Effects of Sunspot Cycles on Diurnal and Seasonal Trend of foF2

Journal of Basic & Applied Sciences, 2017

In this research article, the authors have implemented the Exploratory Data Analysis (EDA) techniques to examine the deviation of the monthly median noon and midnight values of the critical frequency of F2 layer ionosphere (i.e. f0F2) at the Wakkanai station (45.39°N, 141.68°E), Japan, during sunspot cycle 21 st (1976-1986) and 23 rd (1996-2008). Primarily, univariate analysis has been done, which shows the variations in f0F2 at different local times, seasons and in the range of sunspot numbers (SSN), in which winter and semi-annual anomalies are detected in the months of December and March respectively. Secondly, the regression analysis is being used as a bivariate data analysis. The results proved a significantly nonlinear relationship exists between f0F2 and SSN. In both solar cycles, saturation effects are seen in the month of March during the noontime period and immensely in June during the midnight time. The behavior of the ionosphere has been studied for different latitudes, seasonal effects and sunspot dynamic conditions, in which this paper plays an essential role in it.

Indian Journal of Radio …, 2011

This paper presents diurnal, seasonal and solar activity effects on the variability of ionospheric foF2 in the equatorial and low latitude regions. Three ionosonde stations, viz. Huancayo (12.0°S, 75.3°W, dip 1.8°N), Ouagadougou (12.4°N, 1.5°W, dip 2.8°N) and Vanimo (2.7°S, 141.3°E, dip 22.5°S) were considered for the investigation. Generally, the diurnal analysis revealed that the critical frequency of the F2 layer (foF2) is more susceptible to variability during the nighttime than the daytime, with two characteristic peaks, pre-sunset peak (12-50%) and post-midnight peak (22-70%). Seasonally, the June Solstice maximum was observed at Vanimo, while the peaks for other seasons were observed at Huancayo with the overall non-typical pattern of seasonal characterization for foF2 variability. At all stations, foF2 variability was noticed to be highest for the low solar activity year. Overall, equatorial foF2 variability increases with decreasing solar activity.

international journal for research in applied science and engineering technology ijraset, 2020

This paper present the analysis of the F region variability of the ionosphere during the Low solar activity period year 2009 for three stations of low, mid and high latitude Chongqing (29.43ᵒN,106.92ᵒE), Beijing (39.91ᵒN,116.41ᵒE) and Sodankyla (67.40ᵒN,26.59ᵒE) respectively. In the study we discussed the diurnal, seasonal, and monthly variability of foF2 at all the above mentioned stations. We observed that the peak values of foF2 are comparatively much higher at high latitude (25%) than at mid latitude (7%) and low latitude (9%). It is also observed that during the month of November, high and mid latitude shows the maximum variation of foF2 while low latitude location Chongqing shows it maximum in the month of March. Which clearly indicates that the presence of winter anomaly at high and mid latitude whereas low latitude maximum in summer month .

Kirkuk University Journal-Scientific Studies, 2021

The study of the F 2 -layer properties and the critical frequency( f o F 2 ) is necessary to understand the dynamic features and thus more accurately predict the behavior of the F layer,and this research aims to find the relationship (correlation) and interdependence between the critical frequency ( f o F 2 ) of Ionospheric layer F 2 and Sunspot number. In this study the characteristics and behavior of oF 2 layer during Solar cycle 24 were studied, the effect of Sunspots number (Ri) on the critical frequency ( f o F 2 ),were investigated for the years (2012, 2013, 2014) which represents the ascending phase and 2014 represent the peak phase of the solar cycle 24 over Kirkuk city (35°N, 44°E) by finding the critical frequency ( f o F 2 ) values, the layer's impression times are determined for the days of solstice as well as equinox,where the solar activity was examined for the days of the winter and summer solstice and the days of the spring and autumn equinoxes for a period of 24 hours by applied the International Reference Ionosphere model IRI (2016). The output data for f o F 2 were verified by using the IRI-Ne-Quick option by specifying the time, date and Sunspot number parameters. Statistical analysis was carried out through the application of the Minitab (version 2018) in order to find the correlation between the critical frequency ( f o F 2 ) of Ionospheric layer F 2 and Sunspot number. It was concluded that the correlation is strong and positive, this indicate that critical frequency ( f o F 2 ) increase with increasing Sunspots number (Ri) for solar cycle 24.

Journal of Atmospheric and Solar-Terrestrial Physics, 2009

In this paper we examined the variations of the foF2 with solar activity for different local time and different seasons. Beside this we evaluated International Reference Ionosphere (IRI) models at different phases of solar cycle 23, different latitudes and different local time. We studied F2 layer critical frequency (foF2) of the ionosphere by using the flare index calculated by the Kandilli Observatory. For this purpose, we identified the months similar with high flare activity during the solar cycle 23. We chose 6 months which represented the different phases (ascending branch, maximum and descending branch) of the solar cycle. We also took into account the fact that these months were in different seasons. The hourly monthly means of observed foF2 data from four ionosonde stations for 6 months were calculated. On the other hand, the identical foF2 values of the same months were calculated for the year 1996, which is the minimum year of the previous solar activity cycle. We subtracted the foF2 values of 1996 from the values of the selected months of the last solar cycle to obtain the residuals, D(foF2).

