Ionospheric Electric Field Research Articles

Investigating Spatial and Temporal Structuring of E‐Region Coherent Scattering Regions Over Northern Norway

AbstractRecently, it has been shown that the Spread Spectrum Interferometric Multistatic meteor radar Observing Network radar system located in northern Norway is capable of measuring ionospheric E‐region coherent scatter with spatial and temporal resolutions on the order of 1.5 km and 2 s, respectively. Four different events from June and July of 2022 are examined in the present study, where the coherent scatter measurements are used as a tracer for large‐scale ionospheric phenomena such as plasma density enhancements and ionospheric electric fields. By applying a two‐dimensional Fourier analysis to range‐time‐intensity data, we perform a multi‐scale spatial and temporal investigation to determine the change in range over time of large‐scale ionospheric structures (>3 km) which are compared with line‐of‐sight velocities of the small scale structures (∼5 m) determined from the Doppler shift of the coherent scatter. The spectral characteristics of the large‐scale structures are also investigated and logarithmic spectral slopes for scale sizes of 100–10 km were found to be between −3.0 and −1.5. This agrees with much of the previous work on the spatial spectra scaling for ionospheric electric fields. This analysis aids in characterizing the source of the plasma turbulence and provides crucial information about how energy is redistributed from large to small scales in the E‐region ionosphere.

Imaging Ionospheric Electric Fields and Conductances at Small-Scales Globally: Advancing Research on Cross-Scale Coupling in the M-I-T System

Imaging Ionospheric Electric Fields and Conductances at Small-Scales Globally: Advancing Research on Cross-Scale Coupling in the M-I-T System

Enhance ionospheric electric field and current observations to better understand the E-region electrodynamics

Enhance ionospheric electric field and current observations to better understand the E-region electrodynamics

A Model of High Latitude Ionospheric Convection Derived From SuperDARN EOF Model Data

AbstractForecasting of the effects of thermospheric drag on satellites will be improved significantly with better modeling of space weather effects on the high‐latitude ionosphere, in particular the Joule heating arising from electric field variability. We use a regression analysis to build a model of the ionospheric convection drift velocity which is driven by relatively few solar and solar wind variables. The model is developed using a solar cycle's worth (1997–2008 inclusive) of 5‐min resolution Empirical Orthogonal Function (EOF) patterns derived from Super Dual Auroral Radar Network (SuperDARN) line‐of‐sight observations of the convection velocity across the high‐latitude northern hemisphere ionosphere. At key stages of development of the model, we use the percentage of explained variance P to see how well the model reproduces the EOF data. The final model is driven by four variables: (a) the interplanetary magnetic field component By, (b) the solar wind coupling parameter epsilon ε, (c) a trigonometric function of day‐of‐year, and (d) the monthly F10.7 index. The model can reproduce the EOF velocities with a characteristic P = 0.7. The model and EOF data compare best around the solar maximum of 2001. is lower around solar minimum, due to occasional limitations in the geographical and temporal coverage of the SuperDARN measurements. This may indicate the need to modify our model around the minimum of the solar cycle. Our model has the potential to be used to forecast the ionospheric electric field using the real‐time solar wind data available from spacecraft located upstream of the Earth.

PHYSICAL EFFECTS OF THE POWERFUL TONGA VOLCANO EXPLOSION IN THE EARTH – ATMOSPHERE – IONOSPHERE – MAGNETOSPHERE SYSTEM ON JANUARY 15, 2022

PHYSICAL EFFECTS OF THE POWERFUL TONGA VOLCANO EXPLOSION IN THE EARTH – ATMOSPHERE – IONOSPHERE – MAGNETOSPHERE SYSTEM ON JANUARY 15, 2022

Detecting the Auroral Oval through CSES-01 Electric Field Measurements in the Ionosphere

