|
|
| System Message(s). Please correct the following:
Your session has expired. Please re-login to use that resource
|
SPIDR Datasets section
|
|
16-02-2007 15:44:38
|
|
Assimilative Mapping of Ionospheric Electrodynamics (AMIE)
The AMIE procedure is an optimally constrained, weighted least-squares fit of electric potential distribution to diverse types of atmospheric observations. This data set represents global geomagnetic indices derived from that model. The model in this case was run using all available magnetometers and a background driven by IMF but no other data even when available. See: A.J. Ridley and E.A. Kihn, Polar cap index comparisons with AMIE cross polar cap potential, electric field, and polar cap area, Geophys. Res. Lett., 31, doi:10.1029/2003GL019113, 2004 for more information.
For more information on AMIE itself:
http://www.hao.ucar.edu/Public/models/models.html
|
http://spidr.ngdc.noaa.gov
|
|
rating: 1;
views: 2718;
bookmark(s): 4;
replies: 1
Bookmark
|
|
|
2010-10-25T14:42:08
|
|
Ionospheric Total Electron Content (TEC) is the total number of electrons in a column of unit cross section extending from the transmitter to receiver. TEC is calculated from observations of the rotation of a polarized signal (Faraday rotations) transmitted from the satellite. Most of the TEC data have had limited quality control work done and are considered "raw" data. USAF Global Weather Central (GWC) has supplied data from January 1980 through May 1992. During this period, there have been a many as twelve and as few as ten recording stations. The stations are Anchorage (61.2N,210.1E), Athens (38.0N,23.60E), Boulder(40.0N,254.7E), Goose Bay (53.3N,299.2E), La Posta (32.8N,243.5E), Lunping (24.9N,121.2E), Osan (37.2N,127.1E), Palehua (20.7N,203.7E), Patrick (28.2N,279.4E), Ramey (18.1N,293.8E), Sagamore Hill (42.6N,289.2E), and Shemya (52.7N,174.1E). There is a limited amount of TEC data available from Sagamore Hill and Sydney (34.0S,150.7E) from 1967 - 1974. The data consist of hourly values, medians, and median counts. Data are available on magnetic tape or IBM-compatible diskette. The smallest division of data that will be pulled for a data request is a network month. Each month has from one to twelve stations for each network month. For GWC data, there will be at least ten to twelve stations for each month.
|
|
|
rating: 0;
views: 427;
bookmark(s): 0;
replies: 0
Bookmark
|
|
|
16-02-2007 12:56:37
|
|
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
|
http://spidr.ngdc.noaa.gov
|
|
rating: 0;
views: 1789;
bookmark(s): 3;
replies: 0
Bookmark
|
|
|
16-02-2007 12:55:31
|
|
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.
|
http://spidr.ngdc.noaa.gov
|
|
rating: 0;
views: 2808;
bookmark(s): 6;
replies: 0
Bookmark
|
|
|
16-02-2007 12:55:12
|
|
GOES-12 Solar X-ray Imager (SXI) took its first official image on September 7th, 2001 after successfully concluding the first phase of post-launch testing. This SXI is a culmination of more than twenty years of effort. NOAA wishes to acknowledge and thank the USAF for funding the SXI and NASA Marshall for building this fine instrument as well as its in-kind support.
The instrument is a broadband imager operating in the 0.6-6.0 nm bandpass. It has a full width at half maximum (FWHM) of ~10 arcsec sampled with 5 arcsec pixels in a 512x512 array. When operational, it will provide full-disk solar images at a 1-minute cadence around the clock, except for brief periods during orbital eclipse seasons. Available combinations of exposures and filters allow the entire dynamic range of solar x-ray features to be covered: from coronal holes to X-class flares. In addition, using ratio images from different filters allows temperature and emission measure estimates to be made.
To meet operational goals, flexible observing strategies are implemented as recurring sequences of images. Sequences can be selected or modified based on solar activity levels. The operational goals are to:
- Locate coronal holes for geomagnetic storm forecasts,
- Detect and locate flares for forecasts of solar energetic particle (SEP) events related to flares,
- Monitor changes in the corona that indicate coronal mass ejections (CMEs),
- Detect active regions beyond east limb for F10.7 forecasts, and
- Analyze active region complexity for flare forecasts.
