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T. J. Immel, S. B. Mende, H. U. Frey, N. Ostgaard

The Effect of the July 14, 2000, Solar Flare on Terrestrial FUV Emissions. T. J. Immel, S. B. Mende, H. U. Frey, N. Ostgaard Space Sciences Laboratory, University of California, Berkeley G. R. Gladstone, Southwest Research Institute.

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T. J. Immel, S. B. Mende, H. U. Frey, N. Ostgaard

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  1. The Effect of the July 14, 2000, Solar Flare on Terrestrial FUV Emissions T. J. Immel, S. B. Mende, H. U. Frey, N. Ostgaard Space Sciences Laboratory, University of California, Berkeley G. R. Gladstone, Southwest Research Institute

  2. To characterize the variation in dayglow values, specific ranges of solar and spacecraft zenith angle (having similar counting rates) are selected and monitored during the flare.

  3. Flare-time variations in imager signal. WIC : 65% SI-13 : 68% SI-12 : 72% The difference between SI-12 and the other two channels is significant. What is the reason for this?

  4. The terrestrial photoelectron flux is driven by solar emissions in the 26-34 nm range. Photodissociation of N2, with products energetic enough to produce the 120.0-nm emission, is driven by emissions measured mainly by the 1-50 nm channel

  5. Replace this with the one on the website

  6. The variation in the peak GEO Tube1 response is ~20%. The off-earth (H I Ly-alpha only) variation is ~10% The difference is due to the variation in on-earth FUV emissions (mainly O I 1304 and N I 1200)

  7. GEO on-earth measurements Simulation of data (converted to Rayleighs) requires Bishop model be multiplied by factor of 2.5. REDISTER results are scaled by 0.5. Final agreement is good.

  8. The FUV emissions contribute about 15% to the total GEO tube2 response. The relative intensities of the H I and other FUV emissions can be used to help retrieve one missing parameter, the solar 130.4-nm emission

  9. Instrument Pre-Flare Mean Response Max :UT of Peak (Same for Smoothed Data) % Change Post-Flare Mean Response WIC (A-D Units) 4648 A-D Units 7700 A-D Units - 10:30UT 65.6± 1.1% 4275 A-D Units S13 (Counts) 26.0 Counts 43.7 Counts – 10:30 UT 68.3± 2.3% 24.8 Counts S12 (Counts) 5.5 Counts 9.7 Counts  10:30 UT 76.6± 5.1% 4.4 Counts GEO: Tube1 (Counts) 9188 Counts 11110 Counts – 10:30 UT 20.9± 0.6% 9580 Counts GEO: Tube2 (Counts) 3887 Counts 4284 Counts  10:32 UT 10.2± 0.9% 4903 Counts Summary of flare-time variations in 5 IMAGE-FUV channels.

  10. Following the development in the paper, one can derive the relationship shown here. The derived O I 1304 variation depends on FUVI/LyaI, but is found to be 40±14%. The FUV/Lya ratio must be carefully determined!

  11. Flare-time variations in imager signal. WIC : 65% SI-13 : 68% SI-12 : 72%

  12. April 15, 2001 Flare 2x greater X-Ray flux than Bastille Day flare. Observed from near apogee. WIC variation: 55.4% SI-13 variation:64.3% SI-12 variation: 67.8% Flare-time variations are similar, but WIC is showing a significant difference.

  13. What is the explanation for that? Possibly a change in the sensitivity curve of the instrument. Rayleigh scattering components may make up a larger part of the signal in the instrument. Note that the dayglow correction to recent images has to be adjusted well above the default value (1.4 vs. 1.0) representing the quiet-time background determined early the mission.

  14. Results of IMAGE-FUV Bastille Day flare investigation • Most complete set of terrestrial FUV observations during an X-Class flare. • Identification of dayglow emissions in SI-12 channel • Retrieval of otherwise unmeasured solar H I and O I emissions • Close correspondence of SI-13 and WIC channels indicates either: 1. Low sensitivity of WIC to MUV or, 2. Higher than expected variation in solar MUV emissions. • Evidence for change in character in sensitivity curve of WIC instrument after a year of operation.

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