•Properties of gravity waves:
–Auroral origin:
• T ~1h, lhoriz ~1000 km, Vf > 400 m/sec southward, usually at night.
–Meteorological origin:
•T = 15-60 mn, lhoriz = 150-250 km, Vf ~100 m/sec, usually southward
•Mostly during the day, quickly damped over ~1000 km.
•Origin (local) is strongly site dependant
•TEC gradient 2. 1011 m-3 typically
•Electronic density changes (1-10%) occur in F2 layer( ~250 km)
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