On the solar activity dependence of midnight equatorial plasma bubbles during June solstice periods

Ajith, K. K.; Ram, S. Tulasi; Li, Guozhu; Yamamoto, M.; Hozumi, Kornyanat; Yatini, Clara Y.; Supnithi, Pornchai

doi:10.26464/epp2021039

Cited by 6 publications

(5 citation statements)

References 38 publications

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“…Whereas, NSF in LSAY had a maximum occurrence around midnight hours (post-midnight hours) during Equinox (December solstice). This is consistent with the previous studies that a high occurrence rate of midnight/post-midnight ESF was in June solstice (e.g., Ajith et al, 2021;Li et al, 2007Li et al, , 2011, and the post-sunset ESF occurrence rates were high during equinoctial months (Abdu, 2001).…”

Section: Seasonal and Local Time Distributionssupporting

confidence: 93%

Investigation of the Occurrence Characteristics and Possible Origins of Daytime Spread F Irregularities in Low Latitude Region

Wei,

Jiang,

Yokoyama

et al. 2023

JGR Space Physics

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A study of occurrence characteristics and morphology of daytime spread F (DSF) irregularities was conducted using ionosonde from 2013 to 2020 over low‐latitude Puer station in the China sector. In this study, a day with two or more consecutive F‐region diffuse echo ionograms within one hour from local sunrise to sunset at an altitude of 250 km is considered a DSF day. The results show that the DSF irregularities observed in different solar activity years have a similar seasonal distribution, manifesting as frequent occurrences in June solstice with a maximum occurrence near sunrise. Furthermore, the morphology of most DSFs on the ionograms is predominantly frequency spread F, with a few observed near sunrise as MSF and RSF. In contrast to in high solar activity years (HSAY, 2013–2015), an interesting phenomenon of DSF irregularities in low solar activity years (LSAY, 2016–2020) is presented. That is, in the late afternoon hours (15–18 LT), DSFs have an unexpectedly high occurrence rate during the December solstice. By analyzing the virtual height variations for iso‐frequency plots of the DSF event occurring in the afternoon, these DSF irregularities were found to be likely associated with daytime medium‐scale traveling ionospheric disturbances (MSTIDs). Compared with the observed characteristics of the nighttime spread F, the fossils of nighttime plasma bubbles irregularities might play a key role in the development of DSF occurring in the early morning. At the same time, the influence of daytime MSTIDs on DSF irregularities occurring in the late afternoon hours cannot be ignored.

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Section: Seasonal and Local Time Distributionssupporting

confidence: 93%

Investigation of the Occurrence Characteristics and Possible Origins of Daytime Spread F Irregularities in Low Latitude Region

Wei,

Jiang,

Yokoyama

et al. 2023

JGR Space Physics

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“…They simulated the generation of irregularities for both high and low solar activity, but to find little differences. The reason may reside in the zonal wind and plasma drift in the ionospheric E region (Huba, 2022), or the solar cycle dependence of the medium‐scale traveling ionospheric disturbances, upward propagation of the gravity waves and atmospheric tides that have been proposed to be the seeds for the ionospheric instabilities (Ajith et al., 2021; Liu et al., 2017; Mandal et al., 2022; Otsuka, 2018).…”

Section: Discussionmentioning

confidence: 99%

“…One is the overall rate of 2012 being much lower, and the other is the absence of peak after 03 LT in 2012. Ajith et al (2021) argued that, the weak westward electric field during the midnight hours of low solar activity provides an unstable condition by elevating the F layer to higher altitudes. However, in our cases, the downward E×B drift velocity input for the SAMI2 simulation is larger (stronger westward electric field) in 2009 than in 2012 before midnight and is comparable after midnight, as depicted in Figure 2c.…”

Section: 1029/2022ja031211mentioning

confidence: 99%

Destabilizing Influence of the Neutral Winds for the Midnight and Post‐Midnight Ionospheric Irregularities in Brazil Sector

et al. 2023

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“…However, the timeframe for bubble development varies depending on season, solar cycle, and geomagnetic activity. Bubbles develop late at night under certain conditions such as geomagnetic storms and low solar activity (Aa et al., 2020; Ajith et al., 2021; Heelis et al., 2010; Smith & Heelis, 2017; Stoneback et al., 2011; Watthanasangmechai et al., 2016; Yizengaw et al., 2013). Rapid refilling of bubbles occurs after sunrise through photoionization, causing bubbles to be predominantly detected during nighttime.…”

Section: Introductionmentioning

confidence: 99%

The Impact of Vertical Plasma Motion on the Evolution of Predawn Equatorial Plasma Bubbles on the Dayside

Kil,

Huba,

Paxton

2024

Geophysical Research Letters

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This study investigates the impact of vertical ionospheric drift during daytime on the evolution of predawn equatorial plasma bubbles by conducting model simulations using “Sami3 is Another Model of the Ionosphere.” The upward drift of the ionosphere transports bubbles to higher altitudes, where their lifetime is set by the atomic oxygen photoionization rate. While the bubbles generated at predawn persist into dayside, the bubbles generated shortly after sunset diminish before sunrise. Therefore, post‐sunset bubbles do not contribute to daytime electron density irregularities. Bubbles maintain their field‐aligned characteristics throughout the daytime regardless of the vertical ionospheric drift. This property allows bubbles to exist near the magnetic equator despite poleward plasma transport by the fountain process. The shift of irregularity concentration to higher latitudes over time in satellite observations is explained by the combined effect of transport of bubbles to higher altitudes and rapid refilling of depletions near the magnetic equator.

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On the solar activity dependence of midnight equatorial plasma bubbles during June solstice periods

Cited by 6 publications

References 38 publications

Investigation of the Occurrence Characteristics and Possible Origins of Daytime Spread F Irregularities in Low Latitude Region

Investigation of the Occurrence Characteristics and Possible Origins of Daytime Spread F Irregularities in Low Latitude Region

Destabilizing Influence of the Neutral Winds for the Midnight and Post‐Midnight Ionospheric Irregularities in Brazil Sector

The Impact of Vertical Plasma Motion on the Evolution of Predawn Equatorial Plasma Bubbles on the Dayside

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