Geomagnetic Storm Main Phase Effect on the Equatorial Ionosphere over Ile-Ife as measured using GPS Observations (1910.11305v1)

Abstract: The effect of the main phase of two intense geomagnetic storm events which occurred on August 5 - 6 and September 26 - 27, 2011 on the equatorial ionosphere have been investigated using Global Positioning System (GPS) data obtained from an Ile-Ife station (geomagnetic lat. \ang{9.84}N, long. 77.25 degree E, Dip \ang{7.25}N). Total Electron Content (TEC) profiles during the main phase of the two geomagnetically disturbed days were compared with quiet time average profiles to examine the response of the equatorial ionosphere. The results showed that the intensity of both storm events during the main phase which occurred at night-time correlated well with a strong southward direction of the z-component of the Interplanetary Magnetic Field (IMF-Bz) and Solar Wind Speed (Vsw), with the Disturbance storm time (Dst) profile showing multiple step development. TEC depletion was observed during the main phase of the August 5 - 6, 2011 storm event with TEC recording a maximum value of 9.31 TECU. A maximum TEC value of 55.8 TECU was recorded during the main phase of the September 26 - 27, 2011 storm event depicting TEC enhancement. Significant scintillation index value of 0.57 was observed when the main phase started on August 5 - 6, 2011 followed by a prolonged suppression while there was less significant scintillation impact on September 26 - 27, 2011 with a maximum value of 0.33. The present study show that rapid energy input from solar wind during geomagnetic storm events effect large variations in TEC and significant scintillation phenomenon in the equatorial ionosphere over Ile-Ife, Nigeria.

• The paper quantifies ionospheric responses by comparing TEC measurements during storm main phases with quiet-time baselines.
• It reports that an overnight storm led to a TEC depletion of 9.31 TECU, while another storm enhanced TEC up to 55.8 TECU.
• The study links TEC variations and scintillation events with negative IMF-Bz and high solar wind speeds, highlighting potential impacts on GPS accuracy.

Geomagnetic Storm Main Phase Effect on the Equatorial Ionosphere over Ile-Ife as measured using GPS Observations

The paper "Geomagnetic Storm Main Phase Effect on the Equatorial Ionosphere over Ile-Ife as measured using GPS Observations" by Ayomide O. Olabode and Emmanuel A. Ariyibi explores the dynamic response of the equatorial ionosphere to geomagnetic storm events, focusing specifically on the region over Ile-Ife, Nigeria. The paper utilizes GPS-derived Total Electron Content (TEC) measurements to investigate ionospheric perturbations during the main phase of two notable geomagnetic storms on August 5-6 and September 26-27, 2011.

Summary of Findings

The research addresses how intense geomagnetic storms, characterized by significant energy transfer from the solar wind to Earth's magnetosphere, impact the equatorial ionosphere. By examining TEC profiles during geomagnetically disturbed periods against quiet-time averages, the paper reveals substantial variations in the ionosphere resulting from these storm events. Notably, the August 5-6 storm, which occurred overnight, correlated with a TEC depletion reaching a minimum of 9.31 TECU. In contrast, the September 26-27 storm exhibited a TEC enhancement, achieving a peak of 55.8 TECU.

A prominent achievement of the paper is the precise correlation between the intensification of the ring current, as evidenced by a negative Interplanetary Magnetic Field (IMF-Bz) and elevated solar wind speeds (Vsw), and observed TEC variations. The Disturbance Storm Time (Dst) index further corroborated this correlation by showcasing multiple depressions, indicative of the geomagnetic storm's main phase developments.

Ionospheric Scintillation and Variability

The paper also explored ionospheric scintillation, stemming from rapid amplitude and phase fluctuations in transionospheric radio signals due to refractive index variations. This phenomenon was more pronounced during the August storm, with scintillation indices peaking at 0.57 and experiencing a notable suppression thereafter. Alternatively, the September storm's scintillation impact was less significant, attaining a maximum index of 0.33.

Implications and Future Directions

The findings underscore the pronounced sensitivity of the equatorial ionosphere to geomagnetic disturbances, particularly during the main phase of storms. The research has significant implications for GPS-based systems, as TEC variations and scintillation could adversely affect positioning accuracy and signal integrity. Understanding these impacts is crucial for developing mitigation strategies for communication technologies and navigation systems reliant on satellite signals.

Theoretically, the paper enriches the understanding of ionospheric dynamics by linking TEC variability and scintillation with interplanetary magnetic perturbations, specifically during significant geomagnetic events. Future research could extend these findings by exploring longitudinal and altitude-dependent variations in ionospheric response across different equatorial regions, potentially involving multi-GNSS observations to enhance spatial and temporal resolution.

Overall, the paper provides a thorough analysis of geomagnetic storm effects on ionospheric parameters at low latitudes, offering valuable insights for both the scientific community and stakeholders in satellite-based technologies. As space weather events continue to pose challenges to global technological infrastructures, such studies will play an instrumental role in predicting and responding to ionospheric perturbations associated with geomagnetic storms.