A Sudden Ionospheric Disturbance (SID) is any of several radio propagation anomalies due to ionospheric changes resulting from solar or geophysical events.

The National Oceanic and Atmospheric Administration (NOAA) monitors the geospace and solar environments using a variety of space weather sensors aboard its fleet of operational satellites.

Scientists monitor the structure of the solar corona, the outer most regions of the Sun's atmosphere, using radio waves (100’s of MHz to 10’s of GHz). Variations in the radiowave spectrum reveal characteristics of the corona and upper chromosphere in terms of altitude profile for the local plasma temperature, density and magnetic field. Typically, the lower the frequency then the higher the height of origin. The frequency, like the solar electron density, decreases uniformly outwards with 245 MHz originating high in the corona whereas 15,400 MHz originates in the low corona. Radio bursts are associated with solar flares. The delay at Earth of the different radio frequencies during burst events is due to the outward movement of the source. Bursts can have temperatures of 10xE12 degrees Kelvin. Large bursts last 10 to 20 minutes on average. Longer radio noise storms of persistent and variable high levels of radiation originate in sunspot groups, areas of large, intense magnetic fields. These storms are strongly circularly polarized due to the intense magnetic fields. The microwave wavelength 2800 MHz daily radio flux correlates highly with the daily sunspot number and the two databases are used interchangeably. The 2800 MHz, or 10.7 cm, responds to the same conditions that produce changes in the visible and X-ray wavelengths. Schmahl and Kundu (1995) find that the solar radio fluxes in the spectral range 1000-9400 MHz correlate well with the total solar irradiance. The intermediate frequencies (at 2800 and 3750 MHz) are produced mainly by free-free gyroresonance emission from sunspot structures, while 1000 and 9400 MHz flux are produced mainly by free-free processes from structures associated with plages. They can distinguish plage-associated emission from spot-associated emission in the time series of microwave flux, both contributing opposing effects on the total solar irradiance.

Collection includes a variety of indices related to solar activity contributed by a number of national and private solar observatories located worldwide. This metadata record is currently under construction.[SolarIndices A]

The Deep Space Climate ObserVatoRy (DSCOVR) satellite is a NOAA operated asset at the first Lagrange (L1) point. The primary space weather instrument is the PlasMag suite. PlasMag includes a fluxgate magnetometer (MAG) that measures the local magnetic field, and a Faraday Cup (FC) that measures the solar wind bulk properties (wind speed, density and temperature). The PlasMag solar wind data are essential inputs for the forecasts and nowcasts provided to SWPC customers. The PlasMag data are also available to scientists for sensor cal/val and for research purposes. DSCOVR was launched on Feb. 11, 2015, so all data present in the Archive from earlier dates are data used for ground testing, and do not represent the space environment. DSCOVR became operational on July 27, 2016. End Of Life (EOL) is anticipated to be December 2019. NCEI plans to receive data until EOL, and will continue to archive the data in accordance with Data Center policies.

This file is comprised of the variation one minute values of the geomagnetic components X, Y and Z. These data were calculated by the Air Force Geophysics Laboratory magnetometer network during the years 1978-1983. The values are variation values and should not be used in looking at absolute values of the geomagnetic components.

Collection includes a variety of indices related to solar activity contributed by a number of national and private solar observatories located worldwide. This metadata record is currently under construction.[SolarIndices A]

Collection includes a variety of space weather datasets from the National Oceanic and Atmospheric Administration and from the World Data Service for Geophysics, Boulder.

Solar Indices Bulletin is a prompt monthly information product that is distributed within two weeks after the observation month closes. For the month just ended, this 2-page circular tabulates daily values of sunspot numbers and 10.7 cm solar radio flux observed at Penticton (previously at Ottawa); flux measurements at eight other wavelengths are included. Page 2 of the Bulletin gives a table of smoothed monthly mean sunspot numbers for the current solar cycle--a table that begins with smoothed observed values for each month and ends with predictions.

Listings and characterizations of solar x-ray flares