| 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:
| Class | Intensity (in Watts/m2) |
| B | I < 10-6 |
| C | 10-6 <= I < 10-5 |
| M | 10-5 <= I < 10-4 |
| X | I >= 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 |