Todays knowledge of the solar EUV output and the future needs for more accurate measurements for aeronomy

In recent years discrepancies arose in the determination of the solar EUV output. It is difficult and often impossible to remove these discrepancies from the observational data reported so far. However, the EUV data show evidence for a strong variability during the Solar Cycle 20. The measuring methods applied so far create uncertainties of the order of ± 30% or less. Therefore, new methods have to be developed for more accurate measurements. Two approaches offer the possibility of overcoming todays shortcomings. With these methods the EUV indices will be measured with an accuracy better than 10%, using a simple spectrometer on a free-flying long-term mission with recalibration factors provided by short-term mission results e.g. from Soyuz or Spacelab.     

Impact of loading displacements on SLR-derived parameters and on the consistency between GNSS and SLR results

Displacements of the Earth’s surface caused by tidal and non-tidal loading forces are relevant in high-precision space geodesy. Some of the corrections are recommended by the international scientific community to be applied at the observation level, e.g., ocean tidal loading (OTL) and atmospheric tidal loading (ATL). Non-tidal displacement corrections are in general recommended not to be applied in the products of the International Earth Rotation and Reference Systems Service, in particular atmospheric non-tidal loading (ANTL), oceanic and hydrological non-tidal corrections. We assess and compare the impact of OTL, ATL and ANTL on SLR-derived parameters by reprocessing 12 years of SLR data considering and ignoring individual corrections. We show that loading displacements have an influence not only on station long-term stability, but also on geocenter coordinates, Earth Rotation Parameters, and satellite orbits. Applying the loading corrections reduces the amplitudes of annual signals in the time series of geocenter and station coordinates. The general improvement of the SLR station 3D coordinate repeatability when applying OTL, ATL and ANTL corrections are 19.5 %, 0.2 % and 3.3 % respectively, w.r.t. the solutions without loading corrections. ANTL corrections play a crucial role in the combination of optical (SLR) and microwave (GNSS, VLBI, DORIS) space geodetic observation techniques, because of the so-called Blue-Sky effect: SLR measurements can be carried out only under cloudless sky conditions—typically during high air pressure conditions, when the Earth’s crust is deformed, whereas microwave observations are weather-independent. Thus, applying the loading corrections at the observation level improves SLR-derived products as well as the consistency with microwave-based results. We assess the Blue-Sky effect on SLR stations and the consistency improvement between GNSS and SLR solutions when ANTL corrections are included. The omission of ANTL corrections may lead to inconsistencies between SLR and GNSS solutions of up to 2.5 mm for inland stations. As a result, the estimated GNSS–SLR coordinate differences correspond better to the local ties at the co-located stations when applying ANTL corrections.     

Outward transport of CAIs during FU‐Orionis events

Abstract— Evidence from meteorites shows that the first solids to form in the solar system, calcium‐aluminum‐rich inclusions (CAIs), were transported outward from the Sun by several AU in the early solar system. We introduce a new concept of levitation and outward transport of CAIs at the surface of protoplanetary disks. Thermal radiation from the disk and the Sun can cause particles to levitate above the disk and drift outward through a process known as photophoresis. During normal conditions this process only works for dust‐sized particles but during high luminosity events like FU‐Orionis outbursts, the process can provide an efficient lift and transport of CAIs from within the inner 1 AU to a distance of several AU from the Sun. This might explain why CAIs, believed to have formed close to the Sun, are common in meteorites believed to come from the outer asteroid belt but are rare or absent in samples from the inner solar system. Since the process only works during the FU‐Orionis event and only for particles up to cm‐size, it may also explain why the CAIs we find in meteorites appear to have formed within a short period of time and why they rarely exceed cm size.     

Die Einwirkung des Windes auf den mittleren Wasserstand der Deutschen Bucht vom 15. Februar bis 6. März 1951

Zusammenfassung Aus den Wasserstandsaufzeichnungen von zwölf Schwimmer-Schreibpegeln und sechs Hochseepegeln im Gebiet der inneren Deutschen Bucht wurden durch Eliminierung des Gezeitenanteils Windstaukurven bestimmt. Der Verlauf der Kurven wurde mit der Entwicklung des Windes über der mittleren und südlichen Nordsee verglichen und teilweise in topographischen Karten dargestellt, die von sechs zu sechs Stunden die Lage des mittleren Wasserstandes in der Deutschen Bucht an Hand von Linien gleichen Windstaus enthalten. Die Wirkung auflandiger und ablandiger Winde sowie des Luftdrucks wird besprochen. Die Ergebnisse werden mit den Untersuchungen anderer Autoren verglichen.

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The wind's effect on the mean water level in the German Bight as observed between February 15th and March 6th, 1951

Summary By eliminating the tidal portions from the records of twelve self recording tide gauges and six high sea tide gauges in the inner German Bight curves of the wind produced disturbance of the water level were found. The curves were compared with the development of the wind in the central and southern parts of the North Sea. Proceeding from the curves bearing on the periods from 17th to 23rd February and from 2nd to 5th March, 1951, topographical charts for every six hours were plotted on which the mean water level in the German Bight is represented by co-disturbance lines. The effects of on-shore and off-shore winds as well as the influence of atmospheric pressure are discussed and the results are compared with the investigations of other authors.

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Effet du vent sur le niveau moyen de la mer devant les côtes allemandes de la mer du Nord (du golfe Allemand) d'après les observations du 15 février au 6 mars 1951

Résumé En éliminant l'effet de la marée contenu dans les enregistrements de douze marégraphes enregistreurs et de six marégraphes plongeurs installés à l'intérieur du golfe Allemand on obtient les courbes de la montée du niveau de la mer due à la force du vent. Ces courbes sont comparées avec le développement du vent dans la zone centrale et la zone méridionale de la mer du Nord, et partant des courbes relatives à la période du 17 au 23 février et celle du 2 au 5 mars 1951, on a établi des cartes topographiques du niveau de la mer dans le golfe Allemand pour toutes les six heures à l'aide de lignes d'égale montée du niveau due à la force du vent. L'effet des vents de mer et celui des vents de terre ainsi que l'influence de la pression atmosphérique sont discutés. Les résultats de ce travail sont comparés avec les recherches faites par d'autres auteurs.