scholarly journals Dependence of the F2-layer critical frequency median at midlatitudes on geomagnetic activity

2017 ◽  
Vol 3 (4) ◽  
pp. 74-81
Author(s):  
Марат Деминов ◽  
Marat Deminov ◽  
Галина Деминова ◽  
Galina Deminova ◽  
Виктор Депуев ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Geomagnetic Activity ◽  
Confidence Level ◽  
Critical Frequency ◽  
Annual Average ◽  
Middle Latitudes ◽  
Ap Index

We put forward a method of separating the geomagnetic activity contribution to the F2-layer critical frequency median, foF2med, at middle latitudes. It is based on the analysis of dfoF2, which is the ratio foF2med/foF2q in percent, where foF2q is the F2-layer critical frequency for quiet conditions. The quantities foF2q and dfoF2 depend on solar and geomagnetic activity respectively. These dependences are taken into account using indices F12 (the average over 12 months flux of solar radiation at 10.7 cm) and Apm (the average over a month value of Ap-index), thus facilitating the use of this method for forecasting foF2med. With this method, from Slough station (51.5° N, 0.6° W) data for midday and midnight for 1954 to 1995 we have found that at midnight the dfoF2 dependence on Apm is significant at the 95 % confidence level for equinoxes and summer. For midday, this dependence is less pronounced and is significant only from April to July. At equinoxes and summer, an Apm increase causes a dfoF2 decrease. For midnight, this feature is more pronounced than for midday. This regularity is valid also for annual average Apm and dfoF2.

scholarly journals Dependence of the F2-layer critical frequency median at midlatitudes on geomagnetic activity

2017 ◽  
Vol 3 (4) ◽  
pp. 67-73 ◽  
Author(s):  
Марат Деминов ◽  
Marat Deminov ◽  
Галина Деминова ◽  
Galina Deminova ◽  
Виктор Депуев ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Geomagnetic Activity ◽  
Confidence Level ◽  
Critical Frequency ◽  
Annual Average ◽  
Middle Latitudes ◽  
Ap Index

We put forward a method of separating the geomagnetic activity contribution to the F2-layer critical frequency median, foF2med, at middle latitudes. It is based on the analysis of dfoF2, which is the ratio foF2med/foF2q in percent, where foF2q is the F2-layer critical frequency for quiet conditions. The quantities foF2q and dfoF2 depend on solar and geomagnetic activity respectively. These dependences are taken into account using indices F12 (the average over 12 months flux of solar radiation at 10.7 cm) and Apm (the average over a month value of Ap-index), thus facilitating the use of this method for forecasting foF2med. With this method, from Slough station (51.5° N, 0.6° W) data for midday and midnight for 1954 to 1995 we have found that at midnight the dfoF2 dependence on Apm is significant at the 95 % confidence level for equinoxes and summer. For midday, this dependence is less pronounced and is significant only from April to July. At equinoxes and summer, an Apm increase causes a dfoF2 decrease. For midnight, this feature is more pronounced than for midday. This regularity is valid also for annual average Apm and dfoF2.

scholarly journals Local impact of solar variation on NO<sub>2</sub> in the lower mesosphere and upper stratosphere from 2007–2011

2013 ◽  
Vol 13 (12) ◽  
pp. 32327-32351
Author(s):  
F. Friederich ◽  
M. Sinnhuber ◽  
B. Funke ◽  
T. von Clarmann ◽  
J. Orphal
Keyword(s):  
Solar Radiation ◽  
Geomagnetic Activity ◽  
Geomagnetic Latitude ◽  
Direct Response ◽  
Superposed Epoch Analysis ◽  
Mixing Ratios ◽  
Local Impact ◽  
Ap Index ◽  
Epoch Analysis ◽  
The Impact

