Physics
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufmsh52c..08d&link_type=abstract
American Geophysical Union, Fall Meeting 2007, abstract #SH52C-08
Physics
7507 Chromosphere, 7509 Corona, 7526 Magnetic Reconnection (2723, 7835), 7546 Transition Region, 7836 Mhd Waves And Instabilities (2149, 2752, 6050)
Scientific paper
The lower boundary of the corona, or chromosphere, requires of order 100 times more energy than the corona itself, and provides the mass to fill coronal loops. Yet the chromosphere and its coupling to the corona is often overlooked. Recently, observations with the Solar Optical Telescope (SOT) onboard Hinode and ground-based telescopes combined with advanced numerical simulations have provided us with unprecedented views and a better understanding of the (spicular) dynamics of the chromosphere and how the lower boundary couples to the corona and solar wind. We analyze high-resolution, high-cadence Ca II and Hα observations of the solar chromosphere and find that the dynamics of the magnetized chromosphere are dominated by at least two different types of spicules. We show that the first type involves up- and downward motion that is driven by shock waves that form when global oscillations and convective flows leak into the chromosphere along magnetic field lines on on 3-7 minute timescales. The second type of spicules is much more dynamic: they form rapidly (in ~10s), are very thin (<200km wide), have lifetimes of 10-150s (at any one height) and seem to be rapidly heated to (at least) transition region temperatures, sending material through the chromosphere at speeds of order 50-150 km/s. The properties of Type II spicules suggest a formation process that is a consequence of magnetic reconnection. We discuss the impact of both spicules types on the coronal mass and energy balance. Our analysis of Hinode data also indicates that the chromosphere is permeated by strong Alfvén waves. Both types of spicules are observed to carry these Alfvén waves, which have significant amplitudes of order 20 km/s, transverse displacements of order 500-1,000 km and periods of 150-400 s. Estimates of the energy flux carried by these Alfvén waves and comparisons to advanced radiative MHD simulations indicate that these waves most likely play a significant role in the acceleration of the solar wind, and possibly the heating of the quiet Sun corona. We will discuss the implications of these waves on the energy balance of the lower atmosphere.
Carlsson M. P.
de Pontieu Bart
Hansteen Viggo
McIntosh Scott W.
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