NOAA/SEC receives the data, which is being shared with the US Air Force, and NASA in real-time. Products available to the research community are described as Level 0 (raw data) and Level 1. The level 1 data consist of single calibrated images which have had defects removed. All levels of data will be archived at the NOAA National Geophysical Data Center (NGDC). The latest images can be found on SEC's Latest SXI Images web page.
SXI testing is proceeding and images are being put on the Web in near real time, i.e., within a minute or so of being taken. Some of the testing, of course, produces rather indecipherable images. However, we also anticipate long periods of relatively 'normal' imaging. Currently, only 'browse' images in PNG format are available for downloading. SolarSoft compatible FITS files will be available in near real-time when the instrument has been fully checked out.
|
http://spidr.ngdc.noaa.gov
|
|
rating: 0;
views: 1640;
bookmark(s): 1;
replies: 0
Bookmark
|
|
|
16-02-2007 12:56:30
|
|
The National Geophysical Data Center maintains an active database of solar and geomagnetic indices to further the understanding of Earth magnetism and the Sun-Earth environment.
Geomagnetic indices constitute a data series aiming at describing the solar activity and geomagnetic activity at a planetary scale.
The data series are homogeneous since 1932 for Kp and Ap, 1957 for Dst.
|
http://spidr.ngdc.noaa.gov
|
|
rating: 1;
views: 2943;
bookmark(s): 2;
replies: 0
Bookmark
|
|
|
16-02-2007 12:56:26
|
|
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.
|
http://spidr.ngdc.noaa.gov
|
|
rating: 0;
views: 1383;
bookmark(s): 2;
replies: 0
Bookmark
|
|
|
16-02-2007 12:55:28
|
|
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.
|
http://spidr.ngdc.noaa.gov
|
|
rating: 0;
views: 1528;
bookmark(s): 0;
replies: 0
Bookmark
|
|
|
16-02-2007 12:56:33
|
|
The National Geophysical Data Center maintains an active database of 1 min geomagnetic variations to further the understanding of Earth magnetism and the Sun-Earth environment.
To measure the Earth's magnetism in any place, we must measure the direction and intensity of the field. The parameters describing the direction of the magnetic field are declination (D), inclination (I). D and I are measured in units of degrees. The intensity of the total field (F) is described by the horizontal component (H), vertical component (Z), and the north (X) and east (Y) components of the horizontal intensity. These components may be measured in units of Oersted (1 oersted=1gauss) but are generally reported in nanoTesla (1nT * 100,000 = 1 0ersted). The Earth's magnetic field intensity is roughly between 25,000 - 65,000 nT (.25 - .65 oersted). Magnetic declination is the angle between magnetic north and true north. D is considered positive when the angle measured is east of true north and negative when west. Magnetic inclination is the angle between the horizontal plane and the total field vector.
The geomagnetic field measured at any point on the Earth's surface is a combination of several magnetic fields generated by various sources. These fields are superimposed on and interact with each other. More than 90% of the field measured is generated INTERNAL to the planet in the Earth's outer core. This portion of the geomagnetic field is often refered to as the Main Field. The Main Field varies slowly in time and can be described by Mathematical Models such as the International Geomagnetic Reference Field (IGRF) and World Magnetic Model (WMM). The Main Field creates a cavity in interplanetary space called the magnetosphere, where the Earth's magnetic field dominates in the magnetic field of the solar wind. The magnetosphere is shaped somewhat like a comet in response to the dynamic pressure of the solar wind. It is compressed on the side toward the sun to about 10 Earth radii and is extended tail-like on the side away from the sun to more than 100 Earth radii. The magnetosphere deflects the flow of most solar wind particles around the Earth, while the geomagnetic field lines guide charged particle motion within the magnetosphere.
The differential flow of ions and electrons inside the magnetosphere and in the ionosphere form current systems, which cause variations in the intensity of the Earth's magnetic field. These EXTERNAL currents in the ionized upper atmosphere and magnetosphere vary on a much shorter time scale than the INTERNAL Main Field and may create magnetic fields as large as 10% of the Main Field. Other important sources are the fields arising from electrical currents flowing in the ionized upper atmosphere, and the fields induced by currents flowing within the Earth's crust. The Main field component varies slowly in time and can be grossly described as that of a bar magnet with north and south poles deep inside the Earth and magnetic field lines that extend well out into space. The Earth's magnetic field varies both in space and time.
