Swarm Satellite Data Research Articles

Correction: Lithospheric magnetic anomaly map of Indian subcontinent (LAMI-1) from Swarm satellite data

Correction: Lithospheric magnetic anomaly map of Indian subcontinent (LAMI-1) from Swarm satellite data

Lithospheric magnetic anomaly map of Indian subcontinent (LAMI-1) from Swarm satellite data

Lithospheric magnetic anomaly map of Indian subcontinent (LAMI-1) from Swarm satellite data

Study of the response of the upper atmosphere during the annular solar eclipse on October 14, 2023

A solar eclipse is a fascinating event that gives a unique opportunity to study the ionospheric characteristics in a controlled blockage of solar radiation. We present the upper atmosphere’s response, mostly F-layer, during the annular eclipse on October 14, 2023. This eclipse was mostly visible from the North and South American regions with a maximum obscuration of around 91%. We study the response of the ionospheric Total Electron Content (TEC) and the critical frequency of the F2 layer (f0F2) for three consecutive days (October 13 to 15, 2023) using ground and space-based techniques. We present the ionospheric response for a large area that covers the path of the solar eclipse of latitude and longitude range from 50°N to 10°S and 30°W to 150°W. For the ground-based observation, we use fifty-five International GNSS Service (IGS) stations and eleven Global Ionospheric Radio Observatory (GIRO) Digisonde stations that cover the annular and partial solar eclipse and are in the close vicinity of the annularity belt. We compute the vertical TEC (VTEC) and f0F2 from this database and check their temporal and spatial variations. It is found that the VTEC, as computed from the IGS stations, mostly shows decrements during the partial blockage of the sun by the lunar disc. The VTEC, as computed from the GIRO database, also shows a decreasing trend but with comparatively more oscillating in nature. The f0F2 shows a similar decreasing trend due to the solar eclipse. For space-based observation, we use the Swarm satellite data for the tracks that have gone through the annularity belt. Also, a spatiotemporal study is executed using the Global Ionospheric Map (GIM) database. For both cases, the VTEC shows a prominent depletion. We investigate the variation in the percentage change in VTEC as a function of obscuration and observe a positive correlation between them. We also compute the time difference between the maximum eclipse and the maximum TEC modulation to investigate the response time profiles of the ionosphere at different receiving stations. All the methods give satisfactory and consistent outcomes that corroborate the physical mechanism of ionospheric variabilities due to the effect of the solar eclipse. We check the geomagnetic condition to eliminate the scope of contamination and observe that their values are normal during the study.

Online system for analyzing currents in the upper ionosphere according to Swarm satellite data

In this paper, we describe the TeslaSwarm online system [http://aleph.gcras.ru/teslaswarm] for visualizing field-aligned currents in the upper ionosphere, using data from Swarm low-orbit satellites. The system provides researchers with a simple and convenient tool for event selection and detailed analysis of currents and electromagnetic fields in the upper ionosphere. The system user can select satellite passages over a given region, visualize the geomagnetic field structure and field-aligned currents, compare the pattern of field-aligned currents with the auroral particle precipitation map, using the OVATION-Prime model, and save the selected parameters in a file in text format. We demonstrate advantages of the developed system over its foreign analogues. In practice, the collection and pre-processing of raw data for experiments make up about 80 % of all work with data. The proposed online system largely saves the user from the most time-consuming work of choosing the required satellite passage segments and calculating the characteristics of interest from raw measurements.

Ionosphere Heterogeneities at Dawn−Dusk Terminator Related to the Starlink Satellites Launch Disaster on 3−8 February 2022

AbstractWe present an analysis of the evolution of the ionospheric Total Electron Content (TEC) and its variability index Vσ during the Starlink launch disaster on 3–8 February 2022 two‐phase geomagnetic storm. JPL GIM‐TEC global maps with increased spatial (1° in latitude and longitude) and temporal (15 min cadence) resolution as well as SWARM satellite data have been used in the analysis. Comparison of data for five time periods including Starlink launches with geomagnetic Dst index demonstrates thermospheric mass densities increasing by about 50% during the development of the storm on 3–5 February. A spectrum periodogram analysis is applied on TEC at sunrise and sunset solar terminator (STh) at an altitude h = 300 km. Periodicities in the solar terminator TEC generated waves are estimated as 24 hr, 12 hr, 1 hr, 30 min, 20 min, and 15 min. A significant morning−evening asymmetry resulted in the density anomalies concentrated in a certain—evening—sector of terminator when plasma is shifted to the dusk side forming a global asymmetry.

