Ground Magnetic Measurements Research Articles

Lightning and Gravity Wave Signatures Produced by the Hunga‐Tonga Volcanic Eruption on Global Geomagnetic Data

AbstractAcoustic gravity waves (AGWs) have a significant impact on the thermosphere‐ionosphere (T‐I) system by increasing ionisation variability, transporting energy, velocity, momentum, and creating additional horizontal gradients in the T‐I, all of which influence electromagnetic wave propagation and cause changes in the geomagnetic field. Ground magnetic disturbance measurements can thus map the global and local spatial distribution of T‐I current systems. The Hunga‐Tonga volcano eruption released a tremendous amount of mass and energy into the atmosphere on 15 January 2022, causing AGWs. Furthermore, the related lightning strikes disrupt the Global electric circuit. In this study, we look at (a) global geomagnetic disturbances caused by AGW constrained by VTEC amplitudes at two different sectors, (b) Schuman resonances (SR) parameters derived from modulations of ELF observations caused by the intense lightning phenomena that accompanied the volcanic eruption. Our analysis shows that (a) registration timing of geomagnetic disturbance at each observatory indicates the different modes of propagation between 180 and 350 m/s, indicating low‐frequency AGW components, (b) noticeable changes in SR frequency modes (7–21 Hz) occurred in the total power between 04:15 and 05:45 UT hr at Patiyasar, India, linked to heightened lightning activity, (c) velocities are found to be similar at similar distances in the northern and southern hemispheres from Hunga‐Tonga, (d) time difference between the SR and geomagnetic disturbance signature at observatories is found to have no relation with distance from the eruption, (e) fluctuations in VTEC at the Indian and Russian sectors show that the geomagnetic disturbances are linked to ionospheric perturbations.

Volcano‐Magnetic Signal Reveals Rapid Evolution of the Inner Structure of Piton de la Fournaise

AbstractNear‐real time analysis of magnetization can provide important information for the imaging of volcano systems and their spatiotemporal evolution. This study focuses on the contribution of volcano‐magnetic signals from reiterations of ground magnetic measurements to investigate the evolution of active structures at the Piton de la Fournaise volcano from 2017 to 2020. Changes are demonstrated by magnetic anomalies along a reference profile by means of the reiteration periods. These variations are first modeled qualitatively in 2D using electrical resistivity constraints in order to investigate the evolution of magnetization at depth through time, and the model is subsequently compared with the 3D intrusive activity from depth up to the surface from Interferometric Synthetic Aperture Radar (InSAR) inverse modeling. The shallow areas of demagnetization modeled from one reiteration to another are consistent with the geometry and location of the underlying intrusions revealed by the 3D InSAR models, suggesting strong thermal, stress, and electrokinetic effects due to magmatic activity not only at the surface but also at depth, along the main magmatic paths. It also raises a question as to the extent of the associated thermal diffusion processes at the scale of individual magma injections. This study confirms that detecting resistivity and magnetization anomalies, and quantifying their spatiotemporal evolution, can provide powerful tools for imaging volcanic systems at various scales and for providing warning of associated hazards. It also highlights the necessity for 4D monitoring of volcanic edifices using this method to provide greater precision, an important issue that is now made possible by the use of Unmanned Aerial Vehicle measurements.

Power-law dependence of the wavelet spectrum of ground magnetic variations during magnetic storms

We show that time variations in the ring current and auroral electrojets in 2015, during which three major magnetic storms (MSs) occurred, are recorded in several specific ways by ground magnetometers. Specifically, we show that the time variations in magnetic field intensity have power-law wavelet spectra. The variations in ring current intensity are detected in geomagnetic field measurements of ground stations at magnetic mid-latitudes between λ=-50° and +50°. We confirmed the results of Balasis et al. (2006), who had shown that the Dst index wavelet spectrum follows a power law of the form f-β, where f is the frequency, and β is the exponent of the power law, by applying the same wavelet analysis to the SYM-H index version of the Dst index, and also to ground magnetic field measurements. Balasis et al. (2006) also showed that the critical exponent β of the power law, obtains values greater than 2 (or equivalently that the Hurst exponent H>0.5), shortly before the onset and during the main phase of the storms. Here, using wavelet transforms on the Earth’s magnetic field as measured at different magnetic latitudes (MLAT), we showed that at mid-geomagnetic latitudes, where the Earth’s magnetic field is determined mainly by the ring current, the resulting Hurst exponent is greater than 0.5 several hours before and during magnetic storms. Geomagnetic field variation at higher magnetic latitudes between λ=+50° and +73°, also show power-law wavelet spectra. However, here we find a more complex dependence with two power-law exponents. We interpret this double power law as the effect of both the ring current and the auroral electrojets. Finally, for polar latitudes, between λ=+73° and +85°, we find the same complex dependence with two power-law exponents. Our results show that the geomagnetic field at auroral latitudes has much lower power and very different wavelet spectra compared to the geomagnetic field at ranges of lower magnetic latitude. Our results show how wavelet-based measures of ground geomagnetic variations reflect the time evolution of several magnetospheric current systems.

