The 12th generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2014 by the Working Group V-MOD appointed by the International Association of Geomagnetism and Aeronomy (IAGA). It updates the previous IGRF generation with a definitive main field model for epoch 2010.0, a main field model for epoch 2015.0, and a linear annual predictive secular variation model for 2015.0-2020.0. Here, we present the equations defining the IGRF model, provide the spherical harmonic coefficients, and provide maps of the magnetic declination, inclination, and total intensity for epoch 2015.0 and their predicted rates of change for 2015.0-2020.0. We also update the magnetic pole positions and discuss briefly the latest changes and possible future trends of the Earth’s magnetic field.
In December 2019, the International Association of Geomagnetism and Aeronomy (IAGA) Division V Working Group (V-MOD) adopted the thirteenth generation of the International Geomagnetic Reference Field (IGRF). This IGRF updates the previous generation with a definitive main field model for epoch 2015.0, a main field model for epoch 2020.0, and a predictive linear secular variation for 2020.0 to 2025.0. This letter provides the equations defining the IGRF, the spherical harmonic coefficients for this thirteenth generation model, maps of magnetic declination, inclination and total field intensity for the epoch 2020.0, and maps of their predicted rate of change for the 2020.0 to 2025.0 time period.
The scientific research of geomagnetism has been largely driven by new geomagnetic data that are available to scientists. Macau Science Satellite-1 (MSS-1) was successfully launched on 21st May 2023 into a near-circular orbit of altitude of about 450 km with a low inclination of 41°. After careful evaluation and calibration (7th June 2023 to 31st July 2024), the data of MSS-1 were released to the international scientific community on 1 August 2024, providing the highly accurate data of global geomagnetic field with an unprecedented local-time coverage to the community. This special issue of Initial Scientific Results of MSS-1, primarily driven by the new MSS-1 data, contains 27 research articles ranging from the MSS-1 design, satellite data analysis, outer core dynamics, mantle induction, lithospheric field modeling, ocean induced magnetic field, ionosphere and magnetosphere currents, to solar activities.
William Brown, Susan Macmillan, Eleanor Maume
et al.
Abstract This work brings together the contents of previously disparate databases of absolute ground geomagnetic observations, both historic and ongoing, to process the data consistently into a coherent and accessible format for researchers. This includes converting reported time resolutions and coordinate systems into a uniform format, and applying all documented observatory baseline changes to the data records, to create a single unified vector time series of monthly mean values for each geomagnetic observatory. The data are made available freely and anonymously to researchers via a web service, updated on a monthly basis with the latest definitive and non-definitive observations reported to the World Data Centre for Geomagnetism (Edinburgh) and INTERMAGNET or Tromsø Geophysical Observatory, respectively. The current database covers 327 observatories worldwide, with observations from 1883 up until present. A separate effort involved digitising tables of monthly means in the 1841–1925 yearbooks of the Royal Observatory, Greenwich, United Kingdom and converting to homogeneous units. The resulting data represent some of the earliest magnetic data at monthly time resolution and may be of use to future studies. However, they cannot be incorporated into the monthly means database as the field vector information is incomplete; we publicise them here instead. Graphical Abstract
Frederick J. Rich, Samuel Califf, Paul T. M. Loto'aniu
et al.
Abstract GOES‐16 and GOES‐17 are the first of NOAA's Geostationary Operational Environmental Satellite (GOES)‐R series of satellites. Each GOES‐R satellite has a magnetometer mounted on the end (outboard) and one part‐way down a long boom (inboard). This paper demonstrates the relative accuracy and stability of the measurements on a daily and long‐term basis. The GOES‐16 and GOES‐17 magnetic field observations from 2017 to 2020 have been compared to simultaneous magnetic field observations from each other and from the previous GOES‐NOP series satellites (GOES‐13, GOES‐14 and GOES‐15). These comparisons provide assessments of relative accuracy and stability. We use a field model to facilitate the inter‐satellite comparisons at different longitudes. GOES‐16 inboard and outboard magnetometers data suffer daily variations which cannot be explained by natural phenomena. Long‐term‐averaged GOES‐16 outboard (OB) data has daily variations of ±3 nT from average values with one‐sigma uncertainty of ±1.5 nT. Long‐term averaged GOES‐17OB magnetometer data have minimal daily variations. Daily average of the difference between the GOES‐16 outboard or GOES‐17 outboard measurements and the measurements made by another GOES satellite are computed. The long‐term averaged results show the GOES‐16OB and GOES‐17OB measurements have long‐term stability (±2 nT or less) and match measurements from magnetometers on other GOES within limits stated herein. The GOES‐17OB operational offset (zero field value) was refined using the GOES‐17 satellite rotated 180° about the Earth pointing axis (known as a yaw flip).
