Initial Observations of Interplanetary Shocks by STEREO

Initial observations by the magnetometer on the twin STEREO spacecraft reveal much about shock structure and evolution in the solar wind. Alignments of STEREO with Venus Express reveal that none of the shocks associated with stream interactions and observed with the STEREO spacecraft at 1 AU were present in the solar wind at 0.7 AU, indicating that the region between Venus and Earth is an incubator for interplanetary shocks. We find examples from the STEREO data of the coalescing of weak shocks to form stronger shocks. These weak shocks frequently exhibit wave structure upstream and downstream of the shock inconsistent with early ideas of the formation of these wave trains.