  We characterize the nature of magnetic structures in the foreshock region of
Mars associated with discontinuities in the solar wind. The structures form at
the upstream edge of moving foreshocks caused by slow rotations in the
interplanetary magnetic field (IMF). The solar wind plasma density and the IMF
strength noticeably decrease inside the structures' core, and a compressional
shock layer is present at their sunward side, making them consistent with
foreshock bubbles (FBs). Ion populations responsible for these structures
include backstreaming ions that only appear within the moving foreshock, and
accelerated reflected ions from the quasi-perpendicular bow shock. Both ion
populations accumulate near the upstream edge of the moving foreshock which
facilitates FB formation. Reflected ions with hybrid trajectories that straddle
between the quasi-perpendicular and quasi-parallel bow shocks during slow IMF
rotations contribute to formation of foreshock transients.
