  We present Magnetospheric Multiscale observations of electrostatic double
layers in quasi-perpendicular Earth's bow shock. These double layers have
predominantly parallel electric field with amplitudes up to 100 mV/m, spatial
widths of 50-700 m, and plasma frame speeds within 100 km/s. The potential drop
across a single double layer is 2-7% of the cross-shock potential in the de
Hoffmann-Teller frame and occurs over the spatial scale of ten Debye lengths or
one tenth of electron inertial length. Some double layers can have spatial
width of 70 Debye lengths and potential drop up to 30% of the cross-shock
potential. The electron temperature variation observed across double layers is
roughly consistent with their potential drop. While electron heating in the
Earth's bow shock occurs predominantly due to the quasi-static electric field
in the de Hoffmann-Teller frame, these observations show that electron
temperature can also increase across Debye-scale electrostatic structures.
