Magnetic fields and energetic particles near the boundary of the solar system

V. Florinski

University of Alabama in Huntsville

The Sun and its system of planets are immersed in a giant gaseous bubble called the heliosphere. The surface of the bubble, known as the heliopause, separates the solar-wind plasma from the local interstellar medium (LISM). NASA's Voyager 1 left the heliosphere in 2012 and there is evidence that Voyager 2 will do so within a few months. Voyager 1 observations revealed that interstellar space is much less turbulent that the solar wind, creating conditions for nearly scatter free propagation of energetic charged particles. The LISM is not completely quiet, however, because the motion of the heliopause in response to incident solar-wind structures, such as merged interaction regions, injects weak waves and fluctuations into the very local interstellar medium where they continue to propagate through the subsonic partially ionized plasma. The width of these shock-like structures is four orders of magnitude larger than the plasma kinetic scales unlike the familiar narrow shock waves encountered throughout the heliosphere. It is possible that the shocks in the LISM are mediated by ion-ion Coulomb collisions that are relatively frequent owing to low plasma temperature. Galactic cosmic rays, while remarkably steady most of the time in the LISM, showed episodic depletions at the 90 degree pitch angle that are still poorly understood. The heliospheric energetic particles, including the anomalous cosmic rays and accelerated pickup ions, have disappeared shortly after crossing the heliopause. Nonetheless, a fraction of the heliospheric ions was evidently able to overcome the magnetic shear at the heliopause and escape into interstellar space. These ions' contribution to the overall pressure balance at the heliopause can be questioned, on account of the extremely large mean free path in the interstellar medium where the level of magnetic fluctuations is exceptionally low. I will review the energetic particle and magnetic field phenomena in the heliopause transition and beyond and discuss their possible theoretical interpretations.


About the author

Vladimir Florinski has graduated from the University of Arizona in 2001 with a PhD degree in Planetary Science. He spent the next seven year as a postdoctoral and later professional researcher at the University of California, Riverside. In 2008 he accepted a faculty position at the University of Alabama in Huntsville, where he is currently employed at the rank of an Associate Professor. Florinski's areas of expertise include plasma physics of the solar wind, heliosheath, and the local interstellar medium, transport of galactic cosmic rays in turbulent space plasmas, cosmic-ray modulation, the origin and acceleration mechanisms of anomalous cosmic rays, energetic charged particle acceleration by astrophysical shocks, shock mediation by cosmic rays, and high-performance computing. He frequently collaborates with NASA's Voyager and IBEX mission scientists and uses data from these and other NASA space missions. He is an author of 100 publications, including 51 peer reviewed journal articles.