Metadata Catalogue

Hourly Interplanetary Magnetic Field and Solar Wind Plasma Database
The interplanetary magnetic field (IMF) is a part of the Sun's magnetic field that is carried into interplanetary space by the solar wind. The interplanetary magnetic field lines are said to be "frozen in" to the solar wind plasma. Because of the Sun's rotation, the IMF, like the solar wind, travels outward in a spiral pattern that is often compared to the pattern of water sprayed from a rotating lawn sprinkler. The IMF originates in regions on the Sun where the magnetic field is "open"--that is, where field lines emerging from one region do not return to a conjugate region but extend virtually indefinitely into space. The direction (polarity, sense) of the field in the Sun's northern hemisphere is opposite that of the field in the southern hemisphere. (The polarities reverse with each solar cycle.) The IMF is a vector quantity with three directional components, two of which (Bx and By) are oriented parallel to the ecliptic. The third component--Bz--is perpendicular to the ecliptic and is created by waves and other disturbances in the solar wind. When the IMF and geomagnetic field lines are oriented opposite or "antiparallel" to each other, they can "merge" or "reconnect," resulting in the transfer of energy, mass, and momentum from the solar wind flow to magnetosphere The strongest coupling --with the most dramatic magnetospheric effects-- occurs when the Bz component is oriented southward. The IMF is a weak field, varying in strength near the Earth from 1 to 37 nT, with an average value of ~6 nT. The database contains Interplanetary Magnetic Field (IMF) in Geocentric Solar Magnetospheric (GSM) coordinate system and Solar Wind Plasma (SWP) data from many spacecrafts (mostly IMP-8 since 1973) which have explored over the last three decades. Plasma data include ion density and flow bulk speed. The collected heliospheric IMF and SWP data sets have been provided by Principal Investigator J.H. King (Director, National Space Science Data Center, request@nssdca.gsfc.nasa.gov ). All parameters have been quality controlled, corrected and, as far as possible, written in a similar format. The interplanetary field and plasma data were all obtained by spacecraft in geocentric or selenocentric orbit when those spacecraft were outside the Earth's bow shock.

Earth Magnetic Field, Energetic Particle and Solar X-Ray Flux Levels Measured by GOES Satellites
The National Geophysical Data Center maintains an active database of Earth magnetic field, energetic particle and solar X-ray flux levels measured by GOES satellites to further the understanding of Earth magnetism and the Sun-Earth environment. The data are collected by sensors on the GOES geostationary satellites (6.6RE) over the Earth's equator. Usually there are two satellites recording similar data at all possible times. One is the 'Western' satellite nominally located at 135 degrees west longitude. The other is the 'Eastern' satellite at around 75 degrees west longitude. The database contains 5-minute and 1-minute averages of the X-rays, energetic particles, and magnetic field data collected by GOES satellites since January 1986. The data are transmitted via direct telemetry to the Space Environment Center (SEC) in Boulder, Colorado where they are use in real-time alerts and space weather forecasts. At the end of each month these data are transferred to the Solar-Terrestrial Physics Division of the National Geophysical Data Center, an organization known internationally as World Data Center A for Solar-Terrestrial Physics. A twin-fluxgate spinning sensor on board teh sattelite allows Earth's magnetic field to be described by three mutually perpendicular components: Hp, He and Hn. Hp is parallel to the satellite spin axis, which is itself perpendicular to the satellite's orbital plane. He lies parallel to the satellite-Earth center line and points earthward. Hn is perpendicular to both Hp and He, and points westward for SMS-1, SMS-2, GOES-1, GOES-2, GOES-3, and GOES-4, and eastward for later spacecraft. He and Hn are deconvoluted from the transverse component Ht. Field strength changes as small as 0.2 nanoTesla can be measured. The magnetometer samples the field every 0.75 seconds. Solid-state detectors with pulse-height discrimination on board the satellite measure proton, alpha-particle, and electron fluxes. The look direction of the EPS (Energetic Particle Sensor) is perpendicular to the GOES spin axis which is approximately aligned with Earth's rotation axis. Since the satellite spin period, 0.6 seconds, is much shorter than the accumulation times, the EPS provides a spin-averaged estimate of the local high-pitch-angle particle fluxes. The integral electron channel is given in units of count/cm2 sec sr while the other channels are given in count/cm2 sec sr MeV at the average energy. Because GOES spacecraft travel in a geostationary orbit, the E1 and P1 channels are responding primarily to trapped outer-zone particles. The P2 channel may occasionally respond to trapped particles during magnetically disturbed conditions. The geomagnetic cutoff at geostationary orbit is typically of the order of a few MeV as indicated by the lack of trapped P2 response except as noted above. Therefore, the remaining proton and alpha particle channels measure fluxes originating outside the magnetosphere - from the Sun or the heart of the Galaxy. Solar X-ray flux levels, as measured on board the satellite by the space environment monitor system (SEMS), are at two wavelength bands XL: 1-8A and XS: 0.5-4A 'long and short' wavelengths, respectively. They are recorded in units of watts per square meter. These wavelengths provide extremely sensitive full disk measurements and are critical for detection of solar flares. They also are used directly for computing D-region sudden ionospheric disturbances (SID) and short-wave fadeouts (SWF). Counts are made every 3.6 seconds.

