Satellite Environment

Satellites monitor in situ the effect of the Sun on the near-Earth environment. The GOES and SOLRAD satellites orbit at geostationary levels, about 22,000 miles above the Earth's surface. The ACE satellite is stationed in interplanetary space at the L1 libration point where the Earth's and Sun's gravitational fields cancel each other. The satellite instrumentation gives information about solar flares, coronal mass ejection, and geomagnetic storms impacting the near-Earth environment. This information is important to the operations of radio and satellite communication and navigation systems, electric power networks, geophysical exploration, astronauts, high-altitude plane flights and scientific researchers.

Solar and Interplanetary Data from NASA's Advanced Composition Explorer (ACE) mission -- From orbit about the L1 Lagrangian point, ~0.01 astronomical units Sunward of the Earth, ACE measures ions and electrons accelerated at the Sun, in interplanetary space, at the edge of the heliosphere, and in the Galaxy. ACE includes six high-resolution spectrometers that measure the elemental, isotopic and ionic charge-state composition of energetic nuclei with energies ranging from ~1 keV/nucleon (solar wind) to ~0.5 GeV/nucleon (cosmic radiation). In addition, three instruments characterize the interplanetary environment by measuring solar wind ions and electrons, the interplanetary magnetic field, and low-energy ions and electrons of solar and interplanetary origin. The ACE mission and spacecraft (launched on August 25th, 1997), each of the nine instruments, and the ACE Science Center (ASC) are described in detail in a special issue of Space Science Reviews (see Stone et al. 1998a and accompanying articles). These ACE plots are intended to be used for identifying time periods when solar and interplanetary events occur, and for characterizing the solar wind parameters and energetic particle intensities associated with a variety of solar and interplanetary phenomena. For more detailed studies, a wide range of additional data products are available to the community through the ASC, NOAA, and the National Space Science Data Center (NSSDC).

GOES Space Environment Monitor (SEC) -- The SEM consists of four instruments used for in situ measurements and monitoring of the near-Earth (geostationary altitude) space environment and for observing the solar X-ray output. An energetic particles sensor (EPS) and high energy proton and alpha detector (HEPAD) monitor the incident flux density of protons, alpha particles, and electrons over an extensive range of energy levels. Solar output is monitored by an X-ray sensor (XRS) mounted on an X-ray positioning platform, fixed on the solar array yoke. Two redundant three-axis magnetometers, mounted on a deployed 3-meter boom, operate one at a time to monitor Earth's geomagnetic field strength in the vicinity of the spacecraft.

SOLRAD DATA: The source of data are the Naval Research Laboratory's SOLRAD 9 (1968-17A) and SOLRAD 10 (1971-058A) satellites. Both satellites carried detectors sensitive to the 0.5-3A, 1-8A, 8-16A, 1-20A, and 44-60A bands. Each 1-minute data from the 0.5-3A, 1-8A, and 8-16A detectors were stored in the satellite memory which was capable of retaining up to 14.25 hours of data. Therefore, a continuous record of the x-ray emission from the sun, except for gaps due to satellite night and charged particle interference, was available for these 3 bands. The data represented here extends from 14 Mar 68 to 28 Feb 73.

1. ACE Interplanetary Magnetic Field Plots, from MAG instrument - ACE Level 2 Data, Hourly Averages for September 1997-present -- in PDF format ---- Download Data (Documentation)

   The Interplanetary Magnetic Field (IMF) plot shows 1-hour averages of the magnitude of the IMF and its three vector components in the GSE coordinate system. The data plotted are verified Level-2 data from the MAG instrument (see Smith et al. 1998). It is well known that the IMF plays a dominant role in triggering and modulating the dynamics of the terrestrial magnetosphere. When the interplanetary magnetic field has a large negative (southward) component, interconnection between the interplanetary and terrestrial magnetic fields is greatly enhanced, with a resulting release of energy. Large transients and/or prolonged periods of southward magnetic fields often result in geomagnetic storms, with associated auroral displays and space weather effects on communications and space hardware.

