Incoherent scatter observations of traveling ionospheric disturbances

The incoherent scatter technique is used to study large-scale traveling ionospheric disturbances above Puerto Rico. Below the F-region maximum the measurements of disturbance amplitude, period, and direction of phase progression with time (downward) are consistent with the bottomside results of other workers. Above the maximum, however, the surfaces of constant phase are found to become vertical, disturbance amplitude becomes less, and the periods become greater.