Intense Spread-F Event at a Low Latitude Station and Its Possible Relationship with a Geomagnetic Storm and Substorms
摘要
In this study, we analyze an intense spread-F event observed in Tucumán (27°S; 65,5°W), a low latitude station located under the southern crest of the Equatorial Ionization Anomaly. Typically, post-sunset and post-midnight spread-F phenomena can be observed in this region. However, in this particular case, spread-F was observed throughout the entire night and into the daytime hours. In this case study, we investigate the possible linkage between the spread-F observed during March 24th, 2023, in Tucumán with a severe geomagnetic storm (Kp = 8) and several intense substorms. Continuous spread-F was observed in manually corrected ionosonde data from 01:20 UT to 06:50 UT, from 07:40 to 07:50 UT, from 08:10 to 10:50 UT, and also at daytime from 13:30 to 14:30 and from 17:10 to 17:20 UT (LT = UT-3). The onset of a geomagnetic storm (March 23rd at 08:00 UT) was observed one day prior to the spread-F reported here, the main phase peak occurred on March 24th at 02:00 UT (Dst = -163 nT), followed by a recovery phase lasting about 5 days. The spread-F event primarily occurred during both the main and the recovery phases of the geomagnetic storm, including instances of daytime spread-F. SML, SMU and SME geomagnetic indices showed several successive intense substorms on March 24th, with SME reaching up to 2100 nT. Notably, the occurrence of the intense spread-F was predominantly aligned with the expansion phase of these substorms. This study represents the first analysis using data from the aforementioned low-latitude ionospheric station. We intend to incorporate additional analysis, data, and instruments in future studies, as solar activity increases.