2. ACE Solar Energetic Particle Plots, ACE Level 2 Data, Hourly Averages for September 1997-present -- in PDF format ---- Download Data (Documentation)
   The interplanetary intensity of ions and electrons in the MeV energy range and below are highly variable and originate from a number of sources, including solar energetic particle (SEP) events on the Sun, traveling interplanetary shocks, and corotating interaction regions (CIRs). This plot shows ion intensities in three energy ranges and electron intensities in two energy ranges based on data from the EPAM instrument (Gold et al. 1998). Also plotted are higher energy carbon and helium intensities from the SIS instrument (Stone et al. 1998b). The data plotted are all verified Level-2 data.
   
   These energetic particle plots are especially useful for identifying and characterizing SEP events. SEP events are typically categorized into two classes (gradual and impulsive) that reflect the acceleration mechanisms involved. Gradual events result from the acceleration of coronal and interplanetary particles by fast CME-driven shocks, and sometimes extend to energies of hundreds of MeV/nucleon. Because the interplanetary shock can rapidly cross onto field lines in the inner heliosphere that connect to a range of longitudes at 1 AU, gradual events often extend over a wide range of longitudes (e.g., about 120 degrees). Although they derive from a coronal composition, there are frequently large variations in composition, with evidence for several different seed populations of accelerated particles.
3. ACE Solar Wind Plasma Plots from SWEPAM, ACE Level 2 Data, Hourly Averages for February 1998-present -- in PDF format ---- Download Data (Documentation)
   

   The Solar Wind Plasma plot shows the solar wind proton speed, density and temperature. The data plotted are verified Level-2 data from the SWEPAM instrument (McComas et al. 1998). When data from SWEPAM are not available, proton speed data from the SWICS instrument on ACE (Gloeckler et al. 1998) are substituted in red. The IMF and Solar Wind Plasma plots are intended to be used together -- they are especially useful for identifying solar wind variations that include high-speed streams associated with coronal holes and interplanetary transients such as shocks and coronal mass ejections (CMEs). A variety of additional solar wind data products are available through the ACE Science Center (Garrard et al. 1998), NSSDC, and NOAA (see descriptive text).

4. GOES >2MeV Daily Electron fluence Data 1987-present -- in table format ---- Download Data
   

   Please note that the electron detector on GOES responds significantly to protons above the 32 MeV energy level; therefore, the electron data are contaminated when a proton event is in progress. An arbitrary cut off for dropping the electron fluence was set at the 3.0E+05 protons at the >10 MeV fluence level with these days indicated by '-999'. The units are electrons/cm**2-day-sr. Missing data are indicated by dashes.

5. GOES Daily Proton Fluence >1, >10 and >100 MEV 1987-present -- in table format ---- Download Data
   

   Daily proton fluences are the residuals after the background is subtracted; therefore, it is not easy to make any meaningful interpretation of them. They are provided as a tool to distinguish when events occur. Anyone interested in detailed analysis should contact us for an appropriate referral. An updated algorithm for calculating the proton flux went into effect 16 Jan, 90, resulting in lower flux/fluence values. Proton fluences are provided for the >1, >10, and the >100 MeV protons. The units are protons/cm**2-day-sr. Missing data are indicated by dashes.

6. GOES X-ray Background Levels (Watts/meter**2) 2003-present -- in table format ---- Download Data
   

   The GOES X-ray background levels are computed by averaging the 1-minute data for three eight-hourly periods through the day (00-08, 08-16, 16-24). The lowest of the three averages is used as the X-ray background level for the day. The units are Watts/meter**2. Missing data are indicated by dashes and background levels below B1.0 (1.0E-07 W/m**2) are unreliable. On 22 Sep 1986, the lower limit of the background level was changed to A1.0 (1.0E-08 W/m**2).