The Solar X-Ray flux arises from two factors. Firstly, there is flux coming from sunspot regions and other features - the background flux - and this varies slowly from day-to-day. Secondly, solar flares produce large amounts of X-ray flux, but this is concentrated to the duration of the flare which is usually from minutes to several hours.

Solar X-Ray Flux is described as follows:

  Level    Flux (watts/sq meter)          Description     

    A      less than 10-8                  Very Low Background
    A      between 10-8 and 10-7           Low Background
    B      between 10-7 and 10-6           Moderate Background
    C      between 10-6 and 10-5           High Background/Low Flare
    M      between 10-5 and 10-4           Moderate Flare
    X      between 10-4 and 10-3           High Flare
    Y      greater than 10-3               Extreme Flare

The Y classification of flares is new; and these extremely large flares are often still classed as X flares with a qualifying number greater than 10. Hence a Y1.6 flare is exactly the same as an X16 one.

Material Prepared by Richard Thompson. © Copyright IPS - Radio and Space Services.