scholarly journals Airglow observations over the equatorial ionization anomaly zone in Taiwan

2011 ◽  
Vol 29 (5) ◽  
pp. 749-757 ◽  
Author(s):  
J. Y. Liu ◽  
P. K. Rajesh ◽  
I. T. Lee ◽  
T. C. Chow
Keyword(s):  
Global Positioning System ◽  
Ionospheric Disturbances ◽  
Iri Model ◽  
Plasma Bubbles ◽  
Equatorial Ionization Anomaly ◽  
Equatorial Plasma Bubbles ◽  
Global Positioning ◽  
Plasma Depletions ◽  
First Time ◽  
Eastern Wall

Abstract. Airglow imaging at mid-latitude stations often show intensity modulations associated with medium scale travelling ionospheric disturbances (MSTID), while those carried out near the equatorial regions reveal depletions caused by equatorial plasma bubbles (EPB). Two all sky cameras are used to observe plasma depletions in the 630.0 nm emission over the equatorial ionization anomaly (EIA) region, Taiwan (23° N, 121° E; 13.5° N Magnetic) during 1998–2002 and 2006–2007. The results show EPB and MSTID depletions in different solar activity conditions. Several new features of the EPB depletions such as bifurcation, secondary structure on the walls, westward tilt, etc., are discussed in this paper. Evidence of tilted depletions with secondary structures developing on the eastern wall that later evolve to appear as bifurcations, are presented for the first time. Moreover, detail investigations are carried out using International Reference Ionosphere (IRI) model as well as the electron density from Ionosonde and Global Positioning System (GPS) Occultation Experiment (GOX) onboard FORMOSAT-3/COSMIC satellite, to understand the conditions that favor the propagation of MSTID to the latitude of Taiwan.

scholarly journals The climatology of ionospheric plasma bubbles and irregularities over Brazil

2005 ◽  
Vol 23 (2) ◽  
pp. 379-384 ◽  
Author(s):  
F. D. Chu ◽  
J. Y. Liu ◽  
H. Takahashi ◽  
J. H. A. Sobral ◽  
M. J. Taylor ◽  
...  
Keyword(s):  
Global Positioning System ◽  
Ionospheric Plasma ◽  
Electron Content ◽  
Simultaneous Observation ◽  
Total Electron ◽  
Phase Fluctuations ◽  
Plasma Bubbles ◽  
Global Positioning ◽  
Solar Activity Variation ◽  
Plasma Depletions

Abstract. In this paper, we examine ionospheric plasma depletions (or bubbles) and irregularities observed by photometers and a ground-based receiver of the global positioning system (GPS) both located in Brazil, South America. A simultaneous observation reveals that when the ionospheric plasma becomes depleted, the GPS total electron content decreases and the associated phase fluctuations grow. Statistical results show that the plasma bubbles and the significant GPS phase fluctuations generally occur during October-March. The solar activity variation is not obvious in either observation except during the equinoctial months. The GPS phase fluctuations suggest that the most pronounced ionospheric irregularities appear between 20:00 and 01:00 LT, which generally agree with previous ionospheric bubble observations.

scholarly journals Comparison of GPS TEC with IRI models of 2007, 2012, AND 1 2016 over Sukkur, Pakistan

2020 ◽  
Vol 1 (1) ◽  
pp. 1-10
Author(s):  
Adil Hussain ◽  
Munawar Shah
Keyword(s):  
Global Positioning System ◽  
Electron Content ◽  
Iri Model ◽  
Low Latitude ◽  
Total Electron ◽  
Gps Tec ◽  
Global Positioning ◽  
Radio Signals ◽  
Ionospheric Scintillations ◽  
Latitude Region

The international reference ionosphere (IRI) models have been widely used for correcting the ionospheric scintillations at different altitude levels. An evaluation on the performance of VTEC correction from IRI models (version 2007, 2012 and 2016) over Sukkur, Pakistan (27.71º N, 68.85º E) is presented in this work. Total Electron Content (TEC) from IRI models and GPS in 2019 over Sukkur region are compared. The main aim of this comparative analysis is to improve the VTEC in low latitude Sukkur, Pakistan. Moreover, this study will also help us to identify the credible IRI model for the correction of Global Positioning System (GPS) signal in low latitude region in future. The development of more accurate TEC finds useful applications in enhancing the extent to which ionospheric influences on radio signals are corrected. VTEC from GPS and IRI models are collected between May 1, 2019 and May 3, 2019. Additionally, Dst and Kp data are also compared in this work to estimate the geomagnetic storm variations. This study shows a good correlation of 0.83 between VTEC of GPS and IRI 2016. Furthermore, a correlation of 0.82 and 0.78 is also recorded for IRI 2012 and IRI 2007 respectively, with VTEC of GPS. The IRI TEC predictions and GPS-TEC measurements for the studied days reveal the potential of IRI model as a good candidate over Pakistan.

scholarly journals Modeling of equatorial plasma bubbles triggered by non-equatorial traveling ionospheric disturbances

