Tuesday, March 5, 2013

1303.0563 (Steven R. Cranmer et al.)

Connecting the Sun's High-Resolution Magnetic Carpet to the Turbulent Heliosphere    [PDF]

Steven R. Cranmer, Adriaan A. van Ballegooijen, Lauren N. Woolsey
The solar wind is connected to the Sun's atmosphere by flux tubes that are rooted in an ever-changing pattern of positive and negative magnetic polarities on the surface. Observations indicate that the magnetic field is filamentary and intermittent across a wide range of spatial scales. However, we do not know to what extent the complex flux tube topology seen near the Sun survives as the wind expands into interplanetary space. In order to study the possible long-distance connections between the corona and the heliosphere, we developed new models of turbulence-driven solar wind acceleration along empirically constrained field lines. We used a potential-field model of the Quiet Sun to trace field lines into the ecliptic plane with unprecedented spatial resolution at their footpoints. For each flux tube, a one-dimensional model was created with an existing wave/turbulence code that solves equations of mass, momentum, and energy conservation from the photosphere to 4 AU. To take account of stream-stream interactions between flux tubes, we used those models as inner boundary conditions for a time-steady MHD description of radial and longitudinal structure in the ecliptic. Corotating stream interactions smear out much of the smallest-scale variability, making it difficult to see how individual flux tubes on granular or supergranular scales can survive out to 1 AU. However, our models help clarify the level of "background" variability with which waves and turbulent eddies should be expected to interact. Also, the modeled fluctuations in magnetic field magnitude were seen to match measured power spectra quite well.
View original: http://arxiv.org/abs/1303.0563

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