GUVI Level 3 Data Products
What am I looking at?
The thermospheric column number density ratio of O and N2 referenced at N2 column number density level of 1017 cm-2
How were they produced?
There are a few steps of processing to produce the O/N2 ratios.
Select a number of neutral density profiles from MSIS86 model during a big magnetic storm and calculate the model O/N2 ratio from the profiles. Run AURIC for the selected density profiles at different look angles (0-70 degrees) and solar zenith angles (SZA) (0-89 degrees) to get simulated GUVI 135.6nm and LBHS intensities. The simulated LBHS intensities are increased by 60% due to adjustment in the N2 LBH cross section [Strickland et al., 2004]. Two lookup tables are created, table 1 for the simulated 135.6nm and LBHS intensity versus look angle and SZA and table 2 for model O/N2 versus the 135.6nm/LBHS ratio at nadir (look angle =0) and SZA=0. A linear-fit line between O/N2 and the 135.6nm/LBHS ratios is obtained from values in table 2. The fitting line is used to estimate the O/N2 ratios [Zhang et al., 2004]
Grid the GUVI 135.6nm and LBHS dayglow data (SZA < 90), SZA and look angle with a grid size of 1.757ºx1.757º in geographic latitude and longitude or 200x200km at equator. Use table 2 to normalize the GUVI 135.6nm and LBHS data to SZA=0 and look angle=0. Calculate the ratio of the normalized 135.6nm and LBHS intensities. Use the ratio and the fitting line obtained in step 1 to find O/N2 ratio.
Summary Images – Available in both GIF and PostScript files (each for one day). On-line access for download.
Data Files – Available in NetCDF and IDLsave files. On-line access for download.