摘要:

In this paper we have used a kinetic model of the flow of interstellar atoms with updated values of velocity, temperature and density of the circumsolar interstellar cloud, and calculated how quantities which are directly associated to the observations vary as a function of the interstellar proton number densitynp,LIC.These quantities are the degree of filtration, the temperature and the velocity of the interstellar H-atoms in the inner heliosphere, the distances to the bow shock (BS), heliopause (HP) and termination shock (TS), and the plasma frequencies in the LIC, at the BS and in the maximum compression region around the heliosphere which constitutes the “barrier” for radio waves formed in the interstellar medium. Comparing the model results with pick up ion data,Ly–&agr;measurements, and low-frequencies radio emissions, we have searched for a number density of protons in the LIC compartible with all observations. We find it difficult in the frame of this model without interstellar magnetic field to reconcile the distance to the shock and the heliopause deduced from time-delay of the radio emissions with other diagnostics and discuss possible explanations for these discrepancies. We also conclude that, on the basis of this model, the most likely value for the proton density in the LIC is in the range0.04&hthinsp;cm−3<np,LIC<0.07&hthinsp;cm−3.©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58828

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

The latitudinal distribution of the solar wind is one of the main themes in solar wind research. This distribution can be studied by in situ measurements (Ulysses) or by remote sensing methods. Measurements of the interplanetary Lyman &agr; radiation make it possible to study remotely the latitudinal distribution of the solar wind mass flux. The SWAN instrument on board SOHO has continuously measured Lyman &agr; all sky maps since the beginning of 1996. A preliminary analysis of the Lyman &agr; maps measured in 1996 showed that the solar wind mass flux distribution seems to be nearly flat for all solar latitudes outside the equatorial region from −20° to 20°. In this central region the mass flux shows a prominent increase. This result is very similar to the one obtained from the Lyman &agr; measurements by the Prognoz satellites in 1976-77 and to the results from in situ measurements by the Ulysses spacecraft in 1994-95 near solar minimum. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58733

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

It is now reasonably well understood that the interaction of neutral interstellar hydrogen (H) with the heliosphere is highly nonlinear. In particular, neutral H does not stream unimpeded into the heliosphere, experiencing instead considerable “filtration” in the region upstream of the heliopause. This leads to the formation of a hydrogen wall. A recently developed 2D Boltzmann code is used to investigate the entrance of neutral helium, oxygen, carbon, and other heavy species into the heliosphere. The role of filtration for heavy interstellar neutral atoms is described and distribution functions throughout the heliosphere are presented. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58661

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Fluxes of interstellar pickup helium have recently been observed to be strongly anti-correlated with solar wind speed in a manner not explained by the standard picture of local pickup and isotropization. We investigate the possibility that spatial diffusion of these ions between solar wind streams could lead to the observed substantial flux changes. However, we find that such spatial transport produces higher fluxes in fast solar wind, and would yield a dependence which is opposite to that observed. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58734

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

A hydrodynamic plasma simulation of the ionized component of the global heliosphere has been coupled to a nonstationary Boltzmann particle-mesh method which describes the neutral hydrogen present in the same region. This coupling is a numerical model of the physical charge-exchange process through which the two particle species interact. Numerical self-consistency is achieved by iterating the distributions of the two particle species between the two numerical schemes until a steady state is achieved. This approach will contribute to the understanding of the solar wind—LISM interaction. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58662

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

We present results of a global 3D MHD simulation of the interaction of the solar wind with the very local interstellar medium (VLISM). Three different cases are studied: purely hydrodynamic, MHD without charge exchange and MHD with charge exchange with the VLISM neutrals. Latitudinal differences in the solar wind are included as well as the solar cycle dependence of the Interplanetary Magnetic field (IMF). The latitudinal variation in the solar wind causes the polar termination shock at a considerably larger distance than in the ecliptic at the same angle with respect to the VLISM direction. As expected, the presence of magnetic pressure in the VLISM moves the termination shock inward, as does the presence of charge exchange with the neutrals. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58735

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

A 3-D global structure of the outer heliosphere under the interaction of the the solar wind plasma and the interstellar medium is studied by using an MHD simulation. The response of the heliospheric structure to the 11-year solar cycle variations is analyzed in detail. Orbits of galactic cosmic ray protons in the heliosphere are calculated by using this simulation result. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58736

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

The interaction of the heliosphere with interstellar clouds has attracted interest since the late 1920’s, both with a view to explaining apparent quasi-periodic climate “catastrophes” as well as periodic mass extinctions. Until recently, however, models describing the solar wind - local interstellar medium (LISM) interaction self-consistently had not been developed. Here, we describe the results of a two-dimensional (2D) simulation of the interaction between the heliosphere and an interstellar cloud with the same properties as currently, except that theH0density is increased from the current value ofn(H0)∼0.2 cm−3to 10 cm−3. The mutual interaction of interstellar neutral hydrogen and plasma is included. The high density neutral interstellar cloud leads to a considerable reduction in the size of the heliosphere (approximately 9 - 14 AU to the termination shock in the upstream direction) and is highly dynamical. The interplanetary environment at the orbit of the earth changes markedly, with the density of neutral H increasing to ∼2 cm−3. The termination shock forms, disappears, and reforms periodically, and mixing of the shocked/subsonic solar wind and the LISM plasma occurs due to the presence of ion-neutral friction driven instabilities in the vicinity of the heliospheric nose. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.58829

出版商:AIP    

年代:1999

数据来源: AIP