For instance, ground-based magnetometers, used in dense networks, routinely enable the derivation of ionospheric currents and geomagnetic indices. Optical instruments not only encompass imagers observing auroral and airglow emissions, but also consist of scanning Doppler imagers, Fabry-Perot interferometers, and lidars which measure upper atmospheric winds and temperatures, in particular in the thermosphere and mesosphere. Besides, visible spectrometers disentangle the spectral signatures of different auroral processes, enabling discrimination between precipitation-driven emissions and signatures of thermospheric heating. Ionospheric parameters can also be measured with radars, spanning a wide range of active (ionosondes, meteor radars, coherent and incoherent scatter radars, VLF transmitters) and passive (riometers, VLF receivers, GNSS receivers) systems. With increased interest in understanding space weather and atmosphere coupling as a system, polar atmospheric composition measurements of the middle atmosphere are also valuable. Finally, citizen science data such as images taken by aurora chasers are increasingly used to complement observations from instruments.
Combining ground-based observations from various instruments enables the development of novel data analysis methodologies that can provide access to physical quantities previously difficult to quantify, such as Joule heating. Ground-based measurements are also increasingly valuable for data assimilation into numerical models, thanks to which we can both enhance our understanding of the underlying physics of ionosphere–atmosphere processes and improve our space weather forecasting capability.
In this session, we invite contributions featuring the use of ground-based instruments in studies of the ionosphere–atmosphere system at polar and mid-latitudes. We welcome contributions of space weather and ionospheric–atmospheric physics processes of various time and spatial scales.
Orals: Thu, 7 May, 16:15–18:00 | Room 0.15
The Super Dual Auroral Radar Network (SuperDARN) is a collection of 40+ high-frequency radars spanning both hemispheres. For over 30 years, SuperDARN has constantly monitored the high-latitude ionosphere for changes due to the interaction of Earth’s magnetic field with the solar wind, offering one of the most extensive space-weather datasets in existence.
In the past few years, SuperDARN radars operated by the University of Saskatchewan (SuperDARN Canada) have had their capabilities vastly improved due to the implementation of software-defined radio systems. This upgrade moves complex transmit and receive functionality from the analogue domain into digital, allowing vastly enhanced flexibility in experiment design.
In this talk, some of the new capabilities of the digital SuperDARN radars will be highlighted, including experiments that offer multi-static radar imaging, a 16x temporal resolution improvement, and collaborations with satellite missions and ground-based optics. These experiments open the door for a new generation of studies in ionospheric physics, as there is no compromise to the spatial coverage of the radars.
How to cite: Billett, D.: SuperDARN Canada: Recent advances in ground-based space weather monitoring, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2845, https://doi.org/10.5194/egusphere-egu26-2845, 2026.
Led by the National Space Science Center of the Chinese Academy of Sciences, we have built a Chinese dual auroral radar network in northern China, which is called the CN‐DARN. The CN‐DARN consists of three pairs of SuperDARN radar facilities and is one of the key parts of the Chinese Meridian Project Phase II. It has been fully constructed and started trial operations at the end of 2023. The detection range of the radar network extends longitudinally over approximately 9 hr of local times and covers the middle to high latitudes of the entire Asia region above 40°. In this paper, we present the basic design of the CN‐DARN and its preliminary observations of ionospheric irregularities, subauroral polarization streams (SAPSs) and traveling ionospheric disturbances (TIDs). We also investigate its contribution to the ionospheric convection pattern of the Northern Hemisphere derived from Super Dual Auroral Radar Network (SuperDARN) observations. The results indicate that the CN‐DARN provides excellent measurements and better specifications of flows in the Asian sector, improving our understanding of the global‐scale ionospheric convection pattern in the Northern Hemisphere. These encouraging results lead us to believe that the CN‐DARN will play an important role in studies on the evolution of ionospheric irregularities, the characteristics and evolution of SAPSs, the propagation of TIDs, and global‐scale ionospheric convection dynamics.
How to cite: Zhang, J.: Development, Operation and Scentific Applications of the Chinese Dual Auroral Radar Network, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2648, https://doi.org/10.5194/egusphere-egu26-2648, 2026.
Forecasting and mitigating space weather effects requires accurate modelling of the coupled Magnetosphere-Ionosphere-Thermosphere (MIT) system. There are multiple ways to couple the magnetospheric dynamics to a thermosphere-ionosphere model. Most commonly, empirical models such as Heelis and Weimer are applied. To improve upon empirical models, data assimilative techniques such as AMIE and AMGeO have been developed. These techniques assimilate various radar, magnetometer, and satellite-based measurements into an empirical background model. A comparably recent development is the MAGE geospace model, which couples multiple physics-based models of the entire MIT system. We compare these methods with each other and evaluate them with various measurements.
One of the most important geomagnetic impacts on the thermosphere-ionosphere is Joule heating due to Pedersen currents. We evaluate the different forcing approaches by comparing the resulting Joule heating in reference to local measurements with the EISCAT incoherent scatter radar. We show that data assimilative methods provide a significant improvement over empirical forcing.