Abstract. MIPAS/ENVISAT data of nighttime NO2 volume mixing ratios (VMR) from 2007 until 2011 between 40 km and 62 km altitude are compared with the geomagnetic Ap index and solar Lyman α radiation. The local impact of variations in geomagnetic activity and solar radiation on the VMR of NO2 in the lower mesosphere and upper stratosphere in the Northern Hemisphere is investigated by means of superposed epoch analysis. Observations show a clear 27 day period of the NO2 VMR. This is positively correlated to the geomagnetic Ap index at 60–70° N geomagnetic latitude but also partially correlated to the solar Lyman α radiation. However, the dependency of NO2 VMR on geomagnetic activity can be distinguished from the impact of solar radiation. This indicates a direct response of NOx (NO + NO2) to geomagnetic activity, probably due to precipitating particles. The response is detected in the range between 46 km and 52 km altitude. The NO2 VMR epoch maxima due to geomagnetic activity is altitude-dependent and can reach up to 0.4 ppb, leading to mean production rates of 0.029 ppb (Ap d)−1. This is the first study showing the local impact of electron precipitation on trace gases at that altitudes in the spring/summer/autumn hemisphere.

scholarly journals Local impact of solar variation on NO<sub>2</sub> in the lower mesosphere and upper stratosphere from 2007 to 2012

2014 ◽  
Vol 14 (8) ◽  
pp. 4055-4064 ◽  
Author(s):  
F. Friederich ◽  
M. Sinnhuber ◽  
B. Funke ◽  
T. von Clarmann ◽  
J. Orphal
Keyword(s):  
Solar Radiation ◽  
Northern Hemisphere ◽  
Geomagnetic Activity ◽  
Geomagnetic Latitude ◽  
Superposed Epoch Analysis ◽  
Mixing Ratios ◽  
Local Impact ◽  
Ap Index ◽  
Epoch Analysis ◽  
The Impact

Abstract. MIPAS/ENVISAT data of nighttime NO2 volume mixing ratios (VMR) from 2007 until 2012 between 40 km and 62 km altitude are compared with the geomagnetic Ap index and solar Lyman-α radiation. The local impact of variations in geomagnetic activity and solar radiation on the VMR of NO2 in the lower mesosphere and upper stratosphere in the Northern Hemisphere is investigated by means of superposed epoch analysis. Observations in the Northern Hemisphere show a clear 27-day period of the NO2 VMR. This is positively correlated with the geomagnetic Ap index at 60–70° N geomagnetic latitude but also partially correlated with the solar Lyman-α radiation. However, the dependency of NO2 VMR on geomagnetic activity can be distinguished from the impact of solar radiation. This indicates a direct response of NOx (NO + NO2) to geomagnetic activity, probably due to precipitating particles. The response is detected in the range between 46 km and 52 km altitude. The NO2 VMR epoch maxima due to geomagnetic activity is altitude-dependent and can reach up to 0.4 ppb, leading to mean production rates of 0.029 ppb (Ap d)−1. Observations in the Southern Hemisphere do not have the same significance due to a worse sampling of geomagnetic storm occurances. Variabilities due to solar variation occur at the same altitudes at 60–70° S geomagnetic latitude but cannot be analyzed as in the Northern Hemisphere. This is the first study showing the direct impact of electron precipitation on NOx at those altitudes in the spring/summer/autumn hemisphere.

scholarly journals Energetic particle induced intra-seasonal variability of ozone inside the Antarctic polar vortex observed in satellite data

2015 ◽  
Vol 15 (6) ◽  
pp. 3327-3338 ◽  
Author(s):  
T. Fytterer ◽  
M. G. Mlynczak ◽  
H. Nieder ◽  
K. Pérot ◽  
M. Sinnhuber ◽  
...  
Keyword(s):  
Geomagnetic Activity ◽  
Seasonal Variability ◽  
Transport Model ◽  
Three Dimensional ◽  
Polar Vortex ◽  
Quiet Time ◽  
Significance Level ◽  
Antarctic Polar Vortex ◽  
Ap Index ◽  
The Antarctic

