Impact of Stratospheric Sudden Warming on the Occurrence of the Equatorial Spread‐<italic>F</italic>.

Abstract: This study presents the influence of stratospheric sudden warming (SSW) events in modulating the start time of the equatorial spread‐F (ESF) through enhanced planetary wave (PW) activity during the winter months of the SSW years. The analysis based on the data from a digital ionosonde and proton precession magnetometer over Trivandrum (8.5&#176;N, 77&#176;E, 0.5&#176;N dip lat.) revealed that the PWs of quasi‐16&#160;day periodicity influence the start time of the ESF to a significant extent during the SSW years. On the other hand, during a normal year such effect is not very evidently present. It has been observed that the quasi‐16&#160;day wave propagates to ionospheric dynamo region from the atmosphere below and modifies the electrodynamical processes like the equatorial electrojet and prereversal enhancement, which is more pronounced during both the SSW periods. Such a modification in the electrodynamics can modulate the equatorial plasma fountain and influence the F region neutral dynamics, which in turn can affect the occurrence of ESF by modifying the seeding conditions. [ABSTRACT FROM AUTHOR]