Physics-based geomagnetic forcing promises a model representation of small-scale processes that cannot be achieved with empirical methods. However, an initial assessment showed significant discrepancies between the polar plasma convection pattern given by a physics-based geospace model and SuperDARN radar network measurements. Since Joule heating is affected by changes in electron density and plasma convection potential, we evaluate the model representation of these quantities separately with EISCAT, SSUSI, and SuperDARN measurements.
How to cite: Günzkofer, F., Liu, H., Liu, H., Stober, G., Lu, G., Themens, D. R., Heymann, F., and Borries, C.: Geomagnetic forcing in T-I models: comparison of empirical, data assimilative, and physics-based forcing evaluated with radar measurements, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4035, https://doi.org/10.5194/egusphere-egu26-4035, 2026.
Pulsating aurora is a type of aurora generated by the precipitation of electrons into the ionosphere as a result of pitch‐angle scattering through wave–particle interactions with whistler‐mode chorus waves excited near the magnetic equatorial plane in the magnetosphere. This generation mechanism has been established by observations showing a one‐to‐one correspondence between the timing of chorus wave excitation observed by magnetospheric satellites and the luminosity modulation of pulsating aurora at the magnetic conjugate point (Nishimura et al., 2010), as well as by direct observations demonstrating changes in the electron pitch‐angle distribution associated with chorus wave excitation (Kasahara et al., 2018).
Pulsating aurora exhibits a variety of morphological features. Grono and Donovan (2020) classified pulsating aurora into Amorphous Pulsating Aurora (APA), characterized by indistinct structures; Patchy Pulsating Aurora (PPA), which maintains stable patchy structures while pulsating; and Patchy Aurora (PA), which has stable patchy structures with no pulsation, and statistically investigated their occurrence regions. Ito et al. (2024) analyzed an event in which the dominant morphology temporally transitioned from APA to PPA/PA by using simultaneous observations from all‐sky imagers, the Arase satellite, and the EISCAT radar. They interpreted that, when magnetospheric density ducts—regions where the electron density is higher or lower than the surrounding plasma—are present, chorus waves can propagate from the magnetic equator along magnetic field lines to higher‐latitude regions closer to the Earth. Such propagation leads to spatially localized wave–particle interactions, resulting in the visualization of PPA/PA with well‐defined boundaries. Furthermore, by applying an inversion technique to electron density altitude profiles measured by the EISCAT radar, they reported that the energy of precipitating electrons increases during the occurrence of PPA/PA. When the average energy of precipitating electrons becomes higher, the auroral emission altitude is expected to decrease.
In this study, we report observations of pulsating aurora over northern Sweden obtained with the ground‐based multi‐point camera network ALIS_4D and present an analysis of their altitude distributions for different types of pulsating aurora. Based on these results, we further discuss the relationship between the morphological differences of pulsating aurora and the generation and propagation processes of chorus waves.
How to cite: Nanjo, S., Taki, T., Sergienko, T., and Brändström, U.: Analysis of Altitude Structure and Morphological Differences of Pulsating Aurora Using ALIS_4D, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4911, https://doi.org/10.5194/egusphere-egu26-4911, 2026.
The aurora is a significant source of heat in the high latitude upper atmosphere: tens of gigawatts of energy from the solar wind is deposited as heat in the thermosphere and ionopshere (Østgaard et al 2002). Strong electric fields and currents associated with the aurora cause heating through friction between ions and neutrals (Joule heating) and resistive heating by magnetic field-aligned currents (Lanchester et al 2002). This energy input must be included in whole-climate models and models used to predict additional drag on spacecraft and space debris in Low Earth Orbit during geomagnetic storms. We present results from a new technique to measure neutral temperatures in fine-scale aurora at high spatial and temporal resolution (tens of milliseconds) using simultaneous images of emissions in two different parts of the auroral molecular nitrogen spectrum from the University of Southampton’s Auroral Structure and Kinetics (ASK) multi-spectral imager. The technique measures the neutral temperature at the altitude of the auroral emissions so the observations require careful interpretation to separate local neutral temperature changes from spatial variation in auroral altitude across each image. Height profiles of the neutral temperature are therefore obtained using a third image in an atomic oxygen emission to determine the energy of the auroral electron precipitation and hence estimate the altitude of the aurora and temperature measurement. The resulting profiles show rapid neutral temperature changes on the order of several hundred Kelvin across E-region altitudes (between 100 km and 160 km). The coolest temperatures are found within the brightest regions of the aurora, whereas higher temperatures are typically associated with the edges of arcs where the electric field is expected to be strongest. The neutral temperature profiles are compared to ion temperature profiles from the European Incoherant Scatter (EISCAT) Svalbard radar (co-located with ASK) to better understand Joule heating and ion-neutral coupling in the extreme electrodynamic environment surrounding the aurora.
How to cite: Barton, K., Whiter, D., Kavanagh, A., and Samaddar, S.: Neutral Temperature Changes in Fine Scale Aurora, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10006, https://doi.org/10.5194/egusphere-egu26-10006, 2026.
We report recent progress on ground-based studies of optical emissions from airglow and aurora. We used a state-of-the-art hyperspectral imager to collect airglow and auroral data, which were analyzed using updated optical data analysis and modeling tools.
