Physics – Plasma Physics
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufmsh21c..07p&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #SH21C-07
Physics
Plasma Physics
[7807] Space Plasma Physics / Charged Particle Motion And Acceleration, [7827] Space Plasma Physics / Kinetic And Mhd Theory, [7846] Space Plasma Physics / Plasma Energization
Scientific paper
The interaction between the solar system and interstellar medium (ISM) involves multiple populations of ions and neutrals of both heliosphere and local interstellar origin. Of special interest is the pick-up ion population generated in the inner heliosphere, as it carries upwards of 80% the plasma pressure in the outer heliosphere [Richardson et al., 2008]. The Interstellar Boundary Explorer (IBEX) global energetic neutral atom (ENA) maps of the interstellar-heliosphere interaction show temporal variation in the interaction region upwards of 15% in ENA emission over a time scale of < 6 months. The short time scale and magnitude of the variation implies that the origin of this variation comes from the solar system plasma, which has considerable solar cycle variation, and likely not from variability in the interstellar medium. The dynamic properties of the pressure dominant pick-up ions are a likely candidate for this temporal variation. We ask, how does the pick-up ion pressure vary through the heliosheath, spatially and temporally? In previous 3-dimensional magnetohydrodynamic (MHD) simulations of the outer heliosphere, a single plasma fluid was used to describe the behavior of the solar wind plasma and the pick-up ions. For simulating ENA maps, the single plasma fluid was assumed to have a kappa distribution, describing the thermal core of solar wind plasma and the suprathermal tail of pick-up ions [Prested et al., 2008]. These simulations captured the global structure of the heliosphere but lost information on how the pick-up ion population and the pressure it carries evolve through the ISM-heliosphere interaction region. This information is vital for understanding the energy-dependent temporal and spatial variations observed in the IBEX global maps. We have extended our previous 3-d MHD multifluid model [Opher et al., 2009] to include the solar wind and pick-up ions as 2 separate ion fluids [i.e. Glocer et al., 2009 ], in addition to treating 4 separate neutral populations. Additionally, we introduce temporal variation by simulating the global heliosphere with solar-minimum and solar-maximum solar wind conditions. We quantify how the pick-up ion pressure varies through the heliosheath under these conditions and validate our results through comparison with the Voyager 1 and 2 heliosheath measurements. From our analysis of the two extreme solar wind cases, we conclude whether or not variation in pick-up ion pressure could be responsible for the 6-month, large scale variation seen in the IBEX global maps.
Opher Merav
Prested C. L.
Schwadron Nathan A.
Tóth Géza
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