Astronomy and Astrophysics – Astrophysics
Scientific paper
Oct 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999esasp.446..525o&link_type=abstract
8th SOHO Workshop: Plasma Dynamics and Diagnostics in the Solar Transition Region and Corona. Proceedings of the Conference hel
Astronomy and Astrophysics
Astrophysics
2
Scientific paper
Current evidence suggests that physically acceptable models for the origin of the high-latitude solar wind will involve some process(es) which deposits significant heat within a few solar radii of the photosphere [1]. Moreover, the process is likely to rely heavily on the coronal magnetic field [2]. Here we present a candidate mechanism for heating of open field line regions of the corona. The mechanism involves the coupling of LOW frequency Alfven waves generated in the chromosphere, their (partial) reflection off density and field gradients, and MHD turbulence which is quasi-two dimensional (relative to the mean magnetic field). The essentially non-propagating nature of the latter means that energy deposited in these fluctuations by the driving waves can undergo a turbulent cascade to small transverse scales (via, for example, reconnection) at approximately the same height at which the coupling occurs: the fast Alfven wave propagation timescale is not relevant to the quasi-2D dynamics and the speed of the nascent wind is low in this region. Once the energy reaches sufficiently small perpendicular length scales, dissipative processes convert it into heat at a rate expected to be insensitive to the mean field strength. We will present and discuss a phenomenology for the process along with ``proof of principle'' support from reduced MHD simulations. Estimates of achievable heating efficiencies based on both the turbulence modeling and the simulations are consistent and encourage further investigation of the model's quantitative feasibility. Supported by NASA grant NAG5-7164. [1] Habbal, S.R., R. Esser, M. Guhathakurta, and R.R. Fisher, Geophys. Res. Lett., 22, 1465, 1995 [2] McKenzie, J.F., M. Banaszkiewicz, and W.I. Axford, Astron. Astrophys. 303, L45, 1995.
Matthaeus William H.
Oughton Sean
Zank Gary P.
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