How Low-Quality Observations Affect Spicule Properties
Abstract
Spicules have been observed on the sun for more than 80 years, in several chromospheric lines such as H-alpha and Ca II H. Recent work has shown that spicules have the potential to drive the solar wind and heat the chromosphere, making them a hotly contested topic in solar physics. Despite the wealth of observations available, their properties are still a matter of debate. Difficulties in measuring their properties arise because spicules occur on short spatial and temporal scales, and are very abundant (superimposed) at the limb. Most of the older observations lacked either the spatial resolution or cadence necessary to measure spicules. This changed with Hinode/SOT, which has provided seeing-free observations with high cadence and spatial resolution. Using SOT observations, we find that in the quiet sun most spicules are shorter lived and can move much faster than previously measured. In this work we try to reconcile the recent results with results from older observations. We degrade SOT data to match the cadence and resolution of older data sets, and apply the same semi-automated method to detect and measure the properties of spicules to both the original and degraded data. We find that degrading the data has a significant effect on the measured properties of spicules. Most importantly, the results from the degraded data agree very well with older studies (e.g. mean spicule duration more than 5 minutes, and upward velocities of about 25 km/s). These results illustrate how the combination of spicule superposition, low spatial resolution, and cadence affect the measured properties of spicules, and that previous measurements can thus be unreliable.
- Publication:
-
American Astronomical Society Meeting Abstracts #220
- Pub Date:
- May 2012
- Bibcode:
- 2012AAS...22020306P