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  • 1
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    Observing Earth’s magnetic environment with the GRACE-FO mission (2021)
    Stolle, C. ; Michaelis, I. ; Xiong, C. ; [et al.]
    Springer Berlin Heidelberg
    Details
    Publication Date: 2023-06-21
    Description: The Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission carries magnetometers that are dedicated to enhance the satellite’s navigation. After appropriate calibration and characterisation of artificial magnetic disturbances, these observations are valuable assets to characterise the natural variability of Earth’s magnetic field. We describe the data pre-processing, the calibration, and characterisation strategy against a high-precision magnetic field model applied to the GRACE-FO magnetic data. During times of geomagnetic quiet conditions, the mean residual to the magnetic model is around 1 nT with standard deviations below 10 nT. The mean difference to data of ESA’s Swarm mission, which is dedicated to monitor the Earth’s magnetic field, is mainly within ± 10 nT during conjunctions. The performance of GRACE-FO magnetic data is further discussed on selected scientific examples. During a magnetic storm event in August 2018, GRACE-FO reveals the local time dependence of the magnetospheric ring current signature, which is in good agreement with results from a network of ground magnetic observations. Also, derived field-aligned currents (FACs) are applied to monitor auroral FACs that compare well in amplitude and statistical behaviour for local time, hemisphere, and solar wind conditions to approved earlier findings from other missions including Swarm. On a case event, it is demonstrated that the dual-satellite constellation of GRACE-FO is most suitable to derive the persistence of auroral FACs with scale lengths of 180 km or longer. Due to a relatively larger noise level compared to dedicated magnetic missions, GRACE-FO is especially suitable for high-amplitude event studies. However, GRACE-FO is also sensitive to ionospheric signatures even below the noise level within statistical approaches. The combination with data of dedicated magnetic field missions and other missions carrying non-dedicated magnetometers greatly enhances related scientific perspectives.
    Description: European Space Agency (FR)
    Description: HEIBRIDS
    Description: Projekt DEAL
    Description: ftp://isdcftp.gfz-potsdam.de/grace-fo/MAGNETIC_FIELD
    Keywords: ddc:538.7 ; Earth’s magnetic field ; Geomagnetism ; Ionospheric currents ; Magnetospheric ring current ; Satellite-based magnetometers ; Platform magnetometers ; GRACE-FO
    Language: English
    Type: doc-type:article
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    CITATION GEO-LEO
  • 2
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    Monthly Climatologies of Zonal‐Mean and Tidal Winds in the Thermosphere as Observed by ICON/MIGHTI During April 2020–March 2022 (2023)
    Details
    Publication Date: 2024-01-26
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Version 5 (v05) of the thermospheric wind data from the Michelson Interferometer for Global High‐resolution Thermospheric Imaging (MIGHTI) instrument on the Ionospheric Connection Explorer (ICON) mission has been recently released, which largely avoids local‐time dependent artificial baseline drifts that are found in previous versions of the ICON/MIGHTI wind data. This paper describes monthly climatologies of zonal‐mean winds and tides based on the v05 ICON/MIGHTI data under geomagnetically quiet conditions (Hp30 〈 3o) during April 2020–March 2022. Green‐line winds in the lower thermosphere (90–110 km) and red‐line winds in the middle thermosphere (200–300 km) are analyzed, as these data cover both daytime and nighttime. The latitude and height structures of zonal‐mean winds and tides are presented for each month, and the results are compared with the widely used empirical model, Horizontal Wind Model 2014 (HWM14). The ICON/MIGHTI and HWM14 results are in general agreement, providing a validation of the v05 ICON/MIGHTI data. The agreement is especially good for the zonal‐mean winds. Amplitudes of lower thermospheric tides from ICON/MIGHTI tend to be larger than those from HWM14 as well as from an empirical model, Climatological Tidal Model of the Thermosphere (CTMT). This could be due to the influence of interannual variability of the tides. The amplitude structure of lower thermospheric tides in HWM14 does not match those from ICON/MIGHTI and CTMT in some months. Also, HWM14 underestimates the meridional‐wind amplitude of the migrating diurnal tide in the middle thermosphere. These results highlight the need for improved tidal representation in HWM14.〈/p〉
    Description: Key Points: 〈list list-type="bullet"〉 〈list-item〉 〈p xml:lang="en"〉Monthly climatologies of zonal‐mean winds and tides at 90–110 km and 200–300 km are determined using v05 Ionospheric Connection Explorer/Michelson Interferometer for Global High‐resolution Thermospheric Imaging (ICON/MIGHTI) observations〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉ICON/MIGHTI and Horizontal Wind Model 2014 results are in general agreement, providing a validation of the Version 5 ICON/MIGHTI data〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉The agreement is especially good for the zonal‐mean winds, while some discrepancies are found in tidal amplitudes〈/p〉〈/list-item〉 〈/list〉 〈/p〉
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: NASA
    Description: https://icon.ssl.berkeley.edu/Data
    Description: https://kp.gfz-potsdam.de/en/hp30-hp60/data
    Description: https://doi.org/10.5880/Hpo.0002