Preliminary study of topside ionospheric variations using SWARM satellites over the Malaysia Region

The European Space Agency (ESA) launched a satellite constellation mission called Swarm in 2013. The Swarm satellites named A, B and C are equipped with Global Positioning System (GPS) receivers which can be used to study the topside of the ionosphere. In Malaysia, the use of ionospheric data from the Swarm satellites is still new as most researchers previously used GPS receivers on the Earth. This paper presents the preliminary result of topside-ionosphere parameter, Total Electron Content (TEC) over Malaysia using the Swarm satellite data. TEC from the Swarm data were analyzed during quiet and disturbed geomagnetic days. The results showed that the Swarm satellites passed through Malaysia twice in 24 hours and the variations of TEC over Malaysia ranged from 2 to 20 TECU. Analysis of the topside ionosphere during a geomagnetic storm showed a sudden decreased of TEC compared to the quiet days. The findings indicate that the variations of topside TEC using Swarm are in agreement with those found in previous studies.

Analysis of Potential Precursory Pattern at Earth Surface and the Above Atmosphere and Ionosphere Preceding Two Mw ≥ 7 Earthquakes in Mexico in 2020–2021

AbstractComprehensive analyses of seismic precursory characteristics may provide evidence for the possible mechanisms of lithosphere‐atmosphere‐ionosphere coupling (LAIC). The integrated monitoring data from space and ground measurements makes it possible to reveal the potential earthquake precursory pattern obeying LAIC. In this paper, we study seismic precursors from air temperature data of the National Center for Environmental Prediction (NCEP), Global Navigation Satellite System (GNSS) based Total Electron Content (TEC) and electron density retrieved from Swarm satellite (Alpha) data in two Mw 7.0 earthquakes in Mexico in 2020–2021. We find seismic thermal anomalies can be identified from temperature variation in the lithosphere and atmosphere by improved tidal force fluctuant analysis (TFFA). The spatial‐temporal evolution of seismic thermal anomalies is significantly different from that of non‐seismic thermal anomalies. In addition, synergistic observations of the Swarm Alpha satellite and GNSS stations can provide more comprehensive information about perturbations in the ionosphere. The results show that anomalies originate along fault lineaments near the epicenter, leading to air pressure gradient and ionization process in the atmosphere, followed by ionospheric perturbations. Furthermore, composite anomalies of LAIC first appear around a month before earthquakes and tend to recur several times over earthquake preparation phases. Our study provides more evidence for understanding the characteristics of earthquake precursors.

Core Surface Flow Changes Associated With the 2017 Pacific Geomagnetic Jerk.

A geomagnetic jerk was seen in Swarm satellite data in 2017 over the Pacific region. We invert time series of spatial gradient secular variation data between 2014 and 2020, reduced to a grid of points at satellite altitude, for spatially‐ and temporally‐regularized core surface flow. Pacific region flow acceleration was almost constant before and after the jerk, with a sharp change, especially in the azimuthal component, at the jerk epoch, despite the temporal regularization. Azimuthal acceleration is oppositely signed either side of 160°W, where it effectively vanishes, and also reverses sign at the jerk epoch. Acceleration features drift westward at about 900 km year−1. Unlike previous studies, the evidence presented here for low latitude waves does not depend on imposing flow equatorial symmetry, quasi‐ or tangential geostrophy, or band‐pass filtering, and has no reliance on stochastic models or numerical simulations.

Detection of Different Properties of Ionospheric Perturbations in the Vicinity of the Korean Peninsula After the Hunga‐Tonga Volcanic Eruption on 15 January 2022

AbstractThis study reports different properties of ionospheric perturbations detected to the west and south of the Korean Peninsula after the Hunga‐Tonga volcanic eruption on 15 January 2022. Transient wave‐like total electron content (TEC) modulations and intense irregular TEC perturbations are detected in the west and south of the Korean Peninsula, respectively, about 8 hr after the eruption. The TEC modulations in the west propagate away from the epicenter with a speed of 302 m/s. Their occurrence time, propagation direction and velocity, and alignment with the surface air pressure perturbations indicate the generation of the TEC modulations by Lamb waves generated by the eruption. The strong TEC perturbations and L band scintillations in the south are interpreted in terms of the poleward extension of equatorial plasma bubbles (EPBs). We demonstrate the association of the EPBs with the volcanic eruption using the EPB occurrence climatology derived from Swarm satellite data.

