Exploring Euv Spicules Using 304 Ang He II Data from SDO/AIA

Friday, 19 December 2014
Ian Ross Snyder, Alphonse C Sterling, David Allen Falconer and Ron L Moore, National Space Science and Technology Center, Huntsville, AL, United States
We present results from an exploratory study of He II 304 Ĺ EUV spicules at the limb of the Sun.
We also measured properties of one macrospicule; macrospicules are longer than most spicules, and much
broader in width than spicules. We use high-cadence (12 sec) and high-resolution (0.6 arcsec pixels)
data from the Atmospheric Imaging Array (AIA) instrument on the Solar Dynamic Observatory (SDO). All of
the observed events occurred near the solar north pole, in quiet-Sun or coronal-hole environments. We
examined the maximum lengths, maximum rise velocities, and lifetimes of about 30 EUV spicules and the
macrospicule. For the bulk of the EUV spicules the ranges of these quantities are respectively 
~10,000----40,000 km, 20---100 km/s, and ~100--- ~600 sec. For the macrospicule the corresponding
quantities are respectively ~60,000 km, ~130 km/s, and ~1800 sec, which is typical of macrospicules
measured by other workers. Therefore macrospicules are taller, longer-lived, and faster than most EUV
spicules. The rise profiles of both the spicules and the macrospicules fit well to a second-order
("parabolic'') trajectory, although the acceleration was often weaker than that of solar gravity in the
profiles fitted to the trajectories. Our macrospicule also had an obvious brightening at its base at
birth, whereas such brightenings were not apparent for the EUV spicules. Most of the EUV spicules
remained visible during their decent back to the solar surface, although a small percentage of the
spicules and the macrospicule faded out before falling back to the surface. Our sample of
macrospicules is not yet large enough to address whether they are scaled-up versions of EUV spicules, or
independent phenomena. A.C.S. and R.L.M. were supported by funding from the Heliophysics Division of
NASA's Science Mission Directorate through the Living With a Star Targeted Research and Technology
Program, and the Hinode Project. I.R.S. was supported by NSF's Research Experience for Undergraduates