    Description: https://spaceweather.gc.ca/forecast-prevision/solar-solaire/solarflux/sx-5-mavg-en.php
    Description: https://globaldynamics.sites.clemson.edu/articles/ctmt.html
    Description: https://doi.org/10.5281/zenodo.5541913
    Keywords: ddc:551.5 ; thermosphere ; zonal‐mean winds ; tides ; ionospheric connection explorer (ICON) ; MIGHTI ; HWM14
    Language: English
    Type: doc-type:article
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    CITATION GEO-LEO
  • 3
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    September 2019 Antarctic sudden stratospheric warming: quasi-6-day wave burst and ionospheric effects (2020)
    In:  Geophysical Research Letters
    Details
    Publication Date: 2023-02-24
    Description: An exceptionally strong stationary planetary wave with Zonal Wavenumber 1 led to a sudden stratospheric warming (SSW) in the Southern Hemisphere in September 2019. Ionospheric data from European Space Agency's Swarm satellite constellation mission show prominent 6‐day variations in the dayside low‐latitude region at this time, which can be attributed to forcing from the middle atmosphere by the Rossby normal mode “quasi‐6‐day wave” (Q6DW). Geopotential height measurements by the Microwave Limb Sounder aboard National Aeronautics and Space Administration's Aura satellite reveal a burst of global Q6DW activity in the mesosphere and lower thermosphere during the SSW, which is one of the strongest in the record. The Q6DW is apparently generated in the polar stratosphere at 30–40 km, where the atmosphere is unstable due to strong vertical wind shear connected with planetary wave breaking. These results suggest that an Antarctic SSW can lead to ionospheric variability through wave forcing from the middle atmosphere.
    Type: info:eu-repo/semantics/article
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    CITATION PIK
  • 4
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    Search for squarks and gluinos in final states with one isolated lepton, jets, and missing transverse momentum at $$sqrt{s}=13$$ TeV with the ATLAS detector (2021)
    Springer
    Details
    Publication Date: 2021-07-01
    Description: The results of a search for gluino and squark pair production with the pairs decaying via the lightest charginos into a final state consisting of two W bosons, the lightest neutralinos ($$ilde{chi }^0_1$$ χ ~ 1 0 ), and quarks, are presented: the signal is characterised by the presence of a single charged lepton ($$e^{pm }$$ e ± or $$mu ^{pm }$$ μ ± ) from a W boson decay, jets, and missing transverse momentum. The analysis is performed using 139 fb$$^{-1}$$ - 1 of proton–proton collision data taken at a centre-of-mass energy $$sqrt{s}=13$$ s = 13   delivered by the Large Hadron Collider and recorded by the ATLAS experiment. No statistically significant excess of events above the Standard Model expectation is found. Limits are set on the direct production of squarks and gluinos in simplified models. Masses of gluino (squark) up to 2.2  (1.4 ) are excluded at 95% confidence level for a light $$ilde{chi }^0_1$$ χ ~ 1 0 .
    Print ISSN: 1434-6044
    Electronic ISSN: 1434-6052
    Topics: Physics
    Published by Springer
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    PAPER CURRENT
  • 5
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    Erratum to: Search for squarks and gluinos in final states with one isolated lepton, jets, and missing transverse momentum at $$sqrt{s}=13$$ TeV with the ATLAS detector (2021)
    Springer
    Details
    Publication Date: 2021-10-01
    Description: A correction to this paper has been published: 10.1140/epjc/s10052-021-09344-w
    Print ISSN: 1434-6044
    Electronic ISSN: 1434-6052
    Topics: Physics
    Published by Springer
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    PAPER CURRENT
  • 6
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    PCEEJ Equatorial Electrojet Model data for years 2003-2010 and 2014-2018 (2022)
    GFZ Data Services
    Details
    Publication Date: 2023-01-30
    Description: This dataset comprises the PCEEJ equatorial electrojet model current intensity values (mA/m). The PCEEJ is an empirical model based on the principal component analysis of satellite and ground equatorial electrojet data, described in detail in Soares et al. (2022), to which this data publication is supplement to. The model data is provided as text files (.csv extension) and Matlab-formatted files (.mat extension). For text files, there is one file per year (file name labeled with the corresponding year). For the Matlab format, there is only one Matlab file that contains all years as separate variables (variable name labeled with the corresponding year). Each yearly file/variable corresponds to a matrix: the rows represent local time/longitude bins and the columns represent days of year. The local time/longitude bins (rows) always sum up to 432 (12 local time intervals and 36 longitude intervals). The day of year (columns) always starts in January 1st and ends in December 31st, leading to a total of 365 or 366. The PCEEJ model values of 13 years from 2003 to 2010 and from 2014 to 2018 are provided. The PCEEJ basis functions (principal components) are provided in the text and Matlab files labeled as ‘PC\_Functions’. The ‘PC\_Functions’ data is given as a 432x10 matrix, in which 432 stands for the aforementioned local time/longitude bins and 10 represents the 10 principal components used to obtain the PCEEJ model (in ascending order). Two additional auxiliary indices, namely ‘lt\_index’ and ‘lon\_index’ are also contained as text and Matlab files. These indices represent the corresponding local time and longitude values of each row of the PCEEJ yearly files and ‘PC\_Functions’ files.
