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Rodney Viereck NOAA Space Weather Prediction Center Drag Data provided by John Emmert NRL

Neutral Density During the Recent Solar Minimum Contributions from Solar, Geomagnetic Activity, and Anthropogenic. Rodney Viereck NOAA Space Weather Prediction Center Drag Data provided by John Emmert NRL MURI Workshop, Boulder October 2010.

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Rodney Viereck NOAA Space Weather Prediction Center Drag Data provided by John Emmert NRL

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  1. Neutral Density During the Recent Solar MinimumContributions from Solar, Geomagnetic Activity, and Anthropogenic Rodney Viereck NOAA Space Weather Prediction Center Drag Data provided by John Emmert NRL MURI Workshop, Boulder October 2010

  2. 400 km Neutral Density Derived from Satellite Drag(thanks to John Emmert, NRL)

  3. Drag Density at Solar Minima(log plot)

  4. Thermospheric DriversSolar EUV (F10), Geomagnetic Storms (Ap), Climate Change(CO2) Viereck: MURI 2010

  5. Drag Density vs MSIS Density(again thanks to John Emmert) MSIS only has Solar (F10) and Geomagnetic (Ap) inputs (no climate change) Delta: Difference between MSIS and Observed Neutral Density

  6. Estimating the Anthropogenic Contribution Density offset (delta) vs CO2 data. (fitting a line to only the first three minima) Extrapolating the correction to the full extent if the time series Note: This is about twice the rate of Roble’s estimate

  7. Subtracting the Anthropogenic Correction

  8. Detailed Plot of the Observations vs MSIS(With and without the CO2 correction) Minimum Values Note the excellent fit during the first three minima Note the improved fit during the last minimum

  9. Solar IrradianceObservations vs Proxies Mg II index solar min to min variation is about right (7% of max-min) SEM 304 solar min to min variation is too large (14% of max-min) F10 solar min to min variation is too small (2.3% of max-min)

  10. Solar Data and Proxies Scaled to F10 Fitting SEM 304 and Mg II to F10 at the last minimum

  11. MSIS Results Using the Three Solar Inputs(Corrected for CO2)

  12. MSIS Results Using the Three Solar Inputs(Details) Mg II Index provides the best fit to the observed density

  13. Relative Magnitude of the Density ChangesModeled density changes for each input while holding the other two constant Relative Contributions of the change from (1996 to 2009) Solar 1.49E-15 = 48% Geomag 1.03E-15 = 33% Anthro 0.61E-15 = 19% Viereck: SDO and Space Weather

  14. Conclusions • Neutral density at 400 km shows a decrease during the last solar minimum • Significantly lower than previous three minima • Both F10 and Ap are also significantly lower during this most recent solar minimum. • Still can’t account for the observed decrease (using MSIS). • Adjusting for Anthropogenic (CO2) forcing and climate change accounts for some of the remaining difference • Still some density drop that cannot be accounted for • Using the SOHO SEM 304 data instead of F10 provides too much of a decrease in the neutral density • Using the Mg II Index instead of F10 provides a more accurate estimate of the density during this last solar minimum. • Solar 1.49E-15 = 48% • Geomag 1.03E-15 = 33% • Anthro 0.61E-15 = 19% Viereck: SDO and Space Weather

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