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GEOPHYSICAL RESEARCH LETTERS, VOL. 33, L18102, doi:10.1029/2006GL026732, 2006

Solar control of pre-termination shock energetic particle variations observed at Voyager 1

C. J. Mosley

Fundamental Technologies, LLC, Lawrence, Kansas, USA


T. P. Armstrong

Fundamental Technologies, LLC, Lawrence, Kansas, USA


Abstract

We report an analysis of time variations of several Voyager 1 Low Energy Charged Particle (LECP) rate channels for 2004 mostly in the pre-termination shock (TS) region and for 2005 in the heliosheath. Protons and oxygen ions coming from the TS during 2004 show autocorrelation peaks at approximately inline equation and full solar rotation period. We explain the apparent solar control of particle acceleration at the TS by invoking shock drift acceleration (SDA) which depends strongly on the angle ΘBn that the interplanetary magnetic field (IMF) makes with the shock surface. Preferred regions of acceleration occur where ΘBn is near 90°. IMF connection of Voyager 1 to preferred regions on the TS can enhance the access of accelerated particles. This geometrical situation is only available during 2004. Analyses of the data from 2003 and 2005 do not show peaks at inline equation or full solar rotation period.

Received 27 April 2006; accepted 27 June 2006; published 19 September 2006.

Index Terms: 2124 Interplanetary Physics: Heliopause and solar wind termination; 2139 Interplanetary Physics: Interplanetary shocks; 2114 Interplanetary Physics: Energetic particles (7514).

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Citation: Mosley, C. J., and T. P. Armstrong (2006), Solar control of pre-termination shock energetic particle variations observed at Voyager 1, Geophys. Res. Lett., 33, L18102, doi:10.1029/2006GL026732.