The heliopause is where the Solar wind is counter balanced by the particle winds from other stars. This boundary seems to not be spherical and also to fluctuate in shape.
Can the shape of the heliopause be estimated by the pressure from surrounding stars and open clusters?
Can the fluctuations be attributed to specific stars in the Solar neighborhood? Are there single stars both so active and so nearby that they dominate the fluctuations of the Heliopause? Did Voyager in effect observe the effects of a specific event on a specific star's surface when the heliopause boundary billowed back and forth over it?