RESEARCH PROGRAMME

We propose to incorporate a series of physical effects not yet taken into account in our axisymmetric model of the
interaction of the solar wind with the local interstellar medium [1,2,3]. We plan to do this step by step; at each step
the results of the improved model will be compared to the observational data previously or currently gathered from
space experiments.

Two phases of the development are foreseen.

A) First phase

As a first step the existing 2D steady-state self-consistent model will be computed for a wide range of the less
constrained LIC parameters (electron density, H atom density, temperature). The resulting predictions regarding
interstellar atoms entering the heliosphere will be compared to the observations (see I.1 in the detailed description
below). With highest priority the new SWAN (SOHO) and Voyager Lyman-alpha data and the SWICS (Ulysses)
pick-up ion measurements (I.4 and I.5 respectively) will be interpreted. Both experiments are expected to continue
providing a steady flow of data for the next years. The resulting optimal LIC parameters will then be used as input
for the subsequent studies on the influence of the new phenomena on the shape of the heliosphere and on their
impact on the flow structure. For each newly included physical effect the needed corresponding corrections of the
LIC parameters will be estimated. This theoretical study can be structured as follows:

the calculation of pick-up ion energy spectra ( I.2);
the calculation of energetic neutral atom fluxes (I.3);
the development of a heliospheric interface model including the influence of the anomalous cosmic rays in the vicinity of the termination shock (I.8);
the development of a 3D Magnetohydrodynamic (MHD) code (I.7);
the development of a time-dependent model of the interface (I.6, II.1)

The last task (time-dependence) is of particular importance in the theoretical part of our proposal. TheMonte-Carlo methods which have been used until now for the interstellar flow are stationary and can not be
modified easily to introduce temporal evolution. However, a new mathematical technique developed by the
Novosibirsk team provides the possibility to find a time-dependent solution of the Boltzmann equation which
governs the evolution of the flows. The creation of the time-dependent model will take more time than the other
tasks and therefore will be continued during the second phase of the work proposed (I.6, II.1)
At the end of the first period of the study we expect to be able to present:

preliminary optimal values of LIC parameters ;
new sets of data from the spacecrafts with a larger spatial coverage and a better precision;
a better understanding of the processes that must be included in the model to improve its agreement with data of different types.

B) Second phase

    One of the main objectives of the second phase of the study is to combine the different improvements from the first phase in order to develop a 3D time-dependent model simultaneously taking into account the interstellar neutral atoms, the plasma, the magnetic field, and the anomalous and galactic cosmic rays.
    After the creation of this full heliospheric interface model we plan to perform a new parametric study and to
reanalyze the SWAN/SOHO, SWICS/Ulysses and Voyager data (II.3). At this stage, we hope to have reached a
conclusive theoretical model that will reproduce all the different experimental data. We also will determine the
best values for the interstellar parameters, i.e. the interstellar proton number density and the intensity and
direction of the interstellar magnetic field.
    The proposed program requires a close co-operation between the participants of this proposal. We are planning to organize at least two meetings of all participants at the International Space Science Institute in Bern, one at the
end of the first phase, and one during the final phase. ISSI will provide support for these meetings by funding the
daily allowances of the team members while staying in Bern, by offering conference rooms and well equipped
offices and of course by scientific input.