Revised SERF2 Solar EUV Flux Model 1991

Author: W. Kent Tobiska
JPL, MS 264-723
4800 Oak Grove Dr.
Pasadena, CA 91109-8099
Telephone: (818) 393-7742
Fax: (818) 393-4530

Parameter: Solar photon fluxes between 1.8 and 105 nm

Brief Description:
The Revised SERF2 model was developed by Kent Tobiska and colleagues. It describes the solar full-disk photon fluxes at 1 AU for 39 EUV wavelength groups and discrete lines between 1.8 and 105.0 nm (18 - 1050 Angstrom) for a given date. It represents an advance over the previous SERF1 and SERF2 models, (i) by its ability to incorporate new data sets as they become available, and (ii) by extending beyond the SME Lyman-alpha timeframe. The Solar Electro- magnetic Radiation Flux (SERF) study group is part of the World Ionosphere Thermosphere Study (WITS) project organized by the Scientific Committee on Solar-Terrestrial Physics (SCOSTEP). Solar EUV photon fluxes are fundamental input parameters in the study of the terrestrial and planetary upper atmospheres. Earlier EUV models were reviewed by Lean (1987, 1990).

The model is based on the time regression of the fluxes (in the 39 wavelength groups) with four independent solar parameters: (1) H Lyman- alpha, 121.6 nm, (2) He I 1083 nm equivalent width, (3) 10.7 cm radio flux, daily and (4) 81-day running mean. (1) and (2) are used as the independent model parameters for the chromospheric irradiances while (3) and (4) are the independent parameters for the coronal and transition region irradiances. Regression coefficients are determined using EUV measurements of the OSO, AEROS, and AE satellites and of five rocket flights. Using ground-based observations of the solar radio flux (3,4) the model extends from 1947 to the present for coronal EUV full-disk irradiances. Chromospheric EUV full-disk irradiances can be obtained from 1976 to the present based on OSO, AE and SME Lyman-alpha satellite data and ground-based He I 1083 nm equivalent width observations.

The software package was supplied by K. Tobiska and includes the main program and subroutines [EUV91.FOR], the model data files containing date (YYDDD), Lyman-alpha, He I 1083 (converted to units of Lyman-alpha), 10.7 cm solar radio flux (F10.7), and 81-day-mean F10.7 [EUV91INDEX1.DAT, ..2.DAT, ..3.DAT], the model coefficients [EUV91COEF.TXT], and output from a test run of EUV91 [80183.DAT]. Program EUV91 provides energy and photonfluxes for given date between 68178 (178th day of 1968) and 88366. The final flux tables are stored in ASCII files (FYYDDD.DAT, YYDDD is chosen date). To obtain irradiances before 68178 and after 88366 the model index file EUV91INDEX.DAT has to be extended to cover those times. An improved and corrected version of this code was released in April 1991, superseding the 1990 version. Recent updates of the model software are explained in file UPDATE.LOG.

Availability: (1) Retrievable from CCMC's anonymous FTP site in directory /euv.

H.E. Hinteregger, K. Fukui, and B.G. Gilson, Observational Reference and Model Data on Solar EUV, from Measurements on AE-E, Geophys. Res. Lett. 8, 1147-1150, 1981. [SERF1 model]

J. L. Lean, Solar Ultraviolet Irradiance Variations: A Review, J. Geophys. Res. 92, 839, 1978.

W. K. Tobiska and C. A. Barth, A Solar EUV Flux Model, J. Geophys. Res. 95, 8243, 1990. [SERF2 model]

J.L. Lean, A Comparison of Models of the Sun's Extreme Ultraviolet Irradiance Variations, J. Geophys. Res. 95, 11933-11944 (1990)

W. K. Tobiska, Revised Solar Extreme Ultraviolet Flux Model, J. Atmos. Terr. Phys., 53, 1005-1018, 1991.

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