The Rapid Oscillations in the Solar Atmosphere (ROSA) and Hydrogen-Alpha Rapid Dynamics camera (HARDcam) instruments are high cadence broad-band imagers installed as common-user instruments on the Dunn Solar Telescope at the National Solar Observatory in New Mexico since 2012. They are designed, built and maintained by Queen’s University Belfast and are capable of imaging the lower solar atmosphere at frame rates exceeding 30 frames-per-second with a diffraction-limited spatial sampling of 0.069 arcsecs/pixel.
These three images of active region AR 12146 were taken simultaneously on the 24th of August 2014 with ROSA and HARDcam. They show the variation of the active region with height in the solar atmosphere. Height increases from left to right in these images. The green image on the left is a snapshot of the photosphere as observed through a G-band filter (430.5 nm). The blue image shows the boundary between the upper photosphere and the lower chromosphere as observed with a Ca II K filter (393.3 nm). The red image on the right shows the highest region observed by HARDcam, corresponding to the upper chromosphere as captured through an H-alpha filter (656.3 nm). These images show how features change across the solar atmosphere and how they are related. In the leftpanel, granulation (which are convective cells) can be easily identified in regions outside the sunspot. This pattern appears to invert in the middle image in what is termed “reversed granulation”, while granulation is not visible at all in the right-hand panel. The Earth is included for scale.
Image credit: Peter H. Keys, David B. Jess (QUB)
Sunspot observed in Ca II K spectral line
The same sunspot in three different layers
A sunspot observed in multiple spectral lines
The amazing chromosphere above an active region (1/3)
The amazing chromosphere above an active region (2/3)
The amazing chromosphere above an active region (3/3)