scholarly journals Improved characterization and modeling of equatorial plasma depletions

2018 ◽  
Vol 8 ◽  
pp. A38 ◽  
Author(s):  
Estefania Blanch ◽  
David Altadill ◽  
Jose Miguel Juan ◽  
Adriano Camps ◽  
José Barbosa ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Local Time ◽  
Satellite System ◽  
Global Scale ◽  
Electron Content ◽  
Equatorial Anomaly ◽  
Time Duration ◽  
Total Electron ◽  
Latitude Belt ◽  
Independent Observations

This manuscript presents a method to identify the occurrence of Equatorial Plasma Bubbles (EPBs) with data gathered from receivers of Global Navigation Satellite System (GNSS). This method adapts a previously existing technique to detect Medium Scale Travelling Ionospheric Disturbances (MSTIDs), which focus on the 2nd time derivatives of total electron content estimated from GNSS signals (2DTEC). Results from this tool made possible to develop a comprehensive analysis of the characteristics of EPBs. Analyses of the probability of occurrence, effective time duration, depth of the depletion and total disturbance of the EPBs show their dependence on local time and season of the year at global scale within the latitude belt from 35°N to 35°S for the descending phase of solar cycle 23 and ascending phase of solar cycle 24, 2002–2014. These results made possible to build an EPBs model, bounded with the Solar Flux index, that simulates the probability of the number of EPBs and their characteristics expected for a representative day at given season and local time (LT). The model results provided insight into different important aspects: the maximum occurrence of bubbles take place near the equatorial anomaly crests, asymmetry between hemispheres and preferred longitudes with enhanced EPBs activity. Model output comparisons with independent observations confirmed its soundness.

scholarly journals Characteristics of ionospheric irregularities near the northern equatorial anomaly crest

2019 ◽  
Author(s):  
Jinghua Li ◽  
Guanyi Ma ◽  
Klemens Hocke ◽  
Qingtao Wan ◽  
Jiangtao Fan ◽  
...  
Keyword(s):  
Seasonal Variations ◽  
Ionospheric Irregularities ◽  
Lower Latitude ◽  
Occurrence Rate ◽  
Electron Content ◽  
Plasma Bubble ◽  
Equatorial Anomaly ◽  
Total Electron ◽  
Latitude Belt ◽  
Plasma Bubbles

Abstract. This paper detects the ionospheric irregularities with rate of total electron content (TEC) change index, ROTI from GPS observation at Taoyuan (24.95° N, 121.16° E) for the solar medium and minimum years of 2003 and 2008 in the declining phase of cycle 23, the solar maximum of 2014 in solar cycle 24. Local occurrence rate (LOR) is proposed to clarify the characteristics of the irregularities together with monthly occurrence rate (MOR) and ROTI maximum for 3 latitude belts, 20–23° N, 23–26° N, 26–29° N, around the equatorial anomaly crest. MOR in May/June is larger than those in equinoxes in 2008 and 2003, which is different from that of equatorial plasma bubbles. In 2014 although MOR maximum is observed in equinoxes, the MOR in May and June is much larger than that in September. Moreover, MORs in May to August at higher latitude belt 26–29° N are larger than those in lower latitude belts and smaller in the equinoxes. The latitudinal dependence of the LORs tends to be similar to that of MORs. Seasonal variations of LORs have a similar trend for different solar activities. Maximum LORs are observed in Feb/Mar and Sep/Oct, and moderate around June, which resemble those of plasma bubbles in seasonal variations, except for latitude belt 26–29° N where maximum LORs are seen in May–Jul. The seasonal variation of ROTI maximum conforms to that of the LOR. The results suggest that irregularities near the crest in May to August are mainly originated from nonequatorial process, which is more frequently happened but weaker than plasma bubble in both spatiotemporal scale and strength.

scholarly journals Double-thin-shell approach to deriving total electron content from GNSS signals and implications for ionospheric dynamics near the magnetic equator

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Takashi Maruyama ◽  
Kornyanat Hozumi ◽  
Guanyi Ma ◽  
Pornchai Supnithi ◽  
Napat Tongkasem ◽  
...  
Keyword(s):  
Total Electron Content ◽  
Thin Shell ◽  
Spherical Surface ◽  
Satellite System ◽  
Electron Content ◽  
Equatorial Anomaly ◽  
Total Electron ◽  
Functional Fitting ◽  
A New Technique ◽  
Global Navigation Satellite

