scholarly journals Introduction of new data into the South African Ionospheric Map to improve the estimation of F2 layer parameters

2015 ◽  
Vol 58 (2) ◽  
Author(s):  
Nicholas Ssessanga ◽  
Lee-Anne McKinnell ◽  
John Bosco Habarulema
Keyword(s):  
South African ◽  
Solar Minimum ◽  
Critical Frequency ◽  
Solar Maximum ◽  
International Reference Ionosphere ◽  
The South ◽  
International Reference ◽  
Critical Frequency Fof2 ◽  
Better Than

<p>In this paper the South African Ionospheric Map (SAIM) is upgraded with the usage of recent International Reference Ionosphere (IRI)-2012 model and South African Bottomside Model (SABIM) version 5 and validated for the critical frequency (foF2) of the F2 layer by comparing the model’s output with the measured ionosonde data. The SABIM model is also validated before use in the SAIM. The ionosonde stations used in the analysis include; Grahamstown (33.2°S, 26.3°E), Hermanus (34.4°S, 19.2°E), Louisvale (28.5°S, 21.2°E) and Madimbo (22.4°S, 30.9°E). The analysis of the results showed that the updates improved the performance of SAIM by 75% over the first version. The foF2 estimates from the SABIM version 5 model also gave a better estimate to the ionosonde measurements compared to the IRI-2012 model. The SABIM model performed 27% better than the IRI-2012 model during solar maximum and 14.7% better during solar minimum.</p>

scholarly journals Quiet-condition variations in the scale height at F2-layer peak at Jicamarca during solar minimum and maximum

2007 ◽  
Vol 25 (12) ◽  
pp. 2541-2550 ◽  
Author(s):  
C.-C. Lee ◽  
B. W. Reinisch
Keyword(s):  
Solar Minimum ◽  
Critical Frequency ◽  
Solar Maximum ◽  
Peak Height ◽  
Scale Height ◽  
Quiet Condition ◽  
Critical Frequency Fof2 ◽  
Two Parameters ◽  
Thickness Parameter ◽  
Layer Peak

Abstract. This study is the first attempt to examine the quiet-condition variations in scale height (Hm) near the F2-layer peak in the equatorial ionosphere. The data periods of Hm derived from the Jicamarca ionograms are January-December 1996 and April 1999–March 2000. The results show that the greatest and smallest Hm values are generally at 11:00–12:00 LT and 04:00–05:00 LT, respectively. Additionally, the sunrise peak occurs at 06:00 LT only during solar minimum. The post-sunset peaks in the equinoctial and summer months are more obvious during solar maximum. The Hm difference between solar minimum and maximum are significant from afternoon to midnight. On the other hand, the Hm values during 07:00–10:00 LT for solar minimum are close to those for solar maximum. Furthermore, the correlation of Hm with the critical frequency (foF2) of F2-layer is generally low. In contrast, the correlation between Hm and the peak height (hmF2) of F2-layer is high. For Hm and the thickness parameter (B0) of F2-layer, the correlation between these two parameters is almost perfect.

scholarly journals Critical Frequency foF2 Variations at Korhogo Station from 1992 to 2001 Prediction with IRI-2012

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Karim Guibula ◽  
Jean Louis Zerbo ◽  
M’Bi Kaboré ◽  
Frédéric Ouattara
Keyword(s):  
Solar Cycle ◽  
Geomagnetic Activity ◽  
Solar Minimum ◽  
Critical Frequency ◽  
Solar Maximum ◽  
Measured Data ◽  
Night Time ◽  
Maximum Phase ◽  
Critical Frequency Fof2

In this paper we report the foF2 data measured at Korhogo station (Lat. 9.3° N; Long. 354.6° E; dip. 0.6° S) compared to predictions with IRI-2012 subroutine URSI and CCIR for different solar cycle phases (minimum, ascending, maximum, descending) and different geomagnetic activity classes (quiet, fluctuating, recurrent, shock). According to our investigations, predictions with IRI are in agreement with the measured data during daytime and show significant differences between them at night-time and especially before sunrise. Except at solar minimum, the gap between predictions and measured data are more appreciable during recurrent and shock conditions compared to quiet and fluctuating conditions. Our results also show that only URSI model expresses the signature of EXB drift phenomenon at solar maximum phase during the recurrent days and at ascending phase for fluctuating activity.

scholarly journals Comparative Preliminary Ionospheric Forecasting In Romania With Data From The European Ionosonde Service Versus Data Extracted From The International Reference Ionosphere Model

