Indeed they are. It's the visible manifestation of the Night Witches' magic radar - in Sanya and Heidemarie's cases, based on the Hirschgeweih ("stag's antlers") aerials used on early Luftwaffe nightfighter radar sets. Not all of them use the same configuration. There's another one in some of the subsidiary media whose antenna is based on the later, more compact Morgenstern ("morningstar") aerial (she's a princess, so it unsurprisingly resembles a crown), and at least one Liberion witch has a setup that looks like the classic plan position indicator display rather than an antenna.

--G.
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Benjamin D. Hutchins, Co-Founder, Editor-in-Chief, & Forum Mod
Eyrie Productions, Unlimited http://www.eyrie-productions.com/
zgryphon at that email service Google has
Ceterum censeo Carthaginem esse delendam.