ANGEO - recent papers

JUICE-JANUS observations of Earth in preparation for the JANUS investigation of Jupiter's atmosphere

2026-10-13T08:08:53+02:00

JUICE-JANUS observations of Earth in preparation for the JANUS investigation of Jupiter's atmosphere
Ricardo Hueso, Arrate Antuñano, Luisa María Lara, Katrin Stephan, Angelo Zinzi, Athena Coustenis, Yoav Yair, Mitsuteru Sato, Junichi Haruyama, Amy Simon, Cecilia Tubiana, Luca Penasa, Livio Agostini, Alice Lucchetti, Alessio Aboudan, Michael Aye, Elke Kersten, Klaus-Dieter Matz, Romolo Politi, Frank Trauthan, Ry Evill, Ines Belgacem, Takahashi Yukihiro, Jose María Castro-Marin, Vincenzo Della Corte, Stubbe Hviid, Thomas Roatsch, Nicole Schmitz, Manish Patel, Ganna Portyankina, and Pasquale Palumbo
Ann. Geophys., 44, 1043–1073, https://doi.org/10.5194/angeo-44-1043-2026, 2026
JANUS (Jovis, Amorum ac Natorum Undique Scrutator), the high-resolution camera on ESA’s JUICE (JUpiter ICy moons Explorer) mission, observed Earth during the August 2024 Lunar–Earth Gravity Assist. Images from a close flyby captured night- and day-side atmospheric phenomena, and a distant view resulted in a low-resolution Earth portrait. These observations validate JANUS performance and demonstrate the instrument’s capabilities. We focus our analysis on characterizing atmospheric systems that provide relevant examples for future studies of Jupiter’s atmosphere.

Statistical properties of internal modulation in pulsating aurora

2026-10-12T08:08:53+02:00

Statistical properties of internal modulation in pulsating aurora
Sota Nanjo, Tomoe Taki, Keisuke Hosokawa, Urban Brändström, Yoshizumi Miyoshi, and Magnar G. Johnsen
Ann. Geophys., 44, 1023–1042, https://doi.org/10.5194/angeo-44-1023-2026, 2026
Pulsating aurora often contains rapid brightness changes, but their overall behavior has not been well measured. We analyzed high-speed camera images from northern Sweden and Norway with machine learning to identify when these rapid changes occur. We found that they become more common toward the morning and at the lower-latitude sector. This suggests that small-scale auroral fluctuation can help reveal how particles from near-Earth space enter the upper atmosphere.

High-latitude auroral and cloudiness occurrence from automatic image classification

2026-10-01T08:08:53+02:00

High-latitude auroral and cloudiness occurrence from automatic image classification
Noora Partamies and Mikko Syrjäsuo
Ann. Geophys., 44, 1003–1022, https://doi.org/10.5194/angeo-44-1003-2026, 2026
We developed a method to prune colour all-sky images into classes of clear or cloudy skies with and without aurora using supervised learning and pre-trained convolutional neural network. We investigate a 10-year database of auroral images taken from Svalbard. The method accuracy is well over 90 %, and the results show that about 2/3 of auroral images are cloudy with the cloudiest month being November. Aurora are most often observed in the morning hours independent on the solar activity.

Ionospheric currents and auroral signatures during successive earthward bursty bulk flows and dipolarization: a 7 December 2023 case study

2026-09-30T08:08:53+02:00

Ionospheric currents and auroral signatures during successive earthward bursty bulk flows and dipolarization: a 7 December 2023 case study
Vanina Lanabere, Stephan Buchert, Adrian Blagau, Harriet George, Sota Nanjo, Liisa Juusola, Andrew P. Dimmock, Samuel Wharton, Heikki Vanhamäki, Octav Marghitu, Louis Richard, Lei Cai, Alice V. L. Wallner, Daria Kotova, Yaqi Jin, Theresa Hoppe, Jennifer A. Carter, and Anita Aikio
Ann. Geophys., 44, 977–1001, https://doi.org/10.5194/angeo-44-977-2026, 2026
We studied a series of fast plasma streams that connected Earth’s nightside magnetic environment with the high‑latitude ionized upper atmosphere on 7 December 2023. Using satellite, auroral images and ground observations, we showed how each stream disturbed the upper atmosphere. Their repeated impact strengthened these disturbances until a substorm began, revealing how small events can build up to a larger magnetic disruption.

