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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 Beta on a scale of several hours observed by Voyager I (VI) in the heliosheath during 2009. The microscale fluctuations of Beta range from coherent to stochastic structures. The amplitude of microscale fluctuations of Beta 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) I to 331, 2009, is very intermittent. SD(t) has a 1/f or "pink noise" spectrum on scales from I to 100 days, and it has a broad multi fractal spectrum f(alpha) with 0.57 much < alpha much < 1.39. The time series of increments SD(t + r) - SD(t) has a pink noise spectrum with alpha' = 0.88 +/- 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 +/- 0.12. The skewness S and kurtosis K have Gaussian and lognormal distributions, respectively. The largest spikes in K(t) and Set) are often associated with a change in Beta across a data gap and with identifiable physical structures. The "turbulence" observed by VI 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
20120014321
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Burlaga, 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 26, 2013
Publication Date
December 13, 2011
Publication Information
Publication: The Astrophysical Journal
Volume: 744
Issue: 1
Subject Category
Solar Physics
Report/Patent Number
GSFC.JA.6873.2012
Funding Number(s)
CONTRACT_GRANT: NNX10AU53G
Distribution Limits
Public
Copyright
Other

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