An outcrop view of a metaconglomerate: 1  Shale is a sedimentary term. 2  Slate refers to a fine-grained, low-grade metasedimentary rock in which bedding is typically still visible: 3  Schist refers to a medium-to high-grade, medium-to coarse-grained metamorphic rock of any composition that has a fabric.
Total solar irradiance (TSI), is a measure of the solar radiative power per unit area normal to the rays, incident on the Earth's upper atmosphere. The solar constant is a conventional measure of mean TSI at a distance of one Astronomical Unit (AU).
Sunspots and cycles. The sunspots and solar storms that cause the most magnificent displays of the northern lights occur roughly every 11 years. The solar cycle peaked in 2013, but it was the weakest solar maximum in a century. [ Photos: Amazing Auroras of 2014 ].