Observations of magnetotail flank boundary crossings - a Cluster-PEACE perspective

We present examples of the boundary regions and structures observed at the flank magnetopause. PEACE electron data, obtained close to the magnetopause boundary and supported by FGM magnetometer data from the four Cluster satellites, is used to determine the scale and properties of these structures. Many spacecraft have made observations that are consistent with boundary waves on the flanks of the magnetopause. Some of these may have been driven by the Kelvin-Helmholtz instability (KHI). Such waves could transport momentum across the magnetopause and into the magnetosphere, contributing to the magnetospheric convection cycle. It has also been suggested that the cold dense flows observed in this region are supplied by mass transfer across a closed magnetopause. Four spacecraft measurements obtained on either side of the current sheet will be used to examine the nature of energy and mass transport across the boundary. These observations can be used to determine whether, for example, the KHI mechanism is capable of driving the flows observed in the flank magnetopause boundary layers. Observations of electrons close to the magnetopause but in the magnetosheath may also be used to examine whether electrons inside the magnetosphere can cross out into the magnetosheath on open lobe field lines.