future events

The New Heliosphere

Speaker:Prof. Merav Opher
Affiliation:Boston University
Location:Lidow Rosen Auditorium (323)

As the Sun moves through the interstellar medium it carves a bubble
called the heliosphere. A fortunate confluence of missions has
provided a treasury of data that will likely not be repeated for
decades The measurements in-situ by the Voyager spacecrafts, combined
with the all-sky images of the heliospheric boundaries by the
Interstellar Boundary Explorer mission have transformed our
understanding of heliosphere. In particular one of the first surprises
was that both Voyager spacecrafts found no evidence for the
acceleration of the anomalous cosmic rays (ACRs) at the termination
shock as expected for approximately 25 years. Another challenge are
the energetically particles intensities and the plasma flows that are
dramatically different at Voyager 1 and 2. There are several other
observations that are key challenges to the heliospheric models such
as a) Why the azimuthal magnetic flux is not conserved along the
Voyager 1 trajectory? b) What causes the flow stagnation region seen
at Voyager 1? c) What causes the unexpected observation of a
depletion-region beginning in 2012 at Voyager 1? These observations
point to the need to move past the standard description of the
heliosphere. In this talk I will review the state-of-the art of our
understanding of this “new heliosphere”. I will review our model that
proposes that collisionless reconnection is happening within the
sector region (the region where the solar magnetic field reverses
polarity) and can explain the different observational puzzles. I will
review our model as well as describe its consequences for the
transport, acceleration of particles as well as for the flows and
fields in the heliosheath. Finally, recent observations indicate a
magnetic connectivity between the heliosheath magnetic field and the
interstellar medium magnetic field; where the energetic particles of
the heliosheath leaked out while the galactic cosmic rays penetrated
the heliosheath. I will comment on our current effort of understanding
the nature of the heliopause. We argue that these observations can be
explained by Voyager 1 being in the last layer of the heliosheath
where the heliosheath magnetic field reconnect with the interstellar
magnetic field, what we call the “porus heliosheath”. The knowledge
gain from the edge of the heliosphere will have consequences for other
astrospheres and astrosheaths where the magnetic nature of the winds
could be much more complex that previously thought.