Open AccessA study of the effect and consequence of solar cycle variation on low‐energy galactic cosmic rays using Pioneer 10 H Lyman α data as a solar cycle proxy
Author(s) -
Scherer Klaus,
Gangopadhyay P.,
Judge D. L.,
Gruntman Mike
Publication year - 1997
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/96ja03143
Subject(s) - physics , cosmic ray , astrophysics , heliosphere , radiation , solar wind , astronomy , optics , plasma , nuclear physics
The correlation of the 1981–1990 (∼ 23 to ∼ 50 AU) data of three instruments, the ultraviolet photometer (UV), the charged particle instrument (CPI), and the trapped radiation detector (TRD), on board Pioneer 10 is investigated. The reduction of the data necessary for applying a fast Fourier transform (FFT) algorithm is described. A cross correlation function between the hydrogen Lyman a backscattered radiation, used as a solar cycle proxy, and the cosmic ray fluxes is obtained from the FFT algorithm. The time lag in the anticorrelation function between the galactic cosmic rays and the Lyman α line is used to determine the distance to the solar wind termination shock (75 AU), under the assumption that the cosmic ray modulation boundary for low‐energy particles and the termination shock are coincident. The ratio of the upwind termination shock distance to the downwind shock distance is determined to be 2/3 using the Voyager 1 position in 1996.