphere.]

Your solution is therefore working by being far enough under the Horizon that the surface of the planet itself shields you. This largely depends on how much credit you are willing to give your atmosphere. On earth most radiation is stopped in the last 30 km of the atmosphere, therefore i'd give that as the distance under the horizon. The required distance from the hole is therefore simply: distance = sqrt((radius + margin)^2 - (radius)^2). [Yes, it's the Pythagorean theorem.]

Given our sun at a radius of 696340 km and my assumed margin of 30 km this works out to 6463 km, but feel free to make it less. You should note that a wall would not solve the problem unless it was taller then the solar flares coming up behind it, but sufficient distance and a lot of atmosphere should block the radiation from a large solar flare. (When light goes diagonally through atmosphere you can get thousands of kilometer to dissipate all that radiation and heat, despite the atmosphere being only 100 km thick.)

Not What you asked, but cool: the solar flares and dims of the opening would intermittently heat up and cool down the atmosphere around it in extreme ways, creating sort of waves in the air some of them supersonic. So there could be a flare and then a sonic boom from it that hits our distant village some five hours later.