SPECIAL AE-C, D, AND E NEUTRAL DENSITY DATA ------------------------------------------- This directory contains a set of files with data that were deduced from AE mass spectrometer measurements. In general, these files were produced after the Unified Abstract (UA) file was completed and are thus not included in the UA part of this CD. We highly recommend that users of these files consult the listed references for a good understanding of the methods used in establishing these data sets and for a good appreciation of their shortcomings. All data in this directory were provided by A. Hedin (GSFC, Code 914, now retired). They are related to A. Hedin's atmospheric modelling work (Mass Spectrometer and Incoherent Scatter atmospheric model - MSIS; MSIS software and data are included on this CD-ROM). The eight files in this directory are all in ASCII format. Each file contains data for one density parameter from one of the three satellites. There are AE-C and E files for the number densities (in cm-3) of hydrogen (H), AE-C, D, and E files for the number density (in cm-3) of nitrogen (N), and AE-C, D and E files for the number density (in cm-3) of molecular oxygen (O2). In addition to the density, each ASCII record includes also orbit parameters. filename time span/yyddd satellite instrument density of ------------------------------------------------------------------------- C_BIMS_H.DAT 73362 - 78323 AE-C BIMS/OSS/MIMS Hydrogen (H) E_BIMS_H.DAT 75343 - 78361 AE-E BIMS/OSS/MIMS Hydrogen (H) C_OSS_N.DAT 74035 - 75032 AE-C OSS Nitrogen (N) D_OSS_N.DAT 75294 - 76028 AE-D OSS Nitrogen (N) E_OSS_N.DAT 77009 - 78300 AE-E OSS Nitrogen (N) C_OSS_O2.DAT 74041 - 74182 AE-C OSS Mol. Oxy (O2) D_OSS_O2.DAT 75292 - 76028 AE-D OSS Mol. Oxy (O2) E_OSS_O2.DAT 75348 - 76076 AE-E OSS Mol. Oxy (O2) The hydrogen data (*_BIMS_H.DAT) were deduced from OSS, BIMS and MIMS observations by assuming charge exchange equilibrium between the ionic and atomic hydrogen and oxygen gases. The ion densities (H+, O+) were taken from BIMS or MIMS ion mass spectrometer measurements and the atomic oxygen density was taken from the OSS mass spectrometer measurements. The method is described in: H.C. Brinton, H.G. Mayr, and W.E. Potter, Winter bulge and diurnal variations in hydrogen inferred from AE-C composition measurements, Geophysical Research Letters, volume 2, 389-392, 1975. The authors estimate the uncertainty for the H densities to about 50%, because of the uncertainties in the mass spectrometer measurements. The nitrogen data (*_OSS_N.DAT) were obtained by M. Engebretson and his col- leagues from an improved analysis of the OSS mass spectrometer measurements taking into account recombination of N with O within OSS and subtracting the source background component from the total NO signal. The method is described in: M.J. Engebretson and K. Mauersberger, The response of thermospheric atomic nitrogen to magnetic storms, Journal of Geophysical Research, Volume 88, 6331, 1983, and in: M.J. Engebretson and K. Mauersberger, The impact of gas-surface reactions on mass spectrometric measurements of atomic nitrogen, Journal of Geophysical Research, Volume 84, 839, 1979. The authors estimate the accuracy of their N densities at about 30%. The molecular oxygen data (*_OSS_O2.DAT) were obtained with the method described by: A.O. Nier, W.E. Potter, and D.C. Kayser, Atomic and molecular densities in the lower thermosphere, Journal of Geophysical Research, Volume 81, 17-24, 1976 and D.C. Kayser, Solar flux variation of the thermospheric molecular oxygen density, Journal of Geophysical Research, Volume 85, 695-702, 1980. The authors estimate the uncertainty in absolute density to about 20-30%. ---------------------------------------------------------------------- Data Format -------------- 1 Line (A15+Cr/Lf) - Name of experiment 2 Line (A58+Cr/Lf) - Header 3 Line (A59+Cr/Lf) - Header --------------------------------- Logical record for data - 57 bytes + Cr/Lf Type Description ------------------------------------------------ A2 Blanks I5 YYDDD (year, number of day) F7.0 Time (sec.) E10.2 Density (cm-3) E9.1 Density Error (cm-3) F6.1 S/C Altitude (km) F6.1 S/C Latitude (degrees) F6.1 S/C Longitude (degrees) F6.1 Solar Local Time (hours) ---------------------------------------------------