Mesoscale structure of flickering aurora from wide-field high-speed imaging

2026-09-25T08:08:53+02:00

Mesoscale structure of flickering aurora from wide-field high-speed imaging
Sota Nanjo, Satoshi Kurita, Tima Sergienko, Yoshizumi Miyoshi, and Ryuho Kataoka
Ann. Geophys., 44, 959–975, https://doi.org/10.5194/angeo-44-959-2026, 2026
Using a high-speed camera with a wide view of the sky, we observed rapidly blinking aurora across several hundred kilometers. We found that different parts of the same auroral arc can blink at different rhythms at the same time, and that these rhythms move together with the arc. Although larger bright patches sometimes blink more slowly, this pattern does not hold overall. These results improve our understanding of how invisible space processes shape the visible northern lights.

Deducing spatial characteristics of global thunderstorm activity using the observed Schumann resonance frequencies

2026-09-18T08:08:53+02:00

Deducing spatial characteristics of global thunderstorm activity using the observed Schumann resonance frequencies
Oleksandr Koloskov, Masashi Hayakawa, and Alexander P. Nickolaenko
Ann. Geophys., 44, 949–957, https://doi.org/10.5194/angeo-44-949-2026, 2026
To study global thunderstorm activity we analysed the Schumann Resonance electromagnetic field driven by lightning. We developed formulas to calculate both the distance and the size of thunderstorm areas from frequency changes of either the magnetic or the electric resonance modes alone. Our method can be used by observatories worldwide, which mainly record magnetic fields. This novel technique improves our ability to monitor and understand global lightning activity.

Flying through the plasmasphere to optimize low-energy ion measurements

2026-09-17T08:08:53+02:00

Flying through the plasmasphere to optimize low-energy ion measurements
Gabriella Stenberg Wieser, Martin Wieser, Stas Barabash, Philipp Wittmann, Leif Kalla, Markus Fränz, Elias Roussos, Audrey Vorburger, Peter Wurz, Jan-Erik Wahlund, Pontus C. Brandt, Yoshifumi Futaana, Manabu Shimoyama, Angèle Pontoni, André Galli, Andreas Riedo, George Ho, Donald G. Mitchell, George Clark, Peter Kollmann, Malamati Gkioulidou, Leonardo Regoli, Norbert Krupp, Robert Wimmer-Schweingruber, Kazushi Asamura, Esa Kallio, Andrea Opitz, Manuel Grande, Andrew Coates, Geraint Jones, Theodoros Sarris, Andrey Fedorov, Nicolas André, and Ján Baláž
Ann. Geophys., 44, 937–948, https://doi.org/10.5194/angeo-44-937-2026, 2026
We used Juice flyby of Earth in August 2024 to evaluate the performance of the Jovian Plasma Dynamics and Composition analyzer (JDC). JDC measures positive and negative ions as well as electrons. When Juice arrives at Jupiter, one of the most challenging tasks for JDC is to record low energy ion populations. We used the data JDC recorded close to Earth, together with measurement in the laboratory on ground, to improve the future observations the sensor will make around Jupiter’s icy moons.

Non-Maxwellian electron distributions in the D region during artificial heating – Part 1: Model development and electron temperature

2026-09-15T08:08:53+02:00

Non-Maxwellian electron distributions in the D region during artificial heating – Part 1: Model development and electron temperature
Margaretha Myrvang and Björn Gustavsson
Ann. Geophys., 44, 921–935, https://doi.org/10.5194/angeo-44-921-2026, 2026
This paper investigate how radio wave heating affect the electron distribution in the D region. Radio wave heating can lead to absorption of radio wave energy by electrons, thereby increasing the temperature. Electrons are cooled by inelastic collisions with the neutrals atmosphere, affecting the electron distribution since electrons lose energy by exciting different states in neutrals. Thus, electrons are redistributed to lower energies, which changes the shape of the electron distribution.

