Science Opportunities in the TRACERS Back Orbit: Ionospheric Signatures of Magnetotail Reconnection

Abstract The primary scientific objective of the TRACERS (Tandem Reconnection and Cusp Reconnaissance Satellites) mission is to understand the spatial structure and temporal evolution of dayside magnetopause reconnection. TRACERS will accomplish this objective by making high time resolution observations with two closely separated (by about 10–120 seconds along track) satellites sun-synchronously orbiting at an altitude of about 590 km. The TRACERS team has defined a dayside “Region of Interest” (ROI) that maximizes the probable number of cusp crossings during its 1 year prime mission. While the TRACERS instruments will be operating at high cadence throughout the orbit, only data collected during the Region of Interest (about 8 minutes of the 90 minute orbit) will be stored at this high time resolution on board and downlinked for analysis on the ground. Outside of the Region of Interest, in the “Back Orbit”, the high time resolution data will be averaged or decimated by the Central Data Processing Unit before being stored for future downlink. Thus, with additional ground contacts, it may be possible to downlink high resolution data collected in the Back Orbit. Further, while TRACERS has been designed to be favorably magnetically aligned during the northern summer hemisphere cusp ROI, its spin axis will also be aligned with the magnetic field in the southern winter hemisphere nightside auroral zone. This raises the possibility that TRACERS could encounter thousands of nightside auroral zone precipitation events associated with magnetotail reconnection. In this paper, we review some of the outstanding science questions that the Heliophysics community could address using TRACERS data in the nightside auroral zone.