The observations were made by the High Throughput and Multislit Imaging Spectrograph (HiT&MIS), a moderate resolution (λ/Δλ ~15,000) spectrograph with a field of view of 0.1° × 40°. The instrument can be customized for a scientific study by choosing selected spectral bands within the visible to near infrared regime. For the studies reported here, it simultaneously recorded prominent airglow and auroral features such as OI (557.7 nm, 630.0 nm, 777.4 nm), N₂⁺ (427.8 nm), OH (784.1 nm, 786.0 nm, 655.3 nm), as well as the Hα (656.3 nm) and Hβ (486.1 nm) emissions.
For nightglow studies, HiT&MIS collected spectral images between late January to early March in 2022 from Lowell, Massachusetts, USA (42.6° N, 71.3° W). Due to its physical location, zenith observations were not possible, and we developed a 2-D framework for the GLOW model (GLOW-2D). We also updated older versions of the neutral atmosphere, ionosphere, and magnetic field models previously used in GLOW by incorporating NRLMSIS-2.1, IRI-2020 and IGRF-14, respectively. In addition, simultaneous Vertical TEC data provided by the GNSS network and digisonde data from nearby Millstone Hill Observatory were used to derive the GLOW-2D model predictions while comparing against the observed optical measurements.
HiT&MIS was deployed in Kiruna, Sweden (67.8° N, 20.2° E) to support two Oxygen and its Role In Generating and Influencing Nightglow (ORIGIN) sounding rocket missions in January and December 2025, respectively. The characteristic energy and flux of the precipitating electrons in several nighttime auroras were obtained from the measured green and red line intensities constrained by the GLOW-2D model. Currently, we are incorporating other emissions to further refine the model results and preparing a HiT&MIS data processing pipeline to analyze round-the-clock auroral spectroscopic data.
How to cite: Chakrabarti, S., Mukherjee, S., Patel, C., and Cook, T.: Development and validation of observational and modeling tools for ground-based studies of the upper atmosphere and ionosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1901, https://doi.org/10.5194/egusphere-egu26-1901, 2026.
Recently, a network of three scanning Doppler imagers (SDI) has been installed in the Fennoscandian region, at Abisko in Sweden, and at Aakenus and Kevo in Finland. The combined field-of-view of these instruments covers observation volume of the upcoming tristatic and phased array incoherent scatter radar, EISCAT_3D. In parallel, a Fabry-Pérot interferometer (FPI) has been relocated from Tromsø to Skibotn, Norway to complement future EISCAT_3D observation of the thermosphere.
Each SDI instrument measures the line-of-sight (LoS) component of the neutral wind velocity and temperature in the upper atmosphere using all-sky observations of auroral emissions. Measurements are derived from the green-line emissions in the E region and the red-line emissions in the F region of the ionosphere. With about 140° field of view, each SDI provides measurements in 115 distinct viewing directions. Together, the three SDIs form a tristatic configuration with an observation region extending more than 1000 km in both the east–west and north–south directions. However, only a small portion of this region contains overlapping viewing zones from all instruments, which limits the ability to directly retrieve the full three-dimensional neutral wind vector throughout the entire volume.
To address this limitation, here we present a new modeling technique that reconstructs the full neutral wind velocity vector from LoS measurements across observation volume of available SDIs. The method is based on representing the horizontal component of the wind velocity by the spherical elementary basis functions and the vertical component by piecewise constant functions in a gridded observation volume. We validate our approach using synthetic LoS data generated from WACCM-X thermospheric simulation. We also apply the technique to real LoS measurements from two SDIs and compare the result with an independent FPI measurements. In both comparisons, our method shows a good performance, and when combined with EISCAT_3D measurements, this approach will enable more detailed investigations of ionosphere-thermosphere coupling processes.
How to cite: Tesfaw, H. W., Vanhamäki, H., Oyama, S., and Conde, M.: Modeling the neutral wind velocity based on measurements by scanning Doppler imagers, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10917, https://doi.org/10.5194/egusphere-egu26-10917, 2026.
The extreme ultraviolet (EUV) and X-ray radiation emitted during solar flares cause considerable increases in the electron density of the Earth's ionosphere. During flares, quasi-periodic pulsations (QPPs) in coronal X-ray flux have previously been linked to subsequent pulsations in the Earth's ionospheric D-region. Similar pulsations have been detected in chromospheric EUV emission, although their impact on the Earth's ionosphere has not previously been investigated. Here, for the first time, synchronous pulsations have been detected in solar EUV emission and ionospheric total electron content (TEC) measurements. QPPs were identified in chromospheric EUV emission lines (304Å, 972Å and 977Å) during the impulsive phase of the X5.4 flare on 7 March 2012 using SDO/EVE. These lines contribute to ionisation in the ionospheric E- and F-regions, producing corresponding variations in electron density detectable in TEC with delays of ~30 seconds. Building on this analysis, we extend the time-delay investigation to a sample of ten powerful solar flares to quantify the characteristic F-region response timescales. We assess the measured delays in relation to multiple solar and geophysical factors. The results show that the ionosphere responds rapidly and measurably to both small-scale EUV fluctuations and the overall flare-driven increase in EUV irradiance, highlighting the diagnostic potential of QPP-driven ionospheric signatures and their applications in atmospheric modelling, solar–terrestrial coupling, and ionospheric recombination studies.
