Observations and modeling of the ionospheric behaviors over the east Asia zone during the 22 July 2009 solar eclipse

The longest total solar eclipse during the 21st century with a maximum duration of 6 min and 39 s occurred in South and East Asia on 22 July 2009. The TEC data from four GPS stations in the total eclipse region (around 30 degrees N) from 105 degrees E to 135 degrees E are used to study the variation in TEC. Height profiles of electron density from Formosa3/Cosmic satellites are used to study the height dependence of the electron density response. We also modeled the eclipse effects on the ionosphere by an ionospheric model. Both the observations from F3/C and the modeled results show that there is an overall decrease in the electron density below F2 region, with the largest relative decrease occurring at F1 region. The TEC observations show the delay time of the largest TEC decrease at the total eclipse region with regard to the maximum obscuration is less than five minutes and smaller than what is estimated from the time constant of the plasma loss rate at the F2 peak altitude although main contribution to TEC comes from the plasma density in the F2 region. The modeling study shows that, due to the large plasma flux from topside ionosphere to F2 layer, the TEC response around 30 degrees N is mainly due to the electron density response at low altitudes (E and F1 region, 200 km below) where the time delay of electron density response is very short (less than 4 min). Thus the time delay of TEC response would also be short as observed by GPS TEC.