AbstractA new technique was developed to estimate the ionospheric total electron content (TEC) from Global Navigation Satellite System (GNSS) satellite signals. The vertically distributed electron density was parameterized by two thin-shell layers (double-shell approach). The spatiotemporal variation of TEC (strictly speaking, partial electron content) associated with each shell was approximated by the functional fitting of spherical surface harmonics. The major improvements over the conventional single-shell approach were as follows: (1) the precise estimation of TEC was achieved; (2) the estimated TEC was less dependent on the choice of shell heights; and (3) the equatorial anomaly was captured more correctly. Furthermore, higher and lower shells exhibited a different pattern of local time vs latitude variation, providing information on the ionosphere–thermosphere dynamics.

scholarly journals Double-thin-shell Approach to Deriving Total Electron Content From GNSS Signals and Implications for Ionospheric Dynamics Near the Magnetic Equator

2020 ◽  
Author(s):  
Takashi Maruyama ◽  
Kornyanat Hozumi ◽  
Guanyi Ma ◽  
Pornchai Supnithi ◽  
Qingtao Wan
Keyword(s):  
Total Electron Content ◽  
Thin Shell ◽  
Spherical Surface ◽  
Shell Height ◽  
Satellite System ◽  
Electron Content ◽  
Equatorial Anomaly ◽  
Total Electron ◽  
Functional Fitting ◽  
Global Navigation Satellite

Abstract A new technique was developed to estimate the ionospheric total electron content (TEC) from Global Navigation Satellite System (GNSS) satellite signals. The vertically distributed electron density was parameterized by two thin-shell layers (double-shell approach). The spatiotemporal variation of TEC (strictly speaking, partial electron content) associated with each shell was approximated by the functional fitting of spherical surface harmonics. The major improvements over the conventional single-shell approach were as follows: (1) the precise estimation of TEC was achieved; (2) the estimated TEC was less dependent on the choice of shell height; and (3) the equatorial anomaly was captured more correctly. Furthermore, higher and lower shells exhibited a different pattern of local time vs latitude variation, providing information on the ionosphere--thermosphere dynamics.

Toward ionospheric tomography in Antarctica: first steps and comparison with dynasonde observations

1996 ◽  
Vol 8 (3) ◽  
pp. 297-302 ◽  
Author(s):  
J.A.T. Heaton ◽  
G.O.L. Jones ◽  
L. Kersley
Keyword(s):  
Electron Density ◽  
Total Electron Content ◽  
Satellite System ◽  
Electron Density Profile ◽  
Electron Content ◽  
Total Electron ◽  
Ionospheric Tomography ◽  
Contour Maps ◽  
Tomographic Method ◽  
Independent Observations

Total electron content (TEC) measurements obtained at two Antarctic stations over nine months beginning early in 1994 have been analysed as a first step to performing ionospheric tomography. Two receiving systems were deployed at the Faraday and Halley research stations operated by the British Antarctic Survey to monitor signals from a random selection of passes of satellites in the Navy Navigational Satellite System. The resultant measurements of total electron content have been inverted and combined with ionosonde measurements of true height and foF2 to yield two-dimensional contour maps of ionospheric electron density. In spite of the poor geometry of the observations, some 130 satellite passes were found to be suitable for reconstruction using the techniques developed for ionospheric tomography. The contour maps of plasma density have been compared with independent observations of the vertical electron density profile measured by the dynasonde ionospheric sounder located at Halley. An example is presented of a deep trough investigated by the technique, illustrating the potential of the tomographic method for study of an extended spatial region of the ionosphere over inhospitable terrain.

scholarly journals Features of annual and semiannual variations derived from the global ionospheric maps of total electron content

2007 ◽  
Vol 25 (12) ◽  
pp. 2513-2527 ◽  
Author(s):  
B. Zhao ◽  
W. Wan ◽  
L. Liu ◽  
T. Mao ◽  
Z. Ren ◽  
...  
Keyword(s):  
Total Electron Content ◽  
Local Time ◽  
Electric Fields ◽  
Amplitude Ratio ◽  
Mean Amplitude ◽  
Global Scale ◽  
Electron Content ◽  
Total Electron ◽  
Winter Anomaly ◽  
Global Ionospheric Maps

