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Magnetic fields at the solar wind termination shock


A transition between the supersonic solar wind and the subsonic heliosheath was observed by Voyager 1, but the expected termination shock was not seen owing to a gap in the telemetry1,2,3,4. Here we report observations of the magnetic field structure and dynamics of the termination shock, made by Voyager 2 on 31 August–1 September 2007 at a distance of 83.7 au from the Sun (1 au is the Earth–Sun distance). A single crossing of the shock was expected, with a boundary that was stable on a timescale of several days. But the data reveal a complex, rippled, quasi-perpendicular supercritical magnetohydrodynamic shock of moderate strength undergoing reformation on a scale of a few hours. The observed structure suggests the importance of ionized interstellar atoms (‘pickup protons’) at the shock.

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Figure 1: Three crossings of the termination shock, illustrating reformation and the variability of its structure.
Figure 2: TS-3 is a supercritical quasi-perpendicular shock.
Figure 3: The internal structure of the ramp of TS-3.

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We thank T. McClanahan and S. Kramer for support in the processing of the data. We also thank D. Berdischevsky for computing the instrument zero level corrections for the data in this paper, and for helping to solve the problems created by the erroneous decoding of a spacecraft systems command sent to Voyager 2 in 2006. N.F.N. was partially supported by a NASA grant to CUA.

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Correspondence to L. F. Burlaga.

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Burlaga, L., Ness, N., Acuña, M. et al. Magnetic fields at the solar wind termination shock. Nature 454, 75–77 (2008).

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