Locating TID sources with a north‐south chain of rapid‐run ionosondes in western Québec

Abstract

Three rapid‐run ionosondes placed mutually 150 km apart for determination of the vector motion of traveling ionospheric disturbances, near L = 3.3 in northern New Hampshire and Vermont, were augmented with three more ionosondes laid out northward near L = 4.0. 4.5, and 6.0 in western Québec along the predominant direction (north‐northwest) from which daytime TID's arrive at the New Hampshire‐Vermont network. Observations were made for the 3‐month period March, April, May 1982. In a preliminary analysis, records have been reduced by our “slit‐scanner” technique to produce continuous displays of virtual height at selected frequencies moderately below the F layer critical. These isofrequency waveforms show a high degree of correlation among the three network stations, with propagation time delays from which speed and direction of TID travel can be deduced. An example, from 1980 observations, is shown of remarkable correlation over many daytime hours of the waveforms obtained by the network stations with that obtained by a sounder placed 1500 km downstream in the predominant direction (south‐southeast) toward which the TID's go. On the other hand, sources have now been found to be located as little as 200 km upstream from the network. TID's and their causative gravity waves propagate northward from these sources as well as southward. The sources are evidently narrow in north‐south extent for they frequently exist between the stations, spaced some 275 km apart, without causing absorption of ionosonde signals at either adjacent station. However, when they are located at an ionosonde station, they cause complete loss of echoes, thereby confirming that they are zones of energetic particle precipitation. They are believed to be due to precipitation from the outer radiation belt.

Identification of high‐latitude acoustic gravity wave sources using the Goose Bay HF Radar

“…Previous studies have shown that many medium-scale waves have high-latitude sources, and a good correlation has been shown between auroral activity and the observation of mediumscale waves [Chandra et al, 1979]. One study reported the observations of TIDs traveling both equatorward and poleward of an assumed source region [Morgan, 1983]. Also, correlation has been shown between midlatitude travelingionospheric disturbances and magnetometer fluctuations at high latitude [Hunsucker and Tveten, 1967].…”

The height dependence of TID and gravity wave parameters

“…Ionograms (taken every 2 min) were digitized and reduced to true-height profiles of electron density for the 8-hour period 0800-1600 EST (W75 ø standard time) and for each of the three ionosondes of the network which are mutually about 160 km apart . Isoheight time series were then generated for each station between an altitude of 200 km (lower limit for which the true- A study of the sources of the TID's observed with the network has recently been presented by Morgan [1983]. By applying the same technique to isoheight contours at adjacent heights for a single station, vertical cross-spectral density parameters can be derived, and these are illustrated in Figure 3.…”

Case studies of the propagation characteristics of auroral TIDS with EISCAT CP2 data using maximum entropy cross-spectral analysis

“…This technique has been successfully applied using EISCAT and additional facilities at mid and low latitudes (Morgan, 1983;Crowley and McCrea, 1988;Rice et al, 1988;Williams et al, 1988Williams et al, , 1993). An important quantity for the propagation of TIDs/AGWs is the complete wave vector of the wave-like¯uctua-tions.…”