First observation of presunset ionospheric <i>F</i> region bottom‐type scattering layer

Li, Guozhu; Ning, Baiqi; Abdu, M. A.; Wan, Weixing; Wang, Chi; Yang, Guotao; Liu, Kangkang; Liu, Libo; Yan, Chunxiao

doi:10.1002/2016ja023647

Cited by 23 publications

(49 citation statements)

References 24 publications

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“…The center beam is pointed to geographic north with the zenith angle of 28.2°. The 3 dB (half power full beam) beam width is 21° in the north‐south direction, and all the beams can satisfy the perpendicular condition to geomagnetic field lines at both ionospheric E and F regions (e.g., Li et al, ). Figure a shows the radar beam directions (blue lines labeled 1 to 7 from east to west) in the geographic longitude‐latitude plane.…”

Section: Instruments and Datamentioning

confidence: 99%

Coupling Between E Region Quasi‐Periodic Echoes and F Region Medium‐Scale Traveling Ionospheric Disturbances at Low Latitudes

Xie

Zhao

et al. 2020

JGR Space Physics

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E region quasi-periodic (QP) echoes from a VHF coherent backscatter radar, sporadic E (E s ) layer from a digisonde, and F region medium-scale traveling ionospheric disturbances (MSTIDs) from global navigation satellite systems receivers were simultaneously observed at low latitudes. The results on the night of 3 March 2018 show that the QP echoes in radar height-time intensity maps were clustered into groups, coinciding with the periods of MSTIDs and strong E s layer. The MSTIDs had phase fronts elongating in the northwest-southeast direction and propagated southwestward from middle to low latitudes. Similar to the propagation direction of MSTIDs, the low-latitude E s layers also propagated southwestward. For the QP echoing clusters, a westward drift was seen from the radar multibeam observations. The Doppler velocities of QP echoes show beam dependence, with significantly enhanced positive values (motion away from the radar) in the westernmost beam. Based on a preliminary statistical analysis during the period March-June 2018, it was found that out of a total of 102 nights, there are 32 nights when QP echoes were generated. The simultaneous occurrences of QP echoes and MSTIDs were observed on six nights. We suggest that when the MSTIDs coming from middle latitudes approach low latitudes, the polarization electric fields associated with the MSTIDs could modulate the E region plasma instability producing QP echoes at low latitudes through the E-F region electrodynamic coupling.

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Section: Instruments and Datamentioning

confidence: 99%

Coupling Between E Region Quasi‐Periodic Echoes and F Region Medium‐Scale Traveling Ionospheric Disturbances at Low Latitudes

Xie

Zhao

et al. 2020

JGR Space Physics

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“…The radar has a wide 3‐dB beam width (36° in the north‐south direction) that satisfies the perpendicular condition to the magnetic field lines from E to F regions and can receive the coherent echoes arising from field‐aligned irregularities in these regions. For additional details about the radar parameters please see Li et al (, ). The ionosonde (DPS‐4D) colocated at Sanya is employed to get the ionospheric background condition.…”

Section: Datamentioning

confidence: 99%

Statistical Study on the Occurrences of Postsunset Ionospheric E, Valley, and F Region Irregularities and Their Correlations Over Low‐Latitude Sanya

Xie

Zhao

et al. 2018

JGR Space Physics

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The coupling of equatorial and low-latitude ionosphere has been an active area of research for many years. At low latitude, the occurrences of E and valley region irregularities during postsunset hours are obviously different from those around the magnetic equator. In this work, we statistically investigated the occurrences of postsunset ionospheric E, valley, and F region irregularities, the postsunset rise of F layer, and their correlations by using the Sanya (18.4°N, 109.6°E, dip latitude 12.8°N) very high frequency radar and ionosonde observations during equinoctial months of 2012-2016. A statistically significant correlation between the presence of valley region irregularities and that of equatorial spread F (ESF) was found over Sanya. For the days without ESF, valley region irregularity was rarely observed. The Doppler velocities of valley region irregularities were mainly upward which resemble those of simultaneous ESF irregularities. On the other hand, an occurrence peak of E region irregularities was detected around sunset. After sunset, E region irregularity echo was frequently disrupted. The disruption can appear on both ESF and non-ESF days, when the amplitudes of F layer postsunset rise were significantly different. The effects of polarization electric field associated with ESF and of equatorial ionospheric background condition on the E and valley region irregularities over Sanya are discussed.

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“…Many sources such as weather storm, earthquake, and solar storm can launch gravity waves/acoustic waves in the atmosphere. The waves propagate through the thermosphere, generating plasma density disturbances with varying periods of minutes to hours (e.g., Lay et al, ; Negrea et al, ; Negrea & Zabotin, ; Yue et al, ) and triggering plasma thin layer and/or plume‐type irregularities in the ionosphere (e.g., Abdu et al, ; Fritts et al, ; Li et al, ). With regard to the wavelength/period, ionospheric disturbances can be classified into three types: large, middle, and small scales.…”

Section: Introductionmentioning

confidence: 99%

Observation of Short‐Period Ionospheric Disturbances Using a Portable Digital Ionosonde at Sanya

Lan

Ning

et al. 2018

Radio Science

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A number of ionosondes have been operated in China to detect ionospheric disturbances for many years. These ionosondes, however, are not very suitable for the short‐period (<15 min) disturbances due to their poor time resolutions (>5 min). During recent years, the Institute of Geology and Geophysics, Chinese Academy of Sciences, together with the South Central University for Nationalities has been developing a portable digital ionosonde (PDI) equipped with the capability to detect and characterize small‐scale/short‐period ionospheric disturbances and to be quickly assembled and set up at temporary field stations for low‐latitude campaign coordinated observations. The PDI uses a set of technologies (e.g., code multiplexing and antenna/transmitter matching) that allow it to obtain quality Doppler ionograms at a good time resolution with small transmitting antennas. A preliminary analysis of observations by the PDI at Sanya (18.3°N, 109.6°E) shows the presence of ionospheric disturbances with periods ranging between several and tens of minutes. Interestingly, the disturbances (with different periods) were found to simultaneously occur at different F region altitudes, for example, with periods of ~5 and 20 min below and above ~180 km, respectively. The absence of shorter‐period disturbance at higher altitude is consistent with acoustic gravity waves through the region with intrinsic periods above the Brunt‐Väisälä period. The short‐period disturbances observed in F region bottomside are not evident in total electron content. The results demonstrate the capability of PDI to detect ionospheric disturbances with temporal scales down to a few minutes in routine ionogram mode. Future prospects of PDI are outlined.

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First observation of presunset ionospheric F region bottom‐type scattering layer

Cited by 23 publications

References 24 publications

Coupling Between E Region Quasi‐Periodic Echoes and F Region Medium‐Scale Traveling Ionospheric Disturbances at Low Latitudes

Coupling Between E Region Quasi‐Periodic Echoes and F Region Medium‐Scale Traveling Ionospheric Disturbances at Low Latitudes

Statistical Study on the Occurrences of Postsunset Ionospheric E, Valley, and F Region Irregularities and Their Correlations Over Low‐Latitude Sanya

Observation of Short‐Period Ionospheric Disturbances Using a Portable Digital Ionosonde at Sanya

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