The Structure of the Heliotail as probed by a Kinetic-MHD, a Multi-Ion Description of the Heliosphere and Energetic Neutral Maps
Abstract
A critical question regarding the heliosphere is its veryshape and the structure of the heliotail (whether it has a long comet-like shape, is bubble shaped, or "croissant"-like), prompted by observations and modeling (Opher et al. 2015; Pogorelov et al. 2015; Izmodenov & Alexashov 2015; Dialynas et al. 2017; Schwadron & Bzowski 2018). Opher et al. (2015) show that the magnetic tension of the solar magnetic field organizes the solar wind in the heliosheath into two jet-like structures, giving the heliosphere a "croissant"-like shape where the distance to the heliopause downtail is almost the same as that towards the nose.
There have been arguments that with a kinetic treatment of the neutral H, the heliotail extends to large distances (Izmodenov et al. 2018; Pogorelov et al. 2015). We recently developed the Solar-wind with Hydrogen Ion Exchange and Large-scale Dynamics (SHIELD) model, a self-consistent kinetic-MHD model of the outer heliosphere within the SWMF framework (Toth et al. 2012). The SHIELD model couples the MHD solution for a single plasma fluid to the kinetic solution for neutral hydrogen atoms streaming through the system. Our results show that even when the neutral H atoms are treated kinetically, the two-lobe structure remains (Michael et al. 2019). Their results indicate that magnetic reconnection downtail and/or instabilities play a crucial role in the formation of the two-lobe structure. We will present globally distributed flux (GDF) ENA maps from the SHIELD model, including a latitudinal variation of the solar wind corresponding to the conditions in the year 2008 using solar wind data from Sokol et al. (2015). The GDF ENA maps replicate the IBEX observations for solar minima conditions. We have also recently extended our global MHD model (Opher et al. 2019) to treat the pick-up ions (PUIs) created in the supersonic solar wind as a separate fluid from the thermal component of the solar wind. The PUIs charge exchange with the cold neutral H atoms of the ISM in the heliosheath and are quickly depleted. The depletion of PUIs cools the heliosphere downstream of the TS, "deflating" it and leading to a narrower HS and a smaller and rounder shape. With this model, we reproduce the IBEX ENA observations along Voyager 2, as well the magnetic field observations at Voyager 1 and 2 ahead of the heliosphere.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMSH53A..04O
- Keywords:
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- 2114 Energetic particles;
- INTERPLANETARY PHYSICS;
- 2126 Heliosphere/interstellar medium interactions;
- INTERPLANETARY PHYSICS;
- 2144 Interstellar gas;
- INTERPLANETARY PHYSICS;
- 2151 Neutral particles;
- INTERPLANETARY PHYSICS