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

FIGURE 1: F10.7 (units of 10-22 Wm-2 Hz-1), solar wind velocity (SwVel), Kp geomagnetic index, and GUVI orbit-averaged ΣO/ N2 ratio for 2005.

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/ N2 ratio for 2005 including all latitudes, (e) same as (d) but limited to latitude range +/- 60 degrees.

FIGURE 3: (a) raw GUVI ΣO/ N2 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)

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

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Science QuestionHow does density in upper thermosphere respond to Joule heating?

Tools• Density data from GRACE, CHAMP and TIMED (GUVI)•TIMEGCM global 3-D 1st 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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Seasonal Effect for Solar Maximum

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CONCLUSIONS

Focus: Effects of Joule Heating on Neutral Density

TIMEGCM-AMIE realistic runsGlobal Mean Density

Well-defined response with altitudeCorrelation : >0.7 above 130 kmTime Delay: longer time-delay at lower altitudes

4 hrs above 200kmIntercept: reflects exponential density decrease with altitudeMagnitude: increase with height

varies between storms

Produced look-up tables to specify global mean response

CHAMP, GRACE, and GUVI densitiesSimilar altitude responsesTime delays generally smaller ( 1hr above 200 km)

LatestSatellite track, Local times, latitudes, seasonal/F107 variation

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END