Historically, magnetic observatories were established to monitor the secular change of the Earth's magnetic field, and this remains one of their most important functions. This generally involves absolute measurements sufficient in number to monitor instrumental drift and to produce annual means. Over 70 countries operate more than 200 observatories worldwide. The magnetic observatory mean data are crucial to the studies of secular change, investigations into the Earth's interior, and to global modeling efforts. One minute geomagnetic field variations are archived in the database since March 1901.
|
http://spidr.ngdc.noaa.gov
|
|
rating: 0;
views: 1702;
bookmark(s): 1;
replies: 0
Bookmark
|
|
|
16-02-2007 12:56:21
|
|
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.
|
http://spidr.ngdc.noaa.gov
|
|
rating: 0;
views: 1640;
bookmark(s): 1;
replies: 0
Bookmark
|
|
|
16-02-2007 12:55:24
|
|
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.
|
http://spidr.ngdc.noaa.gov
|
|
rating: 0;
views: 1143;
bookmark(s): 0;
replies: 0
Bookmark
|
|
|
16-02-2007 12:56:16
|
|
The ionosphere is that part of the upper atmosphere where free electrons occur in sufficient density to have an appreciable influence on the propagation of radio frequency electromagnetic waves. This ionization depends primarily on the Sun and its activity. Ionospheric structures and peak densities in the ionosphere vary greatly with time (sunspot cycle, seasonally, and diurnally), with geographical location (polar, auroral zones, mid-latitudes, and equatorial regions), and with certain solar-related ionospheric disturbances.
The major part of the ionization is produced by solar X-ray andultraviolet radiation and by corpuscular radiation from the Sun. The most noticeable effect is seen as the Earth rotates with respect to the Sun; ionization increases in the sunlit atmosphere and decreases on the shadowed side. Although the Sun is the largest contributor toward the ionization, cosmic rays make a small contribution. Any atmospheric disturbance effects the distribution of the ionization.
The ionosphere is a dynamic system controlled by many parameters including acoustic motions of the atmosphere, electromagnetic emissions, and variations in the geomagnetic field. Because of its extreme sensitivity to atmospheric changes, the ionosphere is a very sensitive monitor of atmospheric events.
In some circles it is thought that there is persuasive evidence of an ionospheric precursor to large earthquakes that can be used a predictor. Besides the obvious acoustic waves generated before and during an earthquake, a part of the preparation process of large earthquakes is the generation of electromagnetic emissions (EMEs). These EMEs have been detected in the ionosphere up to six days prior to a large earthquake, such as with the May 1960, Chilean 8.3 earthquake.
The most accurate way of measuring the ionosphere is with a ground-based ionosonde, which records data as ionograms. Usually Ionograms are recorded with 15 min or 1 hr time step. The first ionograms in our database are dated by Jan, 1942.
|
http://spidr.ngdc.noaa.gov
|
|
rating: 1;
views: 2111;
bookmark(s): 2;
replies: 0
Bookmark
|
|
|
16-02-2007 12:55:40
|
|
The National Geophysical Data Center maintains an active database of 1 min geomagnetic variations to further the understanding of Earth magnetism and the Sun-Earth environment.
To measure the Earth's magnetism in any place, we must measure the direction and intensity of the field. The parameters describing the direction of the magnetic field are declination (D), inclination (I). D and I are measured in units of degrees. The intensity of the total field (F) is described by the horizontal component (H), vertical component (Z), and the north (X) and east (Y) components of the horizontal intensity. These components may be measured in units of Oersted (1 oersted=1gauss) but are generally reported in nanoTesla (1nT * 100,000 = 1 0ersted). The Earth's magnetic field intensity is roughly between 25,000 - 65,000 nT (.25 - .65 oersted). Magnetic declination is the angle between magnetic north and true north. D is considered positive when the angle measured is east of true north and negative when west. Magnetic inclination is the angle between the horizontal plane and the total field vector.
The geomagnetic field measured at any point on the Earth's surface is a combination of several magnetic fields generated by various sources. These fields are superimposed on and interact with each other. More than 90% of the field measured is generated INTERNAL to the planet in the Earth's outer core. This portion of the geomagnetic field is often refered to as the Main Field. The Main Field varies slowly in time and can be described by Mathematical Models such as the International Geomagnetic Reference Field (IGRF) and World Magnetic Model (WMM). The Main Field creates a cavity in interplanetary space called the magnetosphere, where the Earth's magnetic field dominates in the magnetic field of the solar wind. The magnetosphere is shaped somewhat like a comet in response to the dynamic pressure of the solar wind. It is compressed on the side toward the sun to about 10 Earth radii and is extended tail-like on the side away from the sun to more than 100 Earth radii. The magnetosphere deflects the flow of most solar wind particles around the Earth, while the geomagnetic field lines guide charged particle motion within the magnetosphere.
