Mid-latitude ionospheric plasma drift: A comparison of digital ionosonde, and, Incoherent scatter radar measurements at Millstone Hill

A successful validation of the Digisonde drift technique was performed by comparing local ionospheric plasma drift velocity vectors measured by a Digisonde 256 digital ionosonde and a UHF incoherent scatter radar co-located at Millstone Hill (42{dollar}spcirc{dollar}36{dollar}spprime{dollar}N, 71{dollar}spcirc{dollar}30{dollar}spprime{dollar}W) in Massachusetts, USA. The Digisonde drift technique uses imaging Doppler interferometry, measuring amplitude and phase Doppler spectra of ionospherically reflected signals across an array of receive antennas and processing these as line of sight ionospheric velocity vectors. Line of sight velocities of sufficient orthogonality are combined to calculate 3 dimensional ionospheric plasma drift vectors with 5 minute resolution. A total of 145 hours of simultaneous radar and ionosonde drift vectors from 4 experiments are presented and compared. Geographically aligned, bottom side F-region (200-350 km) velocity components measured by each system were correlated. East-west velocities correlate to +0.90, north-south components to +0.67 and vertical components to +0.51. The Digisonde drift technique works best during moderately disturbed nighttime conditions, and those conditions are the emphasis of the work. The relative smoothness of the daytime mid-latitude ionosphere reduces the technique's ability to measure horizontal drifts.