Hurricane Isaias is expected to make landfall along the U.S. northern Gulf Coast late Friday or early Saturday. A life-threatening storm surge is expected along the coast with damaging wind gusts extending well inland. Areas of heavy rainfall are forecast throughout much of the Southeast U.S. The remnants of Rachel will bring gusty winds and heavy rainfall to the Southwest U.S. this weekend. Read More >
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
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