Observations with an ionosonde in Northern Germany near the mid-latitude trough

A new-vertical incidence ionosonde was installed more than two years ago near Hamburg, in order to improve HF propagation predictions and frequency management. HF propagation in the North-Sea and Baltic-Sea areas - close to the auroral zone, near the mid-latitude trough - is highly variable. This manifests itself also on the ionograms. Many of them show peculiarities normally not seen farther south. The day-to-day variation of measured ionospheric characteristics is compared with those obtained by the CCIR method (Report 340). In addition statistics of ionospherically disturbed days in the years 1983 and 1984 are given and compared with measurements of the variations of the geomagnetic field at the near-by observatory Wingst. Although the ionosonde is used mainly as a tool for up-to-date HF propagation predictions, the collected data can be of considerable use also for the design of new HF radio systems in the area under consideration.