Contours of the solar wind velocity at the Edge of the Solar System AFTER the Termination Shock (blue color). The interstellar wind
is flowing from the left to the right.
Click at the figure for an animation (mpg)
The Voyager spacecraft is now approaching the
edge of the solar system. Near the boundary
between the solar system and the interstellar
medium we find that an unstable "jet-sheet" forms. The
jet-sheet oscillates up and down because of
a velocity shear instability. This result is due to a novel
application of a state-of-the-art three-dimensional
MHD code with a highly refined grid. We assume
as a first approximation that the solar magnetic
and rotation axes are aligned. The effect of a tilt of
the magnetic axis with respect to the rotation
axis remains to be seen. We include in the model
self-consistently magnetic field effects in
the interaction between the solar and interstellar winds.
Previous studies of this interaction had poorer
spatial resolution and did not include the solar
magnetic field. This instability can affect
the entry of energetic particles into the solar system and
the intermixing of solar and interstellar
material. The same effect found here is predicted for the
interaction of rotating magnetized stars possessing
supersonic winds and moving with respect to
the interstellar medium, such as O stars.
(for more details see the article "Probing the
Edge of the Solar System: Formation of an Unstable Jet-Sheet", by Opher
et al. Astrophysical Journal Letters, 591, 61-65 (2003)).
Contours of the solar wind velocity at the Edge
of the Solar System AFTER the Termination Shock (blue color). The
interstellar wind
is flowing from the left to the right.
Click at the figure for an animation (mpg)
Time evolution of the current sheet instability;
contours of the magnetic field between the Termination Shock and Heliopause
(scale
ranging from 0 to 0.3 nT). The nine panels
shown correspond to t = 39.2, 71.8, 89.8, 114.8, 200.0, 258.4,
278.5, 349.0, and 464.0 yr (left to right,
top to bottom). The current sheet is bent to the south and subsequently
to the north.
Click at the figure for an animation
(mpg)
For a more General View of the Instability:
Science Editor's Choice,Science
Vol 300, page 2005 (2003)
To
an Instability and Beyond