We interpret our FAC density profiles by considering the corresponding precipitating electron energy fluxes, as shown in Fig. 6(b). Fluxes are plotted as functions of latitude. The line style code and labels are the same as in Fig. 6(a), the latitudinal size of a HST ACS-SBC pixel is indicated by the dark grey rectangle and the grey solid line indicates the limit of present HST detectability (~1kR; Cowley et al., 2007). We begin by comparing profiles for case ES with EF, which are almost identical and both have maxima at ~74° latitude, equivalent to the location of the ‘main auroral oval’, and at ~80°, the boundary between open (region I) and closed field lines (region II). Therefore, we would expect a fairly bright auroral oval of ~88kR for case ES and ~79kR for case EF. The electron energy flux for case EF (~7.85mWm−2) is ~10% smaller than case ES (~8.8mWm−2) due to ΩT(ES)>ΩT(EF) leading to a smaller flow shear. Our model also predicts the possibility of observable polar emission (region II/I boundary) of ~15kR for both cases ES and EF. However, this region is strongly dependent on the plasma flow model used and poorly constrained by observations.
limit of present HST detectability
~1kR
kR
case ES with EF
maxima
~74° latitude
° latitude
case ES with EF
boundary between open (region I) and closed field lines (region II)
~80°
°
case ES
auroral oval
~88kR
kR
case EF
auroral oval
~79kR
kR
case EF
electron energy flux
(~7.85mWm−2
mWm−2
case EF
electron energy flux
~10%
case ES
electron energy flux
~8.8mWm−2
mWm−2
model also predicts
observable polar emission (region II/I boundary)
~15kR
kR