The differential flow of ions and electrons inside the magnetosphere and in the ionosphere form current systems, which cause variations in the intensity of the Earth's magnetic field. These EXTERNAL currents in the ionized upper atmosphere and magnetosphere vary on a much shorter time scale than the INTERNAL Main Field and may create magnetic fields as large as 10% of the Main Field. Other important sources are the fields arising from electrical currents flowing in the ionized upper atmosphere, and the fields induced by currents flowing within the Earth's crust. The Main field component varies slowly in time and can be grossly described as that of a bar magnet with north and south poles deep inside the Earth and magnetic field lines that extend well out into space. The Earth's magnetic field varies both in space and time.
Historically, magnetic observatories were established to monitor the secular change of the Earth's magnetic field, and this remains one of their most important functions. This generally involves absolute measurements sufficient in number to monitor instrumental drift and to produce annual means. Over 70 countries operate more than 200 observatories worldwide. The magnetic observatory mean data are crucial to the studies of secular change, investigations into the Earth's interior, and to global modeling efforts. One minute geomagnetic field variations are archived in the database since January 1975.
|
http://spidr.ngdc.noaa.gov
|
|
rating: 0;
views: 1633;
bookmark(s): 0;
replies: 0
Bookmark
|
|
|
16-02-2007 12:55:35
|
|
The National Geophysical Data Center maintains an active database of 1 min geomagnetic variations to further the understanding of Earth magnetism and the Sun-Earth environment.
To measure the Earth's magnetism in any place, we must measure the direction and intensity of the field. The parameters describing the direction of the magnetic field are declination (D), inclination (I). D and I are measured in units of degrees. The intensity of the total field (F) is described by the horizontal component (H), vertical component (Z), and the north (X) and east (Y) components of the horizontal intensity. These components may be measured in units of Oersted (1 oersted=1gauss) but are generally reported in nanoTesla (1nT * 100,000 = 1 0ersted). The Earth's magnetic field intensity is roughly between 25,000 - 65,000 nT (.25 - .65 oersted). Magnetic declination is the angle between magnetic north and true north. D is considered positive when the angle measured is east of true north and negative when west. Magnetic inclination is the angle between the horizontal plane and the total field vector.
The geomagnetic field measured at any point on the Earth's surface is a combination of several magnetic fields generated by various sources. These fields are superimposed on and interact with each other. More than 90% of the field measured is generated INTERNAL to the planet in the Earth's outer core. This portion of the geomagnetic field is often refered to as the Main Field. The Main Field varies slowly in time and can be described by Mathematical Models such as the International Geomagnetic Reference Field (IGRF) and World Magnetic Model (WMM). The Main Field creates a cavity in interplanetary space called the magnetosphere, where the Earth's magnetic field dominates in the magnetic field of the solar wind. The magnetosphere is shaped somewhat like a comet in response to the dynamic pressure of the solar wind. It is compressed on the side toward the sun to about 10 Earth radii and is extended tail-like on the side away from the sun to more than 100 Earth radii. The magnetosphere deflects the flow of most solar wind particles around the Earth, while the geomagnetic field lines guide charged particle motion within the magnetosphere.
The differential flow of ions and electrons inside the magnetosphere and in the ionosphere form current systems, which cause variations in the intensity of the Earth's magnetic field. These EXTERNAL currents in the ionized upper atmosphere and magnetosphere vary on a much shorter time scale than the INTERNAL Main Field and may create magnetic fields as large as 10% of the Main Field. Other important sources are the fields arising from electrical currents flowing in the ionized upper atmosphere, and the fields induced by currents flowing within the Earth's crust. The Main field component varies slowly in time and can be grossly described as that of a bar magnet with north and south poles deep inside the Earth and magnetic field lines that extend well out into space. The Earth's magnetic field varies both in space and time.
