Speaker
Description
The South American Magnetic Anomaly (SAMA) evolves in terms of the location of Earth’s magnetic field's weakest point, its span, and its intensity while remaining the region of weakest magnetic-field intensity. This makes the region particularly suitable for examining the coupling between magnetospheric forcing and the lower ionosphere. Previous observations show that cosmic noise absorption (CNA) varies systematically with latitude across the SAMA. This makes the region particularly suitable for examining the coupling between magnetospheric forcing and the lower ionosphere. For example, previous observations show that cosmic noise absorption (CNA) varies systematically with latitude across the SAMA. Nevertheless, it remains unresolved whether the differences observed between stations arise from the regional magnetic-field configuration itself or from the common storm-time forcing experienced during individual disturbances. Earlier studies established the existence of this spatial variation, but they did not quantitatively isolate the contribution of the local geomagnetic field from that of external forcing using contemporary multi-station observations. The upcoming availability of new observations from an expanded riometer network may make it possible to test this question across multiple disturbances rather than infer it from isolated case studies. To advance our understanding, we will use simultaneous riometer observations from stations located across and beyond the SAMA, and analyze a selected set of geomagnetic disturbances and solar events. For each event, CNA onset, maximum amplitude, duration, and integrated absorption will be quantified and related to geographic and geomagnetic latitude, magnetic-field intensity and configuration, and external solar-wind and geomagnetic drivers. Event-by-event and multi-station analyses will then be used to assess whether the observed latitudinal relationships persist across disturbances and stations or instead reflect event-specific particle precipitation patterns. Supporting information may come from ionosonde observations to provide a complementary test of whether enhanced CNA is accompanied by partial or complete ionogram blackout.