Hot diamagnetic cavities upstream of the Martian bow shock

We present Mars Global Surveyor (MGS) observations of hot diamagnetic cavit ies upstream of the Martian bow shock. The events are characterized by a re gion of turbulent magnetic field, high electron temperature, and densities at or below the ambient solar wind density. The region of high temperature is flanked by layers of high magnetic field and electron density and is acc ompanied by a rotation in the interplanetary magnetic field (IMF). We sugge st that the events are generated by interplanetary discontinuities interact ing with the Martian bow shock, i.e., the events are the Martian counterpar t to the hot flow anomalies observed upstream of the Earth's bow shock.