1. Solar Cycle Variations of Topside Electron Density and Temperature: Altitudinal, Latitudinal, and Seasonal Differences. D. Bilitza (1), P. Richards (2), V. Truhlik (3), T. Abe (4), L. Triskova (3) (1) Raytheon ITSS, GSFC, SPDF, Greenbelt, USA (2) NASA, Earth-Sun Systems Division, Washington DC, USA (3) Institute of Atmospheric Physics, Praha, Czech Republic (4) Aerospace Exploration Agency (JAXA), Sagamihara, Japan

2. Summary - Goal: Determine Te solar cycle variation for inclusion in IRI. - Source: Data base of satellite insitu measurements and FLIP model - This Study: Solar activity variation of Ne and Te at 550, 900, and 2000 km, for MLT= 2, and 13, during all seasons

3. Previous Studies – Balan et al., 2001- MU Radar Balance of gain, loss, and transport processes for thermal energy can result in increase or decrease with solar activity.

4. Previous Studies – Oyama et al., 2002 - Akebono At high altitudes the heat transport from the plasmasphere results in an increase with solar activity.

5. Previous Studies – Zhang, Holt, 2004 – Millstone Hill

6. Database Akebono, since Feb 1989, 700 – 10,000 km, -75 - 75

9. Altitudinal Differences – Jicamarca latitude

10. Altitudinal Differences – Jicamarca:

11. Altitudinal Differences – Millstone Hill: Midnight Noon

12. Averages of Akebono electron temperatures versus solar flux for different altitude ranges during daytime for summer (top) and winter (right) conditions seem to indicate an increase with solar flux at higher altitudes and a decrease for the lower height range and no significant seasonal changes.

13. Equinox, mid-latitude, noon 550 km 900 km 2000 km Log(Ne)Te

14. Winter, mid-latitude, midnight 550 km 900 km 2000 km Log(Ne)Te

15. 600 km Noon, Mid-lat 900 km 1500 km 2200 km Midnight, Mid-latMidnight, EquatorNoon, Equator

16. Seasonal Differences

17. Mid-latitude, noon, 550 km Equinox Summer Winter

18. Mid-latitude, noon, 900 km Equinox Summer Winter

19. Mid-latitude, noon, 2000 km Equinox Summer Winter

20. Summer Equinox Winter

21. Results -Ne increases with solar activity for all cases. -Solar cycle effects are strongest at low altitudes. - Te changes over the solar cycle are generally much smaller than those of Ne and show a seasonal dependence during daytime: increases in summer, constant or small decrease in winter, decrease in equinox. -FLIP generally confirms the Ne trends seen in our data base. -FLIP agrees well with the Te daytime values. - During nighttime FLIP overestimates the winter values and underestimates the summer and equinox data