Rylan Dephoure
Research Mentor: Jim Raines
Mentor Department: Climate and Space Sciences and Engineering, Engineering
Author(s): Not Available
Session: Session 2 (10:00 AM – 10:50 AM)
Presentation Type: Poster 32
Abstract
Heavy ions are key tracers of coronal heating and acceleration in the solar wind. Coulomb collisions, primarily through protons, have been thought to thermalize these heavy ions toward thermal equilibrium. However, modern in situ measurements have shown this is not to be the case and demonstrates the need for further research on the mechanism(s) of preferential heating (Tracy et al. 2015). We investigate ion-proton temperature ratios derived from thermal speed for He2+, C5+, O6+, and Fe10+. Past work has shown these ions (excluding alphas), displayed a bump in Tion/Tp at collisional ages of 10-1 rather than follow the expected monotonic decay as collisional age increases. Our work investigates the thermalization of heavy ions using multi-instrument datasets spanning from 1998-2011. Heavy ion thermal speeds were taken from the Solar Wind Ion Composition Spectrometer (SWICS) aboard the Advanced Composition Explorer (ACE) and Solar Orbiter’s Heavy Ion Sensor (HIS) while proton thermal speeds were taken from Solar Orbiter Proton and Alpha Sensor (PAS), WIND SWE (Solar Wind Experiment) and the Solar Wind Electron and Alpha Monitor (SWEPAM) on ACE. These datasets were merged to produce hourly thermal speeds, temperatures, magnetic field directions and magnitudes, and filtered to remove interplanetary coronal mass ejections (ICME). Instrument-specific temperature conversion inconsistencies can greatly influence these ion to proton temperature ratios. WIND-SWE provides a 3D temperature while the instruments aboard ACE measure only the radial (1D) temperature. Further, SWEPAM and SWICS also do not use the same temperature conversion factor. We show that these temperature measurements are incompatible and a conversion factor must be applied to avoid impacting the amplitude of the Tion/Tp “bump†and the outer boundary of the preferential heating zone.
