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Additional file 3: Figure B2. a and b Swarm B residuals dH of the horizontal component H of the geomagnetic field mapped for different levels of geomagnetic activity according to Sym-H index (|Sym-H| ≤ 5 nT and |Sym-H| ≥ 20 nT, respectively); c difference of dH distribution between disturbed (|Sym-H| ≥ 20 nT) and quiet conditions (|Sym-H| ≤ 5 nT). Residuals are displayed for SM latitudes between 50° S and 50° N and the whole DLT range.doi:10.6084/m9.figshare.c.3631688_d10.v1 fatcat:dlcolhaxizhn5p3cvn4xtycanm
Additional file 2: Figure C1. Swarm C residuals dY of the Eastward component Y of the geomagnetic field mapped according to IMF B y â B z polarity sectors. Residuals are displayed for SM latitudes between 50° S and 50° N and the whole DLT range.doi:10.6084/m9.figshare.c.3631688_d5 fatcat:m2nhdp2hhbb4tibs5uhi2pwkgu
Additional file 4: Figure C2. a and b Swarm C residuals dH of the horizontal component H of the geomagnetic field mapped for different levels of geomagnetic activity according to Sym-H index (|Sym-H| ≤ 5 nT and |Sym-H| ≥ 20 nT, respectively); c difference of dH distribution between disturbed (|Sym-H| ≥ 20 nT) and quiet conditions (|Sym-H| ≤ 5 nT). Residuals are displayed for SM latitudes between 50° S and 50° N and the whole DLT range.doi:10.6084/m9.figshare.c.3631688_d12 fatcat:gpxu3fumbbbytey66hv2hfj7da
Additional file 1: Figure B1. Swarm B residuals dY of the Eastward component Y of the geomagnetic field mapped according to IMF B y â B z polarity sectors. Residuals are displayed for SM latitudes between 50° S and 50° N and the whole DLT range.doi:10.6084/m9.figshare.c.3631688_d2.v1 fatcat:3lbcvt5bsjaothtlieiojufw7y
A complex system of electric currents flowing in the ionosphere and magnetosphere originates from the interaction of the solar wind and the Interplanetary Magnetic Field (IMF) with the Earth's magnetic field. These electric currents generate magnetic fields contributing themselves to those measured by both ground observatories and satellites. Here, low-resolution (1 Hz) magnetic vector data recorded between 1 March 2014 and 31 May 2015 by the recently launched Swarm constellation aredoi:10.1186/s40623-016-0484-3 fatcat:ymvlqpptqrciljdk36oqru66uy
more »... The core and crustal magnetic fields and part of that originating in the magnetosphere are removed from Swarm measurements using CHAOS-5 model. Low-and mid-latitude residuals of the geomagnetic field representing the ionospheric and the unmodelled magnetospheric contributions are investigated, in the Solar Magnetic frame, according to the polarity of IMF B y (azimuthal) and B z (north-south) components and to different geomagnetic activity levels. The proposed approach makes it possible to investigate the features of unmodelled contributions due to the external sources of the geomagnetic field. Results show, on one side, the existence of a relation between the analysed residuals and IMF components B y and B z , possibly due to the long distance effect of high-latitude field-aligned currents. On the other side, they suggest the presence of a contribution due to the partial ring current that is activated during the main phase of geomagnetic storms. The perturbation observed on residuals is also compatible with the effect of the net field-aligned currents. Moreover, we have quantitatively estimated the effect of these current systems on computed residuals. which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
Annals of Geophysics
Major geomagnetic storms drive rapid intensification and variability of magnetospheric and ionospheric current systems that give rise to large ground-induced currents (GIC). Space weather associated GIC pose a serious threat to the reliability of power-transmission systems and other electrically conducting infrastructure such as oil and gas pipelines. The most severe effects are observed at high latitudes due to ionospheric currents associated with the aurora. However, as power transmissiondoi:10.4401/ag-7788 fatcat:lhsqkltawvej3nchgkeca47q2e
more »... and pipeline infrastructure continues to grow at middle and low-latitudes, GIC hazards are no longer just concerns of high-latitude regions. We investigate how GIC amplitude varies in latitude during six major geomagnetic storms that occurred between 1989 and 2004. Due to limited direct GIC measurements, a proxy of the geoelectric field is used, i.e. the GIC index. This is calculated for the selected geomagnetic storms using 25 magnetic observatories relatively uniformly distributed in geomagnetic latitude, 14 magnetic observatories with longitudes varying within a range of 45 degrees as well as for the 7 November 2004 storm using 104 observatories. In addition, we suggest a possible way to follow the latitudinal displacement of the auroral oval during geomagnetic storms through the maximum value of GIC index, estimated over 2-hour intervals on a wide number of magnetic observatories.