NOAA/POES Satellites Measurements of Fluxes of Electrons, Protons, and Alpha Particles Resulting from Solar and Geomagnetic Activity
The TIROS/NOAA satellite series is designed to meet the National Oceanic and Atmospheric Administration's (NOAA) need for operational, remote sensing products for numerical weather and space environment forecasts. The TIROS designation represents the experimental classification of a new instrument configuration while NOAA represents the operational classification. For January 1979 through May 1982, the National Geophysical Data Center archives HEPAD (High Energy Proton and Alpha Detector), MEPAD (Medium Energy) and TED (Total Energy) data from TIROS and NOAA satellites. The satellites are in sun-synchronous orbits at 850 kilometers altitude, an orbital period of 102 minutes and an inclination of 99 degrees. The orbital plane is tilted toward the sun in the northern hemisphere. Usually, two satellites are operational at all times. The data include the total magnetic field at 120 and 870 kilometers and the proton flux for 0 to 90 degrees in the following ranges: 30 KEV to 2.5 KEV; 2.5 MEV to greater than 80 MEV; greater than 30, 100, and 300 KEV. The Space Environment Monitor (SEM) flew onboard the NOAA POES series of satellites and continues providing data through the current day.

Hemispheric Power Index from DMSP satellites
The total hemispheric power input is computed from NOAA/TIROS and DMSP satellite measurements of high latitude precipitating energy flux carried by ions and electons with energies between 300 eV and 20 keV (NOAA/TIROS), or carried by electrons with energies between 460 eV and 30 keV (DMSP). The satellite orbits are sun synchronous around 850 km altitude. Times given are the center of the polar pass used to make the estimate where a typical polar pass takes about 25 minutes. Often there are two satellites operating simultaneously providing coverage at 30 to 60 minute intervals between auroral latitude crossings. The energy flux observations made during a single pass over the polar regions (above about 45 degrees of magnetic latitude) are used to estimate the total precipitating power input to a single hemisphere at that time. This power index was devised by David Evans for the NOAA/TIROS satellites, and adapted for the DMSP satellites by Frederick Rich and William Denig. The Air Force Research Laboratory Hemispheric Power Index was provided by the USAF Research Laboratory, Hanscom AFB, MA via the CEDAR Database.

Hemispheric Power Index from NOAA/TIROS satellites
The total hemispheric power input is computed from NOAA/TIROS and DMSP satellite measurements of high latitude precipitating energy flux carried by ions and electons with energies between 300 eV and 20 keV (NOAA/TIROS), or carried by electrons with energies between 460 eV and 30 keV (DMSP). The satellite orbits are sun synchronous around 850 km altitude. Times given are the center of the polar pass used to make the estimate where a typical polar pass takes about 25 minutes. Often there are two satellites operating simultaneously providing coverage at 30 to 60 minute intervals between auroral latitude crossings. The energy flux observations made during a single pass over the polar regions (above about 45 degrees of magnetic latitude) are used to estimate the total precipitating power input to a single hemisphere at that time. This power index was devised by David Evans for the NOAA/TIROS satellites, and adapted for the DMSP satellites by Frederick Rich and William Denig. The Air Force Research Laboratory Hemispheric Power Index was provided by the USAF Research Laboratory, Hanscom AFB, MA via the CEDAR Database.

DMSP SSJ/4 Measurements of High Energy Particles
DMSP SSJ/4 data provide a complete energy spectrum of the low energy particles that cause the aurora and other high latitude phenomena. The data set consists of electron and ion particle fluxes between 30 eV and 30 KeV recorded every second, satellite ephemeris and magnetic coordinated where the particles are likely to be absorbed by the atmosphere. Differential particle fluxes may be as large as 10 (10) at the lowest energies. The detectors also record high energy ions that penetrate both the satellite and the instrument. This is most noticeable in the South Atlantic Anomaly and the "horns" of the radiation belts. The SSJ.4 instrument was designed to measure the flux of charged particles as they enter the Earth's upper atmosphere from the near- Earth space environment. It consists of four electrostatic analyzers that record electrons and ions between 30 eV and 30 KeV as they flow past the spacecraft toward the Earth. The instruments "look" toward the satellite zenith. The curved plate detectors allow precipitating electrons and ions to enter through an aperture of about 2 x 10 (FWHM). Electrons and ions of the selected energy are deflected toward the target by an imposed electric field applied across the two plates. The two low energy detectors consist of 10 channels centered at 34, 49, 71, 101, 150, 218, 320, 460, 670, 960 KeV. The high energy detector measures particles in 10 channels centered at 1.0, 1.4, 2.1, 3.0, 4.4, 6.5, 9.5, 14.0, 20.5, and 29.5 KeV. Each detector dwells at each channel for 9.09 seconds from high energy channel to low. A complete cycle is sampled each second. The nominal response efficiency is 50% at a value of 10% of the central energy for that channel. The instruments are built by Emmanuel College under contract from the Space Physics Division of Phillips Laboratory and calibrated at Rice University. The National Geophysical Data Center (NGDC) has received DMSP precipitating electron and ion data since March 1975 from sensors SSJ/2, SSJ/3, SSJ/4 and F11. Processed data from March 75 to December 92 were received from AFGWC on magnetic tape. Since March 9, 1992 we have received raw satellite data from the ARchive Processing System on 8 mm tapes. Archive tapes are organized by satellite-orbit and they contain an automated format statement, an inventory, header information for each orbit and data records. Each data record consists of the satellite ephemeris in geographic and geomagnetic coordinates and 4 one-second values in units of differential particle flux for the 40 channels. DMSP data can be downloaded through the Space Physics Interactive Data Resource (SPIDR) at http://spidr.ngdc.noaa.gov/spidr/index.html