Open AccessBoundary conditions of the heliosphere
Author(s) -
Frisch P. C.
Publication year - 2003
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2003ja009909
Subject(s) - heliosphere , physics , astrophysics , ecliptic , galactic plane , interstellar medium , radiative transfer , stars , astronomy , cosmic ray , milky way , solar wind , magnetic field , galaxy , quantum mechanics
Radiative transfer equilibrium models of nearby interstellar matter (ISM) are required to determine the boundary conditions of the heliosphere from astronomical observations of nearby stars. These models are also constrained by data on the ISM inside of the solar system, including pickup ion, anomalous cosmic rays, and in situ He o data. The two best ISM models give semiempirical filtration factors for H (0.41–0.52), He (0.86–1.16), N (0.74–1.11), O (0.55–0.77), Ne (1.41–2.80), and Ar (0.61–1.76) when observational uncertainties are included. Uncertainties in the Ne filtration factor may result from poorly known interstellar abundances. These models predict the characteristics of the ISM outside of the solar system: n (H o ) = 0.20–0.21 cm −3 , n (e − ) = 0.10 cm −3 , H + /H = 0.29–0.30, and He + /He = 0.47–0.51. However, if the isotropic 2 kHz emission observed by Voyager [ Kurth and Gurnett , 2003] is formed in the surrounding ISM, an alternate model (Model 25) is indicated. The weakly polarized starlight of nearby stars suggests that the local galactic magnetic field is parallel to the galactic plane and the strongest polarization is toward the upstream direction of the ISM flow and also (coincidently) near the ecliptic plane. Observations of nearby ISM, the radiative transfer models, and historical 10 Be records provide information on past variations in the galactic environment of the Sun.