Crossing the Termination Shock into the Heliosheath: Magnetic Fields

Magnetic fields measured by Voyager 1 show that the spacecraft crossed or was crossed by the termination shock on about 16 December 2004 at 94.0 astronomical units. An estimate of the compression ratio of the magnetic field strength B (± standard error of the mean) across the shock is B2/B1 = 3.05 ± 0.04, but ratios in the range from 2 to 4 are admissible. The average B in the heliosheath from day 1 through day 110 of 2005 was 0.136 ± 0.035 nanoteslas, ∼4.2 times that predicted by Parker's model for B. The magnetic field in the heliosheath from day 361 of 2004 through day 110 of 2005 was pointing away from the Sun along the Parker spiral. The probability distribution of hourly averages of B in the heliosheath is a Gaussian distribution. The cosmic ray intensity increased when B was relatively large in the heliosheath.

[1]  D. C. Hamilton,et al.  Voyager 1 exited the solar wind at a distance of ∼85 au from the Sun , 2003, Nature.

[2]  R. Vogt,et al.  Cosmic ray investigation for the Voyager missions; energetic particle studies in the outer heliosphere—And beyond , 1977 .

[3]  R. Weymann.  Heating of Stellar Chromospheres by Shock Waves and Coronal Evaporation as a Possible Mechanism for Mass Loss in Red Giants. , 1960 .

[4]  N. Sheeley,et al.  Solar wind speed and coronal flux-tube expansion , 1990 .

[5]  T. Holzer.  Interaction Between the Solar Wind and the Interstellar Medium , 1976 .

[6]  Nand Lal,et al.  Enhancements of energetic particles near the heliospheric termination shock , 2003, Nature.

[7]  D. Gurnett,et al.  Electron Plasma Oscillations Upstream of the Solar Wind Termination Shock , 2005, Science.

[8]  J. Brackbill,et al.  Motion of the termination shock in response to an 11 Year variation in the solar wind , 1995 .

[9]  E. Stone.  News from the Edge of Interstellar Space , 2001, Science.

[10]  G. Zank.  Interaction of the solar wind with the local interstellar medium: a theoretical perspective , 1999 .

[11]  G. Zank,et al.  Modelling the heliosphere , 1996 .

[12]  R. E. Marshak,et al.  Interplanetary Dynamical Processes , 1963 .

[13]  E. C. Stone,et al.  Voyager 1 Explores the Termination Shock Region and the Heliosheath Beyond , 2005, Science.

[14]  E. C. Stone,et al.  Search for the heliosheath with Voyager 1 magnetic field measurements , 2003 .

[15]  D. C. Hamilton,et al.  Voyager 1 in the Foreshock, Termination Shock, and Heliosheath , 2005, Science.

[16]  H. Fahr,et al.  Solar cycle induced variations of the outer heliospheric structures , 2003 .