Over 20‐Year Global Magnetohydrodynamic Simulation of Earth's Magnetosphere

AbstractWe present our approach to modeling over 20 years of the solar wind‐magnetosphere‐ionosphere system using version 5 of the Grand Unified Magnetosphere‐Ionosphere Coupling Simulation (GUMICS‐5). As input we use 16‐s resolution magnetic field and 1‐min plasma measurements by Advanced Composition Explorer satellite from 1998 to 2020. The modeled interval is divided into 28 hr simulations including 4 hr overlap. We use maximum magnetospheric resolution of 0.5 Earth radii (RE) up to about 15 RE from Earth and decreasing resolution further away. In the ionosphere we use a maximum resolution of approximately 100 km poleward of ±58° magnetic latitude and decreasing resolution toward equator. With respect to previous version GUMICS‐4, we have parallelized the magnetosphere of GUMICS‐5 using the Message Passing Interface and have made several improvements which have for example, decreased its numerical diffusion. In total we have performed over 8,000 simulations which have produced over 10,000,000 ionospheric files and 2,000,000 magnetospheric files requiring over 100 TB of disk space. We compare these results to several empirical models and geomagnetic indices derived from ground magnetic field measurements. GUMICS‐5 reproduces observed solar cycle trends in magnetopause stand‐off distance and magnetospheric lobe field strength but consistency in plasma sheet pressure and ionospheric cross‐polar cap potential is lower. Comparisons with geomagnetic indices show better results for Kp index than for auroral electrojet index. Our extensive results can serve, for example, as a foundation for combined physics‐based and black‐box approach to real‐time prediction of near‐Earth space, or as input to other physics‐based models of the inner magnetosphere, upper and middle atmosphere, etc.

Geophysical and morphological constraints on active tectonics in the Eastern Pontides (Turkey)

The Eastern Pontides in northern Anatolia (Turkey) offers an exceptional record of significant tectonic evolution from subduction to crustal thickening and Anatolian escape tectonics. Here, we provide ground magnetic measurements at 435 points integrated with aeromagnetic data, remote sensing, and surface geological features from the literature reveal all these tectonic deformation effects on the Eastern Pontides. The region, which is tectonically separated into three sub-zones, clearly revealed from both aero and ground magnetic data. Lineament analysis was carried out to reveal the deformation styles of the region and to compare different data sets. According to the lineament analyzes obtained from the aero&ground magnetic data and all the other data sets, similar results were obtained for the three sub-zones. Although slight differences were obtained results between the used methods and zones, the main lineament orientation is calculated in the E-W direction. Thus, the obtained results emphasize that tectonic deformation effects resulting from long-term ∼N-S convergence and crustal shortening (subduction, collision, obduction) may still dominate the region. In addition to the lineament results, high (low) magnetic zones in the E-W orientation are also evident. Considering the resolution of the data used, these magnetic changes can be associated with large scale geological structures rather than surface lithological changes. Despite the existence of an active dextral the North Anatolian Fault Zone, the zone is not evident from the magnetic results so the transcurrent tectonic regime probably still not dominant in the entire region.

Subsurface structure of Sumani segment in the Great Sumatran Fault inferred from magnetic and gravity modeling

The Great Sumatran Fault (GSF) 1900 km long active and segmented strike-slip faults. One of the segments is the Sumani segment in the province of West Sumatra that passes through a relatively densely populated area. Knowing the geometry of subsurface structures in this segment is one of the efforts to identify potential disasters in the future. To achieve this objective, ground magnetic measurements were carried out and the data were combined with Bouguer anomaly map. Magnetic susceptibility and density were also measured on hand samples collected during the survey so that their values could serve as initial parameters for modeling. The modeling and interpretation stages are carried out through joint forward modeling magnetics and gravity. The equivalent depth of the magnetic and gravity models built under the surface is 20 km. The magnetic and gravity modeling identify several intrusive bodies that do not reach the surface, including one beneath Lake Singkarak. Several slivers of Permian metamorphic rocks encased in the basement rocks were also identified. These unexposed intrusive bodies and slivers of encased metamorphic rocks are probably quite common in the GSF. The magnetic and gravity modeling with 2D modeling also infers an 18 km displacement in Lake Singkarak based on displacement of Quaternary colluvium volcanic deposits. Based on the presence of hot spring at the end of Sumani segment, the pull-apart pattern occurred in Lake Singkarak share similarities with that occur in another segment of GSF, namely Tarutung.

