COMPRESSIBLE 'TURBULENCE' OBSERVED IN THE HELIOSHEATH BY VOYAGER 2

Journal Article · Sun Sep 20 00:00:00 EDT 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/703/1/311· OSTI ID:21371998

Burlaga, L F ^[1]

---

1. Geospace Physics Laboratory, Code 673, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

This paper describes the multiscale structure of the compressible 'turbulence' observed in the high-resolution (48 s) observations of the magnetic field strength B made by Voyager 2 (V2) in the heliosheath behind the termination shock from 2007 DOY 245.0-300.8 and in a unipolar region from 2008 DOY 2.9-75.6. The magnetic field strength is highly variable on scales from 48 s to several hours in both intervals. The distributions of daily averages and 48 s averages of B are lognormal in the post-termination shock (TS) region and Gaussian in the unipolar region, respectively. The amplitudes of the fluctuations were greater in the post-TS region than in the unipolar region, at scales less than several hours. The multiscale structure of the increments of B is described by the q-Gaussian distribution of nonextensive statistical mechanics on all scales from 48 s to 3.4 hr in the unipolar region and from 48 s to 6.8 hr in the post-TS region, respectively. The amplitudes of the fluctuations of increments of B are larger in the post-TS region than in the unipolar region at all scales. The probability density functions of the increments of B are non-Gaussian at all scales in the unipolar region, but they are Gaussian at the largest scales in the post-TS region. Time series of the magnitude and direction of B show that the fluctuations are highly compressive. The small-scale fluctuations are a mixture of coherent structures (semi-deterministic structures) and random structures, which vary significantly from day to day. Several types of coherent structures were identified in both regions.

• OSTI ID: 21371998
• Journal Information: Astrophysical Journal, Vol. 703, Issue 1; Other Information: DOI: 10.1088/0004-637X/703/1/311; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
GAUSS FUNCTION
MAGNETIC FIELDS
PROBABILITY DENSITY FUNCTIONS
RANDOMNESS
RESOLUTION
SOLAR WIND
STATISTICAL MECHANICS
SUN
TURBULENCE
VOYAGER SPACE PROBES
FUNCTIONS
MAIN SEQUENCE STARS
MECHANICS
SOLAR ACTIVITY
SPACE VEHICLES
STARS
STELLAR ACTIVITY
STELLAR WINDS
VEHICLES