We present the results of a systematic study of the ionospheric electric field in the Auroral Oval (AO) region in the southern hemisphere. We exploit one year of electric field measurements taken by the Electric Field Detector (EFD) on board the Chinese Seismo-Electromagnetic Satellite-01 (CSES-01), flying at around 500 km altitude in a sun-synchronous orbit. We exploit the high temporal resolution of the EFD to devise a new technique for the detection of CSES-01 crossing of the AO using electric field measurements only. This new technique combines a Median-Weighted Local Variance Measure with Fast Iterative Filtering to automatically isolate high levels of electromagnetic activity caused by, e.g., particle precipitation and Field Aligned Currents (FACs) at auroral latitudes. We validate this new method against other standard proxies, such as the single-FAC product from the Swarm mission and the auroral radiance emission measured by the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) units on board the Defense Meteorological Satellite Program (DMSP) constellation. Furthermore, we identify ∼3000 orbits (out of a dataset of ∼10,000) where CSES-01 crosses the AO boundary under conditions of high geomagnetic activity. This dataset represents the first step in the systematic study of the auroral electric field, with many potential applications to space weather, thanks to the large amount of continuous observations of the ionosphere by CSES-01 and the forthcoming CSES-02 mission.

Geoeffectiveness of Interplanetary Alfvén Waves. I. Magnetopause Magnetic Reconnection and Directly Driven Substorms

In particular during the descending phase of the solar cycle, Alfvén waves in the high-speed solar wind streams are a major form of interplanetary disturbances. The fluctuating southward interplanetary magnetic field (IMF) of Alfvén waves has been suggested to induce geomagnetic activities through intermittent magnetic reconnection at the magnetopause. In this study, we provide in situ observational evidence for dayside magnetopause reconnection induced by such interplanetary Alfvén waves. Using multipoint conjunction observations, we show that the IMF B z from interplanetary Alfvén waves is transmitted through and amplified by the Earth’s bow shock. Associated with the intensified southward B z to the magnetopause, in situ signatures of magnetic reconnection are detected. Repetitively, interplanetary Alfvén waves transmit the intensified B z to the magnetosheath, leading to intervals of large magnetic shear angles across the magnetopause and magnetopause reconnection. Such intervals are promptly followed by hundreds of nanoTesla (nT) increases in the auroral electrojet indices (AE and AU) within 10–20 minutes. These observations are confirmed in multiple events in corotating interaction region-driven geomagnetic storms. To put the observations into context, we propose a phenomenological model of a strongly driven substorm. The substorm electrojet is linked to the enhanced magnetopause reconnection in the short timescale of re-establishing the ionosphere electric field and the two-cell convection. These results provide insights on the temporal patterns of solar wind magnetosphere–ionosphere coupling, especially during the descending phase of the solar cycle.

Statistical analysis of electric field perturbations in ELF based on the CSES observation data before the earthquake

To explore the correlation between earthquakes and the pre-earthquake ionospheric shallow frequency (ELF) electric field perturbations phenomenon, the paper investigated the pre-earthquake ionospheric perturbations phenomenon, and then the Spatio-temporal evolution characteristics of the electromagnetic field before and after the global Ms ≥6.0 strong earthquakes from 2019 to 2021 were statistically analyzed. In this paper, the power spectrum data of the ELF (19.5–250 Hz) band of ionospheric electric field observed by the China Seismo-Electromagnetic Satellite (CSES) electric field detector are preclinically processed by the C-value method. A stable background field observation model was constructed using the data from 75 to 45 days before the earthquake observed by the CSES in the range of 15° above the epicenter. Then, the amplitude of the spatial electric field disturbance over the epicenter relative to the background field is extracted. Finally, the superposition analysis method statistically analyzes the spatial and temporal evolution of the spatial electric field before and after the earthquake with different characteristics. The statistical results show that the anomalies first appear in the fourth period (15–19 days before the earthquake) and the third period (10–14 days before the earthquake) and then reach the most vital and most evident during the pro-earthquake period (4 days before the earthquake and the day of the earthquake); In terms of the intensity of the anomalies caused, the magnitude seven earthquakes are stronger than the magnitude 6.0–7.0 earthquakes, and marine earthquakes are stronger than land earthquakes; in terms of the ease of observing the anomalies, the magnitude 7.0 and above are more accessible to observe than the magnitude 6.0–7.0 earthquakes, and marine earthquakes are more accessible to observe than land earthquakes.

