The Comparison of Lunar Tidal Characteristics in the Low‐Latitudinal Ionosphere Between East Asian and American Sectors During Stratospheric Sudden Warming Events: 2009–2018
Abstract:Longitudinal differences of low‐latitudinal ionospheric responses during five major, four minor, and a none‐stratospheric sudden warming (SSW) winters from 2009 to 2018 between East Asian and American sectors are studied with total electron content (TEC). The time‐shifted semidiurnal (TS) pattern and the amplitude (AM2), phase angle (PAM2), and relative strength (RSM2) of the lunar semidiurnal tide (M2) harmonic in TEC are compared between the two sectors. Main results are as follows: (1) TS patterns, AM2,and … Show more
“…Similar TEC behavior is also observed in the present study at low latitude stations. Recently, Liu et al (2019) studied low‐latitude ionospheric response to SSW events during 2009–2018 and found that time‐shifted semidiurnal (TS) patterns in TEC can occur before the peak warming of SSW. Fang et al (2012) using the WAM simulations initialized with assimilated measured data and the CTIPe model simulations studied the ionospheric response to the 2009 SSW event.…”
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.
“…Similar TEC behavior is also observed in the present study at low latitude stations. Recently, Liu et al (2019) studied low‐latitude ionospheric response to SSW events during 2009–2018 and found that time‐shifted semidiurnal (TS) patterns in TEC can occur before the peak warming of SSW. Fang et al (2012) using the WAM simulations initialized with assimilated measured data and the CTIPe model simulations studied the ionospheric response to the 2009 SSW event.…”
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.
“…10.1029/2020JA028859 6 of 11 the E-region dynamo and the equatorial plasma fountain it creates (Fejer et al, 2010;Goncharenko, Chan, et al, 2010;Goncharenko, Coster, et al, 2010;J. Liu et al, 2019;Pedatella et al, 2012Pedatella et al, , 2014.…”
Section: The Hemispheric Asymmetry Of Perturbations In the Low Latitudementioning
The ionospheric perturbations during sudden stratospheric warming events (SSWs) have attracted broad attention recently, including depressions and enhancements (
“…Forbes and Zhang (2012) argued that the large semidiurnal lunar tide observed during the January 2009 SSW can arise from resonant amplification associated with the atmospheric Pekeris mode. Enhanced lunar tidal perturbations in the equatorial ionosphere have been reported for a number of SSW events (Fejer et al, 2011;Liu et al, 2019;Siddiqui et al, 2015Siddiqui et al, , 2018Park et al, 2012).…”
An exceptionally strong stationary planetary wave with Zonal Wavenumber 1 led to a sudden stratospheric warming (SSW) in the Southern Hemisphere in September 2019. Ionospheric data from European Space Agency's Swarm satellite constellation mission show prominent 6‐day variations in the dayside low‐latitude region at this time, which can be attributed to forcing from the middle atmosphere by the Rossby normal mode “quasi‐6‐day wave” (Q6DW). Geopotential height measurements by the Microwave Limb Sounder aboard National Aeronautics and Space Administration's Aura satellite reveal a burst of global Q6DW activity in the mesosphere and lower thermosphere during the SSW, which is one of the strongest in the record. The Q6DW is apparently generated in the polar stratosphere at 30–40 km, where the atmosphere is unstable due to strong vertical wind shear connected with planetary wave breaking. These results suggest that an Antarctic SSW can lead to ionospheric variability through wave forcing from the middle atmosphere.
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