How to cite: O'Hare, A. N., Bekker, S., Hayes, L. A., Greatorex, H. J., and Milligan, R. O.: Coupled Solar–Ionospheric Dynamics: EUV Pulsations and Ionospheric Response Timescales During Flares, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-303, https://doi.org/10.5194/egusphere-egu26-303, 2026.
Throughout the high-latitude ionosphere, large-scale plasma structures, such as polar cap patches and blobs, are ubiquitous. These structures can seed smaller-scale irregularities due to instability mechanisms, which can cause scintillation of trans-ionospheric radio signals, such as those used for Global Navigation Satellite Systems (GNSS). The complex nature of these structures along with other processes such as auroral precipitation, means that plasma can be structured on a variety of spatial scale sizes from hundreds of kilometres down to tens of meters. As it is not currently possible for this range of scales to be observed by any singular instrument, the Scales of Ionospheric Plasma Structuring (SIPS) experiment was conducted in winter 2024 using a suite of instrumentation. The European Incoherent SCATter (EISCAT) radars observed structures measuring several hundreds of kilometres in size, while the Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) was able to capture spatial sizes of ~100 m up to ~5 km. The Swarm satellites and GNSS receivers were then able to identify the presence of structures down to, and below ~500 m in size. Additionally, coherent scatter radars (SuperDARN), magnetometers, and other instruments are used to give contextual understanding, for example, providing velocity information and insight into the geophysical conditions. The combination of this range of ground- and space-based instrumentation, in conjunction with modelling techniques gives unprecedented coverage of the varying scale sizes, which is not possible with individual instrumentation alone. This presentation discusses the latest results from the SIPS experiments and showcases the relationship between structures of varying scale sizes in the high-latitude ionosphere.
How to cite: Maguire, S., Themens, D., Wood, A., and Brown, M.: Scales of Ionospheric Plasma Structuring in the High-Latitude Ionosphere and the Associated Effects for GNSS Scintillation , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19664, https://doi.org/10.5194/egusphere-egu26-19664, 2026.
We employ ground magnetometers in North America, Greenland, and Antarctica and use the Spherical Elementary Current (SEC) technique in order to investigate the currents flowing between January 2015 and December 2016. We convert the measurements into altitude-adjusted corrected geomagnetic (AACGM) coordinates to allow us to investigate the hemispheric asymmetries between conjugate points. There are data gaps during the Southern Hemisphere winters due to difficulties of making ground-based observations at these times. We subset the measurements to control for the different spatial extents of the data in either hemisphere, and then average spatially and temporally so that we can compute the asymmetry. We contextualise the asymmetry in terms of AMPERE, Swarm, and DMSP-observed asymmetries, and discuss what this implies for the ionospheric conductance in either hemisphere.
How to cite: Coxon, J., Weygand, J., du Bois, P., Oliveira, D., and Watt, C.: Hemispheric asymmetries in Spherical Elementary Current-derived currents observed from North America, Greenland and Antarctica, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2614, https://doi.org/10.5194/egusphere-egu26-2614, 2026.
The neutral dynamics defining the baseline conditions of the coupled ionosphere-thermosphere (I-T) region are well understood on global scales. However, localised meso-scale behaviours, which significantly influence thermospheric composition and drive subsequent ionospheric changes remain difficult to characterise due to observational gaps and model limitations. Identification and characterisation of such changes is crucial, especially at high latitudes where, alongside lower atmospheric forcings, short-lived space weather events can lead to meso-scale spatial structures. We characterise the changes induced by such events using a comprehensive multi-instrument dataset spanning over three decades from the Scandinavian region. By combining ionospheric measurements from EISCAT and Dynasonde with neutral winds and temperatures from Fabry-Pérot Interferometers (FPIs), we quantify the perturbations in the I-T system during geomagnetically disturbed periods. We will present key findings from these analyses, detailing the causal mechanisms of high-latitude ion-neutral coupling.
How to cite: Mandal, S., Scott, C., Aruliah, A., Reidy, J., Wild, M., and Kavanagh, A. J.: Quantifying Ionosphere-Thermosphere Variability During Geomagnetic Disturbances, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6778, https://doi.org/10.5194/egusphere-egu26-6778, 2026.
The high latitude ionosphere displays highly variable behaviour that can be attributed to a multitude of processes. These originate from sources that range from internal coupling with the neutral atmosphere to electrodynamics driven by external space weather. DRIIVE (DRivers and Impacts of Ionospheric Variability with EISCAT-3D) is a project aimed at identifying this variability across a range of scales and comparing the relative contributions of different drivers. In December 2025 the DRIIVE team ran a 5-day campaign using the mainland EISCAT incoherent scatter radars in conjunction with a suite of additional ground-based instruments to monitor the night side ionosphere. Both the UHF and VHF radars were operated to provide simultaneous measurements in different look directions. The UHF radar ran a scanning mode to provide an estimate of the local ionospheric electric field. Here we present the first observations and analysis of the radar data collected during this campaign; we examine the changes in ionospheric parameters through different substorm phases and quieter periods, identifying both spatial and temporal variability at selected altitudes.