Geophysical assessment of open dumpsite nearby Khamis Mushait industrial zone, Southwestern Saudi Arabia

Vertical electrical soundings, seismic refraction tomography, and ground magnetic measurements were taken or conducted close to an open dumpsite near Khamis Mushait, southwestern Saudi Arabia, which is characterized by shallow groundwater conditions. Structurally, intersected series of north- to northwest-trending faults affect the area. A new urban expansion and the Khamis Mushait industrial zone are close to the open dumpsite. This study evaluates the potential for leachate intrusion into groundwater aquifers. The results of electrical soundings reveal four geoelectric units: the topsoil, weathered layer, partly weathered/fractured basement, and fresh basement bedrock. At the dumpsite, relatively low resistivity values that are less than 30 Ωm characterize the topsoil, weathered layer, and partly weathered/fractured basement because of conductive leachate from the dumpsite. Besides, the results of ground magnetic data indicate that the deformation of varying intensities affects the dumpsite area, resulting in fractures developing in the N–S, NE–SW, NW–SE, and, to a lesser extent, E–W directions. Moreover, geoseismic tomographic models illustrate a low P-wave velocity zone corresponding to a low resistivity zone, and a NE–SW fault was identified from geoseismic cross-sections. Finally, these fractures and faults could become contaminant pathways for shallow aquifers around the dumpsite. To minimize the impact of such leachate, from a dumpsite, on groundwater quality and the environment in general, the dumpsite must be properly designed, constructed, and managed using engineering principles.

Electric Mode Excitation in the Atmosphere by Magnetospheric Impulses and ULF Waves

Variations of vertical atmospheric electric field Ez have been attributed mainly to meteorological processes. On the other hand, the theory of electromagnetic waves in the atmosphere, between the bottom ionosphere and earth’s surface, predicts two modes, magnetic H (TE) and electric E (TH) modes, where the E-mode has a vertical electric field component, Ez. Past attempts to find signatures of ULF (periods from fractions to tens of minutes) disturbances in Ez gave contradictory results. Recently, study of ULF disturbances of atmospheric electric field became feasible thanks to project GLOCAEM, which united stations with 1 sec measurements of potential gradient. These data enable us to address the long-standing problem of the coupling between atmospheric electricity and space weather disturbances at ULF time scales. Also, we have reexamined results of earlier balloon-born electric field and ground magnetic field measurements in Antarctica. Transmission of storm sudden commencement (SSC) impulses to lower latitudes was often interpreted as excitation of the electric TH0 mode, instantly propagating along the ionosphere–ground waveguide. According to this theoretical estimate, even a weak magnetic signature of the E-mode ∼1 nT must be accompanied by a burst of Ez well exceeding the atmospheric potential gradient. We have examined simultaneous records of magnetometers and electric field-mills during >50 SSC events in 2007–2019 in search for signatures of E-mode. However, the observed Ez disturbance never exceeded background fluctuations ∼10 V/m, much less than expected for the TH0 mode. We constructed a model of the electromagnetic ULF response to an oscillating magnetospheric field-aligned current incident onto the realistic ionosphere and atmosphere. The model is based on numerical solution of the full-wave equations in the atmospheric-ionospheric collisional plasma, using parameters that were reconstructed using the IRI model. We have calculated the vertical and horizontal distributions of magnetic and electric fields of both H- and E-modes excited by magnetospheric field-aligned currents. The model predicts that the excitation rate of the E-mode by magnetospheric disturbances is low, so only a weak Ez response with a magnitude of ∼several V/m will be produced by ∼100 nT geomagnetic disturbance. However, at balloon heights (∼30 km), electric field of the E-mode becomes dominating. Predicted amplitudes of horizontal electric field in the atmosphere induced by Pc5 pulsations and travelling convection vortices, about tens of mV/m, are in good agreement with balloon electric field and ground magnetometer observations.

