Reimann et al. Figure of the coordinate system used in the simulation. The three red lines on the first figure below represent the direction of the measurements and the domain. The red dots on the second figure represent the different line of measurement made by Brown. The numbers on the figure are the log10 of the sodium density.
Negative y is towards Jupiter, positive values away from Jupiter.
The dark circles are the measurements made by Brown. The red line is the result of the simulation. The blue crosses on the figures of the column density represents the measurements to which has been substracted a potential contribution coming from Io. We supposed, since Io's torus plane is between 0.77 RJ to 0.47 RJ in the North of Europa at the time of the measurements, that the sodium contribution from Io should be smaller in the south of Europa than in the North.