Instability Mechanisms for the F‐Region Plasma Irregularities Inside the Midlatitude Ionospheric Trough: Swarm Observations

Liu, Yiwen; Xiong, Chao; Wan, Xiaoxia; Lai, Yeping; Wang, Yuhao; Yu, Xiao; Ou, Ming

doi:10.1029/2021sw002785

Cited by 10 publications

(37 citation statements)

References 32 publications

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“…The equatorward boundary of the mid‐latitude trough (blue curve) is less than 60° MLat at nighttime, but larger than 70° MLat at daytime. Such average MLT positions are consistent with previous statistical results (see Figure 2 in Aa et al., 2020 and Figure 4 in Liu et al., 2021). Liu et al.…”

Section: Statistical Resultssupporting

confidence: 93%

“…The identification method used here for the mid‐latitude trough can be found in Liu et al. (2021). It can be seen that the minimum trough (red curve) shows obvious local time asymmetry: at higher latitudes on the dayside and at lower latitudes on the nightside.…”

Section: Statistical Resultsmentioning

confidence: 99%

“…In addition, Liu et al. (2021) compared the positions of MIT with the auroral oval. As shown in their Figure 4, the equatorward boundary of mid‐latitude trough in the post‐noon sector (12–18 MLT) coincided with the equatorward boundary of the auroral oval.…”

Section: Discussionmentioning

confidence: 99%

“…in Aa et al, 2020 and Figure 4 in Liu et al, 2021) Liu et al (2021). compared the positions of MIT with the auroral oval.…”

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confidence: 99%

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Magnetic Local Time and Latitude Distribution of Ionospheric Large‐Spatial‐Scale EMIC Wave Events: Swarm Observations

et al. 2022

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In the present work, the magnetic local time and latitude (MLT and MLat) distributions of ionospheric large‐spatial‐scale (>20° MLat) electromagnetic ion cyclotron waves were investigated using high‐resolution 50‐Hz geomagnetic field data from Swarm A and B satellites. Both parallel and transverse waves were studied in a comparative manner for different geomagnetic activities and seasons. Frequent occurrences of large‐spatial‐scale waves in the South Atlantic Anomaly and North America, where the parallel waves propagate over the longest distance, were observed. Waves appear mostly in the 02–10 MLT sector wherein the pre‐noon parallel waves propagate farthest in latitudinal range. With the enhancement of geomagnetic activity, both transverse and parallel waves increase in occurrence. The dayside occurrence rate is higher during weak geomagnetic activity, whereas the situation is reversed on the nightside and duskside. The dayside waves are located outside the mid‐latitude trough, and the nightside waves are located near (inside) the equatorward boundary of the mid‐latitude trough. Large‐spatial‐scale waves tend to occur at the equinoxes when the absolute value of the dipole tilt angle is less than 10°, while the long‐distance transmission in the waveguide occurs in the pre‐noon in summer. Parallel waves propagate in the region where the electron density is higher than that of the transverse waves. There is a close relationship between EMIC wave and electron density oscillation.

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Section: Statistical Resultssupporting

confidence: 93%

Section: Statistical Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

“…in Aa et al, 2020 and Figure 4 in Liu et al, 2021) Liu et al (2021). compared the positions of MIT with the auroral oval.…”

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confidence: 99%

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Magnetic Local Time and Latitude Distribution of Ionospheric Large‐Spatial‐Scale EMIC Wave Events: Swarm Observations

et al. 2022

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“…This is mainly because the location of the MIT changes greatly with LT, which usually appear as “V‐shape” diurnal distribution, occurring at higher latitudes on the dayside, migrating to lower latitudes on the nightside, and reaching to the lowest latitude in the pre‐dawn sector (Aa et al., 2020; Krankowski et al., 2009; Le et al., 2017; Werner & Prölss, 1997). Our recent work (Liu et al., 2021) fully discussed the reasons for the diurnal differences of higher occurrence rate on the dayside than that on the nightside, that is, the dayside MIT structure resides well inside the aurora/cusp region, but the nightside MIT structure is almost completely outside the auroral oval.…”

