University of Maryland
Atlantic Building, Room 2400 4:30 PM Monday, March 28, 2016
Coffee, Tea & Snacks 4:15-4:30 PM

James Drake
University of Maryland

A Heliosphere with Jets

The conventional picture of the heliosphere is that of a comet-shaped structure with an extended tail produced by the relative motion of the sun through the local interstellar medium (LISM). Recent MHD simulations of the global heliosphere have revealed, however, that the heliosphere drives magnetized jets to the north and south similar to those driven by the Crab Nebula and other astrophysical objects [1]. That the sun's magnetic field can drive such jets when the magnetic pressure in the outer heliosphere is small compared with the local plasma pressure (β = 8πP/B2 ≫ 1) is a major surprise. An analytic model of the heliosheath (HS) between the termination shock (TS) and the heliopause (HP) is developed in the limit in which the interstellar flow and magnetic field are neglected [2]. The heliosphere in this limit is axisymmetric and the overall structure of the HS and HP are controlled by the solar magnetic field even in the limit of very high β. The tension of the solar magnetic field produces a drop in the total pressure between the TS and the HP. This same pressure drop accelerates the plasma flow downstream of the TS into the north and south directions to form two collimated jets. The radii of these jets are controlled by the flow through the TS and the acceleration of this flow by the magnetic field -- a stronger solar magnetic field boosts the velocity of the jets and reduces the radii of the jets and the HP. Magnetohydrodynamic (MHD) simulations of the global heliosphere embedded in a stationary interstellar medium match well with the analytic model. Evidence from the distribution of energetic neutral atoms from the outer heliosphere from IBEX and CASSINI supports the picture of a heliosphere with jets.
[1] Opher et al ApJ Lett. 800, L28, 2015.
[2] Drake et al ApJ Lett., in press, 2015.