AE/AP Trapped Particle Flux Maps 1966-1980


Author: J. I. Vette
retired from NASA, GSFC
Greenbelt, Maryland 20771

Parameter: Trapped electron and proton fluxes in Earth's radiation belt

Brief Description:
These maps contain omnidirectional, integral electron (AE maps) and proton (AP maps) fluxes in the energy range 0.04 MeV to 7 MeV for electrons and 0.1 MeV to 400 MeV for protons in the Earth's radiation belt (L = 1.2 to 11 for electrons, L = 1.17 to 7 for protons). The fluxes are stored as functions of energy, L-value, and B/Bo (magnetic field strength normalized to its equatorial [minimum] value on the field line). The maps are based on data from more than 20 satellites from the early sixties to the mid-seventies. AE-8 and AP-8 are the latest editions in a series of updates starting with AE-1 and AP-1 in 1966. The progress in modeling the trapped particle population is documented in several reports as indicated in the tables below. Included in these reports are (1) a description of model map development, (2) tables and graphs of fluxes, and (3) results from flux integrating along selected (mostly circular) orbits. The different electron models AE can be distinguished as inner (L = 1.2-3) or outer (L = 3-11) zone models and as models for solar cycle maximum or minimum conditions. AE-8 is the first model that covers the whole L range and both solar cycle extrema. The AP maps differ in energy range and solar cycle phase. AP-8 is the first model for the whole energy range and both solar cycle extrema.

None of the flux maps consider time variations beyond the solar cycle minimum/maximum distinction. In the AE-5 report for inner zone electrons, the three dominant time effects were investigated: (1) Magnetic storms strongly affect electrons with energies higher than 0.7 MeV at higher L-shells; (2) the Starfish nuclear explosion of July 9, 1962, increased electrons on low L- shells with intermediate energy (about 1 MeV); (3) the solar cycle effect is most significant for electrons with energies below 0.7 MeV. Magnetic storm effects are not yet included in any of the AE maps. For AE-5 1975 Projected and AE-6, the Starfish residue was subtracted. AE-8 is a synthesis of AE-5 Projected, AE-6, AE-4, and new data from the OV3 3, OV1 19, Azur, and ATS 6 satellites. In the outer zone, because of large temporal variations, averages were taken over long intervals (six months or more). The AE-3, AE-4, and AE-8 reports also include local time functions down to L = 3; however, these were not included in the computer code. AE-3, the model for the region of geostationary (geosynchronous) satellites, provides also tools for radiation exposure assessment. AE-1, AE-2, and AE-5 include both omni- and unidirectional flux maps.

The largest errors occur where steep gradients in spatial and spectral distribution exist and where time variations are not well understood. A widely quoted error estimate is "a factor of 2." An even larger error must be considered for differential fluxes (in angle or energy) created from the omnidirectional, integral flux maps. It should be noted that the Jensen-Cain magnetic field model (see page 4-4) with epoch 1960.0 was used throughout the period when trapped radiation data was collected for all AE/AP models. Therefore, one has to be careful in extrapolating these models to later epochs. It is recommended that the map-specific epochs as listed in the tables below be used for all applications of the models.

Availability:AE-8, AP-8 are part of the RADBELT package that is retrievablefrom CCMC's anonymous FTP site. The AP-8 report is available online as PDF document.

MT-11B (AP-1; Vette, 1966)
MT-12B (AP-2; Vette, 1966)
MT-13B (AP-3; Vette, 1966)
MT-14B (AP-4; Vette, 1966)
MT-15B (AP-5; King, 1967)
MT-16B (AP-6; Lavine and Vette, 1969)
MT-17B (AP-7; Lavine and Vette, 1970)
MT-12B (AP-8; Sawyer and Vette, 1976)

MT-21B (AE-1; Vette, 1966)
MT-22B (AE-2; Vette et al., 1966)
MT-23B (AE-3; Vette and Lucero, 1967)
MT-24B (AE-4; Singley and Vette, 1972a,b)
MT-25B (AE-5; Teague and Vette, 1972)
MT-28B (AE-6; Teague et al., 1976)
MT-2AA,2AB (AE-8; Vette, 1989)

References (in chronological order):

Vette, J., Models of the trapped radiation environment, Volume I: Inner zone protons and electron, NASA SP-3024, Washington, D.C., 1966.

Vette, J., A. Lucero, and J. Wright, Models of the trapped radiation environment - Volume II: Inner and outer zone electrons, NASA SP-3024, Washington, D.C., 1966.

Vette, J. and A. Lucero, Models of the trapped radiation environment - Volume III: Electrons at synchronous altitude, NASA SP-3024, Washington, D.C., 1967.

King, J., Models of the trapped radition environment - Volume IV: Low energy protons, NASA Sp-3024, Washington, D.C., 1967.

Lavine, J. and J. Vette, Models of the trapped radition environment - Volume V: Inner belt protons, NASA SP-3024, Washington, D.C., 1969.

Lavine, J. and J. Vette, Models of the trapped radition environment - Volume VI: High energy protons, NASA SP-3024, Washington, D.C., 1970.

Imhof, W., C. Bostrom, D. Beall. J. Armstrong, H. Heckman, P. Lindstrom, G. Nakano, G. Paulinkas, and J. Blake, Models of the trapped radition environment Volume VII: Long term time variations, NASA SP-3024, Washington, D.C., 1971.

Singley, G. and J. Vette, The AE-4 model of the outer radiation zone electron environment, National Space Science Data Center, NSSDC 72-06, Greenbelt, Maryland, 1972a.

Singley, G. and J. Vette, A model environment for outer zone electrons, National Space Science Data Center, NSSDC 72-13, Greenbelt, Maryland, 1972b.

Teague, M. and J. Vette, The inner zone electron model AE-5, National Space Science Data Center, NSSDC 72-10, Greenbelt, Maryland, 1972.

Teague, M. and J. Vette, A model of the trapped electron population for solar minimum, National Space Science Data Center, NSSDC 74-03, Greenbelt, Maryland, 1974.

Teague, M., K. Chan, and J. Vette, AE 6: A model environment of trapped electrons for solar maximum, National Space Science Data Center, NSSDC 76-04, Greenbelt, Maryland, 1976.

Sawyer, D. and J. Vette, AP-8 trapped proton environment for solar maximum and solar minimum, National Space Science Data Center, Report 76-06, Greenbelt, Maryland, 1976. [Online PDF copy]

Vette, J., The AE-8 trapped electron model environment, National Space Science Data Center, Report 91-24, Greenbelt, Maryland, 1991.

Vette, J., The NASA/National Space Science Data Center trapped radiation environment model program (1964-1991), NSSDC Report 91-29, Greenbelt, Maryland, 1991

Gaffey, J. and D. Bilitza, NASA/National Space Science Data Center trapped radiation models, J. Spacecraft and Rockets 31, #2, 172, 1994.


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