# Why is Earth's bow shock wider on one side of the ecliptic than the other?

These diagrams (both confusingly called "Figure 1") of the James Webb Space Telescope's orbit around the L2 Lagrange point show the Earth's bow shock. It makes sense that the bow shock is asymmetric in the second diagram, which depicts the ecliptic plane, because of Earth's orbit.

My question is: why is the bow shock asymmetric in the first diagram, which I've copied below, that shows the ecliptic edge-on? At the distance of L2, the bow shock is less 450 Mm away "above" the plane, while it's more than 550 Mm away "below" the plane. Why are these two distances different?

• If the bow shock is shown for a given time of year, like for example whenever "Launch + 200 days" was supposed to be, then I'd suggest it might be related to the tilt of Earth's magnetic dipole (with respect to the ecliptic) at that time. Of course parts of the diagram span many years, since each of those orbits of JWST with respect to L2 takes almost exactly 1/2 year. 1, 2, 3
– uhoh
Commented Dec 12, 2023 at 13:56
• The vertical axis is labeled as normal to the ecliptic. Commented Dec 14, 2023 at 3:21
• I can't find a detailed diagram of Earth's magnetosphere which clearly shows the impact of Earth's magnetic dipole on the bow shock, but this artist's rendering kind of shows the (rotational) polar axis: en.wikipedia.org/wiki/Earth%27s_magnetic_field#Magnetosphere Also see en.wikipedia.org/wiki/Van_Allen_radiation_belt Commented Dec 14, 2023 at 4:12