How to cite: Kavanagh, A. J. and Mandal, S.: Ionospheric variability at high latitudes measured by incoherent scatter radar: first observations from the DRIIVE winter campaign, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7816, https://doi.org/10.5194/egusphere-egu26-7816, 2026.
The dayside auroral ionosphere exhibits significant variability because of its strong coupling to the magnetosphere-solar wind system. Dayside aurora is typically driven by soft precipitation, which also produces enhanced electron temperatures at high altitudes and can be easily measured by Incoherent Scatter Radars. Using EISCAT Svalbard radar (ESR) fast elevation scans, we identify the equatorward boundary of the dayside aurora and extract near-simultaneous ionospheric altitude profiles within and outside the auroral region, allowing for an investigation of ionospheric behavior with respect to the relative distance from this boundary. In addition, the large data set of ESR field-aligned observations facilitates statistical analysis over two solar cycles. Together, both field-aligned observations and elevation scans contribute to a characterization of the dayside auroral ionosphere.
How to cite: Frøystein, I., Spicher, A., Oksavik, K., Gustavsson, B., and Johnsen, M. G.: Characterizing the dayside auroral ionosphere with ISR elevation scans and field-aligned observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12983, https://doi.org/10.5194/egusphere-egu26-12983, 2026.
More than 20,000 visible spectra of diffuse auroras were recorded by the Auroral Spectrograph In Skibotn (ASIS), operating since October 2023 within the auroral oval. An AI-based classification was used to identify diffuse auroral intervals. The characteristic energy of precipitating electrons was then estimated from the ratio of calibrated red (630.0 nm) and blue (427.8 nm) emissions, using lookup tables derived from a kinetic electron transport model. Within a Bayesian regression framework, the dependence of the inferred electron energy on magnetic local time was investigated. The results reveal a clear post-midnight hardening of the precipitating electron population toward the dawn sector, with a transition occurring near 04 MLT, consistent with previous optical, radar, and satellite studies.
How to cite: Cessateur, G., Hosokawa, K., Lamy, H., Nanjo, S., Barthelemy, M., Johnsen, M. G., and Maggiolo, R.: MLT dependence of diffuse auroral electron precipitation energy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21007, https://doi.org/10.5194/egusphere-egu26-21007, 2026.
How to cite: Hessen, J. C., Hatch, S. M., and Billett, D.: Auroral proper motion and the dynamics of auroral shear boundaries, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10201, https://doi.org/10.5194/egusphere-egu26-10201, 2026.
Auroral forms can provide information not only on the state of near-Earth space but also on conditions in the lower-thermosphere–ionosphere. The so-called dune aurora, consisting of brighter stripes forming a wave-like pattern in the dim, diffuse green aurora, has been hypothesised as being an optical signature revealing the presence of large-scale atmospheric waves above or near the mesopause. However, only a few dune aurora events have been studied to date, leaving many open questions regarding the nature of this phenomenon. We carry out the first statistical analysis of dune aurora events by collecting citizen science observations of the dunes since 2000 using the Skywarden (https://taivaanvahti.fi) database of observations. From a total of 289 dune aurora observations made during 56 different events by citizen scientists from Northern Europe, North America, Australia, and New Zealand, we investigate the distribution of dune events as a function of location, month, local time, solar wind and interplanetary magnetic field (IMF) conditions, and geomagnetic activity. We compare those distributions to that of all the aurora observations reported in Skywarden since 2000. We also estimate the duration of dune events based on the available observations, and we investigate a possible relationship between dune aurora and equivalent current patterns derived from ground-based magnetometer measurements. We find that the vast majority of dune observations take place near the equatorward boundary of the auroral oval, in the dusk sector earlier than the peak in all auroral report distribution, and in association with strong (in most cases eastward but occasionally westward) auroral electrojet signatures. The dune observations are often associated with elevated solar wind density and IMF magnitude, and the IMF By component may play a role in their formation. Finally, their monthly distribution peaks in March and October, which could be the result of a combination of geomagnetic, atmospheric, darkness, and cloudiness conditions needed for them to form.
How to cite: Grandin, M., Juusola, L., Partamies, N., Bruus, E., Rautiainen, J., Lach, D., Jia, J., van de Kamp, M., Karvinen, E., Kauristie, K., and Hoppe, T.: Dune aurora: Statistical survey from a citizen science database, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1821, https://doi.org/10.5194/egusphere-egu26-1821, 2026.
One of the great challenges of studying the coupled ionosphere-thermosphere system is the difficulty of making distributed in situ measurements simultaneously. Beginning with Birkeland's (1908) pioneering study of ionospheric currents via equivalent currents, many investigations of the complex, coupled, three-dimensional ionosphere-thermosphere system represent this system as a slab or thin shell either out of expedience or necessity. Almost all existing methods for assimilative reconstruction of ionosphere-thermosphere electrodynamics are based on such thin-shell representations. In this study, we use rocket-based measurements of neutral wind profiles and incoherent scatter radar measurements to directly calculate central height-integrated quantities in IT electrodynamics (perpendicular current, Joule heating, Hall and Pedersen conductance) and compare with estimates based on height-integrated quantities derived from the height-integrated Ohm's law and the expression for height-integrated Joule heating. It is shown that when an appropriate estimate of the neutral wind is included, estimates of these height-integrated quantities lie within ~20% of their true values. When the neutral wind is ignored (i.e., assumed to be zero in Earth's corotating frame of reference) estimates differ from their true values by as much as 100%.
