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The depletion of plasma in the nighttime F region ionosphere is called the mid-latitude ionospheric trough (MIT). The objective of this study is to identify and describe the mid-latitude ionospheric trough by using new satellite data and expanding our understanding of the MIT phenomenon.To evaluate the MIT, we used electron density in-situ data derived from GRACE satellite K-Band Ranging system (KBR) measurements. The trough was examined using data collected between 2002 and 2015, including high and low solar activity periods. We analyze the characteristics of the mid-latitude ionospheric trough (MIT) in both the Northern and Southern Hemispheres. The MIT is characterized by its trough’s minimum position, width, depth, and probability. We investigated how MIT parameters were affected by the magnetic local time, geographic distribution, seasons, and solar and geomagnetic activity conditions, including solar wind plasma speed, interplanetary magnetic field components, and high-resolution geomagnetic indices SYM-H and Hp30.In this study, we demonstrate the elliptical distribution of the mean location of the trough minimum over three seasons for the Northern and Southern hemispheres and the MIT parameter dependency on high-resolution geomagnetic indices. Our findings confirm and extend earlier research on MIT.The obtained dependencies related to MIT climatology and occurrence probability can be used to validate existing MIT models and create new MIT models since it has not yet been represented in commonly used 3D electron density models, such as IRI, NeQuick,NEDM2020, etc. The integration of an MIT model may improve the performance of the 3D electron density models.&nbsp, The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Spherical harmonic analysis was performed on the geomagnetic Solar-quiet (Sq) variations observed at approximately 120 ground-based magnetometer stations in the mid- to low-latitude regions. The global equivalent ionospheric current system was estimated at each UT hour during 1-31 May 2020. During this period, geomagnetic activity was particularly low, and the hourly geomagnetic activity index Hpo did not exceed 4. The global Sq current intensity and pattern exhibit hour-to-hour, day-to-day, and longitudinal variability. The spatio-temporal variability of the Sq current system is complex. Fourier-wavelet transform is performed on the Sq current intensity at 31˚N and 33˚S magnetic latitudes to examine the tidal wave composition. We also evaluate the temporal variability of eastward- and westward-propagating wave components with different zonal wavenumbers (s=1, 2, 3). The spectral analysis results show that the migrating (or Sun-synchronous) diurnal tidal wave component dominates considerably in the Northern and Southern Hemispheres but their day-to-day variations are not correlated. This observation indicates that the day-to-day variability of the migrating diurnal tide in Sq currents is dominated by local wind-dynamo effects, rather than by a global process such as the solar radiation effect on the ionospheric conductivity., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

The wind shear theory is widely accepted as an explanation for the formation of a sporadic E (Es) layer, but the direct comparison of Es with the local wind shear has been limited due to the lack of neutral wind measurements. This study examines the role of the vertical wind shear for Es, using signal‐to‐noise ratio profiles from COSMIC‐2 radio occultation measurements and concurrent measurements of neutral wind profiles from the Ionospheric Connection Explorer. It is observed that the Es occurrence rate and average S4 index are correlated with the negative vertical shear of the eastward wind, providing observational support for the wind shear theory. Es can be observed even when the vertical wind shear is positive, which is interpreted as metallic ion layers generated at an earlier time., Plain Language Summary: Sporadic E (Es) is anomalous radio propagation resulting from intense clouds of ionization at heights of the E‐region ionosphere (90–120 km). The formation of an Es layer is generally attributed to the vertical wind shear, which can move metallic ions in the vertical direction by the Lorentz force. According to the wind shear theory, a negative shear of the eastward wind is effective in converging the metallic ions into a thin layer to produce Es. Although previous observations and modeling studies have supported the theory to various degrees, the direct comparison of Es with the vertical wind shear has been limited due to sparse observations of neutral winds at E‐region heights. Neutral wind profiles from the Ionospheric Connection Explorer mission, together with Es data from COSMIC‐2 radio occultation measurements, provide an opportunity to fill this knowledge gap. Direct comparisons of these measurements reveal that the Es occurrence rate is higher and lower for larger negative and positive wind shears, respectively, providing observational evidence for the wind shear theory., Key Points: Conjunction observations of sporadic E (Es) from COSMIC‐2 and neutral wind profiles from Ionospheric Connection Explorer/Michelson Interferometer for Global High‐Resolution Thermospheric Imaging are analyzed. Es occurrence rate correlates with the negative vertical shear of eastward wind, providing observational evidence for the wind shear theory. Es can be observed even when the vertical shear of the local eastward wind is positive., Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659, NASA, DFG Priority Program Dynamic Earth

