The Voyager 1 spacecraft is currently in the vicinity of the heliopause, which separates the heliosphere from the local interstellar medium. There has been a precipitous decrease in particles accelerated in the heliosphere, and a substantial increase in galactic cosmic rays (GCRs), suggesting easy escape of the former across the heliopause, and entry of the latter. The question is, has Voyager?1 actually crossed the heliopause and is it now in the interstellar medium??We contend that the evidence is inconclusive. The direction of the magnetic field observed by Voyager?1 is unchanged from the direction of the heliospheric magnetic field, and different from the expected direction of the interstellar magnetic field. However, the plasma density, which is measured from observations of plasma waves, is similar to the expected interstellar density and much larger than the solar wind plasma density observed by Voyager?2 (which has a working plasma detector) at smaller heliocentric distances than Voyager?1. In this paper, an analytic model is presented that is based upon and is consistent with all Voyager observations, and in which the higher plasma densities measured by Voyager?1 are due simply to compressed solar wind. Thus both the magnetic field and the plasma density observations are consistent with Voyager?1 still remaining well within the heliosheath. The model has a simple test: Voyager?1 should encounter a magnetic sector boundary crossing, where the behavior of particles accelerated in the heliosphere and the GCRs will be different from what Voyager?1 is now observing.
展开▼
