SOLAR FLARES
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."
1.) Solar H-alpha Flare events, 1980-present-- The basic reports sent monthly from the observatories (as soon as possible after the end of the month) consist of data for each flare or subflare and a day-by-day table of times when the sun was under observation by photographic, electronic or visual patrol. The table gives as many of the following measurements as possible: time of beginning; time of maximum brightness; time of any prominent secondary maxima; time of end (all times in UT); area at time of maximum brightness (square degrees of solar disk correct for foreshortening); importance class of flare (IAU 1964 report, updated in 1975); heliographic coordinates of center of gravity of flare at maximum brightness; whether the above information is taken from photographic, electronic or visual data; also, where available, give maximum width, and end of every observing period of each day, distinguishing any gaps of 5 minutes or more. Photographic patrols indicate the normal interval between exposures; visual patrols (without photographic patrol) indicate whether continuous or intermittent and specify the normal interval.
- Descriptive text about the H-alpha solar flare database (text)
- Listings of solar H-alpha flare events 1980-present, excluding a group line of average values -- start and end time, time of maximum, position on the solar disk, importance (area) and brightness values -- includes GOES solar X-ray flares
- PDF Tables of H-alpha Solar Flares
Early H-alpha solar flare data 1938-1999 including solar flares from the IAU Quarterly Bulletin on Solar Activity and the HAO IGY publication data series (keyed in for a NOAA/NASA  data rescue effort) -- format
Multiple year listings -- files can be as large as 17 Megabytes in size
2.) Solar H-alpha Flare Patrol -- 1955-present from a worldwide network
- Annual listings of solar H-alpha flare patrol ( format -- please print before viewing data files)
- Monthly plots of No Flare Patrol 2000 to present in PDF format
3.) Solar X-ray Flares from the GOES satellite 1975 to present (descriptive text) and from the SOLRAD satellite 1968-1974 (descriptive text)
- For GOES x-ray events: The event starts when 4 consecutive 1-minute Xray values have met all three of the following conditions -- a.) All 4 values are above the B1 threshold and b.) All 4 values are strictly increasing and c.) The last value is greater than 1.4 times the value which occurred 3 minutes earlier. The maximum is the time when the flux value reaches maximum. The maximum flux value (the event size) is the flux, as defined by the C-M-X scale, at the time of maximum. The event ends when the current flux reading returns to 1/2 the 'peak' (peak is the sum of the flux at maximum plus the flux value at the start of the event).
- GOES 1975-present annual listings of solar X-ray flares -- please print format before viewing
- Data contains beginning, maximum and end times of events, and Xray class.
- Alternative annual listings of solar X-ray flares by GOES 1992-present -- please print format before viewing
- Data include beginning, maximum and end times of events, also beginning flux, maximum flux and integrated flux. Satellite name is included, e.g. G07 = GOES-7; GO6 = GOES-6,etc.
- SOLRAD 1968-1974 annual listings of solar X-ray flares -- please print format before viewing
- Listing of hard X-ray solar flare data sources -- various satellites.
4.) Solar H-alpha Flare Index -- 1976-present from Kandilli Solar Observatory
- Descriptive text about the Solar Flare Index
- Daily Flare Index = (flare importance) x (duration)
- -- includes annual tables, by North and South Hemisphere, as well as total daily values for the entire solar disk. Values are also given in x-y form (.plt files) suitable for plotting.
- Plot of monthly values for Solar Cycle 22 -- smoothed and unsmoothed data 1986-1996
- Plot of daily values for Solar Cycle 22 -- northern and southern hemisphere data 1986-1996
- Full solar disk daily values -- in annual tables
- 1976 1977 1978 1979
- 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989
- 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999
- 2000
2001
2002
2003
2004
2005
2006
2007
- Monthly Values of the Full Disk Index for Cycles 20, 21, 22 and 23 (1966-2004) -- North, South, and Total Values
- Monthly values for Solar Cycle 21 (Jan 1976-Dec 1985) -- North, South, Total
- Monthly values for Solar Cycle 22 (Jan 1986-Oct 1996) -- North, South, Total
- Monthly values for Solar Cycle 23 (Jan 1996-Dec 2007) -- North, South, Total
- Northern hemisphere daily values
- Southern hemisphere daily values
- Plot files (x-y format suitable for plotting):
- Listing of all daily values Jan 1976-July 2004 with North, South and Total Values
- Listing of Solar Cycle 21 data Jan 1976-Dec 1985 with North, South and Total Values
- Listing of Solar Cycle 22 data Jan 1986-Oct 1996 with North, South and Total Values
- Listing of Solar Cycle 23 data Jan 1996-Dec 2007 with North, South and Total Values
5.) The Comprehensive Flare Index (cfi) 1955-1980 was developed by Helen W. Dodson and E. Ruth Hedeman, McMath-Hulbert Solar Observatory. The first description is printed in WDC-A for STP's Report UAG-14, "An Experimental, Comprehensive Flare Index and Its Derivation for 'Major' Flares, 1955-1969." Subsequent volumes of cfi indices for more recent years are given in Reports UAG-52 (1970-1974) and UAG-80 (1975-1979).
- Five measures of flare importance are added to obtain the cfi:
- 1. Sudden Ionospheric Disturbance importance (scale 0 - 3);
- 2. H-alpha flare importance (scale 0-3);
- 3. 10.7 cm solar radio flux magnitude (characteristic of log of flux);
- 4. solar radio spectral type (Type II=1, Continuum=2, and Type IV with duration greater than 10 minutes=3; and
- 5. magnitude of 200 MHz flux (characteristic of log of flux).
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