Title

Excitation of low-frequency waves in the solar wind by newborn interstellar pickup ions H(+) and He(+) as seen by Voyager at 4.5 AU

Abstract

We report the observation of a spectral enhancement in the magnetic field fluctuations measured by the MAG instrument on the Voyager 2 spacecraft during 4.5 hr on DOY 7, 1979 at a heliocentric radial position of 4.5 AU. This time period is contained within a solar wind rarefaction when the large-scale interplanetary magnetic field was nearly radial. The frequency range and polarization of the enhanced fluctuations are consistent with waves generated by newly ionized interstellar H(+) and He(+). We show sunward propagation of the waves via a cross-helicity analysis. We compare the observation with a theoretical model and find reasonable agreement given the model assumptions. This event is the first indication of pickup ion-generated waves seen at Voyager. It is also the first identification of pickup He(+) waves by any spacecraft.

Publication Date

12-1-2010

Journal Title

Astrophysical Journal

Publisher

IOP PUBLISHING LTD

Digital Object Identifier (DOI)

10.1088/0004-637X/724/2/1256

Document Type

Article

Rights

© 2010. The American Astronomical Society. All rights reserved.