Håkon Skogsrud: High Resolution Observations of Spicules Type II



Spicules are relatively small, narrow and elongated structures that stick out above the edge of the solar disk. They are very dynamic and appear as jets that shoot out into the outer solar atmosphere. Up until recently, in the era before adaptive optics and advanced image post-processing techniques, variable seeing conditions and limited telescope aperture sizes did not allow for major advancement in the understanding of the nature of spicules. In 2007, a new class of highly dynamical spicules was discovered with the solar telescope on-board the Hinode satellite, the "type II" spicules. Recent studies indicate that the type II spicules are very important concerning the mass loading and energy balance of the hot solar corona.

In this thesis, we analyze two unique time sequences of the limb obtained from the Swedish 1-meter Solar Telescope. These observations have high spatial, temporal and spectral resolution. We investigate short-lived streaks in the far wings of the H-alpha spectral line. These events are characterized by a strong spectral asymmetry in the wing associated with high Doppler velocity. Before, these asymmetries have been observed exclusively in the blue wing of strong chromospheric lines in regions close to disc-center and were called "Rapid Blue-shifted Excursions" (RBEs). RBEs have been identified as the on-disk counterpart of the type II spicules seen off-limb by Hinode. We investigate this connection in more detail. We find similar RBE-like events in the red wing of H-alpha, or "Rapid Red-shifted Excursions". This is expected from a target region close to the solar limb. We also investigate the off-limb spicules seen in the wings of H-alpha and their possible connection to type II spicules. Our findings strengthen the connection between the RBEs/RREs and type II spicules and it strongly indicates that the off-limb spicules seen in H-alpha, the RBEs/RREs on-disk and the type II spicules seen by Hinode are the same phenomenon.

Publisert 9. juni 2011 11:15 - Sist endret 20. mars 2012 11:17