POSTER PAPER 1.08
What Controls Spicule Velocities and Heights?
R. Hammer, A. Nesis
Institute: Kiepenheuer-Institut fuer Sonnenphysik
Contact Email: hammer@kis.uni-freiburg.de
Abstract:
Numerous mechanisms have been suggested to drive spicules. Many of
them need a careful fine-tuning of free parameters in order to
achieve the basic characteristics, like velocity and height, of
observed spicules. There might, however, be general physical mechanisms
that control these properties. We show that whenever upper
chromospheric plasma is exposed to a significantly non-hydrostatic
pressure gradient, it starts moving upward at the observed
speeds. The plasma can reach significant heights, at least if it
receives some net chromospheric heating during the rising phase.
Therefore, such a hydrodynamic mechanism might help other (magnetic)
drivers to control the basic properties of spicules. We suggest
therefore to consider a new class of spicule driving mechanisms, in
which the plasma is not only accelerated by wave or magnetic forces from
below, but also by the generation of a low pressure region above the
chromosphere. Such a situation could arise e.g. due to an instability in
magnetic loops or as a result of the reconfiguration of open field
lines.
Index Keywords: Sun ; Spicules
Previous: Rouppe van der Voort
Next: Doyle
Up: Poster Index
Up: Top Index
Manuscript submitted: 2001-Sep-6
"The Future of Cool-Star Astrophysics", 2003, Eds. A. Brown,
G. M. Harper, & T. R. Ayres.
Proceedings of 12th Cambridge Workshop on Cool Stars, Stellar Systems,
& The Sun,
© 2003 University of Colorado.