Limb Spicules from the Ground and from Space

TL;DR

This study combines ground-based and space-based observations to analyze the properties of chromospheric spicules, providing detailed statistics on their sizes, motions, and possible generation mechanisms.

Contribution

It offers new high-resolution statistical data on spicule dynamics and morphology, and compares ground and space observations to support reconnection-based spicule formation theories.

Findings

Spicules have consistent dynamical and morphological properties across observations.

Reconnection mechanisms are supported as a plausible origin for spicules.

UV spicules may form sheath regions around H-alpha spicules.

Abstract

We amassed statistics for quiet-sun chromosphere spicules at the limb using ground-based observations from the Swedish 1-m Solar Telescope on La Palma and simultaneously from NASA's Transition Region and Coronal Explorer (TRACE) spacecraft. The observations were obtained in July 2006. With the 0.2 arcsecond resolution obtained after maximizing the ground-based resolution with the Multi-Object Multi-Frame Blind Deconvolution (MOMFBD) program, we obtained specific statistics for sizes and motions of over two dozen individual spicules, based on movies compiled at 50-second cadence for the series of five wavelengths observed in a very narrow band at H-alpha, on-band and in the red and blue wings at 0.035 nm and 0.070 nm (10 s at each wavelength) using the SOUP filter, and had simultaneous observations in the 160 nm EUV continuum from TRACE. The MOMFBD restoration also automatically aligned the images, facilitating the making of Dopplergrams at each off-band pair. We studied 40 H-alpha spicules, and 14 EUV spicules that overlapped H-alpha spicules; we found that their dynamical and morphological properties fit into the framework of several previous studies. From a preliminary comparison with spicule theories, our observations are consistent with a reconnection mechanism for spicule generation, and with UV spicules being a sheath region surrounding the H-alpha spicules.