Solar cycle variations in equatorial ionospheric zonal electric fields near sunrise

In this study, we investigate the solar cycle dependence of the sunrise ionospheric zonal electric fields at the equator under geomagnetically quiet conditions. Simulations using the Thermosphere–Ionosphere–Electrodynamics General Circulation Model (TIEGCM) reveal that the equatorial eastward electric field at sunrise decreases with the increase in solar activity, independent of longitude, season, and lower atmospheric tides. The solar cycle dependence of the sunrise zonal electric field is mainly related to the zonal wind dynamo. Moreover, this solar cycle dependence of sunrise electric fields at the equator is dominated by the corresponding variation in the F-region dynamo because the response of conductivity and neutral winds near sunrise to increasing solar flux is stronger in the F-region than in the E-region, although the sunrise eastward enhancement of electric fields is mainly driven by the E-region zonal wind dynamo. Specifically, the westward gradient of low-latitude F-region neutral winds near the dawn terminator tends to produce westward electric fields in the equatorial region that are more pronounced at solar maximum, whereas the midlatitude E-region dynamo induces an eastward enhancement of sunrise electric fields at the equator that decreases slightly with increasing solar activity. This study also reveals that the reason the eastward enhancement of equatorial zonal electric fields near dawn and dusk terminators show opposite solar cycle dependence is because of their different generation mechanisms.

A Quantitative Comparison of High Latitude Electric Field Models During a Large Geomagnetic Storm

AbstractModels of the high‐latitude ionospheric electric field (EF) are commonly used to specify the magnetospheric forcing in thermosphere or whole atmosphere models. The use of decades‐old models based on spacecraft data is still widespread. Currently the Heelis et al. (1982, https://doi.org/10.1029/ja087ia08p06339) and Weimer (2005b, https://doi.org/10.1029/2005ja011270) climatology models are most commonly used but it is possible a more recent EF model could improve forecasting functionality. Modern EF models, derived from radar data, have been developed to incorporate advances in data availability (Bristow et al., 2022, https://doi.org/10.1029/2021sw002920; Thomas & Shepherd, 2018, https://doi.org/10.1002/2018ja025280; Walach et al., 2022, https://doi.org/10.1029/2021ja029559). It is expected that climatologies based on this larger and up‐to‐date data set will better represent the high latitude ionosphere and improve forecasting abilities. An example of two such models, which have been developed using line‐of‐sight velocity measurements from the Super Dual Auroral Radar Network (SuperDARN) are the Thomas and Shepherd model (TS18) (Thomas & Shepherd, 2018, https://doi.org/10.1002/2018ja025280), and Walach and Grocott geomagnetic Storm model (WGS21) (Walach et al., 2021, https://doi.org/10.1029/2020ja028512). Here we compare the outputs of these EF models during the September 2017 storm, covering a range of solar wind and interplanetary magnetic field (IMF) conditions. We explore the relationships between the IMF conditions and the model output parameters such as transpolar voltage, the polar cap size and the lower latitude boundary of convection. We find that the electric potential and field parameters from the spacecraft‐based models have a significantly higher magnitude than the SuperDARN‐based models. We discuss the similarities and differences in topology and magnitude for each model.

Mathematical model of the global ionospheric electric field generated by thunderstorms

A model is created for the thunderstorm-related ionospheric part of the global electric circuit in January. This current system consists of both mid-latitude currents and equatorial electrojets, day-time and night-time, westward and eastward, up to 120 A. Data on the atmospheric fair weather electric field obtained during Carnegie cruise VII are plotted as a two dimensional map in Universal Time and month coordinates to show both time and seasonal variations.

A Mathematical Model of the Global Ionospheric Electric Field Generated by Thunderstorms

A Mathematical Model of the Global Ionospheric Electric Field Generated by Thunderstorms

Swarm Thermal Ion Imager measurement performance

We assess the performance of the thermal ion imaging (TII) technique as conceived for the Swarm Earth Explorer satellites. Analysis, simulation, and laboratory testing performed prior to flight provided estimates of systematic and random error sources of the electric field instrument’s vector ion drift, electric field, and ion kinetic temperature measurements. An end-to-end instrument simulator, consisting of models of the TIIs on a prototypical Swarm satellite orbiting Earth with ionospheric plasma, electric field, and magnetic field inputs, was used to generate TII sensor data (level 0 instrument data). These data were processed with a prototype processor (the level 1b processor) to characterize theoretical measurement performance. We describe the methodology used to assess TII measurement uncertainty and present the main findings of the end-to-end measurement performance study. In addition, we assess the measurement performance achieved during approximately eight years of orbital operations. Example measurements demonstrate the quality of ion drift velocity. Unprocessed TII imagery reveals spurious signals which can affect measurement performance. Availability of such imagery has proven vital for diagnosing measurement anomalies associated with sensor operation and spacecraft–plasma interactions.Graphical