An analysis of the Magnetospheric Multiscale (MMS) spacecraft data shows the presence of slow electrostatic solitary waves (SESWs) in the Earth’s plasma sheet, which have been interpreted as slow electron holes (SEHs). An alternative mechanism based on slow ion-acoustic solitons is proposed for these SESWs. The SESWs are observed in the region where double humped ion distributions and hot electrons co-exist. Our theoretical model considers the plasma in the SESW region to consist of hot electrons with a vortex distribution, core Maxwellian protons drifting parallel to the magnetic field, <b>B</b> and beam protons drifting anti-parallel to <b>B</b>. Parallel propagating nonlinear ion-acoustic waves are studied using the Sagdeev pseudopotential technique. The analysis yields four types of modes, namely, two slow ion-acoustic (SIA1 and SIA2) solitons and two fast ion-acoustic (FIA1 and FIA2) solitons. All solitons have positive potentials. Except the FIA1 solitons which propagate parallel to <b>B</b>; the other three types propagate anti-parallel to <b>B</b>. Good agreement is found between the amplitudes of electrostatic potential, the electric field, the widths and speed of SIA1 and SIA2 solitons, and the observed properties of SESWs by the MMS spacecraft.
S. Sobhkhiz‐Miandehi, Y. Yamazaki, C. Arras
et al.
Abstract The Sporadic E layer or Es is an ionospheric phenomenon characterized by enhancements in electron density within 90–120 km above the Earth's surface. Based on the wind shear theory, the formation of Es layers is associated with vertical shears in the horizontal wind, in the presence of the Earth's magnetic field. This study explores the role of planetary waves on inducing these vertical shears and subsequently shaping Es layers. Our investigations benefit from a large amount of data facilitated by the FORMOSAT‐7/COSMIC2 and Spire missions, which offer extensive global coverage. A wave analysis is applied to the Es intensity as represented by the S4 index derived from radio occultation measurements, in search of potential planetary wave signatures. Additionally, measurements from Aura/MLS are used to analyze corresponding spectra for the geopotential height, enabling a comparative examination of planetary wave signatures in the Es layer and geopotential height variations. The findings reveal westward and eastward wave components with specific wavenumbers and periods, suggesting the involvement of westward propagating quasi 6‐day, quasi 4‐day planetary waves, and eastward propagating Kelvin waves with a period of around 3 days in Es layer formation at low latitudes.
The article describes the sources of geomagnetic data, the reduction of geomagnetic data for the territory of Latvia to the epoch 2021.5, the history of previous magnetic observations in Latvia, the information available in the State Geodetic Network database and the information available in the World Geomagnetism Data Centre. The sequence of absolute measurements is described in detail. To visualise the changes in the magnetic declination value in the territory of Latvia, a 2021.5 year declination fluctuation has been created using ArcGIS Pro. The declination values in Latvia range from 6.68° to 10°, the inclination values range from 71.089° to 72.245° and the total magnetic field values from 51100 nT to 52594 nT. The values obtained for the magnetic field components refer to a magnetically clean environment, and there can be, and are, differences in the natural conditions in the Latvian territory, in natural anomalous locations and in locations with artificially high magnetic field noise (e.g. in cities, near railways, near high voltage lines, etc.). In the Latvian network, points have been selected in locations where the magnetic noise is minimal, as this is the technological process for building such stations. Magnetic observatories are even stricter, so the data coming from the observatories reflect the natural magnetic field without the influence of magnetic anomalies. The reduced magnetic field values and their representation on a map can be used for aeronautical navigation, military applications, identification of local magnetic anomaly sites or search for magnetically clean environments.
Geetashree Kakoti, Mala S. Bagiya, Fazlul I. Laskar
et al.
