Looks like a distrail though ‘fallstreak hole’ is another reasonable name for it although it is a special version of one. The following link supplies a good explanation and some more photos.
http://www.weatherscapes.com/album.php?cat=clouds&subcat=distrails
Although distrails usually occur in supercooled cloud, I once saw one in thin stratocumulus which didn’t contain supercooled cloud droplets. The turbulence of the aircraft had created downflow in the middle of the wake and thus evaporation of the descending cloud. Alongside this gap, the rising air had thickened the cloud. The layer of cloud continued to thin until there was only the two narrow bands of thickened cloud along the edge of the aircraft track, thus leaving a pseudo-contrail at a height of about 4,000ft.
