[1] In this paper the method of natural orthogonal components (NOC) is utilized to decompose the daily magnetic variation, expressing the variation as a summation of the eigenmodes. The results show that the first and second NOC eigenmodes represent the solar quiet daily variation, Sq, and the disturbance-daily variation, SD, respectively. The third and fourth eigenmodes may be related to specific currents in the magnetosphere. Remarkable day-to-day (DTD) variations exist in the amplitudes of the eigenmodes. The combination of the eigenmodes reproduces the complicated characteristics in the DTD variation of the daily magnetic variation. The decomposition of the daily magnetic variation presented in this paper is helpful for understanding the mechanism of the daily variation and its DTD variation. In addition, this decomposition method provides a ground-based monitoring of the current systems in several important regions of the near-Earth space.

Decomposition of Daily Geomagnetic Variations by Using Method of Natural Orthogonal Component

The Space Environment Prediction Center (SEPC) has classified geomagnetic activity into four levels: quiet to unsettled (Kp 6). The 3-hourly Kp index prediction product provided by the SEPC is updated half hourly. In this study, the statistical conditional forecast models for the 3-hourly geomagnetic activity level were developed based on 10 years of data and applied to more than 3 years of data, using the previous Kp index, interplanetary magnetic field, and solar wind parameters measured by the Advanced Composition Explorer as conditional parameters. The quality of the forecast models was measured and compared against verifications of accuracy, reliability, discrimination capability, and skill of predicting all geomagnetic activity levels, especially the probability of reaching the storm level given a previous "calm" (nonstorm level) or "storm" (storm level) condition. It was found that the conditional models that used the previous Kp index, the peak value of BtV (the product of the total interplanetarymagnetic field and speed), the average value of Bz (the southerly component of the interplanetary magnetic field), and BzV (the product of the southerly component of the interplanetary magnetic field and speed) over the last 6 h as conditional parameters provide a relative operating characteristic area of 0.64 and can be an appropriate predictor for the probability forecast of geomagnetic activity level.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2015SW001251

Statistical analysis and verification of 3-hourly geomagnetic activity probability predictions

Various factors can increase ionosphere activity, such as the geomagnetic latitude, altitude, and geomagnetic storms. These storms can result in a significant disruption of the Earth’s atmosphere due to the interchange of solar wind energy into the milieu encompassing the Earth. The principal reason for this research is investigating the geomagnetic activity effect on ionospheric delays over Egypt using GPS (Global Positioning System) multi-frequency (L2 and L1) measurements. In this contribution, a GPS network spread over Egypt was utilized to figure ionosphere errors over Egypt, utilizing two models that rely upon GPS observable linear combination and smoothed phase observables. An algorithm was coded in MATLAB® environment and was called the Ionosphere Error Estimation (IEE) program. GPS phase observables were considered in this investigation to avoid blunders from pseudo-range measurements. Data from six ground-based multi-frequency GPS receivers located over Egypt have been chosen to study the impact of geomagnetic storms on ionospheric blunders. This paper presents the consequences of ionospheric blunders during disturbed and quiet days throughout the years of 2013 and 2014. Results clarify that the applied models using unsmoothed and smoothed phase observables show a good agreement in estimating ionospheric blunders, especially in quiet days. Ionospheric blunder standard deviation of mean (SDM) results from using smoothed phase observables that ranges from 16 to 3 cm in quiet conditions and ranges from 21 to 8 cm in stormy conditions. While ionospheric blunder SDM ranges from 17 to 5 cm in quiet days and from 23 to 8 cm in stormy days using unsmoothed phase observables. In The maximum ionosphere delay estimated over stormy days using the unsmoothed phase observables, its magnitude was 13.19 m at ASWN while the highest ionosphere error at ASWN station in quiet days was 6.83 m. In the maximum ionosphere delay estimated over stormy days using the smoothed phase observables, its magnitude was 13.34 m at ALAM while the highest ionosphere error at ALAM station in quiet days was 4.94 m. Finally, geomagnetic storms represent a real problem in equatorial and high-latitude zones, which causes a significant influence on the ionosphere blunder, and they have the capability of upsetting the results.

Ionosphere delay remote sensing during geomagnetic storms over Egypt using GPS phase observations

Wavelet Analysis of Forbush Decreases at High-Latitude Stations During Geomagnetic Disturbances

Analysis of Local Geomagnetic Index Under the Influence of Equatorial Electrojet (EEJ) at the Equatorial Phuket Geomagnetic Station in Thailand

[1] There is an ongoing demand for real-time geomagnetic indices in space services. The traditional 3 h K index and K-derived planetary indices cannot issue alters promptly during large storms, and the 3 h interval is much larger than the time scales of ionospheric responses. To overcome these difficulties, we define a new consecutive and linear geomagnetic activity index, the range of hourly H component index (rH) with 1 min resolution, and develop a local rH index nowcast system for space weather operation, which can issue geomagnetic storm alerts quickly. We also derive Kp/Ap indices conveniently from a single station data to describe the global geomagnetic activity. Then we make a statistic comparison between rH and other definite index values during storm and find that rH is sensitive to the geomagnetic disturbance and can reflect the geomagnetic activity more delicately.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2010SW000609

A sensitive geomagnetic activity index for space weather operation

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A sensitive geomagnetic activity index for space weather operation