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Magnetically Quiet‐Time Traveling Ionospheric Disturbances Over Mid‐Latitude Eastern Europe Observed by the Kharkiv Incoherent Scatter Radar During the 24th Solar Cycle.

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Title: Magnetically Quiet‐Time Traveling Ionospheric Disturbances Over Mid‐Latitude Eastern Europe Observed by the Kharkiv Incoherent Scatter Radar During the 24th Solar Cycle.
Authors: Aksonova, Kateryna D.1,2 (AUTHOR) aksonova@ufa.cas.cz, Panasenko, Sergii V.1,2 (AUTHOR), Buresova, Dalia1 (AUTHOR), Goncharenko, Larisa P.3 (AUTHOR), Zhang, Shun‐Rong3 (AUTHOR), Domnin, Igor F.2 (AUTHOR)
Source: Journal of Geophysical Research. Space Physics. Apr2025, Vol. 130 Issue 4, p1-15. 15p.
Subject Terms: *Solar activity, Ionospheric disturbances, Incoherent scattering, Auroras, Gravity waves, Solar cycle
Abstract: We have detected and characterize traveling ionospheric disturbances (TIDs) in the mid‐latitude ionosphere over Europe using data from the Kharkiv incoherent scatter (IS) radar. The study focused on observations near solstices and equinoxes during solar cycle 24 under magnetically quiet conditions. We examined the diurnal, seasonal, and solar activity dependencies of both large‐scale (LS) and medium‐scale (MS) TIDs, evaluating 140 TID events. Key estimated characteristics included energetic (relative amplitudes), temporal (dominant periods, frequency of occurrence), and spatial (heights of maximum relative amplitudes, vertical and horizontal phase velocities, and wavelengths) parameters. Our findings suggest that moving solar terminators are the primary generation mechanism for magnetically quiet‐time LS TIDs, though a contribution from auroral activity cannot be excluded. In contrast, MS TIDs under magnetically quiet conditions are likely initiated from a broader range of sources, including gravity wave dissipation, severe tropospheric convection, coupling processes between the Es‐layer and F‐region, polarization electric fields, and Perkins instability. We found a positive correlation between the heights of the maximum relative TID amplitudes and the solar activity for LSTIDs. The TID characteristics obtained during extremely quiet conditions provide a useful context for analyzing the possible TID response to localized energy releases including those of anthropogenic origin. Additionally, they enable improvements in global and regional ionospheric models by clarifying the contribution of wave processes to the overall energy budget of the atmosphere and ionosphere. Plain Language Summary: This study provides the propagation properties and characteristics of traveling ionospheric disturbances (TIDs) near equinoxes and solstices during magnetically quiet conditions. We use data from the Kharkiv incoherent scatter radar to analyze the relationship of TIDs with time of day, season and solar activity level. We detected both large‐scale (LS) and medium‐scale (MS) TIDs and found the same probability of their occurrence in all seasons, except summer. Overall, we detect twice as many LS as MS structures. For LS TIDs, the number of daytime and nighttime events is almost equal, while daytime MS TIDs are usually more frequent (more than twice as frequent) than nighttime ones. We calculate vertical and estimate horizontal parameters of TIDs and found a positive correlation with solar indices for LS disturbances. We also discuss potential sources of TIDs, including moving solar terminator, atmospheric gravity waves, sporadic E‐layer, Perkins instability. These results extend our knowledge about the spatial and temporal distribution of TIDs, as well as the dynamics of the atmosphere and ionosphere in general. Key Points: Both large‐ and medium‐scale traveling ionospheric disturbances (TIDs) are detected and characterized during magnetically quiet conditionsThe solar terminator is proposed as the primary source of large‐scale TIDsA statistically significant correlation between the altitude of maximum large‐scale TID relative amplitude and solar indices is found [ABSTRACT FROM AUTHOR]
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Abstract:We have detected and characterize traveling ionospheric disturbances (TIDs) in the mid‐latitude ionosphere over Europe using data from the Kharkiv incoherent scatter (IS) radar. The study focused on observations near solstices and equinoxes during solar cycle 24 under magnetically quiet conditions. We examined the diurnal, seasonal, and solar activity dependencies of both large‐scale (LS) and medium‐scale (MS) TIDs, evaluating 140 TID events. Key estimated characteristics included energetic (relative amplitudes), temporal (dominant periods, frequency of occurrence), and spatial (heights of maximum relative amplitudes, vertical and horizontal phase velocities, and wavelengths) parameters. Our findings suggest that moving solar terminators are the primary generation mechanism for magnetically quiet‐time LS TIDs, though a contribution from auroral activity cannot be excluded. In contrast, MS TIDs under magnetically quiet conditions are likely initiated from a broader range of sources, including gravity wave dissipation, severe tropospheric convection, coupling processes between the Es‐layer and F‐region, polarization electric fields, and Perkins instability. We found a positive correlation between the heights of the maximum relative TID amplitudes and the solar activity for LSTIDs. The TID characteristics obtained during extremely quiet conditions provide a useful context for analyzing the possible TID response to localized energy releases including those of anthropogenic origin. Additionally, they enable improvements in global and regional ionospheric models by clarifying the contribution of wave processes to the overall energy budget of the atmosphere and ionosphere. Plain Language Summary: This study provides the propagation properties and characteristics of traveling ionospheric disturbances (TIDs) near equinoxes and solstices during magnetically quiet conditions. We use data from the Kharkiv incoherent scatter radar to analyze the relationship of TIDs with time of day, season and solar activity level. We detected both large‐scale (LS) and medium‐scale (MS) TIDs and found the same probability of their occurrence in all seasons, except summer. Overall, we detect twice as many LS as MS structures. For LS TIDs, the number of daytime and nighttime events is almost equal, while daytime MS TIDs are usually more frequent (more than twice as frequent) than nighttime ones. We calculate vertical and estimate horizontal parameters of TIDs and found a positive correlation with solar indices for LS disturbances. We also discuss potential sources of TIDs, including moving solar terminator, atmospheric gravity waves, sporadic E‐layer, Perkins instability. These results extend our knowledge about the spatial and temporal distribution of TIDs, as well as the dynamics of the atmosphere and ionosphere in general. Key Points: Both large‐ and medium‐scale traveling ionospheric disturbances (TIDs) are detected and characterized during magnetically quiet conditionsThe solar terminator is proposed as the primary source of large‐scale TIDsA statistically significant correlation between the altitude of maximum large‐scale TID relative amplitude and solar indices is found [ABSTRACT FROM AUTHOR]
ISSN:21699380
DOI:10.1029/2024JA033583