Abstract. Measurements from 2002 to 2011 by three independent satellite instruments, namely MIPAS, SABER, and SMR on board the ENVISAT, TIMED, and Odin satellites are used to investigate the intra-seasonal variability of stratospheric and mesospheric O3 volume mixing ratio (vmr) inside the Antarctic polar vortex due to solar and geomagnetic activity. In this study, we individually analysed the relative O3 vmr variations between maximum and minimum conditions of a number of solar and geomagnetic indices (F10.7 cm solar radio flux, Ap index, ≥ 2 MeV electron flux). The indices are 26-day averages centred at 1 April, 1 May, and 1 June while O3 is based on 26-day running means from 1 April to 1 November at altitudes from 20 to 70 km. During solar quiet time from 2005 to 2010, the composite of all three instruments reveals an apparent negative O3 signal associated to the geomagnetic activity (Ap index) around 1 April, on average reaching amplitudes between −5 and −10% of the respective O3 background. The O3 response exceeds the significance level of 95% and propagates downwards throughout the polar winter from the stratopause down to ~ 25 km. These observed results are in good qualitative agreement with the O3 vmr pattern simulated with a three-dimensional chemistry-transport model, which includes particle impact ionisation.

Analysis of Experimental Solar Radiation Data for Osogbo, Nigeria

2019 ◽  
Vol 8 (1) ◽  
Author(s):  
Abdulhamid Yusuf ◽  
Hakeem Bolarinwa ◽  
Lukman Animasahun ◽  
Yinusa Babatunde
Keyword(s):  
Solar Radiation ◽  
Global Solar Radiation ◽  
Total Radiation ◽  
Wet Season ◽  
Annual Average ◽  
Percentage Frequency ◽  
Monthly Average ◽  
Radiation Data ◽  
Maximum Value ◽  
Daily Total

An analysis of measured global solar radiation (GR) in Osogbo (7.77oN, 4.57oE, 288m) is presented in the form of hourly average, monthly average and percentage frequency distribution. The experimental data corresponds to a year data of 2017. The results reveal that the monthly average values of daily total radiation exhibit seasonal variation with maximum value in dry season month of March (16.59MJ/m2) and minimum value in wet season month of August (8.98 MJ/m2). The annual average GR value is 14.20 MJ/m2 while the annual cumulative GR is 5122 MJ/m2. The solar radiation climate of Osogbo has also been compared to those reported for a number of locations. The percentage frequency of days possessing irradiation rate greater than 15 MJ/m2 is 14 percent whereas that possessing less than 10 MJ/m2 is 61 percent. We conclude, based upon the above analysis that Osogbo is characterized by relatively low global solar radiation.

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.

scholarly journals Pre-storm <I>Nm</I>F2 enhancements at middle latitudes: delusion or reality?

2009 ◽  
Vol 27 (3) ◽  
pp. 1321-1330 ◽  
Author(s):  
A. V. Mikhailov ◽  
L. Perrone
Keyword(s):  
Magnetic Storm ◽  
Electric Fields ◽  
Geomagnetic Activity ◽  
Critical Analysis ◽  
Geomagnetic Storms ◽  
Activity Level ◽  
Quiet Time ◽  
Auroral Activity ◽  
Middle Latitudes ◽  
Plasma Ring

Abstract. A critical analysis of recent publications devoted to the NmF2 pre-storm enhancements is performed. There are no convincing arguments that the observed cases of NmF2 enhancements at middle and sub-auroral latitudes bear a relation to the following magnetic storms. In all cases considered the NmF2 pre-storm enhancements were due to previous geomagnetic storms, moderate auroral activity or they presented the class of positive quiet time events (Q-disturbances). Therefore, it is possible to conclude that there is no such an effect as the pre-storm NmF2 enhancement as a phenomenon inalienably related to the following magnetic storm. The observed nighttime NmF2 enhancements at sub-auroral latitudes may result from plasma transfer from the plasma ring area by meridional thermospheric wind. Enhanced plasmaspheric fluxes into the nighttime F2-region resulted from westward substorm-associated electric fields is another possible source of nighttime NmF2 enhancements. Daytime positive Q-disturbances occurring under very low geomagnetic activity level may be related to the dayside cusp activity.

scholarly journals A short-term ionospheric forecasting empirical regional model (IFERM) to predict the critical frequency of the F2 layer during moderate, disturbed, and very disturbed geomagnetic conditions over the European area