2015 ◽  
Vol 21 (3) ◽  
pp. 706-711
Author(s):  
Simona Miclaus ◽  
Paul Bechet ◽  
Mircea Stanic ◽  
Cora Iftode
Keyword(s):  
Time Of Day ◽  
International Reference Ionosphere ◽  
Quality Data ◽  
Radio Link ◽  
Ionospheric Layer ◽  
International Reference ◽  
Ionosphere Model ◽  
Data Links ◽  
Critical Frequency Fof2 ◽  
Model Versus

Abstract Radiocommunications in the HF band depend on the ionospheric parameters of radiowaves reflexion, though the quality of a radio link depends on: the time of day; season; solar cycle; geographical position. Taking into account the ionosphere characteristics over Romania, a forecasting is made over four cities in our country in order to provide the values of the critical frequency foF2 of the F2 ionospheric layer over a 24 hours cycle. A comparative analysis of this parameter is applied by using the International Reference Ionosphere model and interpolated experimental data collected from the European Ionosonde Service. Results show that the f0F2 values are slightly underestimated in all four locations in the model versus measurements, sustaining the necessity of own measurements in order to prepare quality data links in Romania if HF band is to be used for emergency data communications.

scholarly journals Performance of the IRI-2016 at the Brazilian low-latitude ionosphere over the South America Magnetic Anomaly during solar minimum

2019 ◽  
Author(s):  
Juliano Moro ◽  
Jiyao Xu ◽  
Clezio Marcos De Nardin ◽  
Laysa Cristina Araújo Resende ◽  
Régia Pereira Silva ◽  
...  
Keyword(s):  
South America ◽  
Magnetic Anomaly ◽  
Critical Frequency ◽  
Peak Height ◽  
The South ◽  
Iri Model ◽  
Radio Science ◽  
Critical Frequency Fof2 ◽  
Dip Angle ◽  
Navigation Signals

Abstract. In this work we analyse the ionograms obtained by the recent Digisonde installed in Santa Maria (29.7º S, 53.7º W, dip angle = − 37º), Brazil, to calculate the monthly averages of the F2 layer critical frequency (foF2), its peak height (hmF2), and the E-region critical frequency (foE) acquired during geomagnetically quiet days from September 2017 to August 2018. The monthly averages are compared to the 2016 version of the International Reference Ionosphere (IRI) model predictions in order to study its performance close to the center of the South America Magnetic Anomaly (SAMA), which is a region particularly important for High Frequency (HF) ground-to-satellite navigation signals. The foF2 estimated with the Consultative Committee International Radio (CCIR) and International Union of Radio Science (URSI) options predicts well throughout the year. Whereas, for hmF2, it is recommended to use the SHU-2015 option instead of the other available options (AMTB2013 and BSE-1979). The IRI-2016 model outputs for foE and the observations presented very good agreements.

scholarly journals Investigating the foF2 variations at the Ionospheric Observatory of Rome during different solar cycles minimums and levels of geomagnetic activity

2020 ◽  
Vol 10 ◽  
pp. 52
Author(s):  
Alessandro Ippolito ◽  
Loredana Perrone ◽  
Christina Plainaki ◽  
Claudio Cesaroni
Keyword(s):  
Geomagnetic Activity ◽  
Solar Minimum ◽  
Critical Frequency ◽  
Background Level ◽  
Solar Cycles ◽  
Physical Processes ◽  
Minimum Duration ◽  
Critical Frequency Fof2 ◽  
Definition Of ◽  
Low Activity

The variations of the hourly observations of the critical frequency foF2, recorded at the Ionospheric Observatory of Rome by the AIS-INGV ionosonde (geographic coordinates 41.82° N, 12.51° E; geomagnetic coordinates 41.69° N, 93.97° E) during the low activity periods at the turn of solar cycles 21–22, 22–23 and 23–24, are investigated. Deviations of foF2 greater than ± 15% with respect to a background level, and with a minimum duration of 3 h, are here considered anomalous. The dependence of these foF2 anomalies on geomagnetic activity has been accurately investigated. Particular attention has been paid to the last deep solar minimum 2007–2009, in comparison with the previous solar cycle minima. The lack of day-time anomalous negative variations in the critical frequency of the F2 layer, is one of the main findings of this work. Moreover, the analysis of the observed foF2 anomalies confirms the existence of two types of positive F2 layer disturbances, characterised by different morphologies and, different underlying physical processes. A detailed analysis of four specific cases allows the definition of possible scenarios for the explanation of the mechanisms behind the generation of the foF2 anomalies.