2011 ◽  
Vol 38 (8) ◽  
pp. n/a-n/a ◽  
Author(s):  
J. Krall ◽  
J. D. Huba ◽  
S. L. Ossakow ◽  
G. Joyce ◽  
J. J. Makela ◽  
...  
Keyword(s):  
Ionospheric Disturbances ◽  
Traveling Ionospheric Disturbances ◽  
Plasma Bubbles ◽  
Equatorial Plasma Bubbles

scholarly journals Simultaneous observations of equatorial F-region plasma depletions over Brazil during the Spread-F Experiment (SpreadFEx)

2009 ◽  
Vol 27 (6) ◽  
pp. 2371-2381 ◽  
Author(s):  
P.-D. Pautet ◽  
M. J. Taylor ◽  
N. P. Chapagain ◽  
H. Takahashi ◽  
A. F. Medeiros ◽  
...  
Keyword(s):  
Gravity Wave ◽  
State University ◽  
Large Area ◽  
Plasma Bubbles ◽  
F Region ◽  
Equatorial Plasma Bubbles ◽  
Star Program ◽  
Spread F ◽  
Plasma Depletions ◽  
Bubble Characteristics

Abstract. From September to November 2005, the NASA Living with a Star program supported the Spread-F Experiment campaign (SpreadFEx) in Brazil to study the effects of convectively generated gravity waves on the ionosphere and their role in seeding Rayleigh-Taylor instabilities, and associated equatorial plasma bubbles. Several US and Brazilian institutes deployed a broad range of instruments (all-sky imagers, digisondes, photometers, meteor/VHF radars, GPS receivers) covering a large area of Brazil. The campaign was divided in two observational phases centered on the September and October new moon periods. During these periods, an Utah State University (USU) all-sky CCD imager operated at São João d'Aliança (14.8° S, 47.6° W), near Brasilia, and a Brazilian all-sky CCD imager located at Cariri (7.4° S, 36° W), observed simultaneously the evolution of the ionospheric bubbles in the OI (630 nm) emission and the mesospheric gravity wave field. The two sites had approximately the same magnetic latitude (9–10° S) but were separated in longitude by ~1500 km. Plasma bubbles were observed on every clear night (17 from Brasilia and 19 from Cariri, with 8 coincident nights). These joint datasets provided important information for characterizing the ionospheric depletions during the campaign and to perform a novel longitudinal investigation of their variability. Measurements of the drift velocities at both sites are in good agreement with previous studies, however, the overlapping fields of view revealed significant differences in the occurrence and structure of the plasma bubbles, providing new evidence for localized generation. This paper summarizes the observed bubble characteristics important for related investigations of their seeding mechanisms associated with gravity wave activity.

scholarly journals Occurrence of Equatorial Plasma Bubbles during Intense Magnetic Storms

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
Chao-Song Huang
Keyword(s):  
Electric Field ◽  
Magnetic Storms ◽  
Ion Density ◽  
Plasma Bubbles ◽  
Defense Meteorological Satellite Program ◽  
Equatorial Plasma Bubbles ◽  
Evening Sector ◽  
Plasma Depletions ◽  
Meteorological Satellite ◽  
The Imf

An important issue in low-latitude ionospheric space weather is how magnetic storms affect the generation of equatorial plasma bubbles. In this study, we present the measurements of the ion density and velocity in the evening equatorial ionosphere by the Defense Meteorological Satellite Program (DMSP) satellites during 22 intense magnetic storms. The DMSP measurements show that deep ion density depletions (plasma bubbles) are generated after the interplanetary magnetic field (IMF) turns southward. The time delay between the IMF southward turning and the first DMSP detection of plasma depletions decreases with the minimum value of the IMFBz, the maximum value of the interplanetary electric field (IEF)Ey, and the magnitude of the Dst index. The results of this study provide strong evidence that penetration electric field associated with southward IMF during the main phase of magnetic storms increases the generation of equatorial plasma bubbles in the evening sector.

scholarly journals Dynamics Ionospheric Plasma Bubbles Measured by Optical Imaging System

2015 ◽  
Vol 20 (1) ◽  
pp. 20-27
Author(s):  
Narayan P. Chapagain
Keyword(s):  
Imaging System ◽  
Equatorial Ionosphere ◽  
Navigation Systems ◽  
Plasma Bubble ◽  
Central Pacific ◽  
Central Pacific Ocean ◽  
Plasma Bubbles ◽  
Christmas Island ◽  
Equatorial Plasma Bubbles ◽  
Plasma Depletions

Deep plasma depletions during the nighttime period in the equatorial ionosphere (referred to as equatorial plasma bubbles –EPBs) can significantly affect communications and navigation systems. In this study, we present the image measurements of plasma bubble from Christmas Island (2.1°N, 157.4°W, dip latitude 2.8°N) in the central Pacific Ocean. These observations were made during September-October 1995 using a Utah State University (USU) CCD imaging system measured at ~280 km altitude. Well-defined magnetic field-aligned plasma depletions were observed for 18 nights, including strong post-midnight fossilized structures, enabling detailed measurements of their morphology and dynamics. We also estimate zonal velocity of the plasma bubbles from available images. The zonal drift velocity of the EPBs is a very important parameter for the understanding and modeling of the electrodynamics of the equatorial ionosphere and for the predictions of ionospheric irregularities. The eastward zonal drift velocities were around 90-100 m/s prior to local midnight, and decreases during the post-midnight period that persisted until dawn.Journal of Institute of Science and Technology, 2015, 20(1): 20-27

scholarly journals Pre-earthquake ionospheric anomalies registered by continuous GPS TEC measurements

