Seasonal dependence of the nighttime traveling ionospheric disturbances

in the mid-latitude ionosphereA ． Saito1,2, M.C. Kelley1, T. Tsugawa2, J.J. Makela1,

Y. Otsuka3, and S. Miyazaki4

1. School of Electrical and Computer Engineering, Cornell University 2. Department of Geophysics, Graduate School of Science, Kyoto University3. Solar-Terrestrial Environment Laboratory, Nagoya University4. Geographical Survey Institute

A GPS network in Japan has detected TEC wave fronts that travel to the southwest in the nighttime.

Medium-scale traveling ionosphere disturbances (MSTIDs)

Local time, seasonal, latitudinal and solar cycle dependencies of these MSTIDs

Standard deviation of TEC over the MU radar: amplitude of MSTIDs

May 16-24, 1998 Geomagnetic Activity: Kp

Kp:19 17+ 17

11- 18 22

14- 20- 21

Summer

Equinox

Winter

Standard deviation of TEC Ratio to the background TEC

Standard deviation of TECTsukuba

January 1994 – August 2000

Ratio to the background TECTsukuba

January 1994 – August 2000

CGM-Lat: 38.6 (Receiver 0001) CGM-Lat: 33.3 (Receiver 0183)

CGM-Lat: 21.5 (Receiver 0494)CGM-Lat: 27.4 (Receiver 0428)

European Sector: NotoLong: 15.0, Lat: 36.9, CGM-Lat: 29.1

West Pacific Sector (South): Alice SpringsLong: 133.9, Lat: -23.7, CGM-Lat: -34.2

American Sector (South): La PlataLong: 302.1, Lat: -34.9, CGM-Lat: -23.1

American Sector (South): IsabellaLong: 292.9, Lat: 18.5, CGM-Lat: 28.9

SummaryMedium-scale traveling ionospheric disturbances in the

midlatitude ionosphere detected with total electron content observation by GPS receivers.

Propagation velocity:100m/s, wavelength: 300km Nighttime: Southwestward propagation, Summer and Winter Daytime: Southward (south-southeastward) propagation, Winter Daytime peak is common at any longitudes. Nighttime peaks show

longitudinal differences. Day-to-day variation: No geomagnetic activity dependency Low amplitude in the high solar activity period Amplitude of nighttime TID is large at lower latitudes.

[CGM-Lat: 20-40 degrees]