First Observations of Equatorial Ionospheric Electric Fields Driven by Storm‐Time Rapidly Recurrent Magnetospheric Substorms

AbstractGeomagnetic storm ionospheric electrodynamics at the magnetic equator are examined in detail using upgraded, higher time resolution, Jicamarca incoherent scatter radar drift observations, SuperMAG geomagnetic field, and solar wind data to study equatorial ionospheric electric fields during the 8 September 2017 storm main and early recovery phases. We show that during a period of mostly large and southward Interplanetary Magnetic Field (IMF) Bz there were numerous daytime prompt penetration vertical and zonal plasma drifts. These prompt penetration events were closely associated with rapidly recurring (quasi‐periods ∼30 − 60 min) magnetospheric substorms with expansion phases corresponding to upward and westward drift (eastward and downward electric field) perturbations, and recovery phases to opposite polarity changes. The magnitudes of the zonal prompt penetration drifts were about twice larger than those of the vertical drifts. Our study suggests that magnetospheric substorms are the main drivers of prompt penetration electric fields during extended periods (over ∼2 hr) of nearly steady southward IMF Bz. We also find that in general substorms are major driving factors for disturbance electric fields during geomagnetic active times. Our data highlight the powerful capabilities of the Jicamarca incoherent scatter radar as a tool for detailed studies of short‐lived solar wind‐magnetosphere‐ionosphere coupling processes.

WWLLN Data Used to Model the Global Ionospheric Electric Field Generated by Thunderstorms

Electric currents flowing in the atmospheric global electric circuit (GEC) are closed by ionospheric currents. The physical and mathematical approach to simulate the ionospheric potential which drives these currents has been described in our previous papers. Only the internal electric fields and currents generated by thunderstorms are studied, and without any magnetospheric current sources or generators. The atmospheric conductivity profiles with altitude are empirically determined, and the topography of the Earth’s surface is taken into account. A two-dimensional approximation of the ionospheric conductor is based on the high conductivity along the geomagnetic field; the Pedersen and Hall conductivities are calculated using empirical models. The potentials in the E- and F-layers of the ionosphere are considered to be constant along each magnetic field line. The main progress in comparison with previous versions of the model is obtained through applying the global distribution of thunderstorms obtained from the ground-based World Wide Lightning Location Network. Under typical conditions for July, under low solar activity in 2008, at 18:00 UTC, the calculated maximum potential difference in the ionosphere is 54 V. This newest version of our model contains the equatorial electrojets. There are day-time electrojets, the strengths of which are up to 65 A, and night-time ones (of up to 40 A), while the total current flowing in the GEC is taken to be equal to 1.43 kA in our model to satisfy the Carnegie curve, i.e. the diurnal variation of the vertical electric field at ground level with UTC. The maximum of the electric potential is shifted from Africa to South-East Asia in the new model. The equatorial electrojets also change their position, direction and intensity.

Geospace Concussion: Global Reversal of Ionospheric Vertical Plasma Drift in Response to a Sudden Commencement.

An interplanetary shock can abruptly compress the magnetosphere, excite magnetospheric waves and field-aligned currents, and cause a ground magnetic response known as a sudden commencement (SC). However, the transient (<∼1min) response of the ionosphere-thermosphere system during an SC has been little studied due to limited temporal resolution in previous investigations. Here, we report observations of a global reversal of ionospheric vertical plasma motion during an SC on 24 October 2011 using ∼6s resolution Super Dual Auroral Radar Network ground scatter data. The dayside ionosphere suddenly moved downward during the magnetospheric compression due to the SC, lasting for only ∼1min before moving upward. By contrast, the post-midnight ionosphere briefly moved upward then moved downward during the SC. Simulations with a coupled geospace model suggest that the reversed vertical drift is caused by a global reversal of ionospheric zonal electric field induced by magnetospheric compression during the SC.

