Abstract
Abstract. Phase height measurements of low frequency radio waves are used to study the long-term variability of the mesosphere over Europe. Phase height measurements use a characteristic pattern in field strength registration of radio waves interpreted as phase relations between sky wave and surface wave to obtain the apparent height of the reflection point, the Standard Phase Height (SPH). Based on this SPH-method a homogenized daily series was generated since 1959 at Kühlungsborn. Improvements of the measuring method show that the signal is significantly influenced by lower atmospheric layers. Mesospheric reflection is not the exclusive source of the measured behavior. Tropospheric influence can not be neglected. Taking this into account one has to conclude that the strong coherency of the SPH data to mesospheric heights is not as significant as previously assumed.
Highlights
Indirect phase height measurements of long wave radio frequencies are a common method in order to study the longterm variability of the D region in the ionosphere
It is based onto the assumption that the field strength variations known as Hollingworth pattern (Hollingworth, 1926) is only caused by a change in mesospheric reflection height
The focus in this article is laid to clear some inconsistencies related to the measuring path from Allouis (47◦ N, 2◦ E, Central France) as broadcasting station to Kühlungsborn (54◦ N, 12◦ E, Northern Germany), which is located about 1023 km away and serves as receiving location
Summary
Indirect phase height measurements of long wave radio frequencies are a common method in order to study the longterm variability of the D region in the ionosphere. This zenith angle is used to find a daily height value SPH via H and h0 (Fig. 3) This way one get a time series with one value daily, which is slightly removed from seasonal effects regarding the sun position. Considerable doubts in this simple geometric approach result from the analysis of the data around February 1986. Through an estimation using electron density profiles the reflection height would decrease by less than 80 m, which can be neglected (Singer, 2013) The decrease of 114 m per decade would be much greater because the data after 1986 are shifted upwards by 600 m due to the corrections
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