Abstract Geomagnetic storms of G1-class were observed on 3 and 4 February 2022, which caused the loss of 38 out of 49 SpaceX satellites during their launch due to enhanced neutral density. The effects of storm-time neutral dynamics and electrodynamics over the American sector during this minor storm have been investigated using Global Positioning System—total electron content (TEC) and Global‐scale Observations of the Limb and Disk (GOLD) mission measured thermospheric composition and temperature. Results revealed an unexpected feature in terms of increase in O/N2 and depletion in TEC over the American low-latitudes. This feature is in addition to the classic storm time ionospheric variations of enhancement in ionospheric electron density in presence of enhanced O/N2 and an intense equatorial electrojet (EEJ). Further, significant morning-noon electron density reductions were observed over the southern mid-high latitudes along the American longitudes. Results from Multiscale Atmosphere-Geospace Environment (MAGE) model simulations elucidated storm-induced equatorward thermospheric wind which caused the strong morning counter electrojet by generating the disturbance dynamo electric field. This further explains the morning TEC depletion at low-latitudes despite an increase in O/N2. Sub-storm related magnetospheric convection resulted in significant noon-time peak in EEJ on 4 February. Observation and modelling approaches together suggested that combined effects of storm-time neutral dynamic and electrodynamic forcing resulted in significant ionospheric variations over the American sector during minor geomagnetic storms.
The “Danjon effect” is a phenomenon that presents a tendency to concentrate the so-called “dark” total lunar eclipses (DTLE) near solar sunspot cycle minimum phases. It was a starting point for the present study, whose main subject is a statistical analysis of relationship between solar and volcanic activity for the maximum long time. To this end, the Smithsonian National Museum of Natural History's volcanic activity catalog was used. On its basis, a time series of the total annual volcanic eruptions for the period 1551–2020 AD has been built and explored for cycles of possible solar origin. Cycles with duration of 10–11, 19–25, ∼60, and ∼240 years (all with possible solar origin) has been established. It has also been found that there are two certain peaks of volcanic activity during the sunspot activity cycle: the first one is close to or after the sunspot minimum (sunspot cycle phase 0.9 ≤ Φ ≤1.0 and 0.1 ≤ Φ ≤ 0.2), and the second is wider – close to the sunspot cycle maximum (0.3 ≤ Φ ≤ 0.5). A third maximum is detected about 3–4 years after the sunspot cycle maximum (0.7 ≤ Φ ≤ 0.8) for the “moderate strong” volcanic eruptions with volcanic eruptive index VEI = 5. It corresponds to the geomagnetic activity secondary maximum, which usually occurs 3–4 years after the sunspot maximum. Φ is calculated separately on the basis of each sunspot cycle length. Finally, without any exclusions, all most powerful volcanic eruptions for which VEI ≥ 6 are centered near the ∼11-year Schwabe-Wolf cycle extremes. Trigger mechanisms of solar and geomagnetic activity over volcanic events, as well as their relation to climate change (in interaction with galactic cosmic rays (GCR) and/or solar energetic particles (SEP)), are discussed. The Pinatubo eruption in 1991 as an example of a “pure” strong solar–volcanism relationship has been analyzed in detail.
Some time ago, we considered non-Gaussian shapes of histograms of quantities that were related to residuals in data: we showed at a qualitative level that non-Gaussianity is most likely the result of mixing of Gaussian distributions. In this addendum, we argue that there is a quantitative description that can be used in fairly general situations. Briefly, we present here the same magnetic measurement data that were reported in the original publication: Khokhlov, A.; Hulot, G. On the cause of the non-Gaussian distribution of residuals in geomagnetism. <i>Geophys. J. Int. </i><b>2017</b>, <i>209</i>, 1036–1047.
According to the characteristic requirements of Internet of things of intelligent sensor, an autonomous positioning module is developed by using geomagnetic assisted inertial navigation/BDS combined positioning algorithm. The chip selection is based on the principle of low power consumption and localization. The module structure and circuit schematic diagram are introduced. The national production and low-power design are adopted in the hardware design, at the same time, the zero speed correction algorithm, quaternion method and geomagnetic auxiliary correction algorithm are adopted in the software to realize the storage and inversion of the moving trajectory of the intelligent sensor. The test shows that the moving track is highly similar to the actual loop. The measured distance of 378 m loop is 375.01 m, the difference is 2.99 m, and the relative error is 0.8%.
María Druet, Manuel Catalán, José Martín-Dávila
et al.
