Comparison of methods to determine auroral ionospheric conductances using ground-based optical and riometer data

Abstract

Abstract.Ground-based images of auroral optical emissions and cosmic radio noise absorption provide information on particle precipitation which enhances ionospheric conductances. Knowledge of this conductance field is important to understand the current systems associated with auroral features. Three methods of using ground-based optical and riometer data to estimate ionospheric conductances in the aurora are compared to conductances derived from incoherent scatter radar measurements. It is shown that a method using the 557.7 nm emission intensity alone gives the best results for the Pedersen conductance whilst a method using both this intensity and cosmic noise absorption is best for the Hall conductance. A method using cosmic noise absorption alone gives reasonable performance for the Hall conductance and the Hall/Pedersen conductance ratio, but performs poorly for the Pedersen conductance. It also appears to underestimate the Hall conductance significantly during times when softer precipitation is present, for example in discrete auroral arcs. There is some indication that the methods do not degrade noticeably for angles up to ∼20 • off magnetic zenith.

Electrodynamics of an omega-band as deduced from optical and magnetometer data

“…The DASI optical data are stored at 10 km resolution, and in the energy-map calculations the CNA measurements are interpolated onto the same 10 km grid. Senior et al (2008) compared the emap estimates and two other methods of determining conductances using riometer or optical data against EISCAT incoherent scatter radar measurements for two separate events. They found that for this particular event (9 March 1999) the DASI auroral 557.7 nm intensity values had to be scaled by a factor of 2.8 in order to match the EISCAT conductance measurement.…”

“…Kosch et al (2001) introduced a method to derive maps of the characteristic energy of precipitating electrons from cosmic noise absorption (CNA) and auroral optical intensity at 557.7 nm. Senior et al (2008) extended this "energy map" method so that also the flux of the precipitating electrons can be determined, assuming that the electrons have a Maxwellian energy spectrum. When both the characteristic energy and total energy flux of the precipitation are known, the ionospheric Hall and Pedersen conductances can be calculated by using the Robinson formulae (Robinson et al, 1987).…”

“…Our procedure is a variant of the widely known KRM-method (Kamide et al, 1981), which has been modified by for meso-scale analysis. We also utilize some semi-empirical models connecting observations of auroral luminosity and riometer absorption with height integrated conductance values (Senior et al, 2008).…”

Analysis of ionospheric electrodynamic parameters on mesoscales – a review of selected techniques using data from ground-based observation networks and satellites

“…(43). This thus far overlooked approach may have some applications, as Senior et al (2008) showed that P can be estimated quite accurately from all-sky camera images taken at 557.7 nm. Another extension of the present analysis methods was mentioned in Sect.…”

“…(31) and (32) demonstrated by Murison et al (1985) for the KRM method. Two-dimensional ionospheric conductance distributions are quite difficult to obtain from direct measurements, but estimates may be derived from satellite or all-sky camera images and riometer data (e.g., Lummerzheim et al, 1991;Janhunen, 2001;Aksnes et al, 2005;Senior et al, 2008). However, these estimates rely on semi-empirical formulas that first relate optical emissions to the flux and characteristic energy of the precipitating electrons, which are then used to estimate the height-integrated conductances.…”