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National Space Science Data Center      Data set  MS-13D        June 1992 
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NAME:  	     Revised SERF2 Solar EUV Flux Model 

SCIENTIFIC CONTACT:      W. Kent Tobiska 
			 JPL, MS 264-723
			 4800 Oak Grove Dr.
			 Pasadena, CA 91109-8099
			 Telephone: (818) 393-7742
			 E-mail   : W.Kent.Tobiska@cc2mhb.jpl.nasa.gov
			 Fax      : (818) 393-4530
                            
NSSDC CONTACT:		 D. Bilitza, GSFC/NSSDC code 633/STX, 
			 Greenbelt, MD 20771, USA
			 Telephone: (301) 286-0190
			 NSSDCA:: BILITZA
			 bilitza@nssdca.gsfc.nasa.gov     

FILES:       (1) FORTRAN driver program                SERFD.FOR    7
             (2) FORTRAN EUV91 subroutines          EUV91SUB.FOR   34
             (3) input data file for (2)            EUV91IX2.DAT  587
		   (from 68173 to 88366)
             (4) model coefficients (ASCII)         EUV91COE.TXT    8
             (5) output of test run                   F80183.DAT    4
	     (6) data file from 47001 to 68172      EUV91IX1.DAT  613   
	     (7) data file from 89001 to 90365      EUV91IX3.DAT   58   
             (8) Log-file of recent updates           UPDATE.LOG    9
	     (9) IDL version of EUV91                  EUV91.PRO   19
            (10) This file                          AAREADME.DOC

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.

REFERENCES

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, 839-868 (1987)
 
W.K. Tobiska and C.A. Barth, A Solar EUV Flux Model, J. Geophys. Res.
95, 8243-8251 (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)

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

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National Space Science Data Center      Data set  MS-13D         Jan 1992 
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