Experimental aeromagnetic survey using a rotary-wing aircraft system: A case study in Heizhugou, Sichuan, China

The mid-high mountain area in Western China is an important area for an aeromagnetic survey in China. To solve the problem that a ground survey cannot be carried out in the research area of Heizhugou (Sichuan, China), an unmanned aerial vehicle (UAV) aeromagnetic survey system based on a three-axis fluxgate sensor was developed. It can solve the large-scale magnetic survey problem in special areas (mountains, canyons, lakes, etc.). The noise level test, conformance test, and sensor correction methods used in the development of the UAV aeromagnetic system are discussed. When performing sensor calibration, the error generation mechanism was analyzed according to the basic principle of the sensor. Then, the component output model was established, and the zero offset factor was calibrated, as well as the scale factor. After the nine-element iteration method calibration, the steering error was reduced from hundreds to less than 20 nT, better than the least squares method. The aeromagnetic results were compared with ground magnetic measurements, and the results were good.

An integrated ore prospecting model for the Nyasirori gold deposit in Tanzania

ABSTRACT The Nyasirori gold deposit, located in the middle-western end of the Musoma-Mara Archean greenstone belt in Tanzania, is a tectonic altered rock type gold deposit controlled by shear tectonic zone. This work conducted high-precision ground magnetic measurements to delineate fault structures and favorable prospecting targets, utilized induced polarization (IP) intermediate gradient to roughly determine the distribution and extension of the tectonic altered zone and gold ore (mineralized) bodies, and further carried out IP sounding and magnetotelluric sounding to locate the tectonic altered zone and gold ore (mineralized) bodies. The anomalous gradient belt of the combination of positive and negative micromagnetic measurements reflects the detail of shallow surface tectonic alteration zone and gold mineralization body. Micromagnetic profile anomalies indicate the spatial location and occurrence of concealed tectonic alteration zone and gold (mineralized) ore bodies. Soil geochemical measurements indicate that the ore-forming element Au correlates well with As and Sb, and As and Sb anomalies have a good indication to gold orebodies. Based on the multi-source geological-geophysical-geochemical information of the Nyasirori gold deposit, this work established an integrated prospecting model and proposed a set of geophysical and geochemical methods for optimizing prospecting targets.

Erratum: ‘Contributions to the geomagnetic secular variation from a reanalysis of core surface dynamics’ and ‘Assimilation of ground and satellite magnetic measurements: inference of core surface magnetic and velocity field changes’

Erratum: ‘Contributions to the geomagnetic secular variation from a reanalysis of core surface dynamics’ and ‘Assimilation of ground and satellite magnetic measurements: inference of core surface magnetic and velocity field changes’

Assimilation of ground and satellite magnetic measurements: inference of core surface magnetic and velocity field changes

Assimilation of ground and satellite magnetic measurements: inference of core surface magnetic and velocity field changes

Gravity, magnetic and resistivity investigations of the Okauia Low Temperature Geothermal System in alluvial sediments of the Hauraki Depression, New Zealand

Gravity, ground magnetics, DC resistivity traversing, and time domain electromagnetic soundings (fixed-loop and in-loop) were conducted to investigate the Okauia Low Temperature Geothermal System near the eastern boundary of the Hauraki Depression in North Island of New Zealand. The gravity study revealed a hidden extension of the Tertiary-age Waiteariki Ignimbrite, underlying plio-Pleistocene alluvium deposits of the Hinuera Formation, which locally host an aquifer of warm geothermal fluids. A 3D magnetic model derived from the ground magnetic measurements helped identify probable paleo-channels within the sedimentary sequence of the Hinuera Formation. These paleo-channels could represent higher permeability at shallow (<50 m) depth, although the exact relationship between the locations of the surface thermal manifestations and identified paleo-channels is still unclear. The results of the resistivity surveys suggest that values less than 25 Ωm are indicative of the presence of warm waters at Okauia. Most warm water occurrences at Okauia take place near the Okauia Fault, particularly at 0 m RL (sea level) elevation. The near-surface extent of the Okauia Low Temperature Geothermal System can be approximated from the results of this study.