Historically, magnetic observatories were established to monitor the secular change of the Earth's magnetic field, and this remains one of their most important functions. This generally involves absolute measurements sufficient in number to monitor instrumental drift and to produce annual means. Over 70 countries operate more than 200 observatories worldwide. The magnetic observatory mean data are crucial to the studies of secular change, investigations into the Earth's interior, and to global modeling efforts. One minute geomagnetic field variations are archived in the database since January 1813.
|
http://spidr.ngdc.noaa.gov
|
|
rating: 0;
views: 1491;
bookmark(s): 0;
replies: 0
Bookmark
|
|
|
16-02-2007 12:56:07
|
|
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.
|
http://spidr.ngdc.noaa.gov
|
|
rating: 0;
views: 1647;
bookmark(s): 3;
replies: 0
Bookmark
|
|
|
16-02-2007 12:55:20
|
|
The Nighttime Lights of the World dataset contains the first satellite-based global inventory of human settlements,derived from nighttime data from the Defense Meteorological SatelliteProgram (DMSP) Operational Linescan System (OLS). The DMSP-OLS has the unique capability to observe faint sourcesof visible-near infrared emissions present at the Earth's surface, including cities, towns, villages, gas flares,and fires. NGDC has developed algorithms for producing georeferenced fire and nighttime lights products.
|
http://sabr.ngdc.noaa.gov
|
|
rating: 0;
views: 1872;
bookmark(s): 0;
replies: 1
Bookmark
|
|
|
2010-10-13T14:23:30
|
|
The Ovation Prime Real-Time (OPRT) product is a real-time forecast and nowcast model of auroral power and is an operational implementation of the work by Newell et al (2009). OPRT is run every 5 minutes producing precipitating energy flux for 4 distinct auroral types in 240 distinct geomagnetic latitude / longitude bins for each hemisphere. The model's output is latitudinally bound to polar latitudes greater than 50 degrees geomagnetic latitude.
|
|
|
rating: 0;
views: 455;
bookmark(s): 0;
replies: 0
Bookmark
|
|
|
16-02-2007 15:45:29
|
|
Polar Cap Index : The PC index is an index to monitor the polar cap magnetic activity which is mainly caused by changes in the IMF southward component (BZ) and solar wind velocity. Numerous investigations have shwon that the IMF southward component drives ionospheric convection over the polar caps, which is sensed by ground magnetometers responding to the two-cell system of currents flowing in the ionosphere. As the Earth rotates under this two-cell current system, a near-pole station is always located under the sun-aligned part of the system (i.e. a transpolar current). This allows derivation of an index from data obtained at a single near-pole station simply calculating a magnetic horizontal component disturbance along the dawn-dusk meridian. Based on an availability of geomagnetic data from near-pole stations Thule (Greenland, 86.5° geomagnetic latitude) and Vostok (Antarctica, -83.4° ), the new magnetic activity index PC was introduced and studied by Troshichev and Andrezen [Planet. Space Sci., 33, 415, 1985], and Troshichev et al. [Planet. Space Sci., 36, 1095, 1988].
|
http://spidr.ngdc.noaa.gov
|
|
rating: 0;
views: 1666;
bookmark(s): 0;
replies: 0
Bookmark
|
|
|
16-02-2007 12:55:47
|
|
Cosmic rays are energetic particles that are found in space and filter
through our atmosphere. Cosmic rays have interested scientists for
many different reasons. They come from all directions in space, and
the origination of many of these cosmic rays is unknown. Cosmic rays
were originally discovered because of the ionozation they produce in
our atmosphere. Cosmic rays also have an extreme energy range of
incident particles, which have allowed physicists to study aspects of
their field that can not be studied in any other way.
In the past, we have often referred to cosmic rays as "galactic cosmic
rays", because we did not know where they originated. Now scientists
have determined that the sun discharges a significant amount of these
high-energy particles. "Solar cosmic rays" (cosmic rays from the sun)
originate in the sun's chromosphere. Most solar cosmic ray events
correlate relatively well with solar flares.
Scientists have postulated that cosmic rays can affect the earth by
causing changes in weather. Cosmic rays can cause clouds to form in
the upper atmosphere, after the particles collide with other
atmospheric particles in our troposphere. The process of a cosmic ray
particle colliding with particles in our atmosphere and disintegrating
into smaller pions, muons, and the like, is called a cosmic ray
shower. These particles can be measured on the Earth's surface by
neutron monitors.
