Auroral riometer absorptions and the F-region disturbances observed over a wide range of latitudes |
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Affiliation: | 1. Hand surgery and limb reconstructive surgery department, Timone Adultes Hospital, 191, boulevard Baille, 13005 Marseille, France;2. Orthopedic and Traumatology surgery department, Nord Hospital, Marseille, France;3. Department of Surgical Oncology, Institut Paoli Calmettes, Marseille, France |
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Abstract: | Standard riometer data from a southern auroral station were compared with ionograms obtained at five stations positioned from sub-auroral to equatorial latitudes. The rapid onset in riometer absorption, during intense substorm activities in an equinoctial period, was associated with a sequential propagation of ionospheric disturbances deduced from the F-region parameters h′F and range spread-F. The time shift between absorption maxima and extrapolated commencement times of the disturbances was consistent with the presence of large-scale travelling ionospheric disturbances (TIDs), propagating equatorwards with velocities lying typically in the range 600–900 m s−1, and with a median velocity of 720 m s−1. It is suggested that the onset of TIDs is associated with high-energy particle precipitation, manifested by the occurrence of auroral absorption events. Similarity of absorption increases at the southern and northern conjugate points, found from a previous riometer study, would indicate that large-scale TIDs are simultaneously generated in both hemispheres. |
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