Hot flow anomaly remnant in the far geotail?

A hot flow anomaly (HFA) like event was observed by the Solar TErrestrial RElations Observatory (STEREO) in the night side magnetosheath in the far tail in February March 2007. The magnetic signature of the tangential discontinuity was visible, but the resolution of the plasma ion data is not sufficient for our analysis, so a method is given to identify HFAs without solar wind velocity measurements. The event observed in the night side magnetosheath in the far tail might be the remnant of an HFA event, a not-so-active current sheet. This observation suggests that the lifetime of the HFAs might be several 10 min, much longer than the expected several minutes. (C) 2015 Elsevier Ltd. All rights reserved.