Objective
It is proposed to join the efforts of seven teams who are dealing with theory and experiments in plasma and particle physics of the heliosphere and its boundary to the Local Interstellar Cloud. Based on previous models of the global structure of the heliosphere, it is suggested to construct a new multi-component kinetic model of the solar wind with partitioning of energy between its components in order to predict the structure and properties of the plasma and the neutral gas flow that will be observed, when the Voyager spacecraft passes the solar wind termination shock and enters the heliosheath region. Currently accessible observational constraints on the plasma flow at the solar wind termination shock and in the heliosheath are intended to be compared to numerical simulations developed in the frame of the proposed project.
New observations have motivated the interest in this study:
- new data on the fluxes of energetic neutral atoms (ENAs) originating in the heliospheric interface region have become available from the SOHO mission for the time period of solar activity maximum;
- new data on the heliospheric interface absorption as a function of heliolongitude have become available from the HST mission;
- new data on the energy spectra of the anomalous component of cosmic rays (ACRs) with unprecedented precision have become available from the ACE mission; the interpretation of these data requires refined models for the acceleration of the ACRs at the termination shock and their transport in the heliosphere;
- the Voyager spacecraft may soon reach the solar wind termination shock and continuously transmit new data, which are believed to give information on the solar wind plasma in vicinity to the termination shock.
It is planned to solve the following tasks:
- to theoretically model the heliosheath plasma properties based on the global models of the heliospheric interface with different energy partitioning between the three solar wind components: solar wind protons, pickup ions, and electrons;
- to study in detail the pickup ion transport and acceleration through the heliosphere;
- to model the termination shock structure;
- to model the effects of the solar activity cycle on the termination shock and the heliosheath plasma;
- to model the structure of the heliotail, the downwind region of the heliospheric interface;
- to model the effects of the heliospheric (interplanetary) and interstellar magnetic field on the structure of the termination shock and on the distribution functions of the heliosheath plasma components;
- to interpret the pickup ion spectra observed in the heliosphere by spacecraft instruments in the frame of models on pre-acceleration, injection, and acceleration in the solar wind and at interplanetary shocks;
- to theoretically calculate fluxes of accelerated pickup ions between the termination shock and the heliopause in order to predict fluxes of energetic neutral atoms created by charge exchange with interstellar atoms in the heliosheath;
- to use SWAN/SOHO backscattered Lyman-alpha observations in order to constrain fluxes of hot hydrogen atoms created in the heliosheath;
- to interpret data of the Voyager cosmic ray instrument on ACR spectra and spatial distributions in order to obtain information on the solar wind turbulence and on the location and the strength of the termination shock;
- to interpret Voyager plasma instrument observations in order to estimate the deceleration and heating of the distant solar wind, and therefore the strength of its interaction with the interstellar gas and the thermodynamic coupling strength of the solar wind protons with the pickup protons;
- To evaluate in detail the interstellar absorptions toward nearby stars to constrain the absorption in the heliospheric interface.
As a result of the proposed study it is expected to have a quantitative model of the plasma and neutral gas flow in the heliosheath, the region beyond the solar wind termination shock extending out to the heliopause, and to have detailed knowledge on the structure, shape, and location of the termination shock in accordance with the newest spacecraft data.
Call for proposal
Data not availableFunding Scheme
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3012 Bern
Switzerland