Since I suck at maths, I tend to solve problems visually and then implement that.
Here's what I would do.
1. Make an invisible sprite, as a long line, default 64 x 64 is fine. Set its Height to 10, Width 2* (whatever u want the radius of your vortex pull to be). So if you want it to pull when the ship is within 1600 pixels, make it 3200 pixels.
2. Make the point of origin in the center. Add 1 more image point, at the tip of the line, or (32,64) coordinates.
3. Give it the behavior Rotate. Set it to whatever speed that you want the vortex to look like.
4. Give the vortex line an instance variable "IsActive=0".
5. Give your ship an instance variable "IsVortex=0".
6. Do your distance check, when the ship is <1600 distance, set the ship instance variable IsVortex=1 and Pick the Vortex Line Nearest to Ship.X & Ship.Y (so it filters out only that vortex its close to), and set the instance var IsActive=1. Also, set the angle of the Line Vortex towards the position of your ship (X,Y) so the line will instantly point to "touch your ship".
Now, both ship & vortex will have their instance variable flagged to 1, we consider that On/Active.
7. Do a check for your ship, if IsVortex=1, set it's position to another object, the Line Vortex at image point 1. This will cause the ship to be "stuck" to the line vortex. Now the line vortex is rotating and the ship gets dragged with it, spinning around your vortex.
If there's multiple vortexes, simply do a filter to pick by evaluate VortexLine.IsActive=1 so the ship only attaches to the currently active vortex.
How to get it to spin closer and fall into the vortex?
8. Do a check for your vortex line, if IsActive=1, set its Width to be Self.Width * 0.95 (or whatever speed you want, a lower number will suck the ship in faster).
Done, visually it works exactly like a vortex sucking in your ship if it gets too close.
There's probably a much shorter way to do it with a math formula, but this works and doesn't use much CPU calculations, it's simply a re-sizing of a spinning line's width.