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1. What causes the ionosphere and magnetosphere to change?
   • Background Information

2. What real-time ionosphere and magnetosphere forecasts are available?
   • Real-Time Forecasts

3. What satellite sensors are used to monitor the sun, ionosphere and magnetosphere?
   • Satellite Sensors

Solar-Terrestrial Background Information:

• Solar flares and the solar wind affect the ionosphere and the magnetosphere of the earth.

  Solar flares emit radiation throughout the entire radiation spectrum.

  The impacts of a flare on earth depend on the location of the flare on the sun and the geometry with the earth.

  Introduction to the Space Environment.

  Glossary of Terms: Solar-Terrestrial and Space Weather.

• Solar Flares: Immediate Impacts

  For large flares, the solar X-Rays will cause short wave fadeouts for certain HF frequencies only in the sunlit hemisphere. The solar X-Rays direct affect the ionosphere of the sunlit hemisphere.

  The HF frequencies are typically affected for 15-30 minutes, but may be affected for 1-2 hours during extremely large solar flares.

  X-Rays sensors on the GOES satellites provide real time detection of the onset of X-Rays bombarding the near earth environment.

  GOES X-Ray data are monitored continuously by solar and ionospheric forecasters for NOAA and the US Air Force.

• Solar Flares: Delayed Impacts

  Depending on the type of solar flare and the sun-earth geometry, approximately 15 minutes (or later) after the flare, electrons and protons from the sun will arrive and be detected by GOES satellite sensors.

  These electrons and protons immediately affect the ionosphere, primarily in the polar and auroral (upper middle latitudes) zones of the entire ionosphere (sunlit and dark, both poles).

  A shock wave traveling in the magnetic field between the sun and earth may preceed the onset of the of the electrons and protons. Satellite(s) are located between the sun and earth the detect the shock waves, as well as monitor the solar wind.

  Large proton fluxes into the ionosphere cause the phenomena polar cap absorption event, which absorbs most HF frequencies for several days.

• Solar Flares: Geomagnetic Storms

  The onset of a geomagnetic storm, 2-3 days after a large solar flare, will affect the ionosphere.

  HF communication is degraded, sometimes severely degraded, in the polar and auroral zones of the entire ionosphere.

  The aurora is detected by the visible channel of DMSP.

  Satellite communication (UHF/VHF/SHF) is affected by ionospheric scintillation.

  The discontinuity in the solar wind, accompanying the particles for which cause the geomagnetic storm, are detected by the satellite(s) located between the sun and earth.

  Ionospheric effects of the geomagnetic storm may last 3-5 days.

• Solar Wind

  The solar wind is not constant. The stream of particles, flowing along magnetic field lines between the sun and earth, changes as sunspot regions and other solar features form and decay, and as the sun rotates.

  Satellites, located between the sun and earth, monitor the solar wind and provide real time data for solar forecasters.

• Routine Monitoring of the Ionosphere

  Many satellites (GPS and others) send a signal which travels through the ionosphere to be measured on earth. Total Electron Content (TEC) of the ionospheric column is calculated from the signal. Real Time TEC Map. Movie of Global TEC for the current day.

  Ionosondes are earth-based instruments which measure the critical frequencies of the ionosphere (foF2, D, E, F1, and F2 layers). Solar radiation is absorbed in different layers of the ionosphere.

  From experience and ionospheric climatology, Total Electron Content (TEC) information can be used to approximate critical frquencies of the ionosphere.

  Ionospheric measurements and background solar radio flux information are input into ionospheric models, which can be used to forecast Lowest Usable Frequencies (LUFs), Maximum Usable Frequencies (MUFs), and Optimal Freqencies in the HF Spectrum. realtime MUF

  Ionospheric tutorial (University of Michigan).

• Other Effects

  Satellite Drag causes decaying of the satellite orbit due to the increased number of particles in the near earth environment.

  Satellite Charging is the process of building a differential charge on the satellite skin. Problems arise when there is a discharge through the satellite, which can affect unprotected sensors.