The ESA Swarm mission provides a qualitatively new level of observational 3 geomagnetic data, which allows us to study the spatial features of magnetic 4 field fluctuations, capturing their essential characteristics and at the same 5 time establishing a correlation with the dynamics of the systems responsi-6 ble for the fluctuations. Our study aims to characterize changes in the scal-7 ing properties of the geomagnetic field's spatial fluctuations by evaluating 8 the local Hurst exponent, anddoi:10.1002/2015gl063603 fatcat:oeo3vvcounga7fxuwraw36eafi
more »... construct maps of this index at the Swarm's 9 altitude (∼ 460 km). Since a signal with a larger Hurst exponent is more 10 regular and less erratic than a signal with a smaller one, the maps permit 11 us to localize spatial structures characterized by different scaling properties. 12 This study is an example of the potential of Swarm data to give new insights 13 into ionosphere-magnetosphere coupling; at the same time, it develops new 14 applications where changes in statistical parameters can be used as a local 15 indicator of overall magnetospheric-ionospheric coupling conditions.
AbstractThe nervous system is one of the most complex expressions of biological evolution. Its high performance mostly relies on the basic principle of the action potential, a sequential activation of local ionic currents along the neural fiber. The implications of this essentially electrical phenomenon subsequently emerged in a more comprehensive electromagnetic perspective of neurotransmission. Several studies focused on the possible role of photons in neural communication and provideddoi:10.1038/s41598-021-82622-5 pmid:33542392 fatcat:6y76lsnfc5er3jgqhabfuumepi
more »... e of the transfer of photons through myelinated axons. A hypothesis is that myelin sheath would behave as an optical waveguide, although the source of photons is controversial. In a previous work, we proposed a model describing how photons would arise at the node of Ranvier. In this study we experimentally detected photons in the node of Ranvier by Ag+ photoreduction measurement technique, during electrically induced nerve activity. Our results suggest that in association to the action potential a photonic radiation takes place in the node.
Field-aligned currents (FACs) flowing in the auroral ionosphere are a complex system of upward and downward currents, which play a fundamental role in the magnetosphere–ionosphere coupling and in the ionospheric heating. Here, using data from the ESA-Swarm multi-satellite mission, we studied the complex structure of FACs by investigating sign-singularity scaling features for two different conditions of a high-latitude substorm activity level as monitored by the AE index. The results clearlydoi:10.3390/atmos12060708 fatcat:t3ytbgaydjacbjwh5clkqdorsi
more »... ed the sign-singular character of FACs supporting the complex and filamentary nature of these currents. Furthermore, we found evidence of the occurrence of a topological change of these current systems, which was accompanied by a change of the scaling features at spatial scales larger than 30 km. This change was interpreted in terms of a sort of symmetry-breaking phenomenon due to a dynamical topological transition of the FAC structure as a consequence of FACs and substorm current wedge intensification during substorms.
Complexity and multi-scale are very common properties of several geomagnetic time series. On the other hand, it is amply demonstrated that scaling properties of geomagnetic time series show significant changes depending on the geomagnetic activity level. Here, we study the multiscale features of some large geomagnetic storms by applying the empirical mode decomposition technique. This method, which is alternative to traditional data analysis and is designed specifically for analyzing nonlineardoi:10.1029/2008ja013074 fatcat:inxdmq7uojb6vf4ledsx5zhwke
more »... nd nonstationary data, is applied to long time series of Sym-H index relative to periods including large geomagnetic disturbances. The spectral and scaling features of the intrinsic mode functions (IMFs) into which Sym-H time series can be decomposed, as well as those of the Sym-H time series itself, are studied considering different geomagnetic activity levels. The results suggest an increase of dynamical complexity and multi-scale properties for intermediate geomagnetic activity levels.
Andrea Zangari (A), Roberta Galeazzi (C), Antonio Tozzi(D) provided critical recommendation on data results' significance in relation to current available literature. ...doi:10.1038/s41598-017-18866-x pmid:29323217 pmcid:PMC5764955 fatcat:qstyvljxwrhorawvj32zgqq7da
Annals of Geophysics
The magnetosphere−ionosphere system is recognized as a complex and active element affected by space weather and as a region where important scientific questions related to space weather impacts need to be answered. In this framework, there is a high priority on the un− derstanding of how local, regional, and global−scale phenomena couple to produce observed responses across various scales. Turbulence provides one pathway by which energy cascades across scales from large to small ones wheredoi:10.4401/ag-7789 fatcat:ityuzt7hnjaxli2upe66j43tri
more »... y can be dissipated in the form of heat− ing. The Swarm mission, that is a true multi−point and multi−purpose constellation, represents a unique opportunity to address some of these scientific questions. In detail, it gives us a chance of investigating the nature and the scaling features of magnetic field fluctuations for different geomagnetic activity levels, and unveiling the role played by turbulence of ionospheric plasma medium on the magnetic field fluctuations. Recently, using Swarm magnetic field data at high−latitude in the Northern Hemisphere, the local scaling indices of the 1 st and 2 nd order structure functions of the magnetic field fluctuations have been evaluated, showing their capability both to give new in− sights about the ionosphere−magnetosphere coupling and to provide information on the ionospheric turbulence. Here, we improve and ex− tend the analysis by investigating the scaling features of the geomagnetic field fluctuations of external origin, recorded by Swarm A satellite during a period of 2 years (April 2014 -March 2016. Maps of the local Hurst exponent values, which allow us to study scaling properties of the geomagnetic field's spatial fluctuations are shown, both at high−latitudes (in the Northern and Southern Hemisphere) and at low− and mid−latitudes (±60°) according to two different geomagnetic activity conditions. The aim is to capture the essential features of the spatial fluctuations of the geomagnetic field and understand their origins.
