Wyniki wyszukiwania - Biblioteka Nauki

1

On heliophysical and geophysical phenomena during October-November 2003

100%

Chukwuma V. U.

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tom Vol. 57, no. 3

778-800

EN

A study of the geomagnetic storm of November 20-21, 2003, is presented using Solar X-rays data, solar wind parameters and magnetic index, Dst. The results suggest that very large X class flares may not cause very intense geomagnetic storms, as flares of M importance would do. Furthermore, the results suggest that the solar wind structure that was responsible for this storm is of the shock-driver gas configuration in which the sheath is the most geoeffective element. Presently it is shown that an intense storm can be driven by two successive southward Bz structures without a resultant "double dip" at the boundary of these structures within the corresponding interval of the main phase. Furthermore, this study confirms earlier results that show that pressure enhancement does not cause the direct injection of new particles into the ring current region; rather it causes a local adiabatic energization of the particles already within the ring current region.

2

Measurements of the ionosphere plasma electron density variation by the Kharkov incoherent scatter radar

88%

Cherniak I. , Lysenko V.

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tom Vol. 61, no. 5

1289--1303

EN

The present paper is devoted to the description of an improved method for determination of the ionospheric electron density values by Kharkov Incoherent Scatter Radar. This method allows to improve the resolution of the incoherent signals parameters up to ∼20 km in the range of 100–400 km and ∼100 km in the range of 200–1100 km. This approach was used to investigate variability of the ionospheric electron density over East European region in the heights interval of 100–1000 km during the period from 2003 to 2008, including case-studies of solar eclipses and ionospheric storms.

3

Interplanetary phenomenon, geomagnetic and ionospheric response associated with the storm of October 20-21, 1989

88%

Chukwuma V.

Acta Geophysica Polonica

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2003

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tom Vol. 51, nr 4

549-472

EN

Recent results of the study of March 13-14, 1989, geomagnetic (Dst=-600nT) show that the depletion of foF2 was simultaneously worldwide and extended to very low latitudes. These results appear to indicate that during intense storms there are no distinct local time variations of ionospheric storm effects. Presently, the F2 region global structure response to another intense storm was studies as to confirm the earlier results. The investigation used measured parameters of solar wind plasma and imbedded IMF, and foF2 data obtained from a global network ionosondes. The results obtained from the analysis of the measured parameters of solar wind plasma, Dst and Ap data show that arrival of the shock in the interplanetary medium is indicated by increases in plasma density and velocity , and a large southward turning of Bz. In addition, Ap peak accompanies the beginning of a high-speed stream. The event of October 20-21, 1989, is a triple step storm. The analysis of the foF2 data shows that during the October 20-21 storm the depletion of foF2 was restricted to the high and middle latitudes. Although the depletion diminished in amplitude towards the lower latitude, the F2 region global structure response lacked simultaneity unlike the storm of March 13-14 in which the depletion of foF2 was extended to a latitude as low as 12.4N, and at the same time globally. The present results appear to confirm the suggestion of Chukwuma (2003) that the F2 region global structure response during the storm of March 13-14 may be due to the very intensive nature of that particular storm.

4

Integrated observations on crustal strain‑ionosphere total electron content anomalies before the earthquake

63%

Sharma G. , Singh M. S. , Aggarwal S. P. , Romero-Andrade R.

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tom Vol. 71, no. 3

1173--1185

EN

Changes in strain (Linear and triangular) rate and Ionosphere Total Electron Content (TEC) before Mw 7.9 2018 Alaska Earthquake are investigated. Ten years of global positioning system (GPS) time series solutions were used for strain estimation in the region before the occurrence of the earthquake using the Haversine formula and triangulation method. Linear strain values suggest an anomaly in strain variation trend near the epicenter. Additionally, daily TEC variations for 30 days before the earthquake occurred were monitored and analysed. Analysis suggests TEC depletion on December 26 2017, and January 16 2018, respectively. TEC values from 60 GPS stations data were interpolated to study the spatial variations of TEC anomaly. Hourly TEC data derived from GPS stations on December 26 2017, and January 16 2018, suggest low TEC zone concentration near to the earthquake epicenter during 1 to 4 UTC. Spatial distribution of TEC values in 2-Dimension corresponding to anomaly time at 60 GPS stations in the vicinity of study area suggests lowest TEC values at stations that lie closer to the epicenter. The study suggests Lithosphere-Ionosphere coupling before Mw 7.9 2018 Alaska Earthquake and recommends developing a TEC-Strain Monitoring System for further validation of the work and for the better study of earthquake precursors based on TEC-Strain anomalies.

5

Ionospheric anomalies related to the Mw 6.5 Samar, Philippines earthquake

51%

Eroglu E.

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tom Vol. 71, no. 2

601--611

EN

Models belonging to the ionosphere that is directly affected by factors such as solar activity, geomagnetic storm, earthquake, seasonal changes, and geographical location need to be considered altogether. In this sense, the cause of the ionospheric anomalies should be meticulously distinguished from each other. Ionospheric anomalies that occur before or (and) after an earthquake have a serious place in earthquake prediction studies. Total electron content (TEC) is one of the significant parameters to be able to discuss the anomalies of the ionosphere. This essay investigates ionospheric anomalies before and after the Mw 6.5 Samar, Philippines (12.025° N, 125.416° E and November 18, 2003, at 17:14 UT) earthquake. The paper analyzes anomalies with the aid of the TEC (TECU) map. In the paper, the time-domain TEC variables are transferred to the frequency-domain for observing some clues-peaks by short-term Fourier transformation spectral analysis. The discussion handles the effect of the solar activity with the F10.7 (sfu) index and the effect of geomagnetic storms with Bz (nT), v (km/s), P (nPa), E (mV/m), Kp (nT), and Dst (nT) parameters (index). The lower and upper boundaries of the TEC map obtained from the International Reference Ionosphere (IRI-2016) are calculated with the help of median and standard deviation. The boundary-setting process is named statistical analysis. TEC data exceeding the boundaries are marked as anomaly data. According to the paper, 11-day anomalies (9-day of which belong to pre-earthquake) are detected. Probably, the anomalies observed on November 6, 7, and 12 belong to the Samar earthquake.