How to cite: Hatch, S., Lamarche, L., Laundal, K. M., Mesquita, R., Tesfaw, H., and Vanhamäki, H.: Errors associated with 2D representations of high-latitude ionosphere-thermosphere electrodynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9334, https://doi.org/10.5194/egusphere-egu26-9334, 2026.
Spherical elementary current systems (SECS) provide a method for modeling ionospheric currents and other ionospheric vector fields. The original formulation of the SECS assumes point-like sources for the divergence and curl of the fields, which lead to singularities. Here we formulate a general differentiable alternative for the original SECS and show that any function with a finite Legendre series can be used as the basis of the analysis. We also present how a particular choice of the Legendre coefficients leads to closed-form expressions for the magnetic field and electric currents, making the differentiable SECS no more complicated than the original SECS. A common application of SECS is solving the currents from magnetic field measurements. We demonstrate how to regularize the system with Bayesian tools with intuitive, physically meaningful parameters for the currents. In particular, we show how prior knowledge about the amplitudes and correlation lengths of the currents is transformed to prior information on SECS amplitudes. The differentiable SECS and the inversion method are verified with a test case built using the Average Magnetic field and Polar current System (AMPS) model. In addition, we apply our method to data from a ground magnetometer network and compare our results with results obtained with the original SECS method.
How to cite: Käki, S., Norberg, J., and Kauristie, K.: Bayesian approach to ionospheric elementary current systems using differentiable basis functions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12733, https://doi.org/10.5194/egusphere-egu26-12733, 2026.
The magnetic connection between the ionosphere and the magnetotail current sheet allows for couplings between ionospheric conditions and various phenomena in the magnetotail. Magnetic reconnection in the tail causes fast plasma flow channels that affect the field-aligned currents (FACs) flowing between the tail and the ionosphere. It is currently understood that these plasma flows in the tail result in ionospheric current channels that correspond predominantly to North-South aligned auroral structures called streamers.
We investigate the effects to the FAC systems by making a comprehensive survey of fast plasma sheet flows in the magnetotail and mapping the events to the ionosphere above Fennoscandia, using the T89 magnetic field model. The survey is done for Cluster-, MMS-, and THEMIS-mission data archives between the years 2001 and 2025. The criteria for fast flows are those commonly used for bursty bulk flows; velocity over 400 km/s in the Earthward direction and plasma beta over 0.5 to ensure the satellite is within the plasma sheet. We then utilise the Spherical Elementary Current System (SECS) method with the IMAGE magnetometer network to obtain ionospheric equivalent current densities and estimates of changes to FACs. Where possible, we analyse optical data, and compare auroral structures to the ionospheric current patterns. Studying the signatures of plasma sheet flows from ground-based observations as well as satellite data helps in building a better understanding of the connection between the two domains.
How to cite: Koikkalainen, V., Grandin, M., Juusola, L., Partamies, N., Workayehu, A., Pänkäläinen, L., and Palmroth, M.: Fast magnetotail plasma sheet flows and field aligned currents, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6520, https://doi.org/10.5194/egusphere-egu26-6520, 2026.
In the following study, we aim to investigate the possible impacts of a Solar eclipse on ionospheric conditions. On October 25th, 2022, and March 29th, 2025, a partial Solar eclipse was visible from Borowiec, Poland. In both cases, the LOFAR observations were carried out to study the ionospheric conditions during their occurrence. The LOFAR PL610 station was used in a single mode and continuously observed strong radio sources prior to, during, and after both eclipses.
In case of an eclipse that occurred in October 2022, the observations reveal the diffraction pattern seen on the signal intensity image for CasA, a strong astronomical radio source. No similar patterns were observed for other strong sources, such as CygA or VirA. On the other hand, observations of the Sun show a decrease in visibility of recorded structures during the solar eclipse. In this case, the decreased signal intensity could be caused by partial coverage of the Solar disc.
No evident similar ionospheric effects were observed, which may be related to changes in the ionosphere resulting from the solar eclipse on March 29, 2025. However, the findings presented in this work, linking ionospheric effects observed by LOFAR during the eclipses, should be further investigated.
How to cite: Pożoga, M., Ciechowska, H., Matyjasiak, B., Grzesiak, M., Przepiórka-Skup, D., Phung, T., Tomasik, Ł., Hanna Rothkaehl, H., and Wronowski, R.: Ionospheric effects of solar eclipse observed with PL610 LOFAR station, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17912, https://doi.org/10.5194/egusphere-egu26-17912, 2026.
