I have read dozens of books where gravity magic is a thing. It ocurred to me, while reading one of these stories, that every version of a gravity magic spell that I have heard of, is missing something, namely they dont consider the effect of the spell on fluids in the environment like air or water.
A typical example would be a spell where the caster creates a invisible plane where the acceleration due to gravity is a constant with its vector perpendicular and pointing towards the plane. This is demonstrated in the stories when the spell is cast on the ground, crushing an opponent, or horizontally throwing an opponent, etc.
Realistically though, if a gravity spell was cast on the ground, the column of air over the gravitational plane would also be affected.
My initial thoughts are the air column would fall and compress, which would cause the air to heat dramatically, then a vacuum would form where the air was leaving creating extremely high winds which would could eventually form a fire tornado. Where would it end though? Could it cause a fire hurricane? Would it get hot enough to vaporize rock and bore a tunnel to the Earth's core?
So my question is, what effect would a gravity spell have if its plane of attraction was a 20' diameter circle placed on the ground that increased gravity in a vertical column by 1g and it could last 1min, 10min, or an hour before expiring?
I wasn't trying to cast shade on any other authors for their flavor of gravity magic, I just wanted to explore some possibilities.
This gravity magic works by adding a gravitational force to an area except instead of pulling omnidirectionally to a point it pulls unidirectionally towards a plain. The portion of any object that intersects a line perpendicular to the spells plain starting at the plain and going off into infinity in the opposite direction of the gravitational pull of the plain would be in the spells aeea of effect. The magnitude of the acceleration would fall off as the distance above the plain is increased in the same way the magnitude of acceleration due to earths gravity is reduced as you go further away from the surface of the earth. The magnitude of the force, shape of the plain and duration of the effect can be modified in the spell. For this question I restricted the spell to a 20' circle on the surface of the earth that adds 1g of acceleration in the same direction as the acceleration due to Earth's gravitational pull at that location. I also asked the effects for a 1min, 10min, and 1hour duration under the assumption the spell would cause weather effects that would be pretty different based on the spells duration.
I was hoping for an answer that would take into account the pressure, volume, density equation: PV=nRT, where P=pressure, V=volume, n=number of moles of gas, R=ideal gas law constant, and T=temperature. Answering that would depend on things like how the turbulent boundary layer that would form along the surface of the affected cylinder of falling air would effect the maximum pressure of that air cylinder, how doubling gravity for just that cylinder would affect the terminal velocity of the air, etc. Knowing the pressure, temperature and velocity gradients in the spells direct area of affect should also shed some light on weather affects, etc.