Estimating the source altitude of auroral precipitation from dispersed Alfvén waves in the dayside ionosphere

2026-09-04T08:08:53+02:00

Estimating the source altitude of auroral precipitation from dispersed Alfvén waves in the dayside ionosphere
Etienne Gavazzi, Andres Spicher, Björn Gustavsson, Juha Vierinen, James Clemmons, Robert Pfaff, and Douglas Rowland
Ann. Geophys., 44, 903–920, https://doi.org/10.5194/angeo-44-903-2026, 2026
Auroras are caused by energetic electrons entering the upper atmosphere. For the smallest and most dynamic auroras, scientists think electrons are accelerated by waves (called Alfvén waves) thousands of kilometers above Earth. In this paper, we analyse data from a rocket that flew through auroras, applying existing and new techniques to estimate where the acceleration took place. Our results match theory, and we show how they can be used to study conditions in the near-Earth space environment.

Magnetotail response to corotating interaction region driven geomagnetic storms: Cluster observations

2026-09-01T08:08:53+02:00

Magnetotail response to corotating interaction region driven geomagnetic storms: Cluster observations
Adriane Marques de Souza Franco, Rashmi Rawat, Mauricio José Alves Bolzan, and Ezequiel Echer
Ann. Geophys., 44, 881–901, https://doi.org/10.5194/angeo-44-881-2026, 2026
This study investigates 40 geomagnetic storms driven by corotating interaction regions and their impact on Earth's magnetotail. We find that short, 4 h energy pulses dominate the magnetotail during cyclic substorms. Furthermore, High-Intensity, Long-Duration, Continuous Auroral Activity (HILDCAA) events in the recovery phase facilitate energy distribution across 2–12 h periodicities in the auroral region. Spectral indices indicate strong turbulence in both regions.

Dune aurora: survey from a citizen science database

2026-08-27T08:08:53+02:00

Dune aurora: survey from a citizen science database
Maxime Grandin, Liisa Juusola, Noora Partamies, Emma Bruus, Joona Rautiainen, Donna Lach, Jia Jia, Max van de Kamp, Eero Karvinen, Kirsti Kauristie, and Theresa Hoppe
Ann. Geophys., 44, 855–880, https://doi.org/10.5194/angeo-44-855-2026, 2026
Dune aurora is an intriguing phenomenon recently discovered thanks to citizen science. It is a dim, diffuse auroral form exhibiting wave-like stripes of brighter emission. We carry out the first statistical study of dune aurora, using 308 observation reports submitted to the Skywarden database by citizen scientists from Europe, North America, and Oceania. We find that dunes are an evening phenomenon, most often reported in March and October and associated with currents in the auroral atmosphere.

Post launch spectral and radiometric performances of MAJIS, the VIS-NIR imaging spectrometer of JUICE

2026-08-26T08:08:53+02:00

Post launch spectral and radiometric performances of MAJIS, the VIS-NIR imaging spectrometer of JUICE
Yves Langevin, Sébastien Rodriguez, Sandrine Guerlet, François Poulet, Giuseppe Piccioni, Livio Agostini, Raymond Armante, Emiliano D'Aversa, Gianrico Filacchione, Leigh Fletcher, Fabrizio Oliva, Clément Royer, Benoît Seignovert, Katrin Stephan, Federico Tosi, and Tim Trent
Ann. Geophys., 44, 825–853, https://doi.org/10.5194/angeo-44-825-2026, 2026
We present an updated spectral and radiometric calibration of the Moons and Jupiter Imaging Spectrometer (MAJIS) aboard the Jupiter Icy Moons Explorer (JUICE), based on results of Earth and Moon observations in August 2024 and on observations of the MAJIS internal calibration unit. Very good agreements were obtained with results of other instruments and models. These MAJIS observations provide a promising teaser of what will be achieved by MAJIS in the system of Jupiter.

