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Ionospheric anomalies related to the Mw 6.5 Samar, Philippines earthquake

Eroglu Emre

Acta Geophysica

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2023

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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.

2

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

Sharma Gopal, Singh Mutum Somorjit, Aggarwal Shiv Prasad, Romero-Andrade Rosendo

Acta Geophysica

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2023

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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.

3

Investigation of Ionospheric Response to Geomagnetic Storms over a Low Latitude Station, Ile-Ife, Nigeria

Jimoh O. E., Yesufu T. K., Ariyibi E. A.

Acta Geophysica

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2016

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Vol. 64, no. 3

772--795

EN

Due to several complexities associated with the equatorial ionosphere, and the significant role which the total electron content (TEC) variability plays in GPS signal transmission, there is the need to monitor irregularities in TEC during storm events. The GPS SCINDA receiver data at Ile-Ife, Nigeria, was analysed with a view to characterizing the ionospheric response to geomagnetic storms on 9 March and 1 October 2012. Presently, positive storm effects, peaks in TEC which were associated with prompt penetration of electric fields and changes in neutral gas composition were observed for the storms. The maximum percentage deviation in TEC of about 120 and 45% were observed for 9 March and 1 October 2012, respectively. An obvious negative percentage TEC deviation subsequent to sudden storm commencement (SSC) was observed and besides a geomagnetic storm does not necessarily suggest a high scintillation intensity (S4) index. The present results show that magnetic storm events at low latitude regions may have an adverse effect on navigation and communication systems.

4

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

Cherniak I., Lysenko V.

Acta Geophysica

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2013

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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.

5

On ionospheric phenomena during pre-storm and main phase of a very intense geomagnetic storm

Chukwuma V.U.

Acta Geophysica

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2010

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Vol. 58, no. 6

1164-1192

EN

An investigation to elucidate the mechanisms responsible for the pre-storm and main phase ionospheric phenomena during November 20- 21, 2003, is presented using heliophysical, interplanetary, geomagnetic, and global ionospheric data. The results show that the ionospheric responses in the main phase do not indicate prompt penetration electric fields as the main ionospheric driver. The results also show that the prestorm phenomena do not originate from a local time effect. The simultaneous occurrence of foF2 enhancements at two widely separated longitudinal zones appeared to suggest a role played by the magnetospheric electric field. However, the analysis of hmF2 at the stations could not confirm the notion that these fields are the main drivers of pre-storm phenomena. An investigation of flare effects on the pre-storm phenomena also revealed that solar flares are not the main drivers. The present results appear to suggest that the pre-storm ionospheric phenomena could be a result of some underlying mechanisms that are working together with varying degree of importance.

6

On heliophysical and geophysical phenomena during October-November 2003

Chukwuma V.U.

Acta Geophysica

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2009

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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.

7

GPS observations at quasi-conjugate points under disturbed conditions

Momani M.A., Mohd Ali M.A., Yatim B., Abdullah M., Misran N.

Acta Geophysica

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2008

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Vol. 56, no. 4

1179-1201

EN

The conjugacy effects of the GPS scintillation activities during the geomagnetic storms of October 2003, November 2003 and July 2004 have been investigated at the approximately geomagnetically conjugate stations: Scott Base, Antarctica (SBA) and Resolute Cornwallis Island (RESO) in the high Arctic region. The measurements aim at investigation of the similarities and differences of the scintillation activities occurring at the conjugate points in the polar regions under storm conditions and examine the relationship between the Storm Enhanced Density (SED) and scintillation activity. The measurements of the scintillation activities obtained from total scintillation index during these storm periods at both hemispheres showed asymmetry in the ionospheric scintillation occurrence at the conjugate points. Pronounced scintillation activity was observed at the nightside hemisphere with the total scintillation index higher than at the dayside hemisphere. The results also show that the durations of severe scintillation activity were longer at the nightside hemisphere. The measurements showed that the intense scintillation periods were corresponding to the presence of the SED events where more pronounced SED events were observed over the nightside hemisphere.

8

The structure of the mid- and high-latitude ionosphere during the November 2004 storm event obtained from GPS observations

Krankowski A., Shagimuratov I.I., Baran L.W., Yakimova G.

Acta Geophysica

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2007

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Vol. 55, no. 4

490-508

EN

GPS data from the International GNSS Service (IGS) network were used to study the development of the severe geomagnetic storm of November 7-12, 2004, in the total electron content (TEC) on a global scale. The TEC maps were produced for analyzing the storm. For producing the maps over European and North American sectors, GPS measurements from more than 100 stations were used. The dense network of GPS stations provided TEC measurements with a high temporal and spatial resolution. To present the temporal and spatial variation of TEC during the storm, differential TEC maps relative to a quiet day (November 6, 2004) were created. The features of geomagnetic storm attributed to the complex development of ionospheric storm depend on latitude, longitude and local time. The positive, as well as negative effects were detected in TEC variations as a consequence of the evolution of the geomagnetic storm. The maximal effect was registered in the subauroral/auroral ionosphere during substorm activity in the evening and night period. The latitudinal profiles obtained from TEC maps for Europe gave rise to the storm-time dynamic of the ionospheric trough, which was detected on November 7 and 9 at latitudes below 50N. In the report, features of the response of TEC to the storm for European and North American sectors are analyzed.

9

On the geomagnetic and ionospheric responses to an intense storm associated with weak IMF Bz and high solar wind dynamic pressure

Chukwuma V.U.

Acta Geophysica

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2007

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Vol. 55, no. 4

469-489

EN

A study of the geomagnetic storm of July 13-14, 1982, and its ionospheric response is presented using the low-latitude magnetic index, Dst, and interpreted using solar wind interplanetary data: proton number density, solar wind flow speed, interplanetary magnetic field southward component BZ, and solar wind dynamic pressure. The F2 region structure response to the geomagnetic storm was studied using foF2 data obtained during the storm from a network of various ionosonde stations. Our results appear to show simultaneous abrupt depletion of foF2 that occurred at all latitudes in both the East Asian and African/European longitudinal zone during the period: 18:00–19:00 UT on July 13 and is as result of an abrupt in-crease in the dynamic pressure between 16:00 and 17:00 UT. The dynamic pressure increased from 3.21 to 28.07 nPa within an hour. The aforementioned abrupt depletion of foF2 simultaneously resulted in an intense negative storm with peak depletion of foF2 at about 19:00 at all the stations in the East Asian longitudinal zone. In the African/European longitudinal zone, this simultaneous abrupt depletion of foF2 resulted in intense negative storm that occurred simultaneously at the low latitude stations with peak depletion at about 20:00 UT on July 13, while the resulting negative storm at the mid latitude stations recorded peak depletion of foF2 simultaneously at about 2:00 UT on July 14. The present results indicate that most of the stations in the three longitudinal zones showed some level of simultaneity in the depletion of foF2 between 18:00 UT on July 13 and 2:00 UT on July 14. The depletion of foF2 during the main phase of the storm was especially strongly dependent on the solar wind dynamic pressure.

10

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

Chukwuma V.

Acta Geophysica Polonica

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2003

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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.