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End date: 2023 × Start date: 2020 × Publisher: Heidelberg : Springer × WGL Institute: IAP ×

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Now showing 1 - 5 of 5
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    The revised method for retrieving daytime distributions of atomic oxygen and odd-hydrogens in the mesopause region from satellite observations
    (Heidelberg : Springer, 2022) Kulikov, Mikhail Y.; Belikovich, Mikhail V.; Grygalashvyly, Mykhaylo; Sonnemann, Gerd R.; Feigin, Alexander M.
    Atomic oxygen (O) and atomic hydrogen (H) in the mesopause region are critical species, governing chemistry, airglow, and energy budget. However, they cannot be directly measured by satellite remote sensing techniques and so inference techniques, by airglow observations, are used. In this work, we retrieved daytime O and H distributions at ~ 77 km–100 km from the data of observations by the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) instrument at the TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics) satellite in 2003–2015. The retrieval approach considered the reaction H + O3 → O2 + OH in the ozone balance equation. Moreover, we revised all quenching and spontaneous emission coefficients according to latest published data. We then calculated daytime distributions of OH and HO2 at these altitudes with the use of their conditions of photochemical equilibrium.
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    Solar and lunar daily geomagnetic variations and their equivalent current systems observed by Swarm
    (Heidelberg : Springer, 2022) Yamazaki, Yosuke
    This paper describes solar and lunar daily variations of the geomagnetic field over low- and mid-latitude regions, using vector magnetometer data from Swarm satellites at altitudes of ∼500 km during the solar minimum years of 2017–2020. The average solar variation of the geomagnetic field is within the range of ±14 nT, while the lunar variation is within ±2 nT. The latter is comparable to the ocean tidal field. A spherical harmonic analysis is performed on the solar and lunar variations to evaluate their internal and external equivalent current systems. The results show that both the solar and lunar variations are mainly of internal origin, which can be attributed to combined effects of ionospheric dynamo currents and induced underground currents. Global patterns of the internal solar and lunar current systems are consistent with the corresponding external current systems previously reported based on ground observations. The Swarm external currents are mainly in the meridional direction, and are likely associated with interhemispheric field-aligned currents. Both the internal and external current systems depend on the season and longitude.
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    Note on consistency between Kalogerakis–Sharma Mechanism (KSM) and two-step mechanism of atmospheric band emission (762 nm)
    (Heidelberg : Springer, 2020) Grygalashvyly, Mykhaylo; Sonnemann, Gerd Reinhold
    For more than 30 years, a two-step mechanism was used to explain observed Atmospheric band emission (762 nm) in mesopause region. A new mechanism, which leads to the formation of electronically excited molecular oxygen that gives this emission, was proposed recently. We show, based on an analytical solution, that the fit-functions for Atmospheric band volume emission in the case of the two-step mechanism and the new Kalogerakis–Sharma Mechanism (KSM) have analogous expression. This derivation solves the problem of consistency between the well-known two-step mechanism and the newly proposed KSM.
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    Geomagnetic data from the GOCE satellite mission
    (Heidelberg : Springer, 2022) Michaelis, I.; Styp-Rekowski, K.; Rauberg, J.; Stolle, C.; Korte, M.
    The Gravity field and steady-state Ocean Circulation Explorer (GOCE) is part of ESA’s Earth Explorer Program. The satellite carries magnetometers that control the activity of magnetorquers for navigation of the satellite, but are not dedicated as science instruments. However, intrinsic steady states of the instruments can be corrected by alignment and calibration, and artificial perturbations, e.g. from currents, can be removed by their characterisation correlated to housekeeping data. The leftover field then shows the natural evolution and variability of the Earth’s magnetic field. This article describes the pre-processing of input data as well as calibration and characterisation steps performed on GOCE magnetic data, using a high-precision magnetic field model as reference. For geomagnetic quiet times, the standard deviation of the residual is below 13 nT with a median residual of (11.7, 9.6, 10.4) nT for the three magnetic field components (x, y, z). For validation of the calibration and characterisation performance, we selected a geomagnetic storm event in March 2013. GOCE magnetic field data show good agreement with results from a ground magnetic observation network. The GOCE mission overlaps with the dedicated magnetic field satellite mission CHAMP for a short time at the beginning of 2010, but does not overlap with the Swarm mission or any other mission flying at low altitude and carrying high-precision magnetometers. We expect calibrated GOCE magnetic field data to be useful for lithospheric modelling and filling the gap between the dedicated geomagnetic missions CHAMP and Swarm. Graphic Abstract: [Figure not available: see fulltext.].
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    Machine learning-based calibration of the GOCE satellite platform magnetometers
    (Heidelberg : Springer, 2022) Styp-Rekowski, Kevin; Michaelis, Ingo; Stolle, Claudia; Baerenzung, Julien; Korte, Monika; Kao, Odej
    Additional datasets from space-based observations of the Earth’s magnetic field are of high value to space physics and geomagnetism. The use of platform magnetometers from non-dedicated satellites has recently successfully provided additional spatial and temporal coverage of the magnetic field. The Gravity and steady-state Ocean Circulation Explorer (GOCE) mission was launched in March 2009 and ended in November 2013 with the purpose of measuring the Earth’s gravity field. It also carried three platform magnetometers onboard. Careful calibration of the platform magnetometers can remove artificial disturbances caused by other satellite payload systems, improving the quality of the measurements. In this work, a machine learning-based approach is presented that uses neural networks to achieve a calibration that can incorporate a variety of collected information about the satellite system. The evaluation has shown that the approach is able to significantly reduce the calibration residual with a mean absolute residual of about 6.47nT for low- and mid-latitudes. In addition, the calibrated platform magnetometer data can be used for reconstructing the lithospheric field, due to the low altitude of the mission, and also observing other magnetic phenomena such as geomagnetic storms. Furthermore, the inclusion of the calibrated platform magnetometer data also allows improvement of geomagnetic field models. The calibrated dataset is published alongside this work. Graphical Abstract: [Figure not available: see fulltext.].