Weather Glossary


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X-Band A frequency band of microwave radiation in which radars operate.
X-Ray Background In solar-terrestrial terms, a daily average background X-ray flux in the 1 to 8 angstrom range. It is a midday minimum designed to reduce the effects of flares.
X-Ray Burst In solar-terrestrial terms, a temporary enhancement of the X-ray emission of the sun. The time-intensity profile of soft X-ray bursts is similar to that of the H-alpha profile of an associated flare.
X-Ray Flare Class In solar-terrestrial terms, rank of a flare based on its X-ray energy output. Flares are classified by the order of magnitude of the peak burst intensity (I) measured at the earth in the 1 to 8 angstrom band as follows:

ClassIntensity (in Watts/m2)
BI < 10-6
C10-6 <= I < 10-5
M10-5 <= I < 10-4
XI >= 10-4
X-Rays Very energetic electromagnetic radiation with wavelengths intermediate between 0.01 and 10 nanometers (0.1-100 Angstroms) or between gamma rays and ultraviolet radiation. Essentially all X-Rays from space are absorbed in the Earth's upper atmosphere.
XBT Expendable Bathythermograph
XCITED Excited
XCPT Expecting
XPC Expect
XSEC Cross Section