Учет неоднородностей подсеточного масштаба в рамках численной модели глобального распределения электрических полей в ионосфере Земли

Purpose: Creation of a global numerical model of ionospheric electric fields with the possibility of more detailed description of their small-scale features in some limited subareas. Methods: Formulation of a boundary value task with accounting for underlined subdomain for to describe subgrid scale features and the task solution by modern numerical method. Results: Model testing was conducted. In particular, stable numerical solution was obtained for the case of small-scale localized conductivity increase due to additional ionization of the ionosphere by an auroral ray. Practical significance: The model will make it possible to qualify the picture of ionospheric electric field global distribution in those limited subareas which for, there is fuller set of experimental data on the distribution of conductivity and field-aligned currents.

High‐Resolution Poynting Flux Statistics From the Swarm Mission: How Much Is Being Underestimated at Larger Scales?

AbstractUnderestimation of the transfer of energy between the magnetosphere and ionosphere, the Poynting flux, is a persistent issue in space weather studies and the high‐latitude ionospheric models. Thought to be due to the inability to resolve small‐scale fluctuations of the ionospheric electric field, this underestimation could lead to significant further underestimations in parameters such as the thermospheric mass density and consequential satellite drag. Utilizing 16 Hz ion velocity and magnetic field measurements from the Swarm satellite mission, we examine the observed Poynting flux due to electric field fluctuations on very small spatial scales (∼1 km), and then artificially smooth the data to increase the observed scale. We quantify the decrease of integrated Poynting flux, poleward of 60/‐60° geomagnetic latitude, with increasing spatial scale. The decrease can be underestimated by as much as 15% by increasing scale from 1 km to only 8.6 km, or 16–2 Hz equivalent, with upward Poynting flux decreasing significantly faster. Our results thus point to a significant Alfvén wave driven component of the Poynting flux on kilometer scales. Additionally, we observe a northern hemisphere preference for increased Poynting flux, of which we examine its dependence on scale size and interplanetary magnetic field.

Statistical Study on Small‐Scale (≤1,000 km) Density Irregularities in the Inner Magnetosphere

AbstractA statistical survey of small‐scale density irregularities near the magnetic equatorial region of the inner magnetosphere was performed using 7‐year Van Allen Probes data. The cross‐field sizes of these density irregularities are within the order of 1,000 km, corresponding to typical whistler‐mode wave ducts. Spatial distributions on L‐shells and magnetic local times as well as temporal distributions on geomagnetic indices were analyzed using density data in the plasmasphere, the plasmasphere boundary layer (PBL), and the plasma trough. Inside the plasmasphere, the density fluctuations occur predominantly in the night and dawn sectors at L = 2.5–5. They occur far from PBL and show no significant relation with geomagnetic indices. In the PBL at L &gt; 4.5 and the plasma trough, density irregularities are concentrated in post‐midnight during quiet times and extend to all night sectors during active times. Density fluctuation values in the PBL are much higher than those in the other two regions. We discuss connections of irregularities deep inside the plasmasphere to ionospheric electric field disturbances and those in and near the PBL to interchange instabilities.

Persistent Eastward EEJ Enhancement During the Geomagnetic Storm Recovery Phases

AbstractRecent case studies disclosed that sometimes the dayside ionospheric equatorial electric field underwent persistent long‐duration (&gt;4 hr) eastward enhancements during geomagnetic storm recovery phases, rather than anticipated decrease or reversal. However, it is still unknown the occurrence and morphology of the persistent enhancement as well as its impact on the low‐latitude ionospheric plasma distribution. For the first time, we examined the issue with superposed epoch analyses of equatorial electrojet (EEJ) and GNSS total electron content (TEC) responses in the American (49°W) and Indian (78°E) sectors. The occurrence rates of the persistent enhancement during storm recovery phases are more than 30%, with higher occurrence rates in second to fourth days of the recovery phase, equinoxes, and American sector. The corresponding averaged EEJ and TEC responses were disclosed and compared with those storm samples without the persistent enhancement. On the first day of recovery phase, the dayside equatorial ionosphere was dominated by the prevalent westward electric field and causative inhibited equatorial fountain. In contrast, after the first day, the dayside morphologies showed different patterns: (a) for the persistent cases, the large eastward EEJ and TEC enhancement indicated the enhanced eastward electric field at forenoon and causative intensified equatorial fountain. (b) For the storms without the persistent cases, the general westward EEJ and equatorial TEC enhancements were dominated. Our study indicates that dayside eastward enhancement is an important disturbed pattern of equatorial ionospheric electric field during the late recovery phases, and the enhancement generally causes the intensification of equatorial ionization anomaly.