Just Above the Sun's Visible Surface - Ca II K

The Sun Now October 11, 2005 18:00	Compare to Active Sun
Image Credit: Courtesy of the National Solar Observatory/Sacramento Peak, NOAO.
What layer does the light come from?
About the images: Light from singly-ionized calcium ions in the Sun's upper photosphere and chromosphere (up to 2000 km altitude). Because the blue Calcium K Line (393.3 nm) is sensitive to magnetic fields, magnetically active structures show up in high contrast against the surrounding chromosphere. Places where moderate magnetic fields exist show up bright whereas images of high magnetic fields are dark. These images are taken daily by the ESF Spectroheliograph, National Solar Observatory/ Sacramento Peak.
What to look for: In CaK images, you typically see brightness along the edges of large convection cells called supergranules and in areas called plages. Dark sunspots and filaments are also visible.

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