BOW SHOCK. “The low-density tail lobes in the nightside magnetotail connect magnetically to the high-latitude polar caps at one end and to the interplanetary field at the other end. The effects of the strong dipole are not seen tailward of about 20 RE. Beyond that distance, the fields in the northern and southern tail lobes are nearly antiparallel and have an almost constant intensity of about 20 nT over a long range of distances from the Earth.”
https://link.springer.com/article/10.12942/lrsp-2007-1