The cosmic ray data from neutron monitors, ionization chambers and
muon telescopes are primarily hourly-value data held as tabulations on
paper, or in digital format (currently 130 stations and over 100
Mbytes). Some of these data are regularly published in both tabular
and graphical forms in Solar-Geophysical Data
(http://www.ngdc.noaa.gov/stp/SOLAR/sgdintro.html)
|
http://spidr.ngdc.noaa.gov
|
|
rating: 0;
views: 1592;
bookmark(s): 0;
replies: 0
Bookmark
|
|
|
16-02-2007 12:56:44
|
|
Cosmic rays are energetic particles that are found in space and filter
through our atmosphere. Cosmic rays have interested scientists for
many different reasons. They come from all directions in space, and
the origination of many of these cosmic rays is unknown. Cosmic rays
were originally discovered because of the ionozation they produce in
our atmosphere. Cosmic rays also have an extreme energy range of
incident particles, which have allowed physicists to study aspects of
their field that can not be studied in any other way.
In the past, we have often referred to cosmic rays as "galactic cosmic
rays", because we did not know where they originated. Now scientists
have determined that the sun discharges a significant amount of these
high-energy particles. "Solar cosmic rays" (cosmic rays from the sun)
originate in the sun's chromosphere. Most solar cosmic ray events
correlate relatively well with solar flares.
Scientists have postulated that cosmic rays can affect the earth by
causing changes in weather. Cosmic rays can cause clouds to form in
the upper atmosphere, after the particles collide with other
atmospheric particles in our troposphere. The process of a cosmic ray
particle colliding with particles in our atmosphere and disintegrating
into smaller pions, muons, and the like, is called a cosmic ray
shower. These particles can be measured on the Earth's surface by
neutron monitors.
The cosmic ray data from neutron monitors, ionization chambers and
muon telescopes are primarily hourly-value data held as tabulations on
paper, or in digital format (currently 130 stations and over 100
Mbytes). Some of these data are regularly published in both tabular
and graphical forms in Solar-Geophysical Data
(http://www.ngdc.noaa.gov/stp/SOLAR/sgdintro.html)
|
http://spidr.ngdc.noaa.gov
|
|
rating: 0;
views: 1475;
bookmark(s): 2;
replies: 0
Bookmark
|
|
|
16-02-2007 12:54:06
|
|
Cosmic rays are energetic particles that are found in space and filter
through our atmosphere. Cosmic rays have interested scientists for
many different reasons. They come from all directions in space, and
the origination of many of these cosmic rays is unknown. Cosmic rays
were originally discovered because of the ionozation they produce in
our atmosphere. Cosmic rays also have an extreme energy range of
incident particles, which have allowed physicists to study aspects of
their field that can not be studied in any other way.
In the past, we have often referred to cosmic rays as "galactic cosmic
rays", because we did not know where they originated. Now scientists
have determined that the sun discharges a significant amount of these
high-energy particles. "Solar cosmic rays" (cosmic rays from the sun)
originate in the sun's chromosphere. Most solar cosmic ray events
correlate relatively well with solar flares.
Scientists have postulated that cosmic rays can affect the earth by
causing changes in weather. Cosmic rays can cause clouds to form in
the upper atmosphere, after the particles collide with other
atmospheric particles in our troposphere. The process of a cosmic ray
particle colliding with particles in our atmosphere and disintegrating
into smaller pions, muons, and the like, is called a cosmic ray
shower. These particles can be measured on the Earth's surface by
neutron monitors.
The cosmic ray data from neutron monitors, ionization chambers and
muon telescopes are primarily hourly-value data held as tabulations on
paper, or in digital format (currently 130 stations and over 100
Mbytes). Some of these data are regularly published in both tabular
and graphical forms in Solar-Geophysical Data
(http://www.ngdc.noaa.gov/stp/SOLAR/sgdintro.html)
|
http://spidr.ngdc.noaa.gov
|
|
rating: 0;
views: 1555;
bookmark(s): 1;
replies: 0
Bookmark
|
|
|
16-02-2007 12:56:02
|
|
H-alpha spectroheliograms are generally taken with telescopes equipped
with a half-angstrom bandwidth Halle filter. These H-alpha
observations consist of solar patrols (routine monitoring) of the
whole disk or selected regions of the sun. Faculae, prominences and
filaments and other bright and dark areas are features visible in this
wavelength. Flares, disappearing filaments, surges on the disk, and
eruptive prominences are some of the phenomena studied with these
data. The data center archives mostly photographs 35-mm film data
from 18 stations are sending their H-alpha patrol film to the data
center.
