Statistical Characteristics and Correlation of Low‐Latitude F Region Bottom‐Type Irregularity Layers and Plasma Plumes Over Sanya

2020 ◽  
Vol 125 (8) ◽  
Author(s):  
Lianhuan Hu ◽  
Xiukuan Zhao ◽  
Wenjie Sun ◽  
Zhi Wu ◽  
Jianchang Zheng ◽  
...  
Keyword(s):  
Statistical Characteristics ◽  
Low Latitude ◽  
Bottom Type ◽  
F Region ◽  
Plasma Plumes

scholarly journals Quasi-6-day wave effects in ionospheric E and F region during the recent solar maximum 2014–2015

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Yi Liu ◽  
Qiong Tang ◽  
Guanyi Chen ◽  
Zhuangkai Wang ◽  
Chen Zhou
Keyword(s):  
Solar Maximum ◽  
Lower Thermosphere ◽  
Maximum Amplitude ◽  
Statistical Characteristics ◽  
Plasma Velocity ◽  
Low Latitude ◽  
F Region ◽  
Wave Effects ◽  
Absolute Amplitude ◽  
Latitude Region

AbstractWe show the statistical characteristics of quasi-6-day wave (Q6DW) absolute amplitude in foE and foF2 during 2014–2015 by using six ionosondes at different latitudes. The results show that foE perturbations maximized at mid-latitudes during equinoxes, and the maximum amplitude of Q6DW in foF2 occurred near the northern crest of equatorial ionospheric anomaly (EIA). In addition, the absolute amplitude of Q6DW in foF2 increased with increasing solar activity. Our observations suggest that the dissipative Q6DW-like oscillations in the lower thermosphere may cause variations in the thermospheric neutral density via mixing effect and further result in foE disturbances in Q6DW events. Furthermore, the E region wind dynamo could also be modulated by the 6-day wave, thus leading to the disturbances in vertical plasma velocity via E × B drifts and F region electron density. Our observational investigation provides evidence of thermosphere–ionosphere coupling in the mid- and low-latitude region.

scholarly journals Coherent backscatter radar imaging in Brazil: large-scale waves in the bottomside F-region at the onset of equatorial spread <I>F</I>

2008 ◽  
Vol 26 (11) ◽  
pp. 3355-3364 ◽  
Author(s):  
F. S. Rodrigues ◽  
D. L. Hysell ◽  
E. R. de Paula
Keyword(s):  
Large Scale ◽  
Imaging Technique ◽  
Radar Imaging ◽  
Shear Instability ◽  
Wide Field ◽  
Bottom Type ◽  
F Region ◽  
Type Layer ◽  
Spread F ◽  
Coherent Backscatter

Abstract. The 30 MHz coherent backscatter radar located at the equatorial observatory in São Luís, Brazil (2.59° S, 44.21° W, −2.35° dip lat) has been upgraded to perform coherent backscatter radar imaging. The wide field-of-view of this radar makes it well suited for radar imaging studies of ionospheric irregularities. Radar imaging observations were made in support to the spread F Experiment (SpreadFEx) campaign. This paper describes the system and imaging technique and presents results from a bottom-type layer that preceded fully-developed radar plumes on 25 October 2005. The radar imaging technique was able to resolve decakilometric structures within the bottom-type layer. These structures indicate the presence of large-scale waves (~35 km) in the bottomside F-region with phases that are alternately stable and unstable to wind-driven gradient drift instabilities. The observations suggest that these waves can also cause the initial perturbation necessary to initiate the Generalized Rayleigh-Taylor instability leading to spread F. The electrodynamic conditions and the scale length of the bottom-type layer structures suggest that the waves were generated by the collisional shear instability. These results indicate that monitoring bottom-type layers may provide helpful diagnostics for spread F forecasting.

scholarly journals The story of plumes: the development of a new conceptual framework for understanding magnetosphere and ionosphere coupling

2016 ◽  
Vol 34 (12) ◽  
pp. 1243-1253 ◽  
Author(s):  
Mark B. Moldwin ◽  
Shasha Zou ◽  
Tom Heine
Keyword(s):  
Conceptual Framework ◽  
Ionospheric Plasma ◽  
Short Review ◽  
Auroral Zone ◽  
Causal Chain ◽  
Elevated Plasma ◽  
Polar Cap ◽  
Paper Briefly ◽  
Low Latitude ◽  
F Region

