OI 630.0 nm all-sky image observations of medium-scale traveling ionospheric disturbances at geomagnetic conjugate points

• MSTIDs were detected in geomagnetic conjugate points simultaneously.
• The cases were observed during calm geomagnetically night by all-sky imagers.
• The passage of MSTID produces spread-F in both hemispheres.
• Variations in Hmf2, H′f and foF2 was detected in both hemispheres.

This paper presents a medium-scale traveling ionospheric disturbance (MSTID) occurrence detected through the OI 630.0 nm emission all-sky images, obtained by ground-based imaging systems installed at close geomagnetic conjugate locations: one at the Southern Space Observatory-SSO/CRS/INPE-MCTI, (29.4°S, 53.8°W), in Sao Martinho da Serra, RS, Brazil, and another at the Arecibo Observatory (18.3°N, 66.7°W), in Puerto Rico. The images obtained show the optical signature of MSTIDs (low intensity regions of 630.0 nm airglow emission), propagating simultaneously in both hemispheres, during geomagnetically quiet conditions (Kp<3). Observations using digital ionosonde installed at Falkland Islands (51.4°S, 57.5°W) and Ramey, Puerto Rico (18.5°N, 67.1°W) show an abrupt upward motion of the ionospheric F region plasma and the occurrence of frequency-type spread-F that could be related to the MSTIDs observed optically. Using Global Positioning System (GPS) receiver data, we also obtained the rate of the Total Electronic Content (TEC) change (ROT) for two geomagnetically conjugated sites-Santa Maria (29.7°S, 53.7°W) and Virgin Islands (17.7° N, 64.7°W). The analysis of TEC allows us to identify an irregular ionization in the F layer associated with the passage of an MSTID. The possible effects of the South America Magnetic Anomaly (SAMA) on the electrodynamic processes that control the inter-hemispheric coupling that give origin to the conjugate MSTIDs are highlighted and discussed.