Fifth-Year Performance of Progenies of Selected South African Slash and Loblolly Pine Clones

1981 ◽  
Vol 5 (2) ◽  
pp. 62-65
Author(s):  
John F. Kraus ◽  
Earl R. Sluder
Keyword(s):  
South African ◽  
Pinus Taeda ◽  
Loblolly Pine ◽  
Tree Improvement ◽  
Slash Pine ◽  
The South ◽  
Improvement Program ◽  
Seed Orchards ◽  
Pinus Taeda L ◽  
Better Than

Abstract Control-pollinated polymix progenies of 9 slash pine (P. elliottii Engelm.) and 10 loblolly (Pinus taeda L.) pine from some of the best clones in a South African tree improvement program were tested in Georgia. Overall, the progenies of the South African selections in both species have done well after five years in the field. One of the slash pine and three of the loblolly pine families were better than open-pollinated progeny from established seed orchards.

scholarly journals PREVENTION IS BETTER THAN CURE: Addressing violent crime in South Africa

2006 ◽  
Author(s):  
Sibusiso Masuku
Keyword(s):  
Risk Factors ◽  
South Africa ◽  
South African ◽  
Violent Crime ◽  
The South ◽  
Police Service ◽  
Factors Associated ◽  
South African Police Service ◽  
South African Police ◽  
Better Than

South Africa’s high levels of violent crime have a significant effect on people’s lives. A review of the trends and risk factors associated with violent crime begs the question about who should be leading the effort to prevent violence? The South African Police Service currently has this responsibility – but is this appropriate? And which other departments should be playing a greater role?

scholarly journals Effectiveness of the cricket transformation process in increasing representation and performance of black cricketers at provincial level in South Africa

2009 ◽  
Vol 21 (4) ◽  
Author(s):  
MS Taliep
Keyword(s):  
South Africa ◽  
South African ◽  
Transformation Process ◽  
The South ◽  
Black Africans ◽  
Black African ◽  
Provincial Level ◽  
Batting Performance ◽  
And Performance ◽  
Better Than

Objectives. This study investigates the effectiveness of the crickettransformation process in firstly increasing representation of black players and secondly improving performance of black players in the South African 4-day provincial competition between the 1996/1997 and 2007/2008 cricket seasons.Methods. Cricketers were categorised as white, black African or coloured/Indian. Whenever the category ‘black’ is mentioned alone, it refers to black African and coloured/Indian. All data were obtained from www.cricinfo.com.Results. The number of white players decreased and the numberof black African and coloured/Indian players increased between the 1996/1997 and 2007/2008 seasons. White batsmen had significantlyhigher batting averages than black Africans, but were only better than coloureds/Indians in the 2001/2002 season. Coloureds/Indians had better batting averages than black Africans in all seasons except 2001/2002 and 2004/2005. There was a significant improvement in the batting averages of coloureds/Indians but not of whites and black Africans over the 12 seasons. White bowlers had significantly better bowling averages thancoloured/Indian bowlers for seasons 2002/2003, 2004/2005 and 2006/2007. There were no significant differences in the bowlingaverages between white and black African players and between coloured/Indian and black African players over the 12 seasons.There was a tendency towards a decreased bowling performancefor coloureds/Indians, whereas there was no significant decrementin the bowling performance for whites and black Africans over the 12 seasons.Conclusion. The increase in the number of black cricketers performingaccording to standard suggests a reasonable successful transformation process. However, representation and batting performance of black African batsmen remain a concern.

scholarly journals Performance of the IRI-2016 over Santa Maria, a Brazilian low-latitude station located in the central region of the South American Magnetic Anomaly (SAMA)

2020 ◽  
Vol 38 (2) ◽  
pp. 457-466
Author(s):  
Juliano Moro ◽  
Jiyao Xu ◽  
Clezio Marcos Denardini ◽  
Laysa Cristina Araújo Resende ◽  
Régia Pereira Silva ◽  
...  
Keyword(s):  
Magnetic Anomaly ◽  
Critical Frequency ◽  
Peak Height ◽  
The South ◽  
Iri Model ◽  
Radio Science ◽  
Critical Frequency Fof2 ◽  
Dip Angle ◽  
Navigation Signals ◽  
Santa Maria

Abstract. In this work we analyze the ionograms obtained by the recent digisonde installed in Santa Maria (29.7∘ S, 53.7∘ W, dip angle = −37∘), Brazil, to calculate the monthly averages of the F2 layer critical frequency (foF2), its peak height (hmF2), and the E-region critical frequency (foE) acquired during geomagnetically quiet days from September 2017 to August 2018. The monthly averages are compared to the 2016 version of the International Reference Ionosphere (IRI) model predictions in order to study its performance close to the center of the South America Magnetic Anomaly (SAMA), which is a region particularly important for high-frequency (HF) ground-to-satellite navigation signals. The foF2 estimated with the Consultative Committee International Radio (CCIR) and International Union of Radio Science (URSI) options makes good predictions throughout the year, whereas, for hmF2, it is recommended to use the SHU-2015 option instead of the other available options (AMTB2013 and BSE-1979). The IRI-2016 model outputs for foE and the observations presented very good agreement.

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