The image above is a schematic representation of a Disconnection Event (DE). As the comet moves through the sun's magnetic field, the blue plasma tail is occasionally severed from the comet's head and a new tail grows in its place. The "disconnected" tail is then left behind as the comet continues its path around the sun.

Notice that the yellow dust tail is unchanged during the DE because it is composed of neutral particles that do not interact with the sun's magnetic field.

---

The drawing to the left shows the path of comet Hale-Bopp as it swings around the sun. It passes over the top of the sun where the solar wind is fast and smooth. In these regions the comet's plasma tail should appear smooth and have no DEs. As the comet passes through the plane of the solar system, it will encounter a denser solar wind as well as magnetic sector boundaries. The comet's plasma tail in this region will be much more disturbed and DEs will occur.

A very nice set of 3D comet orbit diagrams (including Hale-Bopp) are available here.