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Metadata Identifier: gov.noaa.ngdc.stp.solar:G01256
MD_DataIdentification
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Solar Flares in Hydrogen Alpha and X-rays |
A solar flare is a short-lived sudden increase in the intensity of radiation
emitted in the neighborhood of sunspots. For many years it was best monitored in the
H-alpha wavelength and occurs in the chromosphere, though occasionally white light
flares are seen in the photosphere. In modern times the solar X-ray wavelengths are
monitored via satellite for solar flares. Flares are characterized by a rise time
of the order of minutes and a decay of the order of tens of minutes. The total energy
expended in a typical flare is about 10**30 ergs; the magnetic field is extraordinarily
high, reaching values of 100 to 10,000 gauss. Optical flares in H-alpha are usually
accompanied by radio and X-ray bursts, and occasionally by high-energy particle emissions.
The optical brightness and size of the flare are indicated by a two-character code
called "importance." The first character, a number from 1 to 4, indicates the apparent
area. For areas of less than 1, an "S" is used to designate a subflare. The second
character indicates relative brilliance: B for bright, N for normal and F for faint.
A general discussion of solar flares is found in Svestka's, SOLAR FLARES (1976). The
National Geophysical Data Center (NGDC) holds archives for about 80 stations, covering
the period 1938 to the present. Currently 5 stations send their data to NGDC Boulder
on a routine monthly basis -- the current main observing emphasis for Space Weather
has transitioned to Coronal Mass Ejections (CMEs) which directly impact the Earth's
geomagnetic field. Solar flares impact the Earth's upper atmosphere and can eject
high energy particles that can cause satellite failures. The flare reports are processed
and published in the monthly report "Solar-Geophysical Data" and in a different format
in the IAU "Quarterly Bulletin on Solar Activity."
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SV_Identification
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NASA/GCMD Data Center Keywords |
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NASA/GCMD Location Keywords |
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GCMD Science Keywords |
NASA/Global Change Master Directory (GCMD) Earth Science Keywords |
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Solar Flares in Hydrogen Alpha and X-rays |
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Solar Geophysical Data (SGD) International Standard Serial Numbers
(ISSN)
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ISSN 0038-0911 Solar Geophysical Data (SGD) Published Monthly
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DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department
of Commerce (comp)
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publisher |
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NASA/GSFC/SED/ESD/GCDC/GCMD > Global Change Master Directory, Global Change Data Center,
Earth Sciences Division, Science and Exploration Directorate, Goddard Space
Flight Center, NASA
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resourceProvider |
http://gcmd.gsfc.nasa.gov/Resources/valids/archives/keyword_list.html |
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Solar Data Manager |
DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department
of Commerce
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solar.ngdc@noaa.gov |
pointOfContact |
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Solar Data Manager |
DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department
of Commerce
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solar.ngdc@noaa.gov |
distributor |
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Solar Data Manager |
DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department
of Commerce
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solar.ngdc@noaa.gov |
custodian |
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ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SOLAR_FLARES |
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http://gcmd.gsfc.nasa.gov/Resources/valids/archives/keyword_list.html |
GCMD Keywords, Version 6.0.0.0.0 |
Thesuarus for earth science keywords and associated directories hosted and maintained
by NASA.
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information |
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http://www.ngdc.noaa.gov/stp/SOLAR/ftpsolarflares.html |
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http://www.ngdc.noaa.gov/stp/SOLAR/ftpsolarimages.html |
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http://www.ngdc.noaa.gov/stp/SOLAR/getdata.html |
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Bounding Box |
Temporal Extent |
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1919-03-01 |
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