Multi-point electric field measurements of short large-amplitude magnetic structures (SLAMS) at the Earth's quasi-parallel bow shock -: art. no. 1177

[1] We present the first direct measurements of the electric field and plasma density with high resolution in Short Large-Amplitude Magnetic Structures (SLAMS) at a quasi-parallel shock crossing. Cluster observations at the Earth's bow shock confirm the fast-mode structure of SLAMS. Using the four Cluster spacecraft, we determine the velocity of the SLAMS v(SLAMS) and find that E = -v(SLAMS) x B. This indicates that locally the SLAMS is moving with the same velocity as the plasma, thus indicating trapping of ions. A small-scale (electron gyroradius) electric field with E 6 not equal -v(SLAMS) x B is found at the leading edge of the SLAMS. Downstream of several SLAMS, a wake-like decrease in the plasma density is observed suggesting the three-dimensional structure of SLAMS. The scale length of these SLAMS is of the order, or larger, than the satellite separation of 600 km.