Relationship Between Foreshock Structures and Magnetosheath Jets

Abstract Plasma structures with enhanced dynamic pressure know as jets are frequently observed in the magnetosheath. We examine a possible connection of these jets with structures reported in the foreshock like SLAMS or plasmoids. A statistical study of the relation of the upstream conditions and the occurrence rates of magnetosheath (MSH) jets and foreshock structures revealed that foreshock structures prefer the low interplanetary magnetic field and high Mach number whereas MSH jets are more frequently observed under extremely high solar wind density. The case studies of simultaneous observations in the foreshock and the magnetosheath have shown that the presence of foreshock structures is not a necessary condition for observations of strong MSH jets in the downstream and vice versa. We suggest that the source of a significant part of MSH jets is the bow shock reformation initiated by the changes of magnetic field orientation just in front of the bow shock.