Abstract. The name “plume” has been given to a variety of plasma structures in the Earth's magnetosphere and ionosphere. Some plumes (such as the plasmasphere plume) represent elevated plasma density, while other plumes (such as the equatorial F region plume) represent low-density regions. Despite these differences these structures are either directly related or connected in the causal chain of plasma redistribution throughout the system. This short review defines how plumes appear in different measurements in different regions and describes how plumes can be used to understand magnetosphere–ionosphere coupling. The story of the plume family helps describe the emerging conceptual framework of the flow of high-density–low-latitude ionospheric plasma into the magnetosphere and clearly shows that strong two-way coupling between ionospheric and magnetospheric dynamics occurs not only in the high-latitude auroral zone and polar cap but also through the plasmasphere. The paper briefly reviews, highlights and synthesizes previous studies that have contributed to this new understanding.

scholarly journals An investigation of the ionospheric F region near the EIA crest in India using OI 777.4 and 630.0 nm nightglow observations

2018 ◽  
Vol 36 (3) ◽  
pp. 809-823 ◽  
Author(s):  
Navin Parihar ◽  
Sandro Maria Radicella ◽  
Bruno Nava ◽  
Yenca Olivia Migoya-Orue ◽  
Prabhakar Tiwari ◽  
...  
Keyword(s):  
Electron Density ◽  
Gravity Waves ◽  
Satellite Mission ◽  
Low Latitude ◽  
Density Maximum ◽  
Density Profiles ◽  
F Region ◽  
Equatorial Ionization Anomaly ◽  
Low Latitude Ionosphere ◽  
Electron Density Profiles

Abstract. Simultaneous observations of OI 777.4 and OI 630.0 nm nightglow emissions were carried at a low-latitude station, Allahabad (25.5° N, 81.9° E; geomag. lat.  ∼  16.30° N), located near the crest of the Appleton anomaly in India during September–December 2009. This report attempts to study the F region of ionosphere using airglow-derived parameters. Using an empirical approach put forward by Makela et al. (2001), firstly, we propose a novel technique to calibrate OI 777.4 and 630.0 nm emission intensities using Constellation Observing System for Meteorology, Ionosphere, and Climate/Formosa Satellite Mission 3 (COSMIC/FORMOSAT-3) electron density profiles. Next, the electron density maximum (Nm) and its height (hmF2) of the F layer have been derived from the information of two calibrated intensities. Nocturnal variation of Nm showed the signatures of the retreat of the equatorial ionization anomaly (EIA) and the midnight temperature maximum (MTM) phenomenon that are usually observed in the equatorial and low-latitude ionosphere. Signatures of gravity waves with time periods in the range of 0.7–3.0 h were also seen in Nm and hmF2 variations. Sample Nm and hmF2 maps have also been generated to show the usefulness of this technique in studying ionospheric processes.

scholarly journals IRI-2001 model predictions compared with ionospheric data observed at Brazilian low latitude stations

2006 ◽  
Vol 24 (8) ◽  
pp. 2191-2200 ◽  
Author(s):  
F. Bertoni ◽  
Y. Sahai ◽  
W. L. C. Lima ◽  
P. R. Fagundes ◽  
V. G. Pillat ◽  
...  
Keyword(s):  
Reasonable Agreement ◽  
Critical Frequency ◽  
Peak Height ◽  
Low Latitude ◽  
F Region ◽  
Model Predictions ◽  
Critical Frequency Fof2

Abstract. In this work, the F-region critical frequency (foF2) and peak height (hmF2) measured by digital ionosondes at two Brazilian low-latitude stations, namely Palmas (10.17° S, 48.20° W, dip –10.80°) and São José dos Campos (23.20° S, 45.86° W, dip –38.41°), are compared with the IRI-2001 model predictions. The comparison at the latter station shows quite a reasonable agreement for both parameters. The former station exhibits a better agreement for hmF2 than for foF2. In general, the model generates good results, although some improvements are still necessary to implement in order to obtain better simulations for equatorial ionospheric regions.