Abstract. In the present work we use the NASA-JPL global ionospheric maps of total electron content (TEC), firstly to construct TEC maps (TEC vs. magnetic local time MLT, and magnetic latitude MLAT) in the interval from 1999 to 2005. These TEC maps were, in turn, used to estimate the annual-to-mean amplitude ratio, A1, and the semiannual-to-mean amplitude ratio, A2, as well as the latitudinal symmetrical and asymmetrical parts, A' and A" of A1. Thus, we investigated in detail the TEC climatology from maps of these indices, with an emphasis on the quantitative presentation for local time and latitudinal changes in the seasonal, annual and semiannual anomalies of the ionospheric TEC. Then we took the TEC value at 14:00 LT to examine various anomalies at a global scale following the same procedure. Results reveal similar features appearing in NmF2, such as that the seasonal anomaly is more significant in the near-pole regions than in the far-pole regions and the reverse is true for the semiannual anomaly; the winter anomaly has least a chance to be observed at the South America and South Pacific areas. The most impressive feature is that the equinoctial asymmetry is most prominent at the East Asian and South Australian areas. Through the analysis of the TIMED GUVI columnar [O/N2] data, we have investigated to what extent the seasonal, annual and semiannual variations can be explained by their counterparts in [O/N2]. Results revealed that the [O/N2] variation is a major contributor to the daytime winter anomaly of TEC, and it also contributes to some of the semiannual and annual anomalies. The contribution to the anomalies unexplained by the [O/N2] data could possibly be due to the dynamics associated with thermospheric winds and electric fields.

scholarly journals Variation in total electron content with sunspot number during the ascending and maximum phases of solar cycle 24 at Birnin Kebbi

2018 ◽  
Author(s):  
Aghogho Ogwala ◽  
Emmanuel Olufemi Somoye ◽  
Olugbenga Ogunmodimu ◽  
Rasaq Adewemimo Adeniji-Adele ◽  
Eugene Oghenakpobo Onori ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Total Electron Content ◽  
Local Time ◽  
Satellite Navigation ◽  
Electron Content ◽  
Total Electron ◽  
June Solstice ◽  
December Solstice ◽  
Radio Signals ◽  
The Impact

Abstract. Satellite radio signals are affected by the presence of electrons in the earth’s upper atmosphere (ionosphere). The more electrons in the path of the satellite radio signals, the more the impact on the accuracy of satellite navigation systems such as the Global Positioning System (GPS)/ Global Navigation Satellite System (GNSS) and GLONASS. These electrons introduce several meters of error in position calculation. Total Electron Content (TEC) is used to monitor possible space weather impacts on satellite to ground communication and satellite navigation. TEC is modified in the ionosphere by changing solar Extreme Ultra-Violet (EUV) radiation, geomagnetic storms, and the atmospheric waves that propagate up from the lower atmosphere. Therefore, TEC depends on local time, latitude, longitude, season, geomagnetic conditions, solar cycle activity, and condition of the troposphere. A dual frequency GPS receiver located at an equatorial station, Birnin-Kebbi in Northern Nigeria (geographic location: 12.64° N; 4.22° E), has been used to investigate variation of TEC during the period of 2011 to 2014. We investigate the diurnal, seasonal and solar cycle dependence of GPS-TEC. The result shows that TEC increases from a minimum at 0400 local time (LT) to maximum daytime peak between 1300–1600 LT and then decreases to a minimum value after sunset for all the years. Slight post-noon peaks in the daytime maximum and post-sunset decrease and enhancement is observed in some months. We observed that TEC were higher in the equinoxes than the solstices only in 2012. Where as in 2011, September equinox and December solstice recorded higher magnitude followed by March equinox and lowest in June solstice. In 2013, December solstice magnitude was highest, followed by the equinoxes and lowest in June solstice. In 2014, March equinox and December solstice magnitude were higher than September equinox and June solstice magnitude. June solstice consistently recorded the lowest values for all the years.

scholarly journals Adjusting CCIR Maps to Improve Local Behaviour of Ionospheric Models

Atmosphere ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 691
Author(s):  
Haris Haralambous ◽  
Theodoros Leontiou ◽  
Vasilis Petrou ◽  
Arun Kumar Singh ◽  
Marios Charalambides ◽  
...  
Keyword(s):  
Satellite System ◽  
Global Scale ◽  
Electron Density Profile ◽  
Radiowave Propagation ◽  
Single Frequency ◽  
Electron Content ◽  
Dual Frequency ◽  
Total Electron ◽  
Positioning Errors ◽  
Ionospheric Models

The objective of this article is to present a concept for single-frequency Global Navigation Satellite System (GNSS) positioning local ionospheric mitigation over a certain area. This concept is based on input parameters driving the NeQuick-G algorithm (the ionospheric single-frequency GNSS correction algorithm adopted by Galileo GNSS system), estimated on a local as opposed to a global scale, from ionospheric characteristics measured by a digital ionosonde and a collocated dual-frequency Total Electron Content (TEC) monitor. This approach facilitates the local adjustment of Committee Consultative for Ionospheric Radiowave propagation (CCIR) files and the Az ionization level, which control the ionospheric electron density profile in NeQuick-G, therefore enabling better estimation of positioning errors under quiet geomagnetic conditions. This novel concept for local ionospheric positioning error mitigation may be adopted at any location where ionospheric characteristics foF2 and M(3000)F2 can be measured, as a means to enhance the accuracy of single-frequency positioning applications based on the NeQuick-G algorithm.

