New Observations of Cosmic Noise Absorption in the South American Magnetic Anomaly (SAMA) Using a Next‐Generation Riometer

This study reports the first observations of cosmic noise power (CNP) and cosmic noise absorption (CNA) obtained with a next‐generation riometer installed at the Southern Space Observatory (SSO/INPE) in Brazil, located within the South American Magnetic Anomaly (SAMA). Data were analyzed during five geomagnetic storms occurring between July 2024 and January 2025. The Quiet Day Curve was developed using a methodology adapted to the specific characteristics of this instrument. Geomagnetic storms driven by Interplanetary Coronal Mass Ejection revealed two distinct CNA responses: (a) nearly continuous but weak CNA (0.50–0.70 dB) during moderate geomagnetic storm, when absorption was sustained for long intervals but remained of low intensity; and (b) long‐lasting CNA responses during intense geomagnetic storms, with absorption persisting for many hours throughout both the main and recovery phases, often exceeding 1.0 dB. Statistical analyses showed weak to moderate correlations between CNA and interplanetary parameters and geomagnetic indices, highlighting the complex role of processes in sustaining the D‐region ionization over the SAMA. In addition, sudden CNA events were observed during M‐ and X‐class solar flares, with peak amplitudes of up to 1.7 dB, showing clear correspondence with solar X‐ray fluxes. Some flares also produced positive CNP spikes, attributed to direct contamination by solar radio bursts. The results confirm that the new riometer can successfully monitor CNP and CNA in the SAMA region, offering valuable new opportunities to advance our understanding of particle precipitation and flare‐induced ionization processes.