Authors: W. S. Kurth (University of Iowa), L. F. Burlaga (Leonard F. Burlaga, Inc.)
The two Voyager spacecraft are nearing completion of their 47th years in flight. While there have been great challenges along the way, each continues to make pathfinding measurements beyond the heliopause in the very local interstellar medium (VLISM). This presentation will be devoted primarily to Voyager 1 observations of electron densities and magnetic field intensities measured to beyond 165 AU although there will be some references to Voyager 2 observations. Both the electron density and magnetic field strength have remained at nearly their highest values since crossing the heliopause in 2012 near 120 AU. The electron density has hovered near 0.15 cm^-3 and the magnetic field magnitude near 0.5 nT since an event known as ‘pressure front 2’ (pf2) occurred in early 2020 near 149 AU. Prior to pf2, the electron densities showed evidence of a radial density gradient starting near 0.04 cm^-3. The general rise in density was punctuated, at times, by shocks and one other pressure front, hence, the density trend was not smooth. The magnetic field, on the other hand, fluctuated between about 0.4 and 0.6 nT with abrupt jumps at two shocks and two pressure fronts. Where both could be measured, the relative jumps in the field and density were identical. For all but pf2, the jumps in the magnetic field were followed by ramps of decreasing intensity. The extended stay at high field strength and high density since pressure front 2 has raised questions about whether pf2 was due to solar transients or a solar cycle effect; or whether the spacecraft had entered a new regime in the VLISM. Both the field and plasma density in the 40+ AU beyond the heliopause provide the backdrop for examining the dynamics and processes occurring in the VLISM.