Longitudinal and Interhemispheric Ionospheric Response to 2009 and 2013 SSW Events in the African‐European and Indian‐East Asian Sectors

Abstract

The ionospheric response to two sudden stratospheric warming (SSW) events that occurred during low (2009) and moderate solar activity (2013) around 10°E (±10°) African-European and 95°E (±10°) Indian-East Asian sectors is investigated. The total electron content (TEC) obtained from a meridional chain of stations in the two sectors are used to understand the interlongitudinal and interhemispheric response to these SSW events. Significant depletion of daytime TEC was observed after the onset of 2009 SSW around the equatorial ionization anomaly (EIA) crest followed by an increase during the decaying phase of SSW. The formation of an early peak in the daytime TEC and semidiurnal variation in the response of TEC in the form of morning enhancement and afternoon depletion was observed at low latitudes. The morning enhancement is prominent at northern low latitudes while afternoon depletion is more at southern low latitudes. The conspicuous TEC perturbations characterized by semidiurnal variation in mid-January of 2013 override the sudden increase in solar activity after the onset of the SSW. SSW impacted semidiurnal perturbations in F2 layer peak electron density (NmF2) and height (hmF2) noticed at Cocos Island, the southern hemisphere low latitude station. Longitudinal and interhemispheric differences in the magnitude and evolution of TEC perturbations were noticed. The longitudinal differences in SSW modulation of TEC might be attributed to the differential impact of the nonmigrating tides and differences in the geomagnetic field elements between the two sectors. The meridional wind in the mesosphere and lower thermosphere region contribute to the TEC enhancement.

A brief review on the Atmosphere-Ionosphere coupling during Stratospheric sudden warming over the tropical region

“…As evident from Figure, the SSW occurred on day number 56 (January 24). Even though the SSW of January 2008 is minor warming (since there is no reversal of zonal wind), it is one of the strongest recorded events in terms of the enhancement in Polar Stratospheric Temperature (PST) (27,28) . As is obvious in Figure 2, the zonal mean zonal wind at 10 hPa do not show any reversal associated with SSW, albeit there is a small decrease at around day number 50.…”

Ionospheric Response to Sudden Stratospheric Warming Events Across Longitudes During Solar Cycle 24

“…Recently, Kakoti et al. (2020) showed semidiurnal modulation to be a primary feature of SSW time TEC variations by studying interhemispheric and interlongitudinal asymmetry in ionospheric responses to SSW events of 2009 and 2013 at African‐European and Indian‐East Asian sectors. Zhang et al.…”

“…Mostly, the observations from various reports discussed above unambiguously confirmed that the stratospheric effect of warming perturbed the upper atmosphere, particularly the ionosphere. Though a number of studies are available that provide a comprehensive account of ionospheric response to SSW, the inferences drawn on the subject are largely based on the very well researched and reported major SSW event of 2009, followed by SSW event of 2013 (e.g., Kakoti et al., 2020; Zhang et al., 2020), or by considering a few other SSW events. With low solar activity and unusual progression, solar cycle 24 lasted from December 2008 to December 2019 and is considered to be the weakest cycle in the last 100 years.…”

“…Such 13-14-day lunar-related periodic oscillations in F 2 region critical frequency (f o F 2 ) and EEJ strength were also reported by Upadhayaya and Mahajan (2013), along with a 6-hr periodicity in ionospheric changes of the equatorial ionization anomaly (EIA) crest. Recently, Kakoti et al (2020) showed semidiurnal modulation to be a primary feature of SSW time TEC variations by studying interhemispheric and interlongitudinal asymmetry in ionospheric responses to SSW events of 2009 and 2013 at African-European and Indian-East Asian sectors. Zhang et al (2020) attributed the semidiurnal ionospheric disturbances and interhemispheric asymmetries during 2009 SSW event to equatorial field-aligned plasma drift which is southward in the morning sector and northward in the afternoon sector.…”

The Ionospheric Response to the 2013 SSW Event Over the Asian‐Australian Sector

“…They attributed this poleward movement to the increased amplitude of the upward E × B drift caused by the SSW event. Similarly, Kakoti et al (2020) linked the enhancement in TEC magnitude during the mid-January 2013 SSW event to the semidiurnal signature associated with the SSW event. During the mid-January 2013 SSW event over the Asian sector along 150°E longitude, Goncharenko et al (2013) reported significant ionospheric perturbations at the northern EIA compared to the southern crest They attributed these perturbations to the influence of the lower atmosphere.…”