Any change in the Sun's appearance or behaviour. The Sun's activity is described as being very low, low, moderate, high or very high.
Phenomena of the solar atmosphere: sunspots, plages, and related phenomena.
Phenomena of the solar atmosphere associated with sunspots, plagues, and related phenomena.
A general term for those processes and changes on the Sun that rise and fall with the sunspot cycle, e.g. flares.
Transient perturbations of he solar atmosphere as measured by enhanced x-ray emissions, typically associated with flares. Five standard terms are used, based on the size and number of x-ray flares observed. Category Type of x-ray flare Very Low Less than class C Low C-class Moderate Isolated (1-4) M-class High Several (=5) M-class or Isolated (1-4) M5 or greater Very High Several (=5) M5 or greater
Activity of sunspots, flares and CME's which follow the solar cycle.
Any type of variation in the appearance or energy output of the sun; usually associated with the variation of sunspots and other features over the 11-year solar cycle. The number and magnitude of these features vary with time, from minimum values to maximum values, that is, from solar minimum to solar maximum. See faculae, flare, granules, plage, prominence, spicules, sunspot.