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Keywords:

  • annular eclipse;
  • electrodynamics;
  • ionospheric F region;
  • meridional wind;
  • recombination

[1] The response of the ionospheric F region over Indian low-latitude regions to the annular solar eclipse of 15 January 2010 is investigated. The foF2 corresponding to an electron density increase of ∼21% at the F2 peak is seen over Gadanki (13.5°N, 79°E) during the course of the eclipse in comparison with the control day behavior. After the peak phase the foF2 shows a large decrease (∼19%) compared to the mean control day pattern. The total electron content (TEC) at Bangalore (13°N, 78°E) which is located very close to Gadanki is expected to follow a similar pattern of temporal evolution. This TEC shows reduction with respect to control day both at the peak phase (17%) and in the postpeak phase (30%). The enhanced foF2 from the start to the peak phase of the eclipse is attributed to the effect of the weakened equatorial ionization anomaly (EIA). At altitude regions below 270 km, the eclipse induced cutoff of solar insolation results in chemical recombination becoming dominant and thus contributes to the decrease in columnar content in spite of foF2 increase. The post peak phase steep decrease of both foF2 and TEC is attributed to the substantial increase in the poleward meridional winds, the inhibition of the EIA, and persistent depletion in the lower-altitude electron densities. In summary, this study demonstrates the modifications in electrodynamics, recombination, and neutral dynamics acting in concert to produce the observed effects at low latitudes during an eclipse.