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Magnetic Field Strength Fluctuations in the Heliosheath: Voyager 1 Observations During 2009We analyze the microscale fluctuations of the magnetic field strength B on a scale of several hours observed by Voyager1 (V1) in the heliosheath during 2009. The microscale fluctuations of B range from coherent to stochastic structures. The amplitude of microscale fluctuations of B during 1 day is measured by the standard deviation (SD) of 48 s averages of B. The distribution of the daily values of SD is lognormal. SD(t) from day of year (DOY) 1 to 331, 2009, is very intermittent. SD(t) has a 1/f or "pink noise" spectrum on scales from 1 to 100 days, and it has a broad multifractal spectrum f(alpha) with 0.57 less than or equal to alpha less than or equal to 1.39. The time series of increments SD(t + tau) -- SD(t) has a pink noise spectrum with alpha(1) = 0.88 plus or minus 0.14 on scales from 1 to 100 days. The increments have a Tsallis (q-Gaussian) distribution on scales from 1 to 165 days, with an average q = 1.75 plus or minus 0.12. The skewness S and kurtosis K have Gaussian and lognormal distributions, respectively. The largest spikes in K(t) and S(t) are often associated with a change in B across a data gap and with identifiable physical structures. The "turbulence" observed by V1 during 2009 was weakly compressible on average but still very intermittent, highly variable, and highly compressible at times. The turbulence observed just behind the termination shock by Voyager 2 was twice as strong. These observations place strong constraints on any model of turbulence in the heliosheath.
Document ID
20120010147
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Brulaga, L. F.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Ness, N. F.
(Catholic Univ. of America Washington, DC, United States)
Date Acquired
August 25, 2013
Publication Date
January 1, 2012
Publication Information
Publication: The Astrophysical Journal
Volume: 744
Issue: 1
Subject Category
Solar Physics
Report/Patent Number
GSFC.JA.00181.2012
Funding Number(s)
CONTRACT_GRANT: NNX10AU53G
Distribution Limits
Public
Copyright
Other

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