HR: 11:00h
AN: SH22A-03    [Abstracts]
TI: Nonextensivity of the Large-scale Magnetic Field Strength Fluctuations in the Solar Wind from 7 to 87 AU
AU: * Burlaga, L
EM: Leonard.F.Burlaga@nasa.gov
AF: NASA/Goddard Space Flight Center, Laboratory for Solar and Space Physics, Code 612.2, Greenbelt, MD 20771 United States
AU: Vinas, A F
EM: Adolfo.Figueroa-Vinas.1@nasa.gov
AF: NASA/Goddard Space Flight Center, Laboratory for Solar and Space Physics, Code 612.2, Greenbelt, MD 20771 United States
AB: The solar wind is a driven nonlinear non-equilibrium system, with large jumps and fluctuations in the temporal profiles of the magnetic field strength B. Relatively large clusters of strong fields ("Merged interactions", MIRs) form beyond 1 AU become prominent at 15 to 30 AU, and they decay slowly between 40 AU and at least 90 AU. We analyze the probability distribution functions (PDFs) of fluctuations of the B observed by Voyager 1 between 7 and 87 AU on scales from 1 to 128 days during each of four years (1980, 1991, 2001, and 2002). The 32 PDFs of the increments of B for all of these data can be described by a single function, the Tsallis distribution of nonextensive statistical mechanics. The tails of the PDFs are described by the nonextensitivity parameter q, which is scale dependent. The Tsallis distribution has a finite variance when q < 5/3 and a divergent variance when q > 5/3. For the 1980 and 1991 data (near 8 and 45 AU respectively), q > 5/3 at all scales, owing to large tails of the PDFs caused by large fluctuations and jumps in B(t). For the 2001 and 2002 data (between 80 and 87 AU), q < 5/3, and q approaches 1 (the PDF tends to a Gaussian) at large scales. The standard deviation of the increments of B increases linearly and quadratically for the 1980 and 1991 data, respectively (q > 5/3) and it increases asymptotically to a limiting value for 2001 and 2002 data (q < 5/3). The transition from q > 5/3 at < 45 AU to q < 5/3 at > 80 AU suggests the possibility of a phase transition in the outer heliosphere.
DE: 2134 Interplanetary magnetic fields
DE: 2149 MHD waves and turbulence
DE: 2199 General or miscellaneous
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2005 Joint Assembly