(I split this from the "new system" thread)
STOP THE PRESSES!!!
I had a suspicion about this, so I tried it out - I removed ALL the planets and just left the belt to evolve on its own for 160 years, just to see what happened. As you can see from the animation below, even with
no other bodies in the system (apart from the sun) the 'flicking' that propagates outward from the inner edge of the belt is still there!! Though obviously since there's no jovian anymore, the bumps at the resonances aren't there anymore.
The only possible reason I can think of for this (unless this is some bug in Gravity Simulator itself or something to do with the timestep?) is that it's because the asteroids aren't massless - when I defined them I gave them a radius of 0.5 km and a mass of 100,000,000 kg (100,000 metric tons). So could they be perturbing
eachother, and that's what's causing the flicking? I also wonder if the reason that the 'flicking' starts at the inner edge of the belt is because those asteroids are the ones that are orbiting the fastest - as the outer asteroids complete their orbits up the 'wave' propagates outward too? Though I still don't know what the flicking actually
is.... Either way, I really can't think of any other cause for the flicking given that there's no other bodies here - I guess the only way to find out for sure would be to recreate the belt but make the asteroids massless points (can we do that in GravSim?) and see what happens...
But at least now we seem to have proven that the 'flicking' is a natural property of the belt itself (or a bug in GravSim or a timestep issue

), not caused by jovians or any other bodies.
Anyone got any ideas about this???