The equatorial electrojet (EEJ) current deduced from CHAMP satellite and ground magnetic measurements in West Africa

The equatorial electrojet (EEJ) is an intense daytime ionospheric current that circulates eastward along the geomagnetic dip equator. In this work, the EEJ current intensity was studied from ground-based magnetic data and CHAllenging Minisatellite Playoad (CHAMP) satellite observations. The ground-based magnetic data were recorded along a meridian chain of three stations across the dip equator in West Africa. These stations were operated by the Institut de Physique du Globe de Paris (IPGP). For the CHAMP satellite data, vector magnetometer records during geomagnetically quiet periods with Kp ≤ 2 were used. To estimate the EEJ current intensity, we have first isolated its magnetic effect from CHAMP satellite observations for 10 years (from July 2000 to September 2010). The results were used to analyze the EEJ seasonal variability and the local time and longitude dependence. In addition, a comparison between ground-based and satellite observations of the EEJ current intensity was made. A good correlation was found between satellite and ground-based EEJ current intensity, with an average correlation coefficient of r 2 ~0.93. This performed correlation show that the technique used in this study can be extended to all ground magnetic stations for modeling the EEJ phenomena.

Comparison of auroral ionospheric and field‐aligned currents derived from Swarm and ground magnetic field measurements

AbstractDerivation of the auroral ionospheric currents from magnetic field measurements can produce drastically different results depending on the data and method used. We have cross tested several methods for obtaining instantaneous field‐aligned and horizontal currents from Swarm satellite and International Monitor for Auroral Geomagnetic Effects (IMAGE) ground magnetic field measurements. We found that Swarm can yield latitude profiles of the east‐west component of the divergence‐free current density at most at ∼200 km resolution, typically resolving the electrojets. The north‐south divergence‐free component, on the other hand, is not always well reproduced due to the small longitudinal distance between the side‐by‐side flying satellite pair. Swarm can yield the field‐aligned and curl‐free current density at a wider range of latitude resolutions (∼7.5–200 km) than the divergence‐free current density. While 7.5 km is suitable for comparison with auroras, 200 km typically resolves the Regions 1 and 2 field‐aligned currents. IMAGE can yield maps of the divergence‐free current density at ∼50 km resolution. Induced telluric currents should be accounted for in the derivation. Not accounting for them in the Swarm analysis, however, does not appear to introduce significant errors. Ionospheric conductances can be estimated by combining the total horizontal current density, consisting of the curl‐free and divergence‐free components, with the electric field measurements. Our results indicate that Swarm can only yield these at ∼200 km scale size when there is no significant dependence on longitude. However, combining the divergence‐free current from IMAGE with the curl‐free current and electric field from Swarm could yield conductance maps at ∼50 km resolution.

The impact of sunlight on high‐latitude equivalent currents

AbstractGround magnetic field measurements can be mathematically related to an overhead ionospheric equivalent current. In this study we look in detail at how the global equivalent current, calculated using more than 30 years of SuperMAG magnetometer data, changes with sunlight conditions. The calculations are done using spherical harmonic analysis in quasi‐dipole coordinates, a technique which leads to improved accuracy compared to previous studies. Sorting the data according to the location of the sunlight terminator and orientation of the interplanetary magnetic field (IMF), we find that the equivalent current resembles ionospheric convection patterns on the sunlit side of the terminator but not on the dark side. On the dark side, with southward IMF, the current is strongly dominated by a dawn cell and the current across the polar cap has a strong dawnward component. The contrast between the sunlit and dark side increases with increasing values of the F10.7 index, showing that increasing solar EUV flux changes not only the magnitude but also the morphology of the equivalent current system. The results are consistent with a recent study showing that Birkeland currents indirectly determine the equivalent current in darkness and that Hall currents dominate in sunlight. This has implication for the interpretation of ground magnetic field measurements and suggests that the magnetic disturbances at conjugate points will be asymmetrical when the solar illumination is different.

Delineating groundwater and subsurface structures by using 2D resistivity, gravity and 3D magnetic data interpretation around Cairo–Belbies Desert road, Egypt

Geophysical tools such as magnetic, gravity and electric resistivity have been used to delineate subsurface structures, groundwater aquifer around Cairo–Belbies Desert road. A dipole–dipole section was measured at the central part of the study area with 2100m length and electrode spacing 50m for greater penetration depth. The results of the inverse resistivity data indicate that the study area includes two groundwater aquifers at different depths. The shallow aquifer water is near the surface and the deep aquifer lies at depth of about 115m and exhibits low resistivity values ranging from 20 to 100ohmm.One hundred and fifty-two gravity stations were measured using Autograv gravimeter (CG3), different gravity corrections (drift, elevation and latitude corrections) were applied. The corrected data represented by Bouguer anomaly map were filtered into regional and residual gravity anomaly maps. The residual gravity map indicates that the area is dissected by many faults with NW-SE, N-S, E-W and NE-SW trends.One hundred and fifty-three ground magnetic measurements are collected using two Proton magnetometers (Envimag). The corrected magnetic data are represented by total magnetic intensity map that was reduced to the magnetic pole. 3D magnetic modeling was applied to detect the depth of basaltic sheet and basement complex. The results indicated that the elevation of upper surface of basalt is ranging from 148 to −153m and the elevation of lower surface of basalt is ranging from 148 to 269m.

