A double-cusp type electrostatic analyzer for high-cadence ring current ion measurements

Friday, 18 December 2015
Poster Hall (Moscone South)
Keiichi Ogasawara1, Frederic Allegrini1,2, James L Burch1, Mihir Indrajit Desai1,2, Robert W Ebert1, Jerry Goldstein1,2, Joerg-Micha John1, Stefano A Livi1,2 and David J McComas1,2, (1)Southwest Research Institute, San Antonio, TX, United States, (2)University of Texas at San Antonio, Department of Physics & Astronomy, San Antonio, TX, United States
Detailed observations of a variety of ion species at a sufficiently high temporal resolution are essential to understanding the loss and acceleration processes of ring current ions. For example, CRESS/MICS observations indicated that the energy density of suprathermal O+ exceeds that of H+ in large magnetic storms (Daglis et al., 1997), while the H+ energy density dominates under quiet conditions. However, the primary ion loss processes during the storm recovery phase are still incompletely understood. The mechanisms to accelerate upflowing ions, regularly observed with energies of a few keV at ~1000 km altitude, up to the 100s-keV range in the geospace are also not fully understood. Our novel electrostatic analyzer (ESA) employs a toroidal double-shell structure to cover the entire ring current ion range of ~3–250 keV/Q with high temporal resolution (<1 minute with a necessary counting statistics for the quiet time), while saving significant resources in mass and size. In this presentation, we discuss the operation principle and the proof of concept study of the ESA in terms of numerical calculations and ion beam calibration activities. This presentation comprehensively covers the expected sensor performance important for the in-flight capabilities, such as sensor parameters (G-factor, K-factor, and energy resolution), cross-shell contaminations, and UV background counts.