Rainbow of the Night: First Direct Observation of a SAR Arc Evolving Into STEVE

AbstractDuring the 17 March 2015 geomagnetic storm, citizen scientist observations from Dunedin (45.95°S, 170.32°E), New Zealand, revealed a bright wide red arc known as stable auroral red (SAR) arc evolving into a thin white‐mauve arc, known as Strong Thermal Emission Velocity Enhancement (STEVE). An all‐sky imager at the Mount John Observatory (43.99°S, 170.46°E), 200 km north of Dunedin, detected an extremely bright arc in 630.0 nm, with a peak of ∼6 kR, colocated with the arc measured at Dunedin at an assumed height of 425 km. Swarm satellite data measured plasma parameters that showed strong subauroral ion drift signatures when the SAR arc was observed. These conditions intensified to extremely high values in a thinner channel when STEVE was present. Our results highlight the fast evolution of plasma properties and their effects on optical emissions. Current theories and models are unable to reproduce or explain these observations.

Worldwide Statistical Correlation of Eight Years of Swarm Satellite Data with M5.5+ Earthquakes: New Hints about the Preseismic Phenomena from Space

Nowadays, the possibility that medium-large earthquakes could produce some electromagnetic ionospheric disturbances during their preparatory phase is controversial in the scientific community. Some previous works using satellite data from DEMETER, Swarm and, recently, CSES provided several pieces of evidence supporting the existence of such precursory phenomena in terms of single case studies and statical analyses. In this work, we applied a Worldwide Statistical Correlation approach to M5.5+ shallow earthquakes using the first 8 years of Swarm (i.e., from November 2013 to November 2021) magnetic field and electron density signals in order to improve the significance of previous statistical studies and provide some new results on how earthquake features could influence ionospheric electromagnetic disturbances. We implemented new methodologies based on the hypothesis that the anticipation time of anomalies of larger earthquakes is usually longer than that of anomalies of smaller magnitude. We also considered the signal’s frequency to introduce a new identification criterion for the anomalies. We find that taking into account the frequency can improve the statistical significance (up to 25% for magnetic data and up to 100% for electron density). Furthermore, we noted that the frequency of the Swarm magnetic field signal of possible precursor anomalies seems to slightly increase as the earthquake is approaching. Finally, we checked a possible relationship between the frequency of the detected anomalies and earthquake features. The earthquake focal mechanism seems to have a low or null influence on the frequency of the detected anomalies, while the epicenter location appears to play an important role. In fact, land earthquakes are more likely to be preceded by slower (lower frequency) magnetic field signals, whereas sea seismic events show a higher probability of being preceded by faster (higher frequency) magnetic field signals.

Local Persistent Ionospheric Positive Responses to the Geomagnetic Storm in August 2018 Using BDS-GEO Satellites over Low-Latitude Regions in Eastern Hemisphere

We present the ionospheric disturbance responses over low-latitude regions by using total electron content from Geostationary Earth Orbit (GEO) satellites of the BeiDou Navigation Satellite System (BDS), ionosonde data and Swarm satellite data, during the geomagnetic storm in August 2018. The results show that a prominent total electron content (TEC) enhancement over low-latitude regions is observed during the main phase of the storm. There is a persistent TEC increase lasting for about 1–2 days and a moderately positive disturbance response during the recovery phase on 27–28 August, which distinguishes from the general performance of ionospheric TEC in the previous storms. We also find that this phenomenon is a unique local-area disturbance of the ionosphere during the recovery phase of the storm. The enhanced foF2 and hmF2 of the ionospheric F2 layer is observed by SANYA and LEARMONTH ionosonde stations during the recovery phase. The electron density from Swarm satellites shows a strong equatorial ionization anomaly (EIA) crest over the low-latitude area during the main phase of storm, which is simultaneous with the uplift of the ionospheric F2 layer from the SANYA ionosonde. Meanwhile, the thermosphere O/N2 ratio shows a local increase on 27–28 August over low-latitude regions. From the above results, this study suggests that the uplift of F layer height and the enhanced O/N2 ratio are possibly main factors causing the local-area positive disturbance responses during the recovery phase of the storm in August 2018.