Section: Resultsmentioning

confidence: 99%

Distribution Characteristics of the Plasma Irregularities Inside the Mid‐Latitude Ionospheric Trough Based on Swarm In Situ Measurements

et al. 2022

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A large number of studies have confirmed the frequent occurrence of mid‐latitude trough irregularities (MTI), but the distribution characteristics of these irregularities are still pending. Based on the Swarm in situ plasma measurements from 2014 to 2020, the dependences of MTI on magnetic local time, season, solar flux, and geomagnetic activities are analyzed. The results show that for the irregularities with scale‐size of about 7.5–75 km. (a) Geomagnetic activity has an obvious inhibitory effect on the formation of MTI, regardless on the dayside or nightside. (b) The daytime MTI occurrence rate is significantly higher than that at nighttime, and the difference between the poleward wall and equatorward wall during daytime is higher than that at nighttime. (c) The dayside MTI occurrence rate appears highest in winter and lowest in summer, but the nightside MTI occurrence rate appears highest in equinoxes and lowest in winter. (d) The nightside MTI show lower occurrence rate under high solar activity conditions, but no obvious solar activity influence is shown on the dayside. It is suggested that the temperature gradient instability plays an important role in causing the seasonal effect of the nightside MTI, but cannot directly support the solar activity effect. The relatively low nightside MTI occurrence rate in high solar activity years probably results from the relatively small electron temperature gradient. It is speculated that the formation of nightside MTI not only requires the antiparallel conditions of density gradient and temperature gradient, but may also needs to meet the enough large magnitude of the two gradients.

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Statistical characteristics of midlatitude ionospheric F-region backscatter observed by the SuperDARN Jiamusi radar

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Zhang

Wang

et al. 2022

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The Jiamusi (JME) radar is the first high-frequency coherent scatter radar independently developed in China. In this study, we investigate the statistical characteristics of the occurrence rate of F-region ionospheric irregularities between 40°N and 65°N geomagnetic latitude by using the Jiamusi radar data from March 2018 to November 2019. Diurnal and seasonal variations in scattering echoes and their dependence on geomagnetic conditions are statistically investigated. It is shown that the local time of the peak echo occurrence rate varies depending on the season, i.e., approximately 20-22.5 magnetic local time (MLT) in summer, 17.5-20.5 MLT in equinox, and 16-17.5 MLT in winter, which is closely associated with the time of sunset. The echo occurrence rate also increases with the enhancement of the geomagnetic index. To further understand the mechanism of these features, we simulate the distribution of the gradient drift instability indicator ([?]n * V E /n) by using the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM). The analysis results indicate that the gradient drift instability is an important mechanism for irregularities in this region. Key points: 1. Diurnal and seasonal variations in the scatter occurrence rate and their dependence on Kp conditions are statistically analyzed. 2. The distribution of the gradient drift instability indicator ([?]n * V E /n) is simulated by using the TIEGCM. 3. The gradient drift instability is an important mechanism for the high occurrence rate of echoes in the midlatitude region.

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Instability Mechanisms for the F‐Region Plasma Irregularities Inside the Midlatitude Ionospheric Trough: Swarm Observations

Cited by 10 publications

References 32 publications

Magnetic Local Time and Latitude Distribution of Ionospheric Large‐Spatial‐Scale EMIC Wave Events: Swarm Observations

Magnetic Local Time and Latitude Distribution of Ionospheric Large‐Spatial‐Scale EMIC Wave Events: Swarm Observations

Distribution Characteristics of the Plasma Irregularities Inside the Mid‐Latitude Ionospheric Trough Based on Swarm In Situ Measurements

Statistical characteristics of midlatitude ionospheric F-region backscatter observed by the SuperDARN Jiamusi radar

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