Pickup Ion Spectrum Downstream of the Termination Shock Inferred from IBEX ENA observations and Comparison with Kinetic Simulations
Abstract
The energetic neutral atom (ENA) fluxes observed by IBEX spacecraft show power-law-like spectra in theenergy range 0.5 to 6 keV. However, the temperature of the thermal core solar wind (SW) protonsdownstream of the heliospheric termination shock (HTS) measured by the Voyager 2 spacecraft is too smallto create ENAs in this energy range. Therefore, these ENAs must come from a suprathermal population ofprotons, known as pick-up ions (PUIs). Some of these PUIs are heated preferentially at the HTS due toreection from the electrostatic cross-shock potential.In this study, we obtain the PUI spectrum downstream of the HTS at multiple directions in the sky from aquantitative comparison of the observed ENA flux from IBEX and global simulations of IHS ENA fluxes for arange of HTS parameters. We use a 3D steady-state simulation of the heliosphere with a multi-Maxwelliandistribution for protons in the IHS to simulate the ENA fluxes. The simulated ENA fluxes are then comparedwith time-exposure-averaged data from IBEX-Hi. The best downstream PUI spectrum at a particular directioncorresponds to the HTS parameters that give the best match between observed and simulated ENA fluxes.Finally, the derived downstream PUI spectrum is compared with the PUI spectrum from kinetic simulations.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFMSH22A..05S