Hot flow anomaly remnant in the far geotail?

TL;DR

This paper reports the observation of a potential hot flow anomaly remnant in the far geotail, suggesting HFAs may last longer than previously thought, based on a novel identification method without solar wind velocity data.

Contribution

It introduces a new method to identify HFAs without needing solar wind velocity measurements and suggests HFAs can have lifetimes of several 10 minutes.

Findings

Observed an HFA-like event in the far tail magnetosheath.

Proposed that the event is a remnant of a long-lived HFA.

Indicated HFAs may persist for several 10 minutes.

Abstract

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 minutes, much longer than the expected several minutes.