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

Abstract

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.

New Ways to Modelling and Predicting Ionosphere Variables

“…Eapen et al (2018) [39] reported their results on the search for TEC time series chaoticity using data from the MIT Madrigal database. They selected one location each from the low latitude, (28 • N and 82 • W), midlatitude, (40 • N and 119 • W), and high latitude (60 • N and 150 • W) for the period from 1 January to 30 April of the solar minimum year 2008.…”

“…Correlation dimension of the deterministic chaos found in TEC time series by different authors under different conditions. The asterisk means that the values are the averages of those shown in Tables1 and 2of the paper mentioned(Eapen et al, 2018). " ---" indicate that the geomagnetic activity is not specified.…”

Estimation of Planar Trend Model Parameters for Midlatitude Ionosphere

“…In the literature, there are also studies that use detrended time series of TEC for a single station by using a broad spectrum of analysis tools, such as correlation dimension, Lyapunov exponent, and multifractals for the investigation of nonlinear or chaotic behavior of TEC (Chandrasekhar et al, 2016;Eapen et al, 2018;Kumar & Eapen, 2013). In Unnikrishnan et al (2006aUnnikrishnan et al ( , 2006b, surrogate data testing is applied to midlatitude TEC for disturbed and quiet ionosphere during daytime and nighttime.…”