Research Note

Uncovering the magnetic environment of our solar system

¹ UPMC Univ Paris 06, UMR7095, Institut d’Astrophysique de Paris, 75014 Paris, France
e-mail: bjaffel@iap.fr
² CNRS, UMR7095, Institut d’Astrophysique de Paris, 75014 Paris, France
³ Institute of Aviation, Warsaw, Poland
⁴ Space Research Center, Polish Academy of Sciences, Warsaw, Poland
e-mail: roma@cbk.waw.pl

Received: 21 May 2012
Accepted: 11 August 2012

Abstract

Since its formation 4.6 billion years ago, our solar system has most likely crossed numerous magnetized interstellar clouds and bubbles of different sizes and contents on its path through the Milky Way. Having a reference model for how the heliosphere and interstellar winds interact is critical for understanding our current Galactic environment, and it requires untangling the roles of two major actors: the time-variable solar wind and the local interstellar magnetic field. Numerical simulations predict a distortion of the heliosphere caused by both solar wind anisotropy and interstellar magnetic field orientation. However, model comparison to deep space probes’ measurements led to contradictory reports by Voyager 1 and Voyager 2 of both several crossings of the solar wind’s termination shock and of the strength of the local interstellar field, with values ranging from 1.8 to 5.7 μG. Here, we show that Voyager 1 and 2 plasma, fields, and Lyman-α sky background measurements, as well as space observations of high-energy particles of heliospheric origin, may all be explained by a rather weak interstellar field 2.2 ± 0.1   μG pointing from Galactic coordinates (l,b) ~ (28,52) ± 3°. For the 2000 epoch Ulysses-based helium parameters assumed thus far, the interstellar bow shock must exist. By contrast, using the 2010 epoch IBEX-based He parameters and a stronger magnetic field leads to a plasma configuration that is not consistent with the Voyagers TS crossings. For the newly proposed interstellar He parameters, more simulations are required before one may determine whether the interstellar bow shock truly does disappear under those assumptions.