Date: 21 Apr 2010
Copyright: ESA

Ripples passing along the Earth's bow shock may be responsible for producing mysterious, high-speed plasma jets. The two main effects of such a shock ripple are illustrated above.

First, a ripple produces an indentation that induces a higher-density region downstream of the shock. Second, it changes the angle of incidence between the solar wind and the shock front. When this angle is large, for instance on the borders of the ripple, the solar wind goes through the bow shock, experiencing only minor effects. This causes the creation of a second (local) shock downstream of the nominal shock. The higher density together with the high speed leads to a jet with very high dynamic pressure.

This mechanism, which was uncovered using data from the ESA Cluster spacecraft, is described in Hietala, H., et al. (2009).