Response of Sporadic E Layer to Sudden Stratospheric Warming Events Observed at Low and Middle Latitudes

Abstract

This paper investigates the variations of middle‐ and low‐latitude sporadic E (Es) layers during 2011–2012 and 2012–2013 sudden stratospheric warming (SSW) events by using observations from six ionosondes in East Asia over China and Japan region. Observations of Es critical frequency (foEs) at all these ionosondes present obvious enhancements around the days of new and full moon during SSW periods. Wavelet spectra of foEs during two SSW events exhibit noticeable enhanced 14.5‐day modulation, which resembles the lunar semimonthly period. In addition, simultaneous wind measurements by meteor radar also show enhancement of 14.5‐day periodic oscillation after SSW onset. Tidal components extracted from meteor radar wind measurements in mesosphere and lower thermosphere region and from ionospheric F region critical frequency (foF2) are noticeably modulated by the lunar phase. These observational evidences reveal that the semimonthly lunar period of 14.5 days can be a contributing factor to variations of Es layer during SSW event.

Lunar Tidal Effect on Equatorial Ionization Anomaly Region in China Low Latitude

“…Although the increase of polar stratospheric temperature is large during the SSW event in 2012, the wave power at the 14-15 day period is particularly low during this event, which may be due to a small decrease of the polar stratospheric zonal wind (Tang et al, 2020). Mo and Zhang (2020) showed that the temporal extent of wave power at 14-15 day period is consistent with the temporal extent of the decrease of the stratospheric zonal mean wind rather than the increase of stratospheric temperature during SSW.…”

“…It can be seen from Figure 3d that the wave power at the 14–15 day period is particularly large during the SSW period in 2006 and 2009, which can be attributed to the evidence that these two SSW events were stronger and longer than the others events ever recorded (Manney et al., 2010). Although the increase of polar stratospheric temperature is large during the SSW event in 2012, the wave power at the 14–15 day period is particularly low during this event, which may be due to a small decrease of the polar stratospheric zonal wind (Tang et al., 2020). Mo and Zhang (2020) showed that the temporal extent of wave power at 14–15 day period is consistent with the temporal extent of the decrease of the stratospheric zonal mean wind rather than the increase of stratospheric temperature during SSW.…”

Review of ionospheric irregularities and ionospheric electrodynamic coupling in the middle latitude region

“…During SSW events, the reversal of zonal winds as well as thermal temperature variations in the stratosphere and mesosphere could affect the propagation of lunar tides (Lindzen and Hong, 1974; Stening et al, 1997; Pedatella et al, 2012). The enhancement of the 14.5‐day semimonthly lunar period component in the MLT region, eventually produces variations in the E S layer, shown in Figure 5 (Tang Q et al, 2020).…”

“… The time variations of f o E S spectrum observed by six ionosondes located at Mohe (122.37°E, 53.50°N), Wakkanai (141.75°E, 45.16°N), Kokubunji (139.49°E, 35.71°N), Yamagawa (130.62°E, 31.20°N), Wuhan (114.61°E, 30.53°N), and Okinawa (128.15°E, 26.68°N) during two SSW events. The warming onset is indicated by the red vertical dashed line, while the red horizontal dashed line denotes the 14.5‐day period (after Tang Q et al, 2020). …”

“…The 14.5‐day period is marked with a red horizontal dashed line. The left column is meridional wind, and the right column is zonal wind (afterTang Q et al, 2020).…”