H-alpha solar flares are available in cooperation with the Department
d'Astronomie Solaire et Planetaire, Observatoire de Paris. These are
published as part of the Solar-Geophysical Data Reports (SGD) and are
available since 1980 from:
http://www.ngdc.noaa.gov/stp/SOLAR/ftpsolarflares.html
Solar H-alpha flare index data is available from the University
Kandilli Observatory, Istanbul, Turkey since 1976. These are also
available from:
http://www.ngdc.noaa.gov/stp/SOLAR/ftpsolarflares.html
Non-flare H-alpha observations are published in the Solar_Geophysical
Data (SGD) Reports going back to 1955. See:
http://www.ngdc.noaa.gov/stp/SOLAR/sgdintro.html.
Solar data can also be obtained through the Space Physics Interactive
Data Resource (SPIDR): http://spidr.ngdc.noaa.gov/spidr/index.html
|
http://spidr.ngdc.noaa.gov
|
|
rating: 0;
views: 1591;
bookmark(s): 0;
replies: 0
Bookmark
|
|
|
16-02-2007 12:55:16
|
|
The National Geophysical Data Center maintains an active database of solar activity indices to further the understanding of Earth magnetism and the Sun-Earth environment.
The sun emits radio energy with a slowly varying intensity. This radio flux, which originates from atmospheric layers high in the sun's chromosphere and low in its corona, changes gradually from day-to-day, in response to the number of spot groups on the disk. Radio intensity levels consist of emission from three sources: from the undisturbed solar surface, from developing active regions, and from short-lived enhancements above the daily level. Solar flux density at 2800 megaHertz has been recorded routinely by radio telescope near Ottawa since February 14, 1947. Each day, levels are determined at local noon (1700 GMT) and then corrected to within a few percent for factors such as antenna gain, atmospheric absorption, bursts in progress, and background sky temperature. Beginning in June 1991, the solar flux density measurement source is Penticton, B.C., Canada.
The relative sunspot number is an index of the activity of the entire visible disk of the Sun. It is determined each day without reference to preceding days. Each isolated cluster of sunspots is termed a sunspot group, and it may consist of one or a large number of distinct spots whose size can range from 10 or more square degrees of the solar surface down to the limit of resolution (e.g., 1/25 square degree). The relative sunspot number is defined as R = K (10g + s), where g is the number of sunspot groups and s is the total number of distinct spots. The scale factor K (usually less than unity) depends on the observer and is intended to effect the conversion to the scale originated by Wolf.
The data contain fluxes from the entire solar disk at a frequency of 2800 megaHertz in units of 10 to the -22 Joules/second/square meter/Hertz. Each number has been multiplied by 10 to suppress the decimal point. Three sets of fluxes - the observed, the adjusted, and the absolute - are summarized. Of the three, the observed numbers are the least refined, since they contain fluctuations as large as 7% that arise from the changing sun-earth distance. In contrast, adjusted fluxes have this variation removed; the numbers in these tables equal the energy flux received by a detector located at the mean distance between sun and earth. Finally, the absolute levels carry the error reduction one step further; here each adjusted value is multiplied by 0.90 to compensate for uncertainties in antenna gain and in waves reflected from the ground.
Group Sunspot Numbers (Rg) were derived to provide a homogeneous record of solar activity from 1610 to 1995. Care was taken that the long-term changes are more self-consistent than are the changes using the Wolf Sunspot Numbers.
Daily standard deviations of the Group Sunspot Numbers for 1610 to 1995 represent the random errors in the daily means.
|
http://spidr.ngdc.noaa.gov
|
|
rating: 0;
views: 2149;
bookmark(s): 2;
replies: 0
Bookmark
|
|
|
2010-10-25T14:41:50
|
|
The US Total Electron Content (US-TEC) product is designed to specify TEC over the Continental US (CONUS) in near real-time. The product uses a Kalman Filter data assimilation model, described in the Technical Documentation. This technique is driven by data from ground-based Global Positioning System (GPS) dual frequency receivers. The primary data stream comes from the Maritime and Nationwide Differential GPS (M/NDGPS) real time network of stations operated by the US Coast Guard (USCG). As of January 2006, there were about 130 stations ingested into the model. This number has been gradually increasing and will be augmented by Federal Aviation Administration/Wide Area Augmentation System (FAA/WAAS) data, and new stations in areas with poor coverage. This product has evolved through a collaboration between the Space Weather Prediction Center (SWPC), the National Geodetic Survey (NGS), the National Geophysical Data Center (NGDC), and the Global Systems Division (GSD).