2004 ◽  
Vol 22 (5) ◽  
pp. 1585-1593 ◽  
Author(s):  
J. Y. Liu ◽  
Y. J. Chuo ◽  
S. J. Shan ◽  
Y. B. Tsai ◽  
Y. I. Chen ◽  
...  
Keyword(s):  
Key Words ◽  
Global Positioning System ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
Positioning System ◽  
Total Electron ◽  
Gps Tec ◽  
Global Positioning ◽  
Continuous Gps ◽  
Large Earthquakes

Abstract. In this paper we examine pre-earthquake ionospheric anomalies by the total electron content (TEC) derived from a ground-based receiver of the Global Positioning System (GPS). A 15-day running median of the TEC and the associated inter-quartile range (IQR) are utilized as a reference for identifying abnormal signals during all of the 20M≥6.0 earthquakes in the Taiwan area from September 1999 to December 2002. Results show that the pre-earthquake ionospheric anomalies appear during 18:00–22:00LT (LT=UT+8h) within 5 days prior to 16 of the 20M≥6.0 earthquakes. This success rate of 80% (=16/20%) suggests that the GPS TEC is useful to register pre-earthquake ionospheric anomalies appearing before large earthquakes. Key words. Ionosphere (ionospheric disturbances; ionosphere-atmosphere interactions)

scholarly journals Study of ionospheric disturbances over the China mid- and low-latitude region with GPS observations

2018 ◽  
Vol 36 (1) ◽  
pp. 81-89 ◽  
Author(s):  
Yafei Ning ◽  
Jun Tang
Keyword(s):  
Global Positioning System ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
Differential Rate ◽  
Low Latitude ◽  
Total Electron ◽  
Ionospheric Variability ◽  
Global Positioning ◽  
Latitude Region ◽  
Gps Observations

Abstract. Ionospheric disturbances constitute the main restriction factor for precise positioning techniques based on global positioning system (GPS) measurements. Simultaneously, GPS observations are widely used to determine ionospheric disturbances with total electron content (TEC). In this paper, we present an analysis of ionospheric disturbances over China mid- and low-latitude area before and during the magnetic storm on 17 March 2015. The work analyses the variation of magnetic indices, the amplitude of ionospheric irregularities observed with four arrays of GPS stations and the influence of geomagnetic storm on GPS positioning. The results show that significant ionospheric TEC disturbances occurred between 10:30 and 12:00 UT during the main phase of the large storm, and the static position reliability for this period are little affected by these disturbances. It is observed that the positive and negative disturbances propagate southward along the meridian from mid-latitude to low-latitude regions. The propagation velocity is from about 200 to 700 m s−1 and the amplitude of ionospheric disturbances is from about 0.2 to 0.9 TECU min−1. Moreover, the position dilution of precession (PDOP) with static precise point positioning (PPP) on storm and quiet days is 1.8 and 0.9 cm, respectively. This study is based on the analysis of ionospheric variability with differential rate of vertical TEC (DROVT) and impact of ionospheric storm on positioning with technique of GPS PPP. Keywords. Ionosphere (ionospheric disturbances)

Virtual fencing - past, present and future

2007 ◽  
Vol 29 (1) ◽  
pp. 65 ◽  
Author(s):  
D. M. Anderson
Keyword(s):  
Control Systems ◽  
Global Positioning System ◽  
Geometrical Shape ◽  
Research Needs ◽  
Proof Of Concept ◽  
Sensory Cues ◽  
Gps Satellites ◽  
Rf Signals ◽  
Global Positioning ◽  
First Time

Virtual fencing is a method of controlling animals without ground-based fencing. Control occurs by altering an animal’s behaviour through one or more sensory cues administered to the animal after it has attempted to penetrate an electronically-generated boundary. This boundary can be of any geometrical shape, and though unseen by the eye, is detected by a computer system worn by the animal. The most recent autonomous programmable systems use radio frequency (RF) signals, emanating from global positioning system (GPS) satellites to generate boundaries. Algorithms within a geographic information system (GIS) within the device’s computer use the GPS and other data to determine where on the animal a cue, or cues, should be applied and for how long. The first commercial virtual fencing system was patented in 1973 for controlling domestic dogs. Virtual fencing was used for the first time to control livestock in 1987. Since then proof-of-concept research using commercial, as well as custom designed systems have demonstrated that virtual fencing can successfully hold as well as move livestock over the landscape. Commercial virtual livestock control systems do not yet exist but research continues towards this goal. Pending research needs relating to this method of animal control are discussed in light of currently available technologies.

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