Ionospheric effects of total solar eclipse on July 22, 2009 according to the data from dense Japanese GPS network (GEONET)

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Experimental observations of the ionosphere during solar eclipses (SE) provide the information on the char-
acter of the behavior of various ionospheric parameters. It is possible to distinguish two types of SE ionospheric
effects, they are regular effects and wave disturbances. Regular effects imply an increase of effective reflection
heights, a reduction in concentration in the F-layer maximum, and a decrease in total electron content (TEC)
in the ionosphere, which is typical for the transition to the nighttime ionosphere. However there is no absolute
clearness in the study of SE regular effects though many works are devoted to this. There is big scatter of the
main parameters of regular ionospheric effects depending on SE event. The more difficult situation is in the
research of wave disturbances accompanying SE. Authors of [Chimonas G., Hines C.O. Atmospheric gravity
waves induced by a Solar Eclipse // J. Geophys. Res. V. 75, P. 875-876, 1970] suggested that SE can generate
atmospheric gravity waves (AGW) with so-called oblique fronts which manifest themselves in the ionosphere
as travelling ionospheric disturbances. However until now there are no experimental evidence of SE-generated
oblique waves.
Total solar eclipse on July 22, 2009 is a unique event. It is the first time when moon shadow appeared
near the densest GPS receivers network – GEONET. To study different scale SE ionosphere disturbances ISTP
SB RAS developed algorithms and methods of spatial mapping of TEC measurement data from multichannel
GPS-receiver network.