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A Foreshock Model for Interstellar Shocks of Solar Origin: Voyager 1 and 2 Observations

Gurnett, D. A. and Kurth, W. S. and Stone, E. C. and Cummings, A. C. and Heikkila, B. and Lal, N. and Krimigis, S. M. and Decker, R. B. and Ness, N. F. and Burlaga, L. F. (2021) A Foreshock Model for Interstellar Shocks of Solar Origin: Voyager 1 and 2 Observations. Astronomical Journal, 161 (1). Art. No. 11. ISSN 1538-3881. doi:10.3847/1538-3881/abc337.

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The Voyager 1 (V1) and Voyager 2 (V2) spacecraft were launched in 1977 on a mission to explore the outer planets and reach the heliopause, the boundary between the hot solar plasma and the relatively cool interstellar plasma. V1 reached the heliopause on 2012 August 25, at 121.6 au, and V2 reached the heliopause on 2018 November 5, at 119.0 au. One of their remarkable discoveries was the detection of shocks propagating into the interstellar plasma from energetic solar events. These shocks are typically preceded by electron plasma oscillations excited by electron beams streaming along interstellar magnetic field lines ahead of the shocks. The frequencies of the plasma oscillations have now provided radial electron density profiles in the outer heliosphere and in the interstellar medium to radial distances of more than 145 au. The oscillations are typically preceded by bursts of high-energy ~5–100 MeV electrons. These electron bursts are interpreted as being due to the reflection (and acceleration) of cosmic-ray electrons by the shock at the time the shock first contacts the magnetic field line that passes through the spacecraft. Relative timing between the cosmic rays reflected by the shock and the onset of the plasma oscillations allow us, for the first time, to estimate the energy, ~20–100 eV, of the electron beams responsible for the plasma oscillations. These observations are combined into a self-consistent model called the foreshock model that describes the interaction of shocks of solar origin with the interstellar plasma.

Item Type:Article
Related URLs:
URLURL TypeDescription
Gurnett, D. A.0000-0003-2403-0282
Kurth, W. S.0000-0002-5471-6202
Stone, E. C.0000-0002-2010-5462
Cummings, A. C.0000-0002-3840-7696
Krimigis, S. M.0000-0003-2781-2386
Burlaga, L. F.0000-0002-5569-1553
Additional Information:© 2020. The American Astronomical Society. Received 2020 August 31; revised 2020 October 19; accepted 2020 October 19; published 2020 December 3. The research at the University of Iowa was supported by NASA through Contract 1622510 with the Jet Propulsion Laboratory. The research at Caltech was supported by NASA award NNN12AA01C, and the research at the Johns Hopkins Applied Physics Laboratory was supported by the Voyager Interstellar Mission under NASA contract NNN06AA01C. The research at Goddard Spaceflight Center was supported by NASA contract 80GSFC19C0012. The Voyager PWS data are regularly archived with the Planetary Data System at
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Subject Keywords:Interstellar medium
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Interstellar medium (847)
Record Number:CaltechAUTHORS:20201204-110355753
Persistent URL:
Official Citation:D. A. Gurnett et al 2021 AJ 161 11
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106909
Deposited By: George Porter
Deposited On:05 Dec 2020 00:28
Last Modified:16 Nov 2021 18:57

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