  Radar Interference occurs for radars using the ionosphere (for example, Over the Horizon Backscatter Radars, OTH-B) in or near the auroral zone.

Real-Time Forecasts

Ionosphere and Solar Forecasting Page

Satellite Sensors

• GOES: Space Environment Monitor (SEM) data.

  Magnetometer. "The Magnetometer measures the magnitude and direction of the Earth's ambient magnetic field with three orthogonal sensors, located in a sensor assembly and attached to a boom that places the sensor three meters away from the body of the spacecraft" (from http://osdacces.nesdis.noaa.gov/goes.htm, GOES Mission).

  X-Ray sensors. "The XRS performs real-time measurements of the solar X-ray emissions in two channels covering the spectral ranges of 0.5 to 3 Angstroms (shortwave) and 1 to 8 Angstroms (longwave). The sensitivity of the sensor was chosen to permit quiet sun background measurements at as low a level of solar activity as possible while detecting events at the lowest practicable threshold for early event warning" (from http://osdacces.nesdis.noaa.gov/goes.htm, GOES Mission).

  Electron and proton sensors. "The EPS and HEPAD monitor solar protons and alpha particles, and produced during large flares, which are a radiation hazard to manned and unmanned operations in space and the ionosphere at high latitudes. The HEPAD instrument covers the very high-energy protons and alpha particles that are produced in large solar flares" (from http://osdacces.nesdis.noaa.gov/goes.htm, GOES Mission).

• DMSP

  Aurora is detected by the visible channel. Example.

  Precipitating Particle Data.

  • SSJ4 - Spectrometer for Precipitating 30ev to 30kev Ions/Electrons. "The SSJ4 (Special Sensor for Precipitationing Particles, Version 4) has flow on DMSP spacecraft since Flight 6 (F6, launched in 1978) and will continue through DMSP spacecraft F15. Presently F12 and F13 are the operational DMSP spacecraft. For spacecraft F16 through F20, an improved version of the particle detector, known as SSJ5, will be used" (from http://www.plh.af.mil/gps/dmspssj4.html).

  • SSM - Magnetic Fields & Field Aligned Currents. "The triaxial magnetometer on the DMSP spacecraft measure the magnetic field. This field has three sources: (1) The magnetic field from the solid Earth, (2) The magnetic field from electrical currents flowing in the ionosphere and magnetosphere, and (3) The magnetic field from the spacecraft. Measurement of source 2 is the principal objective of the SSM and measurement of source 1 is a secondary objective" from http://www.plh.af.mil/gps/dmspssm.html).

  • SSIES - Thermal Plasma Electric Field. "The Topside Ionospheric Plasma Monitor (acronym SSIES) measures the thermal plasma at the location of the DMSP spacecraft. The SSIES (Special Sensor for thermal Ions, Electrons and their Spatial variations) have been carried onboard spacecraft of the DMSP series since 1987" from http://www.plh.af.mil/gps/ssiesgeneral.html).

• TIROS

  Space Environment Monitor (SEM). "The Space Environment Monitor (SEM) that is regularly flown on the NOAA/TIROS series of low-altitude (850 km), polar-orbiting (98 degree inclination) spacecraft contains two instruments to monitor the energetic charged-particle environment near Earth" (from http://www.sel.noaa.gov/pmap/PoesSem.html).

  • "The Total Energy Detector (TED) provides the data used to determine the level of auroral activity and generate the statistical maps presented here. This instrument monitors the energy fluxes carried into the atmosphere by electrons and positive ions over the energy range between 300 and 20,000 electron Volts (eV). Particles of these energies are stopped by the atmosphere of the Earth at altitudes above 100 km, producing aurora" (from http://www.sel.noaa.gov/pmap/PoesSem.html).

