Abstract:
A case of the westward disturbance dynamo (DD) electric field, influencing the daytime
equatorial and low-latitude ionosphere, during a geomagnetic storm that occurred on 28–29 June 2013
is presented. The GPS total electron content (TEC) observations from a network of stations in the Indian
equatorial, low and middle latitude regions along with the radio beacon TEC, ionosonde, and magnetic
field observations are used to study the storm time behavior of the ionosphere. Negative ionospheric
storm effects were seen over the low and middle latitudes during the storm time due to the presence of a
westward DD electric field. Observations show that the suppression of the equatorial ionization anomaly
(EIA) from the morning hours itself on 29 June 2013 took place due to the prevailing westward DD electric
field, providing evidence for the model calculations by Balan et al. (2013). Simulations using the GITM model
also agree well with our results. The present study gains importance as the direct observational evidences
for disturbance dynamo effects on the daytime low-latitude ionosphere and the EIA are sparse, as it has
been difficult to delineate it from the compositional disturbances.