scholarly journals Post midnight spread-F occurrence over Waltair (17.7° N, 83.3° E) during low and ascending phases of solar activity

2003 ◽  
Vol 21 (3) ◽  
pp. 745-750 ◽  
Author(s):  
K. Niranjan ◽  
P. S. Brahmanandam ◽  
P. Ramakrishna Rao ◽  
G. Uma ◽  
D. S. V. V. D. Prasad ◽  
...  
Keyword(s):  
Solar Activity ◽  
Atmospheric Composition ◽  
Activity Period ◽  
Sunspot Activity ◽  
Low Latitude ◽  
F Region ◽  
Composition And Structure ◽  
Spread F ◽  
Solar Activity Period ◽  
Night Airglow

Abstract. A study carried out on the occurrence of post midnight spread-F events at a low-latitude station, Waltair (17.7° N, 83.3° E), India revealed that its occurrence is maximum in the summer solstice months of the low solar activity period and decreases with an increase in the sunspot activity. The F-region virtual height variations show that 80% of these spread-F cases are associated with an increase in the F-region altitude. It is suggested with the support of the night airglow 6300 A zenith intensity data obtained with co-located ground-based night airglow photometer and electron temperature data from the Indian SROSS C2 satellite that the seasonal variation of the occurrence and probable onset times of the post midnight spread-F depend on the characteristics of the highly variable semipermanent equatorial Midnight Temperature Maximum (MTM).Key words. Ionosphere (ionospheric irregularities; ionosphere atmosphere interactions) Atmospheric composition and structure (airglow and Aurora)

scholarly journals Longitudinal differences observed in the ionospheric F-region during the major geomagnetic storm of 31 March 2001

2004 ◽  
Vol 22 (9) ◽  
pp. 3221-3229 ◽  
Author(s):  
Y. Sahai ◽  
P. R. Fagundes ◽  
F. Becker-Guedes ◽  
J. R. Abalde ◽  
G. Crowley ◽  
...  
Keyword(s):  
Geomagnetic Storm ◽  
Recovery Period ◽  
Negative Phase ◽  
Quiet Period ◽  
Geomagnetic Disturbances ◽  
Low Latitude ◽  
F Region ◽  
Similarities And Differences ◽  
Worldwide Network ◽  
Ionospheric Sounding

Abstract. A new ionospheric sounding station using a Canadian Advanced Digital Ionosonde (CADI) was established for routine measurements by the "Universidade do Vale do Paraiba (UNIVAP)" at São José dos Campos (23.2° S, 45.9° W), Brazil, in August 2000. A major geomagnetic storm with gradual commencement at about 01:00 UT was observed on 31 March 2001. In this paper, we present and discuss salient features from the ionospheric sounding measurements carried out at S. J. Campos on the three consecutive UT days 30 March (quiet), 31 March (disturbed) and 1 April (recovery) 2001. During most of the storm period, the foF2 values showed negative phase, whereas during the two storm-time peaks, large F-region height variations were observed. In order to study the longitudinal differences observed in the F-region during the storm, the simultaneous ionospheric sounding measurements carried out at S. J. Campos, El Arenosillo (37.1° N, 6.7° W), Spain, Okinawa (26.3° N, 127.8° E), Japan and Wakkanai (45.5° N, 141.7° E), Japan, during the period 30 March-1 April 2001, have been analyzed. A comparison of the observed ionospheric parameters (h'F and foF2) in the two longitudinal zones (1. Japanese and 2. Brazilian-Spanish) shows both similarities and differences associated with the geomagnetic disturbances. Some latitudinal differences are also observed in the two longitudinal zones. In addition, global ionospheric TEC maps from the worldwide network of GPS receivers are presented, showing widespread TEC changes during both the main and recovery phases of the storm. The ionospheric sounding measurements are compared with the ASPEN-TIMEGCM model runs appropriate for the storm conditions. The model results produce better agreement during the quiet period. During the disturbed period, some of the observed F-region height variations are well reproduced by the model results. The model foF2 and TEC results differ considerably during the recovery period and indicate much stronger negative phase at all the stations, particularly at the low-latitude ones.

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