Large-amplitude compressive "sawtooth" magnetic field oscillations in the Martian magnetosphere

We present Mars Global Surveyor mapping observations of large-amplitude "sawtooth" magnetic field oscillations in the induced magnetosphere of Mars and discuss their possible origin. These highly compressive, linearly polarized, quasiperiodic features occur above the sunlit hemisphere of Mars, below the magnetosheath, but outside of photoelectron-dominated regions. The correlation between solar zenith angle and estimated solar wind dynamic pressure at the sawtooth observation time and location at similar to 400 km altitude suggests an association with a flared boundary, possibly the ionopause. Magnetic reconnection, ionospheric instabilities and/or irregularities, and crustal magnetic field effects may all play a role in generating these compressional features, with individual observations suggesting that each may at times prove important. These processes each have implications for magnetospheric dynamics and nonthermal ion escape from the Martian system.