Distribution of buried hydrothermal alteration deduced from high‐resolution magnetic surveys in Yellowstone National Park

AbstractYellowstone National Park (YNP) displays numerous and extensive hydrothermal features. Although hydrothermal alteration in YNP has been extensively studied, the volume, geometry, and type of rock alteration at depth remain poorly constrained. In this study, we use high‐resolution airborne and ground magnetic surveys and measurements of remanent and induced magnetization of field and drill core samples to provide constraints on the geometry of hydrothermal alteration within the subsurface of three thermal areas in YNP (Firehole River, Smoke Jumper Hot Springs, and Norris Geyser Basin). We observe that hydrothermal zones from both liquid‐ and vapor‐dominated systems coincide with magnetic lows observed in aeromagnetic surveys and with a decrease of the amplitude of short‐wavelength anomalies seen in ground magnetic surveys. This suggests a strong demagnetization of both the shallow and deep substratum within these areas associated with the removal of magnetic minerals by hydrothermal alteration processes. Such demagnetization is confirmed by measurements of rock samples from hydrothermal areas which display significantly decreased total magnetization. A pronounced negative anomaly is observed over the Lone Star Geyser and suggests a significant demagnetization of the substratum associated with areas displaying large‐scale fluid flow. The ground and airborne magnetic surveys are used to evaluate the distribution of magnetization in the subsurface. This study shows that significant demagnetization occurs over a thickness of at least a few hundred meters in hydrothermal areas at YNP and that the maximum degree or maximum thickness of demagnetization correlates closely with the location of hydrothermal activity and mapped alteration.

Rock magnetic investigation of possible sources of the Bangui magnetic anomaly

The Bangui magnetic anomaly (BMA) is the largest lithospheric magnetic field anomaly on Earth at low latitudes. Previous studies investigated its geological source using constraints from satellite and ground magnetic field measurements, as well as from surface magnetic susceptibility measurements on rocks from the Panafrican Mobile Belt Zone (PMBZ). Here we combine magnetic field data modelling and rock magnetic property measurements (susceptibility and natural remanent magnetization, NRM) on many samples from this PMBZ and the surrounding formations. It reveals that NRM is a significant component of the total magnetization (Mt) of the BMA source, which reaches 4.3A/m with maximum thicknesses of 38 and 54km beneath the western and eastern parts of the BMA. Only the isolated and relatively thin banded iron formations and some migmatites show such Mt values. Thus we suggest that the thick BMA source may be composed either by overlapped slices of such metamorphic rocks, or by an iron-rich mafic source, or by a combination of these two geological structures.

Rocket borne in-situ Electron density and Neutral Wind measurements in the equatorial ionosphere—Results from the January 2010 annular solar eclipse campaign from India

One of the recent developments in the form of a novel probe for simultaneous in-situ measurements of Electron density and Neutral Wind (ENWi) parameters was extensively made use of during the annular solar eclipse that passed right over the magnetic dip equatorial station, Trivandrum in India. The response of the equatorial ionosphere to the annular solar eclipse of January 2010 is investigated using the data from ENWi and other ground based instruments like digital Ionosonde, HF radar, magnetometer etc. Significant effects on the neutral wind components and electron densities during the peak phase of the eclipse are brought out by the ENWi data. A clear reversal in the zonal neutral wind is observed during the rocket flights at the peak phase of the eclipse as well as in the flight conducted 3h later. The ground magnetic field measurements revealed the reversal of electrojet during the eclipse alongwith blanketing Es layers vindicating the earlier hypothesis that blanketing Es layers manifest over magnetic equatorial regions only during periods of either weak or reversed electrojet (counter electrojet). The HF radar results independently substantiate the in situ measurements with regard to the location of the irregularities and their Doppler velocities. The regional scale changes that have been brought about by the Solar eclipse both in the neutral and ionized medium and the consequent electrodynamics are highlighted.