The Gravity field and steady-state ocean circulation explorer (GOCE) satellite mission carries three platform magnetometers. After careful calibration, the data acquired through these can be used for scientific purposes by removing artificial disturbances from other satellite payload systems. This dataset is based on the dataset provided by Michaelis and Korte (2022) and uses a similar format. The platform magnetometer data has been calibrated against CHAOS7 magnetic field model predic-tions for core, crustal and large-scale magnetospheric field (Finlay et al., 2020) and is provided in the ‘chaos’ folder. The calibration results using a Machine Learning approach are provided in the ‘calcorr’ folder. Michaelis’ dataset can be used as an extension to this dataset for additional infor-mation, as they are connected using the same timestamps to match and relate the same data points. The exact approach based on Machine Learning is described in the referenced publication. The data is provided in NASA CDF format (https://cdf.gsfc.nasa.gov/) and accessible at: ftp://isdcftp.gfz-potsdam.de/platmag/MAGNETIC_FIELD/GOCE/ML/v0204/ and further de-scribed in a README.

This data publication includes the half-hourly Hp30 and ap30 indices as well as the hourly Hp60 and ap60 indices. All are unitless and collectively denoted as Hpo or Hpo index family. The dataset is based on near real-time geomagnetic observatory data provided by 13 contributing observatories. It is derived and distributed by GFZ German Research Centre for Geosciences. When using the Hpo index, please cite this data publication as well as the accompanying publication Matzka et al. (in prep), which serves as documentation of the Hpo index family. The dataset is organised in yearly files, which, for the current year, are updated on a monthly basis. Typically, during the second week of a month, the data for the previous month is appended to the current year's file. The files are in ASCII files and start with header lines marked with # (hash). The Hpo index was developed within the H2020 project SWAMI (grant agreement No 776287) and is produced by Geomagnetic Observatory Niemegk, GFZ German Research Centre for Geosciences. It derives from the same 13 geomagnetic observatories that also contribute to the Kp index (Matzka et al., 2021). They are listed as contributors to this data publication. With the introduction of the DOI ‘https://doi.org/10.5880/Hpo.0001’, this DOI landing page and the associated FTP server linked to the DOI become the primary archive of Hpo (while the other established index distribution mechanisms at GFZ will be maintained in parallel). With the DOI, the dataset can grow with time, but a change of the data, once published, is not possible. If necessity arises in the future to correct already published values, then the corrected dataset will be published with a new DOI. Older DOIs and data sets will then still be available. For each DOI, an additional versioning mechanism will be available to document changes to the files such as header or format changes, which do not affect the integrity of the data. The DOI https://doi.org/10.5880/Hpo.0001 identifies the current version. A format description is provided in the data download folder. As ocean tides are usually described as a superposition of so-called partial tides, the presented mass variations can be attributed to single partial tide frequencies and are thus represented for single partial tide frequencies. Here, not only the effect of direct gravitation exerted by the ocean water is included but also gravity variations due to the elastic yielding of the solid earth in response to water mass redistribution (the load tide) are allowed for. The information describing the partial tides has been transformed to fully normalized Stokes Coefficients describing in-phase and quadrature fields as those are especially handy for gravimetric purposes. The next section describes the creation of the data in more detail. As support for the COSC drilling project, an extensive seismic survey took place in 2014 in and around the newly drilled borehole COSC-1. The active seismic survey, among others, consisted of a high-resolution Zero-Offset Vertical Seismic Profiling (ZOVSP) experiment where seismic receivers were placed inside the borehole. For the seismic source signal a hydraulic hammer source (VIBSIST 3000) was used and activated over a period of 20 s as a sequence of impacts with increasing hit frequency. The wavefield was recorded in the borehole by 15 three-component receivers using a Sercel Slimwave geophone chain with an inter-tool spacing of 10 m. The ZOVSP was designed to result in a geophone spacing of 2 m over the whole borehole length. The source was about 30 meters away from the borehole. For component rotation, a check shot position was located about 1.9 km away from the borehole. This data set contains two data sets: (1) the decoded, pre-processed three-component shot gather, and (2) the final-processed shot gather of only the vertical component.

