Solar Cycle Variations of Solar Cycle Variations of Topside Electron Density and Topside Electron Density and

Temperature: Altitudinal, Temperature: Altitudinal, Latitudinal, and Seasonal Latitudinal, and Seasonal

Differences. 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

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

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.

Previous Studies – Oyama et al., 2002 - Akebono

At high altitudes the heat transport from the plasmasphere results in an increase with solar activity.

Previous Studies – Zhang, Holt, 2004 – Millstone Hill

Database

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

Altitudinal Differences – Jicamarca latitude

Altitudinal Differences – Jicamarca:

Altitudinal Differences – Millstone Hill:

Midnight Noon

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.

Equinox, mid-latitude, noon

550

km90

0 km

2000

km

Log(Ne) Te

Winter, mid-latitude, midnight55

0 km

900

km20

00 k

m

Log(Ne) Te

600 kmNoon, Mid-lat

900 km1500 km

2200 kmMidnight, Mid-latMidnight, EquatorNoon, Equator

Seasonal Differences

Mid-latitude, noon, 550 km

Equ

inox

Sum

mer

Win

ter

Mid-latitude, noon, 900 km

Equ

inox

Sum

mer

Win

ter

Mid-latitude, noon, 2000 kmE

quin

oxS

umm

erW

inte

r

Summer

EquinoxWinter

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