From the very first measurements made by the magnetometers onboard Swarm satellites launched by European Space Agency (ESA) in late 2013, it emerged a discrepancy between scalar and vector measurements. An accurate analysis of this phenomenon brought to build an empirical model of the disturbance, highly correlated with the Sun incidence angle, and to correct vector data accordingly. The empirical model adopted by ESA results in a significant decrease in the amplitude of the disturbancedoi:10.1186/s40623-016-0583-1 fatcat:dk6zrabaqjbrve4j6tclpfnri4
more »... g VFM measurements so greatly improving the vector magnetic data quality. This study is focused on the characterization of the difference between magnetic field intensity measured by the absolute scalar magnetometer (ASM) and that reconstructed using the vector field magnetometer (VFM) installed on Swarm constellation. Applying empirical mode decomposition method, we find the intrinsic mode functions (IMFs) associated with ASM-VFM total intensity differences obtained with data both uncorrected and corrected for the disturbance correlated with the Sun incidence angle. Surprisingly, no differences are found in the nature of the IMFs embedded in the analyzed signals, being these IMFs characterized by the same dominant periodicities before and after correction. The effect of correction manifests in the decrease in the energy associated with some IMFs contributing to corrected data. Some IMFs identified by analyzing the ASM-VFM intensity discrepancy are characterized by the same dominant periodicities of those obtained by analyzing the temperature fluctuations of the VFM electronic unit. Thus, the disturbance correlated with the Sun incidence angle could be still present in the corrected magnetic data. Furthermore, the ASM-VFM total intensity difference and the VFM electronic unit temperature display a maximal shared information with a time delay that depends on local time. Taken together, these findings may help to relate the features of the observed VFM-ASM total intensity difference to the physical characteristics of the real disturbance thus contributing to improve the empirical model proposed for the correction of data. which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
AbstractThe present work focuses on the analysis of the scaling features of electron density fluctuations in the mid- and high-latitude topside ionosphere under different conditions of geomagnetic activity. The aim is to understand whether it is possible to identify a proxy that may provide information on the properties of electron density fluctuations and on the possible physical mechanisms at their origin, as for instance, turbulence phenomena. So, we selected about 4 years (Aprildoi:10.1038/s41598-021-84985-1 pmid:33731772 fatcat:5tmii5cn2be6tgs3vblxmdr4mi
more »... y 2018) of 1 Hz electron density measurements recorded on-board ESA Swarm A satellite. Using the Auroral Electrojet (AE) index, we identified two different geomagnetic conditions: quiet (AE < 50 nT) and active (AE > 300 nT). For both datasets, we evaluated the first- and second-order scaling exponents and an intermittency coefficient associated with the electron density fluctuations. Then, the joint probability distribution between each of these quantities and the rate of change of electron density index was also evaluated. We identified two families of plasma density fluctuations characterized by different mean values of both the scaling exponents and the considered ionospheric index, suggesting that different mechanisms (instabilities/turbulent processes) can be responsible for the observed scaling features. Furthermore, a clear different localization of the two families in the magnetic latitude—magnetic local time plane is found and its dependence on geomagnetic activity levels is analyzed. These results may well have a bearing about the capability of recognizing the turbulent character of irregularities using a typical ionospheric plasma irregularity index as a proxy.
The ionospheric plasma density irregularities are known to play a role in the propagation of electromagnetic signals and to be one of the most important sources of disturbance for the Global Navigation Satellite System, being responsible for degradation and, sometimes, interruptions of the signals received by the system. In the equatorial ionospheric F region, these plasma density irregularities, known as plasma bubbles, find the suitable conditions for their development during post-sunsetdoi:10.3390/rs14040918 fatcat:xwggs7nubrfolpxzdkurasrewm
more »... . In recent years, important features of plasma bubbles such as their dependence on latitude, longitude, and solar and geomagnetic activities have been inferred indirectly using their magnetic signatures. Here, we study the scaling properties of both the electron density and the magnetic field inside the plasma bubbles using measurements on board the Swarm A satellite from 1 April 2014 to 31 January 2016. We show that the spectral features of plasma irregularities cannot be directly inferred from their magnetic signatures. A relation more complex than the linear one is necessary to properly describe the role played by the evolution of plasma bubbles with local time and by the development of turbulent phenomena.
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