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 telemetry. 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.
Burlaga
L F
LF
NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771, USA. Leonard.F.Burlaga@nasa.gov
Ness
N F
NF
Acuña
M H
MH
Lepping
R P
RP
Connerney
J E P
JE
Richardson
J D
JD