Title: Jets in the Solar Chromosphere

Dr. Reiner Hammer
Kiepenheuer Institute for Solar Physics, Germany

The solar chromosphere shows numerous needle-shaped extensions into the overlying corona, in which plasma shoots up at high speeds. These phenomena are variously called spicules, mottles, or dynamic fibrils, depending on where and how they are observed on the Sun. Many different explanations have been suggested for how these phenomena might be generated in the dynamic solar atmosphere. The currently most popular suggestion is that global solar oscillations propagate as longitudinal waves along magnetic flux tubes. These long-period waves suffer from a cutoff restriction, but if the flux tubes are sufficiently inclined to the vertical they can propagate nevertheless.
I will discuss the cutoff behavior of other wave modes, namely kink and torsional flux tube waves, and show that they have better chances to transport energy upward. Such waves must therefore be taken into account in order to understand spicules. Moreover, some observations indicate that not all spicules can be explained by waves, in particular if they are more vertically oriented. Other mechanisms seem to be operating as well, like reconnection or mechanisms that lead to a strong pressure decrease in the upper chromosphere.

UT Arlington Physics