Space Weather Impact of Three Solar Flares Observed by the POEMAS Telescope at 45 and 90 GHz

Abstract Solar flares are often associated with coronal mass ejections (CMEs) that, when directed toward Earth, can disrupt the magnetosphere and impact space weather. In this study, we investigate three long‐duration solar flares observed in 2012 by the POlarization Emission of Millimeter Activity at the Sun (POEMAS) telescopes at 45 and 90 GHz. We analyze the correlation between their radio spectral properties, associated CMEs, and geomagnetic and ionospheric responses, to assess the possibility of space weather prediction. Spectral fitting of the radio data using a gyrosynchrotron model reveals accelerated electron populations with a hard energy distribution (spectral index ) that hardens with time, and magnetic fields of G. The most energetic flare involved a source region 3–6 times larger than the others and produced 10 times more energetic electrons. In all three events, CMEs were launched simultaneously with the flares. The July 12 X1.4 flare was associated with a fast (884 km/s) halo CME that led to a moderate geomagnetic storm (Dst = −139 nT, Kp = 6). VLF radio data show that all three flares increased ionospheric electron density, lowering its boundary from 70 km to 58–67 km. These results suggest that long‐duration flares with high flux at 45 GHz and hard radio spectra are associated with more energetic events characterized by higher GOES class, greater SXR energy, faster and more energetic CMEs, and stronger geomagnetic disturbances, highlighting the potential of high‐frequency radio observations as a tool for space weather prediction.