2012 ◽  
Vol 30 (2) ◽  
pp. 343-355 ◽  
Author(s):  
M. Pietrella
Keyword(s):  
Geomagnetic Activity ◽  
Critical Frequency ◽  
Ionospheric Disturbance ◽  
Geomagnetic Disturbance ◽  
Regional Model ◽  
Quiet Time ◽  
Short Term ◽  
Iri Model ◽  
Disturbance Index ◽  
European Area

Abstract. A short-term ionospheric forecasting empirical regional model (IFERM) has been developed to predict the state of the critical frequency of the F2 layer (foF2) under different geomagnetic conditions. IFERM is based on 13 short term ionospheric forecasting empirical local models (IFELM) developed to predict foF2 at 13 ionospheric observatories scattered around the European area. The forecasting procedures were developed by taking into account, hourly measurements of foF2, hourly quiet-time reference values of foF2 (foF2QT), and the hourly time-weighted accumulation series derived from the geomagnetic planetary index ap, (ap(τ)), for each observatory. Under the assumption that the ionospheric disturbance index ln(foF2/foF2QT) is correlated to the integrated geomagnetic disturbance index ap(τ), a set of statistically significant regression coefficients were established for each observatory, over 12 months, over 24 h, and under 3 different ranges of geomagnetic activity. This data was then used as input to compute short-term ionospheric forecasting of foF2 at the 13 local stations under consideration. The empirical storm-time ionospheric correction model (STORM) was used to predict foF2 in two different ways: scaling both the hourly median prediction provided by IRI (STORM_foF2MED,IRI model), and the foF2QT values (STORM_foF2QT model) from each local station. The comparison between the performance of STORM_foF2MED,IRI, STORM_foF2QT, IFELM, and the foF2QT values, was made on the basis of root mean square deviation (r.m.s.) for a large number of periods characterized by moderate, disturbed, and very disturbed geomagnetic activity. The results showed that the 13 IFELM perform much better than STORM_foF2,sub>MED,IRI and STORM_foF2QT especially in the eastern part of the European area during the summer months (May, June, July, and August) and equinoctial months (March, April, September, and October) under disturbed and very disturbed geomagnetic conditions, respectively. The performance of IFELM is also very good in the western and central part of the Europe during the summer months under disturbed geomagnetic conditions. STORM_foF2MED,IRI performs particularly well in central Europe during the equinoctial months under moderate geomagnetic conditions and during the summer months under very disturbed geomagnetic conditions. The forecasting maps generated by IFERM on the basis of the results provided by the 13 IFELM, show very large areas located at middle-high and high latitudes where the foF2 predictions quite faithfully match the foF2 measurements, and consequently IFERM can be used for generating short-term forecasting maps of foF2 (up to 3 h ahead) over the European area.

scholarly journals Study of Linke Turbidity Factor on Solar Radiation over Jumla

2019 ◽  
Vol 9 ◽  
pp. 141-149
Author(s):  
Prakash M. Shrestha ◽  
Indra B. Karki ◽  
Narayan P. Chapagain ◽  
Khem N. Poudyal
Keyword(s):  
Air Pollution ◽  
Solar Radiation ◽  
Global Solar Radiation ◽  
Spectral Measurements ◽  
Annual Average ◽  
Average Value ◽  
Strong Relation ◽  
Rain Fall ◽  
Linke Turbidity Factor ◽  
Temperature Water

 Population growth, mechanization, and industrialization are the by product of human civilization and its resultant impacts goes to degrade the natural environment by the affecting of air-pollution and also associated with climatic change. Linke turbidity factor (LT) is an important parameter for assessing the air pollution at Jumla (Lat.:29.28o N, Long.: 82.16o E and Alt. 2300 masl). Because of the unavailability of spectral measurements data , a model has been used to estimate the Linke turbidity factor (TL) from broadband measurement of Global Solar radiation in 2012 .The annual average solar insolation, clearness index (KT) and extinction coefficient (K) are 5.11 ±2.34kWh/m2/day ,0.71 ± 0.12 and 0.25 ± 0.13 respectively. Similarly, the annual average value of Linke turbidity factor (LT) and visibility 1.97± 0.47 and 28.09 ± 21.08 km are found. Finally it is found that there is strong relation between Linke turbidity factor and meteorological parameters i.e. relative humidity, temperature, water content, ozone and rain fall.

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