Exploring the Edge of the Solar System: The nature of the Heliosheath and Heliopause

The measurements in-situ by the Voyager spacecrafts, combined with the all-sky images of the heliospheric boundaries by the Interstellar Boundary Explorer (IBEX) mission, have radically transformed our knowledge of the boundaries of the heliosphere (the bubble formed by the solar wind).  Concepts that resisted decades are being revisited due to these puzzling measurements. In particular, one of the surprises was that both Voyagers found no evidence for the acceleration of the anomalous cosmic rays at the TS as expected for approximately 25 years. This has consequences on understanding how efficient shocks are on accelerating particles or if there are other competing mechanisms, e.g., in sheaths. Another challenge are the energetic particle intensities and flows that are dramatically different at Voyager 1 and 2.  More recently, observations of Voyager 1 indicate that the spacecraft is magnetically connected to the interstellar medium while being inside the heliosheath. In this talk I will review the state-of-the art of our understanding of the global heliosphere as our effort on understanding the nature of the heliosheath and heliopause. In particular, I will review our recent work that proposes that reconnection is happening in the heliosheath within the sector region (the region where the solar magnetic field reverses polarity) and its consequences for the nature of the heliosheath, affecting both the flows and transport of energetic particles.  I will comment as well on our current effort to understand the nature of the heliopause, indicating that this boundary is porous with multi-layered structure that is threaded by complex magnetic fields. These discoveries have consequences beyond the solar system as they charter our understanding of how stars interact with the surrounding media.

http://people.bu.edu/mopher/