On the Generation of an Unseasonal EPB Over South East Asia

Abstract

An unseasonal equatorial plasma bubble (EPB) event over South‐East Asia was observed on July 22, 2014 that has not been studied before. An investigation into this event is presented with the 26th July, 2014 as a comparison, non‐bubble day. The 22nd July EPB event occurred in the late post‐sunset sector and was associated with a small upward plasma drift. This event was highlighted using a new filter on the SCINDA S4 data. Ionosonde data show that sporadic E was present during the growth period for the EPB event. Modeling results from Thermosphere‐Ionosphere Electrodynamics (TEC) Global Circulation Model were used to conduct a numerical experiment investigating the direct effect of sporadic E on the linear R‐T growth rate. It was shown that sporadic E located in the correct latitude and local time can increase the linear growth rate. The seeding conditions were investigated using TEC data from Patumwan, Thailand. Wave‐like structures were observed for both days of interest, with larger amplitudes on 22nd July compared with the 26th July. Finally, simulations using the high‐resolution model PBMOD showed that for forcing from above conditions similar to the days of interest, EPBs would form in the presence of large seed perturbations. Therefore, it is likely that this unseasonal event was caused by large seed perturbations in TEC.

The Importance of Counting: A New Index to Correctly Quantify Equatorial Plasma Bubble Occurrence in COSMIC Radio Occultation Data

“…Many papers have employed the use of GPS ground station data, UHF ground station data, ionosonde data, and/or Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Radio Occultation (RO) data. The results in Currie et al (2021) showed a clear example of an EPB that was missed in GPS ground data in previous studies. Further analysis of the data to include low elevation angles highlighted the event, and other data sets were used to verify the presence of other EPB indicators, confirming that the enhanced scintillation was not contamination from multipath effects.…”

“…The results in Currie et al. (2021) showed a clear example of an EPB that was missed in GPS ground data in previous studies. Further analysis of the data to include low elevation angles highlighted the event, and other data sets were used to verify the presence of other EPB indicators, confirming that the enhanced scintillation was not contamination from multipath effects.…”

“…The scintillation data are provided as an S4 index. These S4 data have been used for EPB detection in the post sunset ionosphere (e.g., Carter et al, 2013Carter et al, , 2018Currie et al, 2021). The global coverage of S4 data provided in the "scnLv1" profiles extends ground-based measurements to provide a global scintillation database.…”

“…The best-case scenario for calculating occurrence comes from having data every day that clearly and reliably shows an event or no event. Currie et al (2021) highlights the importance of detecting events that may be missed in standard data processing techniques but applies the concept to identifying case studies of unseasonal events. However, the same is true if a complete understanding of climatology and the factors affecting climatology are to be understood.…”

The Ionospheric Effects of the 2022 Hunga Tonga Volcano Eruption and the Associated Impacts on GPS Precise Point Positioning Across the Australian Region

“…First, it is worth mentioning that a moderate geomagnetic storm occurred in the late hours of 14 January, with Dst reaching −91 nT and Kp reaching 6- (Le et al, 2022). A useful way to analyze temporal changes in ionograms is by representing the data in a format similar to a "range-time-intensity" plot (Carter et al, 2018;Currie et al, 2021;Pradipta et al, 2015). Instead of using total power, Pradipta et al (2015) integrated over the dBm amplitudes across all sounding frequencies, effectively creating a sum of digitized echoes.…”