  • "The Medium Energy Proton and Electron Detector (MEPED). This instrument includes four solid-state detector telescopes, two to measure the intensity of electrons between 30 and 1000 keV and two to measure the intensity of protons (positive ions) between 30 and 2500 keV, as well as solid-state "dome" detectors that measure the intensities of protons between 16 meV and 215 meV. In addition, the MEPED contains "dome" detectors that have very large fields of view (nearly 180 degrees) and are mounted on the side of the spacecraft facing away from Earth to monitor particles incident upon the atmosphere. These detectors are designed to detect and monitor energetic solar particles that cause severe ionospheric disturbances--blackouts--during solar particle events. " (from http://www.sel.noaa.gov/pmap/PoesSem.html).

  Auroral Activity.

  "Instruments on board the NOAA/TIROS polar-orbiting meteorological spacecraft continually monitor the power flux carried by the protons and electrons that produce aurora in the atmosphere. The Space Environment Center (SEC) has developed a technique that uses the power flux observations obtained during a single pass of the satellite over a polar region (which takes about 25 minutes) to estimate the total power deposited in an entire polar region by these auroral particles. The power input estimate is converted to an auroral activity index that ranges from 1 to 10."

  Source: http://www.sel.noaa.gov/pmap/index.html.

  Real Time Image and Description.
  Examples: N. Hemisphere, and S. Hemisphere.

  How to interpret these images.

• Satellite Ionosphere Monitor Systems

  Global Positioning Satellite (GPS)

  "Data from over 100+ continuously operating GPS receivers in a global network are being used to produce global maps of the ionosphere's total electron content (TEC). These Global Ionosphere Maps (GIM) provide instantaneous "snapshots" of the global TEC distribution, by interpolating, in both space and time, the 6-8 simultaneous TEC measurements obtained from each GPS receiver every 30 seconds. The maps can be produced unattended in a real-time mode, with an update rate of 5-15 minutes." Map of GPS receiver sites.

  "Global Ionosphere Maps (GIM) represent a new tool for monitoring global patterns of ionospheric weather, a key component of the space weather, which is driven by changes in solar ultra-violet radiation, the interplanetary particle stream known as the solar wind, and the underlying composition, wind patterns and electrodynamics of the thermosphere (the upper atmosphere at altitudes between 100 and 1000 km). GIMs are being used for global ionospheric delay calibrations, for scientific investigations of the upper atmosphere, and will be an important data source for the National Space Weather Program." Example of a Global Ionosphere Map.

  Source: http://sideshow.jpl.nasa.gov/gpsiono/gim.html.

• Solar Wind

  NASA's WIND Satellite.

  "NASA's WIND satellite was launched 1 November 1994. The spacecraft carries an array of scientific instruments for measuring the charged particles and electric and magnetic fields that characterize the interplanetary medium (or solar wind) - a plasma environment."

  "WIND provides nearly continuous monitoring of the solar wind conditions near Earth. These measurements are being used to investigate the disturbances and changes in the solar wind that drive important geomagnetic phenomena in the near-Earth geospace (such as aurorae and magnetic storms), as detected by other satellites and ground-based instruments. A primary goal of WIND is to advance understanding of the relationship between the dynamic solar wind and the near-Earth geospace. Additionally, WIND measurements are being used to study the nature of the solar wind itself."

  "The WIND satellite is one of a number of satellites, ground-based experiments, and theory investigations that are all part of the International Solar Terrestrial Physics (ISTP) program. Also included in the ISTP program are NASA's IMP-8 satellite , launched in 1973, NASA's POLAR satellite , launched in February, 1996, and the ISAS's Geotail satellite , launched in July, 1992."

  Source: http://web.mit.edu/afs/athena/org/s/space/www/wind.html.

  Others

References

• Source Book of the Solar-Geophysical Environment, 1982, Air Force Global Weather Central Technical Note, TN-82/002.

• Space Weather Resource Links, Rice University

• Ionospheric Systems Development, Jet Propulsion Laboratory

• Tropospheric and Ionospheric Remote Sensing using GPS Satellites, University Corporation for Atmospheric Research (UCAR).

Author: Mary S. Jordan, Department of Meteorology, Naval Postgraduate School, jordan@nps.edu
Last updated: January 2006