Abstract
Abstract. The CRISTA/MAHRSI experiment on board a space shuttle was accompanied by a broad campaign of rocket, balloon and ground-based measurements. Supporting lower ionospheric ground-based measurements were run in Europe and Eastern Asia between 1 October-30 November, 1994. Results of comparisons with long ionospheric data series together with short-term comparisons inside the interval October-November, 1994, showed that the upper middle atmosphere (h = 80-100 km) at middle latitudes of the Northern Hemisphere in the interval of the CRISTA/MAHRSI experiment (4-12 November, 1994) was very close to its expected climatological state. In other words, the average results of the experiment can be used as climatological data, at least for the given area/altitudes. The role of solar/geomagnetic and "meteorological" control of the lower ionosphere is investigated and compared with the results of MAP/WINE, MAC/SINE and DYANA campaigns. The effects of both solar/geomagnetic and global meteorological factors on the lower ionosphere are found to be weak during autumn 1994 compared to those in MAP/WINE and DYANA winters, and they are even slightly weaker than those in MAP/SINE summer. The comparison of the four campaigns suggests the following overall pattern: in winter the lower ionosphere at northern middle latitudes appears to be fairly well "meteorologically" controlled with a very weak solar influence. In summer, solar influence is somewhat stronger and dominates the weak "meteorological" influence, but the overall solar/meteorological control is weaker than in winter. In autumn we find the weakest overall solar/meteorological control, local effects evidently dominate.Key words. Ionosphere (ionosphere · atmosphere interactions; mid-latitude ionosphere)
Highlights
The CRISTA/MAHRSI (CRyogenic Infrared Spectrometers and Telescopes for the Atmosphere/Middle Atmosphere High Resolution Spectrometer Instrument) experiment/campaign has been described by Oermann et al (1998), Conway et al (1998) and several other papers in a special section of the Journal of Geophysical Research, series D ± Atmospheric Chemistry
The most important contribution of groundbased ionospheric measurements to the CRISTA/MAHRSI project is the use of very long data series to answer the question whether the CRISTA/MAHRSI campaign/experiment was run under typical conditions or under anomalous conditions
For question (1), comparisons of the CRISTA/ MAHRSI experiment period data (4±12 November, 1994) with various long (25±30 y) ionospheric data series and data over the interval October±November 1994 show that the state of the lower ionosphere (h = 80±100 km) in the interval of the CRISTA/MAHRSI experiment is close to the expected average state in Europe and Japan
Summary
The CRISTA/MAHRSI (CRyogenic Infrared Spectrometers and Telescopes for the Atmosphere/Middle Atmosphere High Resolution Spectrometer Instrument) experiment/campaign has been described by Oermann et al (1998), Conway et al (1998) and several other papers in a special section of the Journal of Geophysical Research, series D ± Atmospheric Chemistry. The most important contribution of groundbased ionospheric measurements to the CRISTA/MAHRSI project is the use of very long data series to answer the question whether the CRISTA/MAHRSI campaign/experiment was run under typical (climatological) conditions or under anomalous conditions. The A3 absorption of radio waves (oblique incidence on the ionosphere), IPHA (indirect phase reection height analysis) and fmin data, reduced to a constant solar zenith angle, v, are used to describe the behaviour of the lower ionosphere over Europe and Eastern Asia based on data provided by`ionospheric'' participants of the project CRISTA/MAHRSI. Values of fmin from Juliusruh are not used because almost 80% of values are at the lowest instrumental limit, 1.5 MHz, they do not allow to detect ionospheric variability
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