scholarly journals Anomalous variations of <I>Nm</I>F2 over the Argentine Islands: a statistical study

2009 ◽  
Vol 27 (4) ◽  
pp. 1363-1375 ◽  
Author(s):  
A. V. Pavlov ◽  
N. M. Pavlova
Keyword(s):  
Solar Activity ◽  
Electron Density ◽  
Conditional Probability ◽  
Statistical Study ◽  
Expected Value ◽  
Diurnal Variations ◽  
High Solar Activity ◽  
Winter Anomaly ◽  
Anomalous Feature ◽  
The Mean

Abstract. We present a statistical study of variations in the F2-layer peak electron density, NmF2, and altitude, hmF2, over the Argentine Islands ionosonde. The critical frequencies, foF2, and, foE, of the F2 and E-layers, and the propagation factor, M(3000)F2, measured by the ionosonde during the 1957–1959 and 1962–1995 time periods were used in the statistical analysis to determine the values of NmF2 and hmF2. The probabilities to observe maximum and minimum values of NmF2 and hmF2 in a diurnal variation of the electron density are calculated. Our study shows that the main part of the maximum diurnal values of NmF2 is observed in a time sector close to midnight in November, December, January, and February exhibiting the anomalous diurnal variations of NmF2. Another anomalous feature of the diurnal variations of NmF2 exhibited during November, December, and January when the minimum diurnal value of NmF2 is mainly located close to the noon sector. These anomalous diurnal variations of NmF2 are found to be during both geomagnetically quiet and disturbed conditions. Anomalous features are not found in the diurnal variations of hmF2. The statistical study of the NmF2 winter anomaly phenomena over the Argentine Islands ionosonde was carried out. The variations in a maximum daytime value, R, of a ratio of a geomagnetically quiet daytime winter NmF2 to a geomagnetically quiet daytime summer NmF2 taken at a given UT and for approximately the same level of solar activity were studied. The conditional probability of the occurrence of R in an interval of R, the most frequent value of R, the mean expected value of R, and the conditional probability to observe the F2-region winter anomaly during a daytime period were calculated for low, moderate, and high solar activity. The calculations show that the mean expected value of R and the occurrence frequency of the F2-region winter anomaly increase with increasing solar activity.

scholarly journals A Neural Network-Based TEC Model Capable of Reproducing Nighttime Winter Anomaly

2021 ◽  
Vol 13 (22) ◽  
pp. 4559
Author(s):  
Marjolijn Adolfs ◽  
Mohammed Mainul Hoque
Keyword(s):  
Neural Network ◽  
Solar Activity ◽  
Geomagnetic Latitude ◽  
Machine Learning Techniques ◽  
High Solar Activity ◽  
Electron Content ◽  
Solar Cycles ◽  
Total Electron ◽  
The Neural Network ◽  
Winter Anomaly

With the availability of fast computing machines, as well as the advancement of machine learning techniques and Big Data algorithms, the development of a more sophisticated total electron content (TEC) model featuring the Nighttime Winter Anomaly (NWA) and other effects is possible and is presented here. The NWA is visible in the Northern Hemisphere for the American sector and in the Southern Hemisphere for the Asian longitude sector under solar minimum conditions. During the NWA, the mean ionization level is found to be higher in the winter nights compared to the summer nights. The approach proposed here is a fully connected neural network (NN) model trained with Global Ionosphere Maps (GIMs) data from the last two solar cycles. The day of year, universal time, geographic longitude, geomagnetic latitude, solar zenith angle, and solar activity proxy, F10.7, were used as the input parameters for the model. The model was tested with independent TEC datasets from the years 2015 and 2020, representing high solar activity (HSA) and low solar activity (LSA) conditions. Our investigation shows that the root mean squared (RMS) deviations are in the order of 6 and 2.5 TEC units during HSA and LSA period, respectively. Additionally, NN model results were compared with another model, the Neustrelitz TEC Model (NTCM). We found that the neural network model outperformed the NTCM by approximately 1 TEC unit. More importantly, the NN model can reproduce the evolution of the NWA effect during low solar activity, whereas the NTCM model cannot reproduce such effect in the TEC variation.

scholarly journals The Galactic Electron Distribution from a Pulsar Survey

1974 ◽  
Vol 60 ◽  
pp. 87-95 ◽  
Author(s):  
A. G. Lyne
Keyword(s):  
Electron Density ◽  
Electron Distribution ◽  
Statistical Study ◽  
High Sensitivity ◽  
Upper Limit ◽  
The Mean

The recent high-sensitivity pulsar survey at Jodrell Bank has allowed a statistical study of more distant objects. The longitude distribution suggests that many of the pulsars observed have distances greater than 5 kpc, leading to an upper limit of about 0.03 cm-3 for the mean electron density. The electron density averaged over distances of a few hundred parsecs seems to be very constant. The width of the electron distribution in the z-direction appears to be greater than about 600 pc.

scholarly journals Long term ionospheric electron content variations over Delhi

2000 ◽  
Vol 18 (12) ◽  
pp. 1635-1644 ◽  
Author(s):  
J. K. Gupta ◽  
L. Singh
Keyword(s):  
Solar Activity ◽  
Magnetic Activity ◽  
High Solar Activity ◽  
Electron Content ◽  
Solar Cycles ◽  
Positive Correlation ◽  
Radio Science ◽  
Ionospheric Physics ◽  
Winter Anomaly ◽  
Ionospheric Electron Content

Abstract. Ionospheric electron content (IEC) observed at Delhi (geographic co-ordinates: 28.63°N, 77.22°E; geomagnetic co-ordinates: 19.08°N, 148.91°E; dip Latitude 24.8°N), India, for the period 1975–80 and 1986–89 belonging to an ascending phase of solar activity during first halves of solar cycles 21 and 22 respectively have been used to study the diurnal, seasonal, solar and magnetic activity variations. The diurnal variation of seasonal mean of IEC on quiet days shows a secondary peak comparable to the daytime peak in equinox and winter in high solar activity. IECmax (daytime maximum value of IEC, one per day) shows winter anomaly only during high solar activity at Delhi. Further, IECmax shows positive correlation with F10.7 up to about 200 flux units at equinox and 240 units both in winter and summer; for greater F10.7 values, IECmax is substantially constant in all the seasons. IECmax and magnetic activity (Ap) are found to be positively correlated in summer in high solar activity. Winter IECmax shows positive correlation with Ap in low solar activity and negative correlation in high solar activity in both the solar cycles. In equinox IECmax is independent of Ap in both solar cycles in low solar activity. A study of day-to-day variations in IECmax shows single day and alternate day abnormalities, semi-annual and annual variations controlled by the equatorial electrojet strength, and 27-day periodicity attributable to the solar rotation.Key words: Ionosphere (equatorial ionosphere) · Magnetospheric physics (magnetosphere · ionosphere interactions) · Radio science (ionospheric physics)

scholarly journals RESPONSE OF F2- REGION MAXIMUM ELECTRON DENSITY (NmF2/foF2) TO SOLAR ACTIVITY USING PEARSON PRODUCT MOMENT CORRELATION

2018 ◽  
Vol 5 (1) ◽  
Author(s):  
Eugene Onori
Keyword(s):  
Puerto Rico ◽  
Solar Activity ◽  
Correlation Analysis ◽  
Electron Density ◽  
Upper Atmosphere ◽  
High Solar Activity ◽  
The Sun ◽  
Pearson Product Moment Correlation ◽  
Maximum Electron Density ◽  
Temporal And Spatial

Introduction: The ionosphere owes its origin primarily to ultraviolet radiation from the Sun. The ionosphere is an essential part of the Earth’s upper atmosphere. It is ionized by solar radiation and influences transionospheric radio wave propagation. Maximum electron density of the F2- layer (NmF2) is an important parameter for studying the ionosphere. The ionospheric F2-region maximum electron density (NmF2) depends strongly on solar activity, it also suffers temporal and spatial variations. Aim: The aim of this paper is to investigate the response of NmF2 to solar activity during high solar activity (HSA), moderate solar activity (MSA) and low solar activity (LSA) years using correlation analysis. Materials and Methods: The data used in this work are the hourly NmF2 values derived from foF2 data observed at Jicamarca (Lat.11.9 oS, Long.76.8 oW) and Puerto Rico (Lat.18.5 oN, Long.67.2 oW) during high solar activity HSA (2002), moderate solar activity MSA (2011) and low solar activity LSA (2006) years. The NmF2 data were evaluated using the relation in equation 1 NmF2 = 1.24 x 1010 (foF2)2 (1) Where NmF2 is in el/m3 and foF2 is in MHz. Pearson Product Moment Correlation (PPMC) was used to further analyse the NmF2 data. Results: Our results revealed two unequal NmF2 peaks. The NmF2 peaks values at Jicamarca (60 - 240; 63– 204) x 1010 el/m3 are observed to be higher in values than those at Puerto Rico (63 – 187; 57 – 164) x 1010 el/m3. The highest NmF2 peak values of 240 and 187x 1010 el/m3 occurred during March equinox at 09:00 and 14:00 hours at Jicamarca and Puerto Rico respectively during HSA year. Conclusion: Correlation analysis for the three epochs of solar activity revealed that NmF2 showed positive correlation with sunspot number with highest correlation values of 0.904 and 0.976 at Jicamarca and Puerto Rico stations respectively during MSA year.

scholarly journals Equinoctial asymmetry in solar activity variations of <I>Nm</I>F2 and TEC

2012 ◽  
Vol 30 (3) ◽  
pp. 613-622 ◽  
Author(s):  
Y. Chen ◽  
L. Liu ◽  
W. Wan ◽  
Z. Ren
Keyword(s):  
Solar Activity ◽  
Electron Density ◽  
High Solar Activity ◽  
Solar Cycles ◽  
Low Latitude ◽  
Middle Latitudes ◽  
Low Latitudes ◽  
Increase Rate ◽  
Dip Equator ◽  
The Difference

Abstract. The ionosonde NmF2 data (covering several solar cycles) and the JPL TEC maps (from 1998 through 2009) were collected to investigate the equinoctial asymmetries in ionospheric electron density and its variation with solar activity. With solar activity increasing, the equinoctial asymmetry of noontime NmF2 increases at middle latitudes but decreases or changes little at low latitudes, while the equinoctial asymmetry of TEC increases at all latitudes. The latitudinal feature of the equinoctial asymmetry at high solar activity is different from that at low solar activity. The increases of NmF2 and TEC with the solar proxy P = (F10.7+F10.7A)/2 also show equinoctial asymmetries that depend on latitudes. The increase rate of NmF2 with P at March equinox (ME) is higher than that at September equinox (SE) at middle latitudes, but the latter is higher than the former at the EIA crest latitudes, and the difference between them is small at the EIA trough latitudes. The phenomenon of higher increase rate at SE than at ME does not appear in TEC. The increase rate of noontime TEC with P at ME is higher than that at SE at all latitudes, and the difference between them peaks at both sides of dip equator. It is mentionable that the equinoctial asymmetries of NmF2 and TEC increase rates present some longitudinal dependence at low latitude. The influences of equinoctial differences in the thermosphere and ionospheric dynamics processes on the equinoctial asymmetry of the electron density were briefly discussed.

scholarly journals Characterization of GPS total electron content (GPS-TEC) in Antarctica from 2004 to 2011

2013 ◽  
Vol 56 (2) ◽  
Author(s):  
Emília Correia ◽  
Amanda Junqueira Paz ◽  
Mauricio A. Gende
Keyword(s):  
Solar Activity ◽  
Total Electron Content ◽  
Electron Content ◽  
Vertical Total Electron Content ◽  
Total Electron ◽  
Annual Variations ◽  
Solar Radiation Intensity ◽  
Winter Anomaly ◽  
Semiannual Variation ◽  
The Mean

<p>The vertical total electron content (VTEC) obtained from 2004 to 2011 at Comandante Ferraz Brazilian Antarctic Station (62.1°S, 58.4°W) is analyzed to study the mean diurnal, seasonal and annual variations. The maximum daytime VTEC had an annual variation that decreased from 2004 to 2008, and then starting to increase in 2009, which followed the variation of the solar activity. The daily VTEC shows good linear correlation with solar radiation intensity, which is also dependent on the solar zenithal angle. The mean diurnal VTEC shows a semiannual variation, with larger peaks in equinoxes for all years; no winter anomaly was observed, and in summer, there was no clear diurnal variation. The semiannual variation of the VTEC is also modulated by solar activity, with larger VTEC peaks when the solar activity was higher.</p>

Sign in / Sign up

Export Citation Format

Share Document