GRACE-FO carries a magnetometer as part of its attitude orbit control system (AOCS). The magnetometer does not belong to the scientific payload of the mission. However, after postprocessing of the data, information on the geomagnetic field and on electric currents in near Earth space are derived. Each GRACE-FO satellite (GF1 and GF2) carries two fluxgate magnetometers (FGM), an active one, FGM A, and a redundant one, FGM B. So far, the redundant magnetometers were not switched and are not included in the data set. The provided data consists of raw magnetic field data as provided by L1b (RAW), Magnetic field data aligned, calibrated and corrected (ACAL_CORR), CHAOS7 magnetic model predictions for core, crustal and large-scale magnetospheric field (CHAOS7), Magnetic coordinates (APEX) and Radial and field-aligned currents derived from magnetic data in ACAL_CORR (FAC). The data are provided in NASA CDF format (https://cdf.gsfc.nasa.gov/).

Matzka et al. (2021) describe the state of the Kp index 70 years after its introduction and serve as a reference for users of the IAGA-endorsed Kp index as well as for the derived indices ap, Ap, Cp and C9 in their definitive and nowcast version as well as for the International Quiet and Disturbed Days. This dataset is provided by GFZ and derived from indices or near real-time geomagnetic observatory data provided by 13 contributing observatories. Please cite this data publication as well as the accompanying publication (Matzka et al., 2021) when using the Kp index or any of the derived indices obtained from this dataset or from its copies provided by GFZ or other institutions. The Kp index The Kp index was introduced by Bartels (1949). We follow here generally the notation of Bartels (1957). A comprehensive list of references on the Kp index is provided in Matzka et al. (2021), which also describes the near real-time distribution of the indices. DOI and versioning With the introduction of the DOI ‘https://doi.org/10.5880/Kp.0001’ for the dataset, the DOI landing page and the associated FTP server linked to this DOI become the dataset's primary archive (while the other established index distribution mechanisms at GFZ will be maintained in parallel). With the DOI, the dataset can grow with time, but a change of the data, once published, is not possible. If necessity arises in the future to correct already published values, then the corrected dataset will be published with a new DOI. Older DOIs and data sets will then still be available. For each DOI, an additional versioning mechanism will be available to document changes to the files such as format changes, which do not affect the integrity of the data. The DOI 10.5880/Kp.0001 identifies the current version.

The lower-thermosphere–ionosphere (LTI) system consists of the upper atmosphere and the lower part of the ionosphere and as such comprises a complex system coupled to both the atmosphere below and space above. The atmospheric part of the LTI is dominated by laws of continuum fluid dynamics and chemistry, while the ionosphere is a plasma system controlled by electromagnetic forces driven by the magnetosphere, the solar wind, as well as the wind dynamo. The LTI is hence a domain controlled by many different physical processes. However, systematic in situ measurements within this region are severely lacking, although the LTI is located only 80 to 200 km above the surface of our planet. This paper reviews the current state of the art in measuring the LTI, either in situ or by several different remote-sensing methods. We begin by outlining the open questions within the LTI requiring high-quality in situ measurements, before reviewing directly observable parameters and their most important derivatives. The motivation for this review has arisen from the recent retention of the Daedalus mission as one among three competing mission candidates within the European Space Agency (ESA) Earth Explorer 10 Programme. However, this paper intends to cover the LTI parameters such that it can be used as a background scientific reference for any mission targeting in situ observations of the LTI.

The GRACE (Gravity Recovery and Climate Experiment) satellites, which comprises two spacecraft, GRACE-A and GRACE-B, were launched on 17 March 2002 into a near-circular, polar (inclination = 89◦ ) orbit with an initial altitude of about 490 km. The two satellites follow each other at a distance of about 200 km. The primary objective of the GRACE mission is to provide global high-resolution models of the Earth’s gravity field. The instruments supporting our study are the K-Band Ranging System (KBR), and the GPS Space Receiver (GPS). The K-Band Ranging System (KBR) system is the key science instrument of GRACE which measures the dual one-way range change between both satellites with a precision of about 1 μm per second. From the KBR1B data we can get the change of Total Electron Content (TEC). In addition the GPS Navigation Data (GNV1B) can provide us the position of the two satellites. From these data we can derive the average electron density between the two satellites. The data are stored as daily ASCII files using the file naming convention 'KBRNE_YYYY_MM_DD.dat'. Headers in each data file contain a short name for each column. A more detailed description is provided in the readme file.