A Statistical Study of F‐Region 3.2‐m‐Scale Field‐Aligned Irregularities Occurrence and Vertical Plasma Drift Over Hainan: Solar Activity, Season, and Magnetic Activity Dependences

Abstract

Equatorial plasma bubbles (EPBs) are plasma density depletions, which initiate in the equatorial or low-latitude F-region ionosphere bottom side and grow to the topside in the form of magnetic field-aligned structures. They usually occur after local sunset, when the conductivity at the E-region ionosphere becomes negligible that creates a favorable condition for the EPBs development. Density gradient at the EPBs boundaries may cascade into irregularities with a wide range of scale sizes, ranging from 10 −2 to 10 5 m (Kelley, 1989), and thus could affect the radio waves spanning a wide frequency range. Different terms have been used to characterize the F-region irregularities observed by different instruments, such as "spread F" in ionosonde observation, "plumes" of field-aligned irregularities (FAIs) in radar backscatter observations, and density "depletions" or "bite-outs" in in situ satellite observations. The dynamics and characteristics of the ionospheric irregularities have been extensively studied for many decades due to its adverse impact on radio communication and navigation systems between satellites and ground. Studies have been carried out to investigate the occurrence characteristics of the F-region irregularities by using data from various equipment, such as coherent and incoherent scatter radars, ionosonde, low-Earth orbiting satellite, radio scintillation detector, and airglow imager (e.g.

Interaction Between Equatorial to Low‐Latitude Postmidnight F‐Region Irregularities and LSTIDs in China During Geomagnetic Disturbances Based on Ground‐Based Instruments

“…Another group of weak plume echoes emerged in Beam 1 and Beam 7 at ∼21:30 UT (∼04:48 LT) and decayed quickly before extending to higher altitudes and other beams. We performed a statistical analysis of the HCOPAR observations and found that few cases of FAIs could persist later than 02 LT at Fuke latitude under quiet conditions in a previous study (Jin et al., 2021). Therefore, this postmidnight case of fresh FAI plumes emerging near 04 LT could be related to geomagnetic disturbances on that day.…”

Multi‐Source Perturbations in the Evolution of a Low‐Latitudinal Equatorial Plasma Bubble Event Occurred Over China

“…Jin et al. (2021) recently used the same method to further compare the occurrence characteristics of EPBs between Fuke in China and Kototabang in Indonesia in June 2015. Both results suggested that an Intertropical Convergence Zone (ITCZ), located near the longitude of Kototabang, was more active, contributing to the high incidence of EPBs there.…”

“…Based on the same radar, Jin et al. (2021) statistically investigated the solar activity, season, and magnetic activity dependence of F ‐region 3.2‐m scale FAIs occurrence and vertical plasma drift over Fuke; Sun, Xu, Zhu, Xiong, et al. (2021) investigated the interaction of an EMSTID and an EPB that occurred over the equatorial ionization anomaly (EIA) crest region of China; Jin et al.…”

Imaging Radar Observations of the Daytime F‐Region Irregularities in Low‐Latitudes of China

“…For a long time, EPBs in the equatorial and low‐latitudes F ‐region have been considered as nighttime phenomena, because they develop at night and are assumed to vanish after sunrise (e.g., Huang & Hairston, 2015; Kil et al., 2019). Statistical studies show that the F ‐region plasma irregularities occur after local sunset with the maximum occurrence during pre‐midnight hours when the conductivity at the E ‐region ionosphere becomes negligible to create a favorable environment for the generation and development of the EPBs (Jin et al., 2021). Plasma bubbles usually decay rapidly after sunrise due to the filling of the photo‐ionized oxygen atoms (Kil et al., 2019).…”