Identifying the 630 nm auroral arc emission height: A comparison of the triangulation, FAC profile, and electron density methods

Abstract We present a comprehensive survey of 630 nm (red‐line) emission discrete auroral arcs using the newly deployed Redline Emission Geospace Observatory. In this study we discuss the need for observations of 630 nm aurora and issues with the large‐altitude range of the red‐line aurora. We compare field‐aligned currents (FACs) measured by the Swarm constellation of satellites with the location of 10 red‐line (630 nm) auroral arcs observed by all‐sky imagers (ASIs) and find that a characteristic emission height of 200 km applied to the ASI maps gives optimal agreement between the two observations. We also compare the new FAC method against the traditional triangulation method using pairs of all‐sky imagers (ASIs), and against electron density profiles obtained from the Resolute Bay Incoherent Scatter Radar‐Canadian radar, both of which are consistent with a characteristic emission height of 200 km. Key Points Field‐aligned currents derived from in situ observations are an acceptable method to estimate red‐line auroral emission altitude The standard emission altitude of discrete red‐line auroral arcs, that of 230 km, may be overestimated This new height estimate is confirmed using ISR estimates from RISR‐C