scholarly journals Variability of ionospheric scintillation near the equatorial anomaly crest of the Indian zone

2013 ◽  
Vol 31 (4) ◽  
pp. 697-711 ◽  
Author(s):  
S. Chatterjee ◽  
S. K. Chakraborty
Keyword(s):  
Dominant Role ◽  
Onset Time ◽  
Magnetic Equator ◽  
High Solar Activity ◽  
Ionospheric Scintillation ◽  
Spatial And Temporal Variability ◽  
Electron Content ◽  
Equatorial Anomaly ◽  
Time Duration ◽  
Total Electron

Abstract. Multistation observations of ionosphere scintillation at VHF (250 MHz) and GNSS L1 frequency from three locations – (i) Bokkhali (BOK) (geographic 21.6° N, 88.2° E, dip 31.48°, (ii) Raja Peary Mohan College Centre (RPMC) (geographic 22.66° N, 88.4° E, dip 33.5°) and (iii) Krishnath College Centre (KNC), Berhampore (geographic 24.1° N, 88.3° E, dip 35.9°) – at ~ 1° latitudinal separations near the northern crest of the equatorial ionization anomaly (EIA) of the Indian longitude sector are investigated in conjunction with total electron content (TEC) data and available ionosonde data near the magnetic equator to study fine structure in spatial and temporal variability patterns of scintillation occurrences. The observations are carried out in the autumnal equinoctial months of a high solar activity year (2011). In spite of smaller latitudinal/spatial separation among the observing stations, conspicuous differences are reflected in the onset time, duration, fade rate and fade depth of VHF scintillations as well as in spectral features. Scintillations are mostly associated with depletion in TEC around the anomaly crest and occurrence of ESF near the magnetic equator at an earlier time. Not only the strength of EIA, but also the locations of observing stations with respect to the post-sunset resurgence peak of EIA seem to play dominant role in dictating the severity of scintillation activity. A secondary enhancement in diurnal TEC in the post-sunset period seems to accentuate the irregularity activities near the anomaly crest, and a threshold value of the same may fruitfully be utilized for the prediction of scintillation around the locations. An idea regarding latitudinal extent of scintillation is developed by considering observations at L1 frequency from the GPS and GLONASS constellation of satellites. A critical value of h'F near the magnetic equator for the occurrence of simultaneous scintillation at the three centres is suggested. The observations are discussed considering electrodynamical aspect of equatorial irregularities.

scholarly journals Investigation of Pre-Earthquake Ionospheric and Atmospheric Disturbances for Three Large Earthquakes in Mexico

Geosciences ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 16
Author(s):  
Christina Oikonomou ◽  
Haris Haralambous ◽  
Sergey Pulinets ◽  
Aakriti Khadka ◽  
Shukra R. Paudel ◽  
...  
Keyword(s):  
Chemical Potential ◽  
Atmospheric Model ◽  
Satellite System ◽  
Seismic Events ◽  
Electron Content ◽  
Total Electron ◽  
Atmospheric Disturbances ◽  
Global Ionospheric Maps ◽  
Global Navigation Satellite ◽  
Large Earthquakes

The purpose of the present study is to investigate simultaneously pre-earthquake ionospheric and atmospheric disturbances by the application of different methodologies, with the ultimate aim to detect their possible link with the impending seismic event. Three large earthquakes in Mexico are selected (8.2 Mw, 7.1 Mw and 6.6 Mw during 8 and 19 September 2017 and 21 January 2016 respectively), while ionospheric variations during the entire year 2017 prior to 37 earthquakes are also examined. In particular, Total Electron Content (TEC) retrieved from Global Navigation Satellite System (GNSS) networks and Atmospheric Chemical Potential (ACP) variations extracted from an atmospheric model are analyzed by performing statistical and spectral analysis on TEC measurements with the aid of Global Ionospheric Maps (GIMs), Ionospheric Precursor Mask (IPM) methodology and time series and regional maps of ACP. It is found that both large and short scale ionospheric anomalies occurring from few hours to a few days prior to the seismic events may be linked to the forthcoming events and most of them are nearly concurrent with atmospheric anomalies happening during the same day. This analysis also highlights that even in low-latitude areas it is possible to discern pre-earthquake ionospheric disturbances possibly linked with the imminent seismic events.

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