The NW Iberian margin is a hyperextended continental margin, formed during the opening of the North Atlantic Ocean, where a subsequent partial tectonic inversion has undergone during the Alpine Orogeny. This succession of tectonic episodes determines the magnetic signature of the margin. The Spanish Exclusive Economic Zone Project has carried out seven one-month cruises between 2001 and 2009. To extend and densify the spatial coverage, we have used data from the World Digital Magnetic Anomaly Map. Here, we describe the methodology used for the acquisition and data processing of the magnetic field data. The use of diverse instrumentation, a non-complete external field’s cancelation, and the use of different magnetic core field models, contributed to the total error budget. To reduce it, we have used a leveling algorithm which minimizes all these contributions. Finally, a statistical analysis was applied using crossover residuals, showing a resolution better than 28 nT.
Simultaneous observations of OI 777.4 and OI 630.0 nm nightglow
emissions were carried at a low-latitude station, Allahabad
(25.5° N, 81.9° E; geomag. lat. ∼ 16.30° N), located near the crest of the Appleton anomaly in India
during September–December 2009. This report attempts to study the F region
of ionosphere using airglow-derived parameters. Using an empirical approach
put forward by Makela et al. (2001), firstly, we propose a novel technique to
calibrate OI 777.4 and 630.0 nm emission intensities using Constellation
Observing System for Meteorology, Ionosphere, and Climate/Formosa Satellite
Mission 3 (COSMIC/FORMOSAT-3) electron density profiles. Next, the electron
density maximum (Nm) and its height (hmF2) of the F layer have been derived
from the information of two calibrated intensities. Nocturnal variation of Nm
showed the signatures of the retreat of the equatorial ionization anomaly (EIA)
and the midnight temperature maximum (MTM) phenomenon that are usually observed
in the equatorial and low-latitude ionosphere. Signatures of gravity waves
with time periods in the range of 0.7–3.0 h were also seen in Nm and hmF2
variations. Sample Nm and hmF2 maps have also been generated to show the
usefulness of this technique in studying ionospheric processes.
Abstract Global geomagnetic field models using spherical harmonic basis functions are important in space physics research, space weather and applications like navigation and mineral resources exploration. These models are based on various geomagnetic field data sets ranging from Earth surface magnetic observatory measurements to low-Earth orbit satellites equipped with highly sensitive and accurate magnetometers. Although these field models are derived by fitting harmonic functions to data distributed across the Earth, they are applied on regional scales within fixed boundaries in many instances and one can therefore question how well do these models perform on restricted areas. Three recently published global geomagnetic field models, IGRF-12, CHAOS-6 and POMME-10, have been statistically evaluated over Southern Africa using repeat station data as well as measurements from 4 INTERMAGNET observatories located at Hermanus and Hartebeesthoek in South Africa as well as Tsumeb and Keetmanshoop in Namibia for 2015. Apart from the observatory data, the field survey repeat station data do not form part of the data set on which these global field models are based and therefore can be regarded as an independent test of these field models over an area like Southern Africa which is well known for its rapid change of the geomagnetic field. Results obtained in this investigation for both main field and secular variation models clearly showed the importance of timely ground-based geomagnetic field observations in the derivation of accurate field models, particularly in regions characterised by rapid and unpredictable secular variation changes.
The change of the paradigm in the applied geomagnetism due to experimental effects, discovered in the Earth’s atmosphere by Van Vleuten, Benkova, Chetaev, and the observations during the two international geophysical years: 1933 and 1957/58 as well as by the world-wide magnetic survey in 1964/65, was substantiated and confirmed. The paradigm (introduced by Gauss) of the potential magnetic field is noted to require the correction due to the occurrence of hydromagnetic effects in the observed main geomagnetic field and its variations. Such effects cannot be described by classical Maxwell’s equations. The minor correction of the effects in question is needed at the expense of the introduction of spherical (toroidal) electric currents and non-force electromagnetic fields which differential operators differ from those commonly accepted that are used in Maxwell’s equations. The use of the solenoidal feature of the magnetic field, which is valid everywhere on the Earth, makes possible to identically introduce the definitions of non-force and force magnetic fields, to write down the original electromagnetic equations and on their basis to formulate a self-sustained theory of the applied geomagnetism. Also, it will aliow one to interpret the observed data with allowance for hydromagnetic effects as well as to construct sources of the Earth’s main geomagnetic field and sources of calm solar-daily variations.