Spatio-temporal development of large-scale auroral electrojet currents relative to substorm onsets

Abstract. During auroral substorms, the electric currents flowing in the ionosphere change rapidly, and a large amount of energy is dissipated in the auroral ionosphere. An important part of the auroral current system is the auroral electrojets whose profiles can be estimated from magnetic field measurements from low-earth orbit satellites. In this paper, we combine electrojet data derived from the Swarm satellite mission of the European Space Agency with the substorm database derived from the SuperMAG ground magnetometer network data. We organize the electrojet data in relation to the location and time of the onset and obtain statistics for the development of the integrated current and latitudinal location for the auroral electrojets relative to the onset. The major features of the behaviour of the westward electrojet are found to be in accordance with earlier studies of field-aligned currents and ground magnetometer observations of substorm temporal statistics. In addition, we show that, after the onset, the latitudinal location of the maximum of the westward electrojet determined from Swarm satellite data is mostly located close to the SuperMAG onset latitude in the local time sector of the onset regardless of where the onset happens. We also show that the SuperMAG onset corresponds to a strengthening of the order of 100 kA in the amplitude of the median of the westward integrated current in the Swarm data from 15 min before to 15 min after the onset.

A regional geomagnetic field model over Southern Africa derived with harmonic splines from Swarm satellite and ground-based data recorded between 2014 and 2019

A regional harmonic spline geomagnetic main field model, Southern Africa Core Field Model (SACFM-3), is derived from Swarm satellite and ground-based data for the southern African region, in the eastern part of the South Atlantic Anomaly (SAA) where the field intensity continues to decrease. Using SACFM-3 and the global CHAOS-6-×9 model, a detailed study was conducted to shed light on the high spatial and temporal geomagnetic field variations over Southern Africa between 2014 and 2019. The results show a steady decrease of the radial component Z in almost the entire region. In 2019, its rate of decrease in the western part of the region has reached high values, 76 nT/year and 78 nT/year at Tsumeb and Keetmanshoop magnetic observatories, respectively. For some areas in the western part of the region the radial component Z and field intensity F have decreased in strength, from 1.0 to 1.3% and from 0.9 to 1.2%, respectively, between the epochs 2014.5 and 2019.5. There is a noticeable decrease of the field intensity from the south-western coast of South Africa expanding towards the north and eastern regions. The results show that the SAA area is continuing to grow in the region. Abrupt changes in the linear secular variation in 2016 and 2017 are confirmed in the region using ground-based data, and the X component shows an abrupt change in the secular variation in 2018 at four magnetic observatories (Hermanus, Hartebeesthoek, Tsumeb and Keetmanshoop) that needs further investigation. The regional model SACFM-3 reflects to some extent these fast core field variations in the Z component at Hermanus, Hartebeesthoek and Keetmanshoop observatories.Graphical

A study to investigate the relationship between ionospheric disturbance and seismic activity based on Swarm satellite data

The 7 years electron density data observed by the Swarm constellation and 527 earthquakes with M ≥ 6.0 are used to investigate the relationship between ionospheric disturbances and seismic events. The disturbances of the ionospheric electron density, defined as the difference between the orbital observation data and its fitting data, are considered to be possible signals of the seismic activity and are often reported before or after earthquakes near the epicenter. To investigate the relationship between them, the spatial distribution characteristics of the disturbances are analysed, taking into account the influence of solar and geomagnetic activity on the disturbances; the variation characteristics of the disturbances in seismic and non-seismic regions are compared; the numbers of the disturbances before and after earthquakes are statistically analysed; and the statistical results of different earthquake groups are verified by comparison with random events. Finally, according to these analysis results, it can be concluded that most of the disturbances are related to ionospheric activities; some of disturbances are indeed related to seismic activity; the disturbances caused by seismic activities usually appear before the earthquakes. In terms of standardized probability, the results for M ≥ 6 earthquakes and sea earthquakes are most significant, exceeding two times the standard deviation at least 10 and 25 days before the earthquake, while the results for deep earthquakes (D ≥ 60 km) and land earthquakes are not significant. However, the disturbances caused by seismic activities are very weak and are hidden in those strong ionospheric activities. Therefore, the seismic ionospheric phenomena are so difficult to extract and identify, and more caution should be taken in the identification in future seismo-ionospheric phenomena research.