SuperDARN radars have traditionally been calibrated using two methods: electrical measurements on site, and phase measurements between the main and auxiliary arrays. These methods are imperfect, as site visits are infrequent and array-level calibration neglects antenna-based errors. Aircraft measurements are a superior calibration method. Aircraft are ideally suited for SuperDARN radar calibrations, as they are numerous, compact, fly within the radar field-of-view, and their positions are catalogued frequently. This work uses the OpenSky Network air traffic database in conjunction with SuperDARN radar measurements to identify airplanes and use them to calibrate the Saskatoon SuperDARN Canada radar on a per-antenna basis.
How to cite: Hussey, G., Rohel, R., Pitzel, B., and Ponomarenko, P.: SuperDARN Antenna Calibration using Air Traffic Data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8262, https://doi.org/10.5194/egusphere-egu26-8262, 2026.
The ICEBEAR (Ionospheric Continuous-wave E-region Bistatic Experimental Auroral Radar) radar is a low-elevation radar, primarily designed for the observation of E-region radar aurora and meteor trails echoes. ICEBEAR uses interferometric processing (imaging) to geographically locate echoes within a wide field-of-view. The imaging process requires the phase of the received signal on the 10 independent antennas in the radar receiver array, so phase calibration of the receiver antenna array is of vital importance for confident and accurate measurements. In addition to observing radar aurora and meteor trails, ICEBEAR regularly receives both the signal from the radio galaxy Cygnus A and radar echoes scattered from aircraft. This presentation will explain how the radio galaxy signal and aircraft echoes are utilised to perform ICEBEAR receiver phase calibrations. The results of the radio galaxy and aircraft calibration techniques will be evaluated and validated qualitatively and quantitatively alongside the results of the current spectrum analyser calibration technique. The radio galaxy technique will be shown to be the preferred calibration method, though all three methods produce acceptable azimuthal results.
How to cite: Pitzel, B., Hussey, G., Marei, S., Rohel, R., Galeschuk, D., and Huyghebaert, D.: Phase Calibration of the ICEBEAR Radar Using Three Independent Methods , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8193, https://doi.org/10.5194/egusphere-egu26-8193, 2026.
The extreme geomagnetic storm on May 10, 2024, caused an unprecedented expansion of auroral activity toward the equator over Europe. This provided a unique opportunity to study ionospheric disturbances associated with auroras at mid-latitudes. In this study, we analyze the ionosphere's response based on observations from a dense network of Global Navigation Satellite System (GNSS) receivers and simultaneous measurements made with an all-sky imaging camera. We analyzed total electron content (TEC), TEC gradients and anomalies, and the rate of TEC index (ROTI), comparing them with the spatial and temporal evolution of auroral emissions.
Our results indicate that increased TEC amplitudes, strong TEC gradients, and elevated ROTI values are closely associated with auroral precipitation and stable red auroral arcs. We observed visible TEC disturbances spreading southward, but their propagation was spatially limited and closely corresponded to the expansion of the auroral boundary. These disturbances did not extend to subauroral regions or mid-latitudes outside the auroral zone.
Combined GNSS and optical observations suggest that auroral particle precipitation and related electrodynamic processes predominated during this event. There was limited evidence of large-scale, freely propagating ionospheric disturbances. This study underscores the importance of multi-instrument observations for correctly interpreting ionospheric disturbances during storms and for assessing the impact of space weather on GNSS-based systems in mid-latitudes.
How to cite: Nykiel, G., Kanska, J., Sato, H., Oyama, S., and Themens, D.: Aurora-Associated Ionospheric Disturbances at European Mid-Latitudes During the May 10, 2024, Geomagnetic Storm, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21291, https://doi.org/10.5194/egusphere-egu26-21291, 2026.
Analysis of very low frequency (VLF) radio waves offers a valuable opportunity to investigate the response of both the lower ionosphere and the magnetosphere to a wide range of transient and long-term physical phenomena originating on Earth (e.g., atmospheric waves) or in space (e.g., coronal mass ejections). In this study, we use broadband VLF measurements recorded at Kannuslehto in northern Finland to characterize and examine their links to different geophysical and solar phenomena. The main findings are: (i) the semiannual oscillation in VLF data is associated with geomagnetic activity, while a 27-day solar rotation signal dominates during the declining phase of the solar cycle; (ii) sunrise-related VLF phase perturbations are primarily caused by the attenuation of short-wavelength solar UV radiation by stratospheric ozone; and (iii) banded VLF emissions were detected in the 16–39 kHz range, a frequency band not typically used to study magnetospheric whistler-mode emissions. We further examine the seasonal dependence of the banded emissions using continuous data from 2022 and discuss their possible origin, including the potential role of magnetospheric plasma instabilities, similar to those responsible for auroral hiss.
How to cite: Macotela, L. and Manninen, J.: VLF Observations of Solar and Geophysical Forcing on the Polar Ionosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20468, https://doi.org/10.5194/egusphere-egu26-20468, 2026.
Accurate characterization of the Earth–ionosphere waveguide (EIWG) is fundamental to Very Low Frequency (VLF) remote sensing of space weather variability and mesospheric lower ionospheric dynamics. Conventional wave-hop propagation models, however, are prone to parameter degeneracy, whereby uncertainties in assumed ground conductivity are offset by non-physical adjustments to ionospheric reflection parameters, undermining physical interpretability.