    Language: English
    Type: info:eu-repo/semantics/workingPaper
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  • 7
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    Ionospheric Current Variations by Empirical Orthogonal Function Analysis: Solar Activity Dependence and Longitudinal Differences (2022)
    In:  Journal of Geophysical Research: Space Physics
    Details
    Publication Date: 2023-01-30
    Description: The solar quiet (Sq) ionospheric current variations exhibit spatial and temporal patterns that can be identified by the prevailing eigenmodes based on the empirical orthogonal function (EOF) analysis. In this study, the Sq current function over the American and European/African sectors are derived using ground magnetometer data from 2006 to 2019 based on the spherical harmonic analysis technique. Subsequently, we decomposed the Sq current function into eigenmodes by applying the EOF analysis, where the first three eigenmodes capture 96% of the overall Sq current variance. Additionally, these eigenmodes are utilized to model the Sq current function and compare its properties between the two longitudinal sectors. We observed that the EOF model could reconstruct the observed Sq current function with the first three eigenmodes in both longitudinal sectors. Moreover, the EOF model unveils a clear association of the Sq current function with several driven features, such as magnetic latitude, local time, season, and solar activity. Both longitudinal sectors had comparable Sq current patterns under varying solar activity, while their amplitudes varied. Besides, the newly developed model could reproduce a refined Sq current variability over the two longitudinal sectors as long as the observed Sq variations have sufficient duration. Our EOF model shows that the variations of the Sq current function with solar activity can be explained by the first three eigenmodes, which could be used as a basis for further numerical modeling of the Sq current variations.
    Type: info:eu-repo/semantics/article
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  • 8
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    Geomagnetic Activity Index Hpo (2022)
    In:  Geophysical Research Letters
    Details
    Publication Date: 2023-01-30
    Description: The geomagnetic activity index Kp is widely used but is restricted by low time resolution (three-hourly) and an upper limit. To address this, new geomagnetic activity indices, Hpo, are introduced. Similar to Kp, Hpo expresses the level of planetary geomagnetic activity in units of thirds (0o, 0 + , 1 − , 1o, 1 + , 2 − , …) based on the magnitude of geomagnetic disturbances observed at subauroral observatories. Hpo has a higher time resolution than Kp. 30-minute (Hp30) and 60-minute (Hp60) indices are produced. The frequency distribution of Hpo is designed to be similar to that of Kp so that Hpo may be used as a higher time-resolution alternative to Kp. Unlike Kp, which is capped at 9o, Hpo is an open-ended index and thus can characterize severe geomagnetic storms more accurately. Hp30, Hp60 and corresponding linearly-scaled ap30 and ap60 are available, in near real time, at the GFZ website (https://www.gfz-potsdam.de/en/hpo-index).
    Type: info:eu-repo/semantics/article
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  • 9
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    Using principal component analysis of satellite and ground magnetic data to model the equatorial electrojet and derive its tidal composition (2022)
    In:  Journal of Geophysical Research: Space Physics
    Details
    Publication Date: 2023-01-30
    Description: The intensity of the equatorial electrojet (EEJ) shows temporal and spatial variability that is not yet fully understood nor accurately modeled. Atmospheric solar tides are among the main drivers of this variability but determining different tidal components and their respective time series is challenging. It requires good temporal and spatial coverage with observations, which, previously could only be achieved by accumulating data over many years. Here, we propose a new technique for modeling the EEJ based on principal component analysis (PCA) of a hybrid ground-satellite geomagnetic data set. The proposed PCA-based model (PCEEJ) represents the observed EEJ better than the climatological EEJM-2 model, especially when there is good local-time separation among the satellites involved. The amplitudes of various solar tidal modes are determined from PCEEJ based tidal equation fitting. This allows to evaluate inter- and intra-annual changes of solar tidal signatures in the EEJ. On average, the obtained time series of migrating and non-migrating tides agree with the average climatology available from earlier work. A comparison of tidal signatures in the EEJ with tides derived from neutral atmosphere temperature observations show a remarkable correlation for non-migrating tides such as DE3, DE2, DE4 and SW4. The results indicate that it is possible to obtain a meaningful EEJ spectrum related to solar tides for a relatively short time interval of 70 days.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 10
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    Geomagnetic Hpo index. V. 2.0 (2022)
    GFZ Data Services
    Details
    Publication Date: 2023-01-30
    Description: This data publication includes the half-hourly Hp30 and ap30 indices as well as the hourly Hp60 and ap60 indices, collectively denoted as Hpo. This 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 Yamazaki et al. (submitted), which serves as documentation of the Hpo. 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, https://doi.org/10.5880/Kp.0001). They are listed as contributors to this data publication. With the introduction of the DOI for the Hpo index (Matzka et al, 2021, https://doi.org/10.5880/Hpo.0001), this DOI landing page and the associated HTTPS 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.0002 identifies the current version. A format description and a version history are provided in the data download folder.
    Language: English
    Type: info:eu-repo/semantics/workingPaper
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