SH52B-04
Interstellar neutral flow characteristics, composition, and interaction with the heliosphere – neutral gas and pickup ion analysis from ongoing observations and perspectives for IMAP
Friday, 18 December 2015: 12:08
2009 (Moscone West)
Eberhard Moebius1, Maciej Bzowski2, Christian Drews3, Priscilla C Frisch4, Stephen A Fuselier5, Andre Galli6, George Gloeckler7, Marzena A. Kubiak8, Harald Kucharek9, Martin A Lee10, Trevor Leonard9, David J McComas5, Jeewoo Park9, Nathan Schwadron11, Pawel Swaczyna2, Justyna M Sokol2, Brian E. Wood12 and Peter Wurz6, (1)University of New Hampshire, Institute for the Study of Earth, Oceans and Space, and Department of Physics, Durham, NH, United States, (2)Space Research Center Polish Academy of Sciences, Warszawa, Poland, (3)University of Kiel, Kiel, Germany, (4)University of Chicago, Chicago, IL, United States, (5)Southwest Research Institute, San Antonio, TX, United States, (6)University of Bern, Bern, Switzerland, (7)University of Michigan Ann Arbor, Ann Arbor, MI, United States, (8)Space Research Center Polish Academy of Sciences, Warsaw, Poland, (9)University of New Hampshire Main Campus, Durham, NH, United States, (10)Univ of New Hampshire, Durham, NH, United States, (11)University of New Hampshire Main Campus, Space Science Center, Durham, NH, United States, (12)US Naval Research Laboratory, Washington, DC, United States
Abstract:
The Sun’s motion relative to the surrounding interstellar medium leads to an interstellar neutral (ISN) wind through the heliosphere that is moderately depleted by ionization. This situation allows remote sensing of the ISN through resonant scattering of solar UV and in-situ sampling, first via pickup ions (PUI) and most recently with direct neutral atom imaging. PUI observations have revealed the gravitational focusing cone of interstellar He and Ne as well as the composition of high ionization potential elements. After the first direct ISN He observations with Ulysses GAS, the Interstellar Boundary Explorer (IBEX) observes with high collecting power the ISN flow trajectories very close to their perihelion in Earth’s orbit for H, He, O, and Ne from December through March. Meanwhile, IBEX has recorded seven years of ISN observations, with changing solar activity and varying viewing strategies. These recurring and remarkably repeatable observations allow us to consolidate the derived physical parameters and some key compositional aspects of the interstellar medium. IBEX observations provide a very precise relation between ISN flow longitude and speed via the hyperbolic trajectory equation, but with larger uncertainties separately for longitude and speed. Recent concerted studies have led to a velocity vector that is consistent between IBEX and Ulysses, with a substantially higher temperature than found previously. The fact that the IBEX He and O ISN observations contain a substantial secondary neutral contribution adds complexity to the quantitative analysis of the physical interstellar medium parameters. However, their discovery also provides invaluable insight into the interstellar plasma interaction in the outer heliosheath, which is shaped strongly by the interstellar magnetic field. The longitude range of the IBEX observations limits the precision of the ISN velocity vector. The IBEX collection power and its sensitivity to the Earth’s magnetosphere limit composition and secondary component observations. So far, PUIs have only been observed with sensors that were not optimized for interstellar PUIs. The Interstellar Mapping and Acceleration Probe (IMAP) to be placed at L1 will take these observations to the next level with more powerful sensors.