Journal of National Science of Foundation in Srilanka, 2018

For many decades ionospheric researchers investigated the variations in the ionosphere due to solar activity. The suggested relevant models are based on single-station data, considering regional and global geographic conditions. The present study investigated the impact of the solar cycles 21st (1976 to 1986) and 23rd (1996 to 2008) on the ionospheric F2 layer’s critical frequency (f0F2) at mid-latitude over the Wakkanai region (45.39o N, 141.68o E), Japan. The statistical analyses showed that monthly median f0F2 has a significant non-linear association with high sunspot numbers (SSN) over Wakkanai, which represents a saturation effect depending on the time of the day in different months and on the magnitude of the solar cycle. Polynomial empirical models of f0F2 based on parameters such as SSN and geomagnetic index Ap were examined. Considering the rate of change in solar activity factor much improved the accuracy of our empirical model and also reduces the hysteresis effect. The most appropriate empirical model for single-station diurnal models of f0F2 was developed using Fourier series. Diurnal models incorporate Japanese standard time, months and sunspot numbers. The computed f0F2 models were compared with the IRI-2012 model’s predicted f0F2 values, which demonstrated the better accuracy of the Fourier model compared to the global IRI model. The models obtained in this study are useful for researchers and organizations working in the field of sunspot performance relating to the dynamics of the ionosphere.

The present work places emphasis on foF2, the critical frequency of the F2 layer variations during peak Dst ≤ -100 nT class of geomagnetic disturbances at the rise of solar cycle 23. Geomagnetic, interplanetary and solar wind parameters were employed, as well as foF2 data from some ionosonde stations in the Asian sector. The results obtained revealed that (i) foF2 variations for stations with altitude height (h)≤ 80m, recorded a percentage depletion > 75% as recorded at Petropavlovsk and Salekhard, whereas for h ≥ 80m, the enhancement/depletion variability level is ≈50%. It may therefore be inferred that foF2 cannot be much localized, (ii) the observed enhancement immediately after sunset at Petropavlovsk compared with foF2 upwelling after sunrise at Magadan after the storm of February 12, 2000 revealed that there is no simultaneity in foF2 during the activity (iii)the variation of foF2 along a line of fixed latitude, as it occurs at four stations during the August 12, 2000 storm...

2017

Correspondence Eugene O. Onori, Department of Physics, Faculty of Science, Lagos State University, Nigeria. Email:[email protected] Abstract: Introduction: The ionosphere displays a wide range of variations ranging from diurnal, seasonal, annual and solar cycle variation. In this paper we present a study of the comparison of diurnal, seasonal and semiannual variation of the variability (VR) of the critical frequency of the F2 layer (foF2) over Ilorin (Lat. 8.47oN, 4.6oE, dip 4.1oS) in the African sector,Jicamarca (Lat. 11.9oS, Long.76.8oW, dip 1oN) in the American sector and Okinawa (26.3oN, 127.8oE, dip 36.8oN) in the Asian sector during solar minimum period. These stations lie within the equatorial anomaly region of the ionosphere. Aims: To compare the diurnal, seasonal and semi-annual variation of the variability (VR) of the critical frequency of the F2 layer (foF2) over Ilorin in the African sector, Jicamarca in the American sector and Okinawa in the Asian sector during sola...

1998

The critical frequencies were obtained for every half-hour interval. The data obtained during this campaign, on the descending branch of solar cycle 22, and the data measured earlier in Istanbul for cycle 20 were analysed and the characteristic behaviour of the F2 region ionosphere over Istanbul has been determined. This is a unique data set for this area. Several markers of the solar cycle activities in terms of the daily relative sunspot numbers, F10.7 cm solar radio flux and solar flare index, and the magnetic daily index of Ap were then used to seek the possible influence of the solar and ionospheric activities on the critical frequencies observed in Istanbul. It was found that the solar flare index, as a solar activity index, was more reliable in determining quiet ionospheric days. It is shown that the minimum and maximum time values of the solar activity are more convenient for ionospheric prediction and modelling.

Journal of Earth System Science

Diurnal, seasonal and annual foF2 variability and the response of the F2-layer height over Jicamarca (11.9◦S, 76.8◦W, 1◦N dip) during periods of low (LSA), moderate (MSA) and high (HSA) solar activities was investigated. The relative standard deviation (VR) was used for the analysis. The F2-layer critical frequency pre-noon peak increases by a factor of 2 more than the post-noon peak as the solar activity increases. The variability coefficient (VR) is lowest during the day (7–16%) for the three solar epochs; increases during nighttime (20–26%, 14–26%, and 10–20%, respectively for the LSA, MSA and HSA years); and attained highest magnitude during sunrise (21–27%, 24–27%, and 19–30%, respectively in similar order). Two major peaks were observed in VR – the pre-sunrise peak, which is higher, and the post-sunset peak. Generally, the variability increases as the solar activity decreases. Annually, VR peaks within 23–24%, 19–24% and 15–24% for the LSA, MSA, and HSA periods, respectively. ...