A Spherical Harmonic Model of Earth's Lithospheric Magnetic Field up to Degree 1050

AbstractDetailed mapping of the Earth's magnetic field brings key constraints on the composition, dynamics, and history of the crust. Satellite and near‐surface measurements detect different length scales and are complementary. Here, we build a model, selecting and processing magnetic field measurements from the German CHAMP and ESA Swarm satellites, which we merge with near‐surface scalar anomaly data. We follow a regional approach for modeling the magnetic field measurements and next transform the series of regional models into a unique set of spherical harmonic (SH) Gauss coefficients. This produces the first global model to SH degree 1050 derived by inversion of all available measurements. The new model agrees with previous satellite‐based models at large wavelengths and fits the CHAMP and Swarm satellite data down to expected noise levels. Further assessment in the geographical and spectral domains shows the model to be stable when downward continued to the Earth's surface.

Spatial Structure of Polarization Jet according to NorSat-1 and Swarm Satellite Data

Spatial Structure of Polarization Jet according to NorSat-1 and Swarm Satellite Data

Indonesian Earth’s Lithospheric Magnetic Field modelling using Spherical Cap Harmonic Analysis Method

The earth’s lithospheric magnetic field is part of the main earth’s magnetic field. The lithospheric field has a very small value compared to the Earth’s main magnetic field, approximately less than 1%, and this field is generated at the earth’s crust and upper mantle. Modelling of lithospheric field is useful mainly for predicting the distribution of the value of lithospheric fields and to determine the magnetic anomaly. In this research, modelling the Earth’s lithospheric magnetic field uses Spherical Cap Harmonic Analysis (SCHA) method and this method can do modelling using regional magnetic data. The data used for the modelling are magnetic repeat station data in Indonesia region (BMKG’s Epoch) and SWARM satellite data. The results of the modelling using integrated SWARM satellite and repeat station data produce RMSE values of 64.0834 nT and the expansion of index K is 70. In addition, the results of the modelling resolution is 1.50. The value’s range of modelling’s result are -987.192 – 998.239 nT for X component, -968.189 – 949.438 nT for Y component, -981.266 – 608.676 nT for Z component, and -904.151 – 997.389 nT for total intensity are.

Signs of a new geomagnetic jerk between 2019 and 2020 from Swarm and observatory data

Following the observed pattern of a new geomagnetic jerk every 3–4 years, certain predictions suggested that a new event should occur around 2020 after the one observed around 2017.5. In this work, we explore this scenario by analysing the secular variation of the East geomagnetic field component in both ground and satellite geomagnetic data. At ground, we use the available data from 2015 to 2021 in 10 observatories worldwide distributed. This analysis shows the occurrence of the mentioned jerk in mid-2017 at observatories located in the Pacific region, but also reveals a new jerk between mid-2019 and early 2020 with a clear global character. Swarm satellite data also corroborate these findings by means of the secular variation estimated using virtual observatories at 440 km altitude. In addition, a general view using the most recent CHAOS geomagnetic model confirms the global character of the 2020-jerk with V-shaped secular variation changes in meridional sectors covering the Eastern Pacific, America, Asia and the Indian Ocean; and Λ-shapes in Europe, Africa and Western Pacific. The radial geomagnetic field at the core–mantle boundary is investigated as the origin of the new jerk. Results show that the global-average secular acceleration of the radial field exhibits a new pulse at mid-2018, establishing the starting epoch of the 2020-jerk.

Multispacecraft Current Density Estimates in the Low‐ and Mid‐Latitude F‐Region Ionosphere Using the Swarm Constellation

AbstractWe present a new application of a multispacecraft method which provides estimates of the full electric current density vector in the ionospheric low‐ and mid‐latitude F region. The method uses the three satellites of the Swarm constellation in configurations when they were close to each other. The current density is calculated inside triangular prisms defined by the satellite positions. The technique is inspired by similar approaches such as the curlometer. Here, we propose an alternative mathematical treatment, which involves the use of the well‐known curl‐B technique and a least squares minimization. The proposed formalism provides a rigorous way to propagate the errors through the problem and special care is taken to validate the algorithm and assess the relevance of the derived currents. Such techniques are powerful tools to study the F‐region ionosphere currents as they naturally exclude all the other contributions outside the considered volumes. The F region is known to host currents with a complex spatiotemporal variability. Besides the intrinsic interest of this system itself, understanding the dynamics of these currents is also critical for global geomagnetic field modeling as they are an important source of error in the models. In this paper, we present the full algorithm and test the method on both synthetic and real Swarm satellite data on February 15, 2014. Several sources of error are investigated. Additionally, the results reveal expected characteristics of F‐region interhemispheric field‐aligned currents. Some new characteristics of F‐region currents, potentially associated with dynamo and pressure currents, are also observed.