Tidal wind

Daily fluctuations in temperature and wind at an altitude of 100 km in September 2005. The animation is based on observations made by the SABER and TIDI instruments on board the TIMED satellite.

A tidal wind is a fast, equatorial wind in the thermosphere that arises from pressure differences caused by solar radiation . The name of this wind comes from its 24-hour periodicity .

The daytime solar radiation creates a high pressure zone in equatorial latitudes, the maximum of which is reached in the afternoon. This zone is because of their shape as pressure bump (English. Pressure bulge ), respectively. There is a corresponding low pressure zone offset twelve hours from this, the pressure minimum of which, however, is less pronounced than the pressure maximum.

There is a pressure difference of about 4 µPa between these two zones, which is sufficient to allow a balancing wind to flow that reaches a speed of up to 200 m / s (~ 700 km / h). This is directed westward during the day.

One consequence of the tidal wind is the so-called fountain effect , which affects the equatorial ionosphere .

literature

• Prölss, Gerd W .: Physics of Near-Earth Space , ISBN 3-540-40088-5 , Springer-Verlag, 2nd edition 2004