Hj. Fahr et D. Ruciniski, Neutral interstellar gas atoms reducing the solar wind Mach number and fractionally neutralizing the solar wind, ASTRON ASTR, 350(3), 1999, pp. 1071-1078
Many stars are known to drive stellar winds of the solar wind type. Thus wh
en moving through the ambient interstellar medium these stars not simply io
nize this medium but also interact as moving stellar wind systems. Only neu
tral interstellar gas components can directly enter the inner stellar wind
region and there undergo charge exchange reactions with the supersonic stel
lar wind protons. Thereby the dynamical identities of plasma and gas compon
ents are partially exchanged. The net effect is that energy is extracted fr
om the wind plasma and transferred to newly created energetic neutral atoms
(ENA) transporting the former wind energy over large distances into the di
stant interstellar medium. As example for stellar wind systems in general,
in the following we study quantitatively the effect of a loading of the ini
tial solar wind plasma with transcharged neutral atoms connected with the i
ncorporation of suprathermal pick-up ions and an associated reduction of th
e effective solar wind sonic Mach number. In addition the removal of kineti
c solar wind energy by neutralized solar wind protons leads to a nonclassic
al reduction of the solar wind ram pressure and thereby a reduction of the
location of the heliospheric termination shock. Our results indicate that a
substantial percentage of the original solar wind energy is converted into
a global flow of energetic neutral atoms and that the effective solar wind
Mach numbers in the outer heliosphere are drastically reduced if presently
quoted neutral H-atom densities in the outer heliosphere of 0.1 less than
or equal to n(H infinity) less than or equal to 0.3 [cm(-3)] are in fact pr
evailing.