Geomagnetic and Solar Dependencies of Midlatitude E‐Region Irregularity Occurrence Rate: A Climatology Based on Wuhan VHF Radar Observations

Abstract

By using Wuhan VHF radar, we show the morphological features of E‐region field‐aligned irregularity (FAI) occurrence at Wuhan during 2015–2020. Statistical results present that E‐region FAI occurrence reaches a maximum after sunset in summer season. According to Doppler spectrum features, type‐2 irregularity is predominantly observed at Wuhan. In addition, we observed a remarkable correlation between E‐region FAI occurrence and geomagnetic activity, which includes periods of positive correlation and negative correlation depending on different geomagnetic conditions. The strong negative correlation also exists between E‐region FAI occurrence and solar activity. In our observed results, we find that E‐region FAI occurrence shows a strong linkage with local sporadic E (ES) layer. A quantitative analysis of linear theory of plasma instability in the E‐region at midlatitudes is also presented in our study. The calculated results of linear growth rate indicate the importance of plasma density gradient of local ES layer and field‐line‐integrated Pedersen conductivity ΣPE+F ${{\Sigma}}_{P}^{E+F}$ on the generation of E‐region FAI. The geomagnetic and solar variations of E‐region FAI occurrence are also discussed in this study, which show a dependence on the geomagnetic and solar variations of both meteor rate and medium‐scale traveling ionospheric disturbance occurrence.

Blanketing Sporadic‐E Layer Occurrences Over Santa Maria, a Transition Station From Low to Middle Latitude in the South American Magnetic Anomaly (SAMA)

“…On the other hand, ∆ f Es and the E ‐region Field‐Aligned‐Irregularities (FAIs) (Ecklund et al., 1981), caused by Gradient Drift Instabilities, seem to have a close relation. Several works reported a positive correlation between ∆ f Es and FAIs, and high ∆ f Es values are favorable for the FAIs occurrences after sunset (Haldoupis & Schlegel, 1996; Lee et al., 2000; Liu et al., 2022; Yan et al., 2022; Zhou et al., 2018). Unfortunately, we do not have ionosonde and VHF radar to observe the Es b layers simultaneously.…”

High-Resolution Observation of Ionospheric E-Layer Irregularities Using Multi-Frequency Range Imaging Technology

“…Ionospheric field-aligned irregularities (FAIs) are ionized "clumps" or "wave-like" structures of various scales floating in a normal ionospheric structure, and they are of critical importance for electromagnetic signal propagation [1][2][3]. Therefore, FAIs are one of the most important sources of disturbance for navigation, communication, and radar systems, and a remarkable set of comprehensive statistical studies have been conducted on ionospheric FAIs [4][5][6][7][8][9][10][11][12][13][14][15][16][17]. In addition, modeling and case studies have been carried out to reproduce ionospheric irregularities and to understand their mechanism [18][19][20][21][22][23][24][25][26][27][28].…”

“…In addition, modeling and case studies have been carried out to reproduce ionospheric irregularities and to understand their mechanism [18][19][20][21][22][23][24][25][26][27][28]. Among them, midlatitude ionospheric E-region FAIs have been investigated for more than four decades since the first observation was made with a VHF radar over Arecibo [4][5][6]14,15,[17][18][19][20][21][22][23][24][25][26][27][28][29][30][31].…”

Simulation of Es Layer Modulated by Nonlinear Kelvin–Helmholtz Instability

“…Based on the electrojet theory (Farley, 1963), the polarization electric field mechanism associated with Es layer has been proposed (Haldoupis et al, 1996a;Kagan & Kelley, 1998;Liu, Deng, et al, 2022, 2022bMaruyama et al, 2000;Rosado-Roman et al, 1999;Saito et al, 2006;Shalimov et al, 1998;Tsunoda et al, 1994;Woodman et al, 1991). Simulations reveal that QP echoes associated with FAIs are related to the horizontal structure in the Es layer and that the polarization electric fields are induced by the ambient electric field, neutral wind, or the gravity waves (Haldoupis & Pancheva, 2006;Yokoyama et al, 2003Yokoyama et al, , 2004.…”