Abstract:
Low latitude ionospheric behavior during solar transient disturbances of solar flares and storm
time penetrating electric fields comprises an important part of the Earth’s space weather. The flares enhance
the electron density of the sunlit ionosphere by supplying excess solar radiation. However, the degree of
these density changes is subjective if a geomagnetic storm persists simultaneously. The present case study
addresses the ionospheric variations over the Indian longitudes under the combined effects of the solar flares
and a geomagnetic storm during 6 to 8 September 2017 and probably the first of its kind in delineating
the effects of these two over the low latitude ionosphere. The X9.3 class flare of 6 September, which occurred
during non-storm conditions, produced an intense E region ionization (~500% over the ambient). However,
the total electron content response to this flare was comparatively weak. The flares on 7 and 8 September
occurred during the 7–8 September geomagnetic storm. Though the 8 September flare occurred with higher
intensity (M8.1) and early in local time compared to the flare of 7 September (M7.3), the equatorial electrojet
current enhancement was lesser on 8 September (~75% over the ambient) than that of 7 September
(~110% over the ambient). This aspect is discussed in view of the storm time convection effects over the low
latitudes during 7–8 September storm. The total electron content did not respond to the flares of 7 and 8
September. This behavior is attributed to the varying center-to-limb distance of the solar active region 12673
during this period.
