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Forman, Miriam A

Publications and source records attributed to Forman, Miriam A.

3 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

THIRD MOMENTS AND THE ROLE OF ANISOTROPY FROM VELOCITY SHEAR IN THE SOLAR WIND

We have extended the recent analyses of magnetohydrodynamic third moments as they relate to the turbulent energy cascade in the solar wind to consider the effects of large-scale shear flows. Moments from a large set of Advanced Composition Explorer data have been taken, and chosen data intervals are characterized by the rate of change in the solar wind speed. Mean dissipation rates are obtained in accordance with the predictions of homogeneous shear-driven turbulence. Agreement with predictions is best made for rarefaction intervals where the solar wind speed is decreasing with time. For decreasing speed intervals, we find that the dissipation rates increase with increasing shear magnitude and that the shear-induced fluctuation anisotropy is consistent with a relatively small amount.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

DETAILED FIT OF 'CRITICAL BALANCE' THEORY TO SOLAR WIND TURBULENCE MEASUREMENTS

We derive the reduced spectrum of turbulent magnetic fluctuations at different frequencies f which would be observed by a single spacecraft in the solar wind when the magnetic field was at an angle {theta}{sub B} to the solar wind flow, if the wavevector spectrum in the solar wind frame were in anisotropic 'critical balance' (CB) as proposed by Goldreich and Sridhar in 1995 (GS95). The anisotropic power spectrum in the inertial range, P(f, {theta}{sub B} ), is scaled onto one curve with f-{sup 5/3} behavior at {theta}{sub B} near 90{sup 0} and f{sup -2} behavior at small {theta}{sub B}. The transition between the two limiting spectra depends on the form of the GS95 wavevector spectrum and the CB scaling parameter L. Using wavelet analysis of Ulysses magnetic field data in three 30-day periods in the high-latitude solar wind in 1995, we verify that the scaling of power with angle and frequency is qualitatively consistent with GS95 theory. However, the scale length L required to fit the observed P(f, {theta}{sub B} ) to the original CB theory is rather less than the scale predicted by that theory for the solar wind. Part, possibly all, of this discrepancy is removed when the GS95 theory modified for imbalanced turbulence is used.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2010

Smith et al. Reply:

A Reply to the Comment by J. J. Podesta.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