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11.
Spectroscopic observations of the hydrogen Lyα lines from nearby stars taken by the Hubble Space Telescope (HST) sometimes show absorption signatures from the heliosphere. This absorption is a unique diagnostic of material in the outermost parts of our heliosphere. We summarize how the HST data have been used to test various models of the heliosphere, particularly new 3-dimensional MHD models that have recently become available. We also focus on new detections of heliospheric absorption in very downwind directions, which can only be modeled using heliospheric model codes with extended grids in the downwind direction. We illustrate a couple attempts to reproduce this absorption using a couple of these extended tail models. 相似文献
12.
M. Bzowski E. Möbius S. Tarnopolski V. Izmodenov G. Gloeckler 《Space Science Reviews》2009,143(1-4):177-190
We discuss a consolidation of determinations of the density of neutral interstellar H at the nose of the termination shock carried out with the use of various data sets, techniques, and modeling approaches. In particular, we focus on the determination of this density based on observations of H pickup ions on Ulysses during its aphelion passage through the ecliptic plane. We discuss in greater detail a novel method of determination of the density from these measurements and review the results from its application to actual data. The H density at TS derived from this analysis is equal to 0.087±0.022 cm?3, and when all relevant determinations are taken into account, the consolidated density is obtained at 0.09±0.022 cm?3. The density of H in CHISM based on literature values of filtration factor is then calculated at 0.16±0.04 cm?3. 相似文献
13.
V. V. Izmodenov 《Space Science Reviews》2007,130(1-4):377-387
Interstellar atoms penetrate deep into the heliosphere after passing through the heliospheric interface—the region of the
interaction of the solar wind with the interstellar medium. The heliospheric interface serves as a filter for the interstellar
atoms of hydrogen and oxygen, and, to a lesser extent, nitrogen, due to their coupling with interstellar and heliospheric
plasmas by charge exchange and electron impact ionization. The filtration has great importance for the determination of local
interstellar abundances of these elements, which becomes now possible due to measurements of interstellar pickup by Ulysses
and ACE, and anomalous cosmic rays by Voyagers, Ulysses, ACE, SAMPEX and Wind. The filtration of the different elements depends
on the level of their coupling with the plasma in the interaction region. The recent studies of the filtration of the interstellar
atoms in the heliospheric interface region is reviewed in this paper. The dependence of the filtration on the local interstellar
proton and H atom number densities is discussed and the roles of the charge exchange and electron impact ionization on the
filtration are evaluated. The influence of electron temperature in the inner heliosheath on the filtration process is discussed
as well. Using the filtration coefficients obtained from the modeling and SWICS/Ulysses pickup ion measurements, the local
interstellar abundances of the considered elements are determined. 相似文献
14.
A new kinetic model of distribution of interstellar hydrogen atoms in the heliosphere is suggested in this paper. It takes
into account global effects associated with charge exchange of interstellar atoms near the heliospheric boundary. The constructed
model allows one to find efficiently the detailed distribution of hydrogen atoms over space and velocities. For the axisymmetric
steady-state case a comparison is made of the parameters of interstellar hydrogen atoms that were obtained using the classical
hot model, two modifications of the improved hot model, and a global self-consistent kinetic gas-dynamic model of the heliospheric
interface. The results of calculations of the spectral moments of scattered solar Lα radiation are presented. They were derived on the basis of different models of distribution of hydrogen atoms in the heliosphere. 相似文献
15.
Vlad Izmodenov 《Space Science Reviews》2001,97(1-4):385-388
In this paper we present first results of a numerical computation of the velocity distribution function of interstellar H
atoms in the heliospheric interface, the region of the solar and interstellar wind interaction. The velocity distribution
is a key tool to evaluate uncertainties introduced by various simplified models of the interface. We numerically solve the
kinetic equation for gas of H-atoms self-consistently with the hydrodynamic equations for plasma. Neutral and plasma components
are efficiently coupled by charge exchange. The interaction disturbs the atom velocity distribution, which is assumed to be
Maxwellian in the circumsolar local interstellar medium. It is shown that besides ‘original’ interstellar atoms, there are
three other important atom populations originating in the heliospheric interface. Velocity distribution functions of these
populations at the heliopause are presented and discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献