High latitude, dayside rapid geomagnetic variations observed with ground-based magnetometers in Greenland

2026-08-24T08:08:53+02:00

High latitude, dayside rapid geomagnetic variations observed with ground-based magnetometers in Greenland
Marie Vigger Eldor, Magnar Gullikstad Johnsen, Nils Olsen, and Anna Naemi Willer
Ann. Geophys., 44, 811–823, https://doi.org/10.5194/angeo-44-811-2026, 2026
Rapid geomagnetic variations in the ultra-low frequency band are observed using ground-based magnetometers. We apply four years of data from West Greenland in a statistical analysis of the distribution of such variations. We identify a rapid geomagnetic variation population associated with the magnetospheric cusp that is separate from the auroral oval during summer. Earlier studies, which were mainly performed in winter, failed to unambiguously identify these variations.

Juice/SWI during the Lunar-Earth-Gravity-Assist (LEGA) – Part 3: Observations of the Earth as calibration target

2026-08-21T08:08:53+02:00

Juice/SWI during the Lunar-Earth-Gravity-Assist (LEGA) – Part 3: Observations of the Earth as calibration target
Christopher Jarchow, Ladislav Rezac, Paul Hartogh, Ali Schulz-Ravanbakhsh, Thibault Cavalié, Fabrice Herpin, Raphael Moreno, and Axel Murk
Ann. Geophys., 44, 795–809, https://doi.org/10.5194/angeo-44-795-2026, 2026
The Jupiter Icy Moons Explorer is a spacecraft sent towards Jupiter to perform detailed observations of the giant gas planet & its Galilean satellites. The Submillimetre Wave Instrument onboard this spacecraft is a newly built instrument, which first of all has to demonstrate proper performance before the observed data can be trusted. Using the Earth as a well-known observation target, proper functionality of this instrument has been verified during the Lunar Earth Gravity Assist in August 2024.

Storm-time energy budget in the high latitude lower thermosphere–ionosphere: quantification of energy exchange and comparison of different drivers in TIE-GCM

2026-08-19T08:08:53+02:00

Storm-time energy budget in the high latitude lower thermosphere–ionosphere: quantification of energy exchange and comparison of different drivers in TIE-GCM
Stelios Tourgaidis, Theodoros Sarris, Dimitrios Baloukidis, Stephan Buchert, Panagiotis Pirnaris, Konstantinos Papadakis, and Athanasios Balafoutis
Ann. Geophys., 44, 773–793, https://doi.org/10.5194/angeo-44-773-2026, 2026
The Lower Thermosphere-Ionosphere energy balance is driven by complex interactions between ions, neutrals and electrons. These processes are understood theoretically, but their estimates show large discrepancies between models. We calculate the storm-time energy budget according to the neutrals, ions and electrons using TIE-GCM (Thermosphere Ionosphere Electrodynamics General Circulation Model) using two different external drivers. Discrepancies between the model runs are discussed and the way forward to close the gaps in present knowledge is highlighted.

A near-sunset atmospheric sounding during the 14 October 2023 annular solar eclipse over Natal

2026-08-18T08:08:53+02:00

A near-sunset atmospheric sounding during the 14 October 2023 annular solar eclipse over Natal
Igo Paulino, Francisco Raimundo da Silva, Ana Roberta Paulino, and Gilvan Borba
Ann. Geophys., 44, 765–772, https://doi.org/10.5194/angeo-44-765-2026, 2026
The study utilized a stratospheric balloon over Natal, Brazil, to investigate the atmospheric response to the 14 October 2023 annular solar eclipse near sunset. Measurements included temperature, pressure, relative humidity and ozone. Significant changes in these parameters were found at different altitudes. These complex changes confirm the importance of the annular eclipses as a driver of localized atmospheric dynamics.

Magnetosphere–ionosphere response to the 21 and 25 June 2015 coronal mass ejections

2026-08-17T08:08:53+02:00

Magnetosphere–ionosphere response to the 21 and 25 June 2015 coronal mass ejections
Somaiyeh Sabri and Stefaan Poedts
Ann. Geophys., 44, 743–763, https://doi.org/10.5194/angeo-44-743-2026, 2026
Coronal mass ejections (CMEs) threaten Earth. We studied their interaction with the magnetosphere and ionosphere. Using the European Heliospheric Forecasting Information Asset (EUHFORIA), we calculated CME arrival times and investigated Earth's responses. Results show EUHFORIA and Gorgon-Space codes agree well in simulating CME propagation and interactions.

Analysis of 3GM High Accuracy Accelerometer data collected during