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National Oceanic and Atmospheric Administration

Monday, December 05, 2016 04:22:37

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More about the NOAA Space Weather Scales

GOES Magnetometer

Since 1975, each of NOAA’s Geostationary Operational Environmental Satellites (GOES), located in Earth’s geographic equatorial plane, approximately 6.6 Earth radii from the center of Earth, have carried magnetometers to monitor the geomagnetic field and its variations. Typically there are two GOES operational satellites: GOES East, located over the east coast of the U.S. and GOES West, located over the Pacific, just west of the U.S. mainland. At times, though, data are available from more than the two prime operational satellites.

The geomagnetic field measurements are important for interpreting GOES energetic particle measurements and for providing alerts to many customers, specifically for indicating the onset of a geomagnetic storm (known as a sudden storm commencement). GOES magnetometer data have been used for constructing magnetic field models, and to help forecasters identify the buildup and release of energy in Earth’s magnetosphere that occurs during geomagnetic storms and substorms. The magnetic field measurements can also indicate when the solar wind has pushed the boundary of the magnetosphere, the magnetopause, inside of geosynchronous orbit. Those situations are usually during very disturbed space weather conditions and can be important for spacecraft operations.  

GOES Magnetometer data are also important in research, being among the most widely used spacecraft data by the national and international solar and space weather research community (see e.g. NASA CDAWeb usage statistics).  The data have often been used to support launch decisions for research sounding rockets. The measurements can also be used to validate large-scale space environment models of the coupled magnetosphere and ionosphere; SWPC will implement such a model in the near the future.

The GOES magnetometer products are an integral part of the National Oceanic and Atmospheric Administration (NOAA) space weather operations, providing information on the general level of geomagnetic activity and permitting detection of magnetic storms and substorms. In addition, these measurements will be used to validate large-scale space environment models that will be added to SWPC operations in the future.

Historically, the data have been presented in the E (earthward), P (parallel) and N (normal) coordinate system where:

Hp:  magnetic field vector component, points northward, perpendicular to the orbit plane which for a zero degree inclination orbit is parallel to Earth's spin axis.

He:  magnetic field vector component, perpendicular to Hp and Hn and points earthward.

Hn:  magnetic field vector component, perpendicular to Hp and He and points eastward.

Ht:  the total field.

The GOES 3-day Hp plot shows the 1-minute averaged parallel component of the magnetic field in nanoTeslas (nT), currently measured at GOES-13 (~75 degrees west geographic longitude) and GOES-15 (~135 degrees west geographic longitude). The longitudes can vary, so for any particular case it is important to check the satellite location. A diurnal variation is observed in these data as a result of magnetospheric currents systems that, at geosynchronous orbit, produce a stronger magnetic field on the dayside of Earth and weaker magnetic fields on the nightside. If these data drop to near zero, or less, when the satellite is on the dayside, it may be due to a compression of the Earth's magnetopause into the geosynchronous orbit boundaries, exposing satellites to negative and/or highly variable magnetic fields. On the nightside, the smaller field values indicate strong currents in the magnetotail that are often associated with the stretching and subsequent release of energy in Earths tail. This is one signature of a “substorm” that results in aurora at Earth’s high latitudes and energetic particle injections in the vicinity of geosynchronous orbit.

Noon and midnight local time at the satellite are plotted as N and M. Default scaling is 0 to 200 nanoTesla. Non-default scaling to include infrequent extreme values is labeled in red to emphasize the change in scale.

This page updates dynamically every 5 minutes

GOES magnetic field observations have been made since the first GOES satellite was launched in 1975, and prior to that they were made on the NASA Synchronous Meteorological Satellites (SMS 1 and 2). SMS were the forerunners to the GOES operational system.

The magnetometers on GOES have changed, from one block of satellites to the next. In more recent years, NOAA has operated the GOES 8 to 12 series (from about 1994 to 2011 for the magnetometers), and currently we are using the GOES 13, 14, and 15 series of satellites. Each GOES 8-12 satellite was three-axis stabilized and carried two fluxgate magnetometers on a three-meter boom. Only one magnetometer could be operated at a time. The highest resolution magnetic field data was 0.512 s. On the GOES 13, 14 and 15 series, there are two fluxgate magnetometers that can be operated simultaneously on an 8.5 m boom. Again, the highest resolution is 0.512 s.

Most recent two hours of the primary GOES satellite 1-min digital magnetometer data:  http://services.swpc.noaa.gov/text/goes-magnetometer-primary.txt

Historic 3-day plots of the GOES Hp magnetometer data: ftp://ftp.swpc.noaa.gov/pub/warehouse/ or by following the archive link under “Data Access”

The official archive for GOES Magnetometer data are at NOAA’s National Centers for Environmental Information (NCEI):

 http://www.ngdc.noaa.gov/stp/satellite/goes/index.html

For convenience and for correlative science with NASA satellite and related data, many years of GOES magnetometer 1-min and some high-resolution (0.5 s) data can be found at NASA Coordinated Data Analysis Web: http://cdaweb.gsfc.nasa.gov/

A description of the GOES 8-12 Magnetometer data can be found at:

Singer, H.J., L. Matheson, R. Grubb, A. Newman and S.D. Bouwer, Monitoring Space Weather with the GOES Magnetometers. SPIE Conference Proceedings, Vol. 2812, p. 299-308, GOES-8 and Beyond, Edward R. Washwell, ed., 1996.

Additional information can be found at the National Centers for Environmental Information (NCEI).  http://www.ngdc.noaa.gov/stp/satellite/goes/