Here, we introduce a physically constrained modeling framework that combines deep learning (DL) based terrain classification with asymmetric ionospheric parameterization to improve the realism and identifiability of sub-ionospheric VLF simulations. High-resolution satellite imagery along the great-circle propagation path is classified into six terrain categories using a convolutional neural network based on the ResNet-50 architecture. Each terrain class is assigned a representative electrical conductivity, thereby replacing the common assumption of laterally homogeneous ground properties. In parallel, an asymmetric temporal ionospheric model driven by solar zenith angle is implemented to capture the hysteresis associated with unequal ionization and recombination rates across sunrise and sunset terminators.
Model performance is evaluated using narrowband observations from the AWESOME and WALDO receiver networks. Results demonstrate that incorporating spatially varying, AI derived ground conductivity substantially improves agreement between modeled and observed VLF amplitudes and phases. Importantly, although multiple parameter sets may reproduce similar signal amplitudes, only models constrained by physically realistic ground conductivity yield ionospheric reflection heights that remain within geophysical reasonable ranges. This approach mitigates long-standing identifiability issues in VLF propagation modeling and enhances the robustness of VLF-based diagnostics of lower ionospheric variability.
How to cite: Reuveni, Y. and Romano, B.: Integrating Convolutional Neural Networks and Wave Hop Theory for Enhanced Sub-ionospheric VLF Remote Sensing via Satellite-Derived Terrain Mapping, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4496, https://doi.org/10.5194/egusphere-egu26-4496, 2026.
Collisions between CO2 molecules and O(3P) atoms dominate the excitation of CO2 in the MLT and its 15 µm emission. However, the current non-LTE models of CO2 are inconsistent with laboratory and space observations of this emission. We have proposed a new model for the non-LTE 15 µm cooling of the MLT [1], which is consistent with both types of observation and shows that standard non-LTE models significantly overestimate this cooling. This casts serious doubt on the widespread belief that the 15 µm emission is the primary cooling mechanism of the MLT. A significant reduction in 15 µm cooling will have a significant impact on the modelling of the current MLT and the estimation of its future changes due to increasing CO2.
This research was funded by US NSF grants AGS-2312191/92 and AGS-2125760, and by NASA grant 80NSSC21K0664.
1. Kutepov et al., Remote Sens., 2025, 17(11), 1896. https://doi.org/10.3390/rs17111896
How to cite: Kutepov, A., Feofilov, A., Rezac, L., and Kalogerakis, K.: New Model of the 15 µm Cooling of the Mesosphere and Lower Thermosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13388, https://doi.org/10.5194/egusphere-egu26-13388, 2026.
Posters virtual: Mon, 4 May, 14:00–18:00 | vPoster spot 4
EGU26-16003 | ECS | Posters virtual | VPS27
Cutting-Edge Projects in Aurora Participatory ScienceMon, 04 May, 14:51–14:54 (CEST) vPoster spot 4
Participatory science, also called citizen science, connects scientists with the public to enable discovery by engaging broad audiences across the world. In aurora science, direct collaborations, crowdsourced efforts, and community engagement bridge aurora chasers with scientists to do research. These efforts have been fueled by recent large geomagnetic storms, evolving consumer camera technologies, social media, and dedicated citizen science projects. In this presentation, we highlight recent, cutting-edge participatory science efforts with a primary focus on the Aurorasaurus project and how it can be used to study major storm-time auroral activity.
Aurorasaurus is an award-winning citizen science platform that has been operating for over a decade. Aurora observers submit visibility reports and photos, which are filtered and cleaned to generate science-quality datasets. We highlight Aurorasaurus data from recent major geomagnetic storms in 2024 and 2025, emphasizing how rapid, widespread reporting during extreme events enables mapping of storm-time auroral extent and tracking changes in the auroral oval boundary at low latitudes. During the May 10-11, 2024 geomagnetic storm, Aurorasaurus compiled more than 5,000 vetted reports from 50+ countries, allowing for unique data-model comparisons and tracking of the extent of auroral visibility.
We also address the efficacy of using citizen science photos for research. We discuss how submitted images not only provide additional perspectives and validation of reported auroral forms, but can also constitute unique scientific datasets beyond the capabilities of traditional instrument networks. For example, modern consumer cameras can capture high spatial resolution views of fine-scale auroral structure, and photos from multiple observers can be combined to enable stereoscopic and tomographic reconstructions of auroral morphology and its evolution.
Finally, we briefly note complementary campaign-style participatory science efforts, including the AurorEye project’s low-cost deployable all-sky timelapse units, the SolarMaX mission in coordination with SpaceX’s Fram2 launch, and collaborations between aurora chasers and the SuperDARN team to supplement radar measurements with optical aurora data. With the ongoing solar maximum, it is important to harness the excitement and enthusiasm surrounding the aurora and space weather. Participatory science efforts build important relationships between public communities and scientists and unlock unique research benefits.
How to cite: Ledvina, V., MacDonald, E., Edson, L., and Natsheh, F.: Cutting-Edge Projects in Aurora Participatory Science, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16003, https://doi.org/10.5194/egusphere-egu26-16003, 2026.