|
|
|
rating: 0;
views: 408;
bookmark(s): 0;
replies: 0
Bookmark
|
|
|
16-02-2007 12:55:43
|
|
Visible and infrared (IR) imagery from the U.S. Air Force Defense
Meteorological Satellite Program (DMSP) Operational Linescan System
(OLS) instruments are used to monitor the global distribution of
clouds and cloud top temperatures twice each day during day time and
night time. The archive data set consists of low resolution, global
coverage, and high resolution, regional coverage, imagery recorded
along a 3,000 km scan, satellite ephemeris and solar and lunar data.
IR pixel values vary from 190 to 310 Kelvins in 256 equally spaced
steps. Onboard calibration is performed during each scan. Visible
pixels are currently relative values ranging from 0 to 63 rather than
absolute values in Watts per square meter. Instrumental gain levels
are adjusted to maintain constant cloud reference values under varying
conditions of solar and lunar illumination. Telescope pixel values
are replaced by Photo Multiplier Tube (PMT) values at night. A
telescope pixel is 0.55 km at high resolution and 2.7 km at low
resolution. Low resolution values are the mean of the appropriate 25
high resolution values. A PMT pixel is 2.7 km at nadir.
The OLS instrument consists of two telescopes and a photo multiplier
tube. The visible telescope is sensitive to radiation from 0.40 -
1.10 micron (0.58 - 0.91 micron FWHM) and 10(-3) - 10 (-5) Watts per
m(2) per steradian. The infrared telescope is sensitive to radiation
from 10.0 - 13.4 micron (10.3 - 12.9 micron FWHM) and 190 to 310
Kelvins. The PMT is sensitive to radiation from 0.47 - 0.95 micron
(0.51 - 0.86 micron FWHM) at 10(-5) - 10(-9) Watts per m(2) per
steradian. The detectors sweep back and forth in a "whisk broom" or
pendulum-type motion. The continuous analog signal is sampled at a
constant rate so the Earth-located centers of each pixel are roughly
equidistant, i.e., 0.5 km apart. 7,325 pixels are digitized across the
108 deg swath from limb to limb. The instruments are built by
Westinghouse Corporation.
DMSP satellites are in a sun-synchronous, low altitude polar orbit.
Current equatorial crossing times are 0536 and 1052 local time. The
orbital period is 101 minutes and the nominal altitude is 830 km.
DMSP data are downlinked to Thule AFB and transmitted to Air Force
Weather Agency (AFWA) via communications satellite. At AFWA, the
data are decrypted and sent to NGDC via T1 (Note: March 1992 -
November 1996 data were sent on 8mm tape). The incoming data are
inventoried and copied to tape. Currently, NGDC receives and processes
approximately 8.5 Gb of data per day from 4 satellites.
Recent results obtained at NOAA-NGDC with the digital DMSP-OLS data
(Elvidge et al., 1996 and 1997) suggest that nightly broad area
inventories of fires and power outages could be readily
produced. Algorithms have been developed to identify and geolocate
visible-near infrared emission sources in nighttime OLS imagery. This
paper describes the procedures which have been developed for detection
of ephemeral events (fires and power outages) in DMSP-OLS data. The
method relies on identifying a reference set of stable lights (cities,
towns, villages, gas flares) database using a time series of OLS
observations. Once the stable lights data set has been derived, it is
possible to overlay the lights from an individual orbit to detect new
visible-near infrared emission sources (e.g. fires) or locations where
visible-near infrared emission was expected, but not observed (power
outages). http://dmsp.ngdc.noaa.gov/html/download_Night_time_lights_94-95.html
The DMSP sample imagery and other data and documentation can be found on
the DMSP Home Page at http://dmsp.ngdc.noaa.gov/dmsp.html
DMSP imagery can also be found at the Space Physics Interactive
Data resource (SPIDR) at http://spidr.ngdc.noaa.gov/spidr/index.html
|
http://sabr.ngdc.noaa.gov
|
|
rating: 0;
views: 2127;
bookmark(s): 0;
replies: 0
Bookmark
|
|
Mail to Administrator