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Periodic Modulations in Thermospheric Composition by Solar Wind High Speed Streams G. Crowley, A. Reynolds, J. P. Thayer, J. Lei, L.J. Paxton, A.B. Christensen,

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Presentation on theme: "Periodic Modulations in Thermospheric Composition by Solar Wind High Speed Streams G. Crowley, A. Reynolds, J. P. Thayer, J. Lei, L.J. Paxton, A.B. Christensen,"— Presentation transcript:

1 Periodic Modulations in Thermospheric Composition by Solar Wind High Speed Streams G. Crowley, A. Reynolds, J. P. Thayer, J. Lei, L.J. Paxton, A.B. Christensen, Y. Zhang, R.R. Meier, D.J. Strickland GRL, in press

2 FIGURE 1: F10.7 (units of 10 -22 Wm -2 Hz -1 ), solar wind velocity (SwVel), Kp geomagnetic index, and GUVI orbit-averaged ΣO/ N 2 ratio for 2005.

3 FIGURE 2: Lomb-Scargle periodogram of (a) F10.7 (units of 10 -22 Wm -2 Hz -1 ), (b) solar wind velocity (SwVel), (c) Kp geomagnetic index, (d) GUVI orbit-averaged ΣO/ N 2 ratio for 2005 including all latitudes, (e) same as (d) but limited to latitude range +/- 60 degrees.

4 FIGURE 3: (a) raw GUVI ΣO/ N 2 ratio as a function of latitude and time for the first 100 days of 2005, with Kp superposed (black line); (b) Residuals 10° latitude bands after bandpass filtering and removal of the of 11-day running mean, expressed as a percentage of the running mean values. Broken line shows Kp after similar bandpass filtering. a) b)

5 Conclusions Builds on density work by Lei et al. Geomagnetically forced periodicity in composition Largest effect at high latitudes High/low latitudes anticorrelated Composition responding to vertical winds, versus thermal expansion experienced by total density Continuous forcing produces continuous disturbance without recovery

6 6  Science Question How does density in upper thermosphere respond to Joule heating?  Tools Density data from GRACE, CHAMP and TIMED (GUVI) TIMEGCM global 3-D 1 st Principles I-T Model AMIE (assimilates high latitude electrodynamic data) Effect of EUV and High Latitude Forcing on Thermospheric Densities Geoff Crowley (ASTRA) with thanks to the GRACE, CHAMP and GUVI teams

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13 Seasonal Effect for Solar Maximum

14 14 CONCLUSIONS Focus: Effects of Joule Heating on Neutral Density TIMEGCM-AMIE realistic runs Global Mean Density Well-defined response with altitude Correlation : >0.7 above 130 km Time Delay: longer time-delay at lower altitudes 4 hrs above 200km Intercept: reflects exponential density decrease with altitude Magnitude: increase with height varies between storms Produced look-up tables to specify global mean response CHAMP, GRACE, and GUVI densities Similar altitude responses Time delays generally smaller ( 1hr above 200 km) Latest Satellite track, Local times, latitudes, seasonal/F107 variation

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