Physics
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufmsh52a..02p&link_type=abstract
American Geophysical Union, Fall Meeting 2006, abstract #SH52A-02
Physics
2124 Heliopause And Solar Wind Termination, 2126 Heliosphere/Interstellar Medium Interactions, 2134 Interplanetary Magnetic Fields, 4455 Nonlinear Waves, Shock Waves, Solitons (0689, 2487, 3280, 3285, 4275, 6934, 7851
Scientific paper
With Voyager 1 (V1) crossing the termination shock in the autumn of 2004 and Voyager 2's (V2's) crossing imminent, the opportunity of adjusting modeling parameters to observational data and further deriving important information about fundamental processes occurring in the heliosheath is of great importance. There are strong indications that interstellar magnetic field (ISMF) is responsible for several important phenomena related to the Voyager observations: (i) the ISMF strength and direction can be related to the distribution of the 2-3 kHz radio emission sources which are believed to originate ahead of the heliopause that separates the solar wind from the LISM; (ii) nonalignment of the interplanetary magnetic field (IMF) with the termination shock (TS) surface can result in transverse streaming anisotropies of energetic charged particles observed by V1 at 92~AU in cases when the ISMF component parallel to the ecliptic plane makes the TS east-to-west asymmetric. This could have happened if V1 was connected to an IMF line re-entering the supersonic solar wind region after previous penetration into the heliosheath; (iii) V2, which is now at about 79 AU from the Sun, and moving in the southern hemisphere at approximately the same angle to the ecliptic plane as V1 in the northern hemisphere, has already started measuring similar anisotropies. This suggests that termination shock distances to the Sun in the V1 and V2 directions should differ by about 7-10 AU; (iv) all ISMF-induced asymmetries are readily seen on the energetic neutral particle all-sky maps. We show that asymmetries of the termination shock due to the ISMF influence are considerably smaller in the presence of neutral hydrogen atoms, which "symmetrize" the heliopause, the termination shock, and the bow shock due to charge exchange with plasma particles. This leads to a much stronger restriction on the ISMF direction and its strength. We demonstrate that the plane defined by the LISM velocity and magnetic field vectors does not necessarily coincide with the plane defined by the interstellar neutral helium and hydrogen velocity vectors in the supersonic solar wind region, which makes it difficult to predict the ISMF angle with respect to the ecliptic plane. We take into account the tilt of the LISM velocity vector to the ecliptic plane, non-alignment between the Sun's rotation and magnetic axes, and cycle-related asymmetries of the SW to show that, for the realistic neutral hydrogen density in the LISM and suitable ISMF orientations, magnetic fields much higher than commonly expected may be necessary to acquire the desired TS asymmetry. We use our 3D modeling results to analyze the width of the region where IMF lines in the heliosheath connect to the Archimedean spiral inside the TS, and derive some estimates for unrolling ACR spectra. We also quantitatively estimate the strength of the TS east-west asymmetry that would be able to conform with the Voyager data.
Florinski Vladimir
Pogorelov Nikolai V.
Stone Edward C.
Zank Gary P.
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