An empirical model for IEC over Lunping

Jain, Sudhir; Vijay, S. K.; Gwal, A. K.

doi:10.1016/0273-1177(95)00935-3

Cited by 15 publications

(8 citation statements)

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“…Irregular variations, which are mainly due to abnormal solar behavior such as sudden changes in solar radiation, cannot be predicted in advance. Examples of regular variations are diurnal, annual, and solar cycle variations (Jain et al 1996). Possible modulations of the diurnal signal with other frequencies are also identified as regular variations.…”

Section: Introductionmentioning

confidence: 97%

Harmonic analysis of total electron contents time series: methodology and results

Amiri-Simkooei

Asgari

2011

GPS Solut

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In an attempt to model regular variations of the ionosphere, the least-squares harmonic estimation is applied to the time series of the total electron contents (TEC) provided by the JPL analysis center. Multivariate and modulated harmonic estimation spectra are introduced and estimated for the series to detect the regular and modulated dominant frequencies of the periodic patterns. Two significant periodic patterns are the diurnal and annual signals with periods of 24/n hours and 365.25/n days (n = 1, 2, …), which are the Fourier series decomposition of the regular daily and yearly periodic variations of the ionosphere. The spectrum shows a cluster of periods near 27 days, thereby indicating irregularities at this solar cycle period. A series of peaks, with periods close to the diurnal signal and its harmonics, are evident in the spectrum. In fact, the daily signal harmonics of x i = 2pi are modulated with the annual signal harmonics of x j = 2pj/365.25 as x ijM = 2pi(1 ± j/365.25i). Among them, at low and midlatitudes, the largest variations belong to the diurnal signal modulated to the semiannual signal. Some preliminary results on the modulated part are presented. The maximum ranges of the modulated daily signal are ±15 TECU and ±6 TECU at high and low solar periods, respectively. A model consisting of purely harmonic functions plus modulated ones is capable of studying known regular anomalies of the ionosphere, which is currently in progress.

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Section: Introductionmentioning

confidence: 97%

Harmonic analysis of total electron contents time series: methodology and results

Amiri-Simkooei

Asgari

2011

GPS Solut

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“…Such variations include changes due to diurnal, annual, and solar cycle signals, to name a few. The irregular parts, however, are mainly due to abnormal solar behavior, such as Sporadic E, caused by unusual and irregular cloud-like patches of high ionization; sudden ionospheric disturbances, occurring without warning and usually related to solar eruption; and ionospheric storms caused by disturbances in the Earth's magnetic field related to the rotation of the sun and solar eruptions [5,19]. However, modeling of irregular parts of the ionosphere is rather difficult.…”

Section: Introductionmentioning

confidence: 99%

Modeling and Prediction of Regular Ionospheric Variations and Deterministic Anomalies

et al. 2020

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Knowledge on the ionospheric total electron content (TEC) and its prediction are of great practical importance and engineering relevance in many scientific disciplines. We investigate regular ionospheric anomalies and TEC prediction by applying the least squares harmonic estimation (LS-HE) technique to a 15 year time series of the vertical TEC (VTEC) from 1998 to 2014. We first detected a few new regular and modulated signals in the TEC time series. The multivariate analysis of the time series indicates that there are diurnal, annual, 11 year, and 27 day periodic signals, as well as their higher harmonics. We also found periods matching with the global positioning system (GPS) draconitic year in the TEC time series. The results from the modulated harmonic analysis indicate that there exists a set of peaks with periods of 1 ± 0.0027 j ( j = 1 , … , 5 ) and 1 ± 0.00025 j ( j = 1 , 2 , 3 ) days. The same situation holds also true for the harmonics higher than the diurnal signal. A model is then adopted based on the discovered periods. This model, which consists of pure and modulated harmonic functions, is shown to be appropriate for assessing the regular variations and ionospheric anomalies. There is a clear maximum TEC at around 22:00 h, which we called the “evening anomaly”. The evening anomaly occurs in the winter and autumn, and is dependent on the solar activities. Also, the Semiannual, Winter, and Equatorial anomalies were investigated. Finally, to investigate the performance of the derived model, the TEC values have been predicted monthly, and the results show that the modulated signals can significantly contribute to obtaining superior prediction results. Compared with the pure signals, the modulated signals can improve a yearly average root mean squared error (RMSE) value in the lower and higher solar activities by 20% and 15%, respectively.

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“…Many factors ranging from geographical location to solar cycles influence electron density variations in the ionosphere (Schunk & Nagy, ). Regular variations in the ionospheric parameters due to diurnal, seasonal, and solar cycle can be predicted in advance with reasonable accuracy since their occurrence is more or less in cycles (Jain et al, ). However, the irregular variations, caused mostly by abnormal solar effects, are harder to predict due to their random nature.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Variations of TEC at Disturbed and Quiet Time Using Nonlinear Dynamics Tools

Eapen¹,

Asokan²,

Kumar

et al. 2018

JGR Space Physics

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We analyze the underlying dynamics at three different latitudes of ionosphere through total electron content‐series for 4 months. The global dynamics reconstructed from the data is shown to be deterministic with low dimensional chaotic attractors at all the locations, and the dynamics is seen to be less complex at the midlatitude station with smaller dimension of correlation (CD) and maximum Lyapunov exponent (MLE). The influence of geomagnetic storms on the ionospheric dynamics is studied, by analyzing the local dynamics during disturbed and quiet periods, reconstructed from segments of total electron content‐series of shorter duration. With positive MLEs and smaller CDs, the local dynamics is seen to be deterministic and chaotic at the low latitude, midlatitude, and high latitude during both the disturbed and quiet days. However, it is interesting to observe that the dynamics is less chaotic and complex during the disturbed days of the entire period of observation compared to the adjacent quiet days at the three locations. This is further evidenced by sample predictions made using nonlinear tools, yielding better predictions during storms. The smaller CD value during disturbed periods indicates that the geomagnetic activities tend to make a few of the variables dominant enough to control the essential dynamics of the system. Further, the MLEs of the disturbed days are found to increase nearly in a linear fashion from beginning to end of the observation period at all the locations considered. This is an indication of the strong influence of geomagnetic activities on the ionosphere and might have caused the restructuring of the ionospheric dynamics.

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An empirical model for IEC over Lunping

Cited by 15 publications

References 0 publications

Harmonic analysis of total electron contents time series: methodology and results

Harmonic analysis of total electron contents time series: methodology and results

Modeling and Prediction of Regular Ionospheric Variations and Deterministic Anomalies

Comparison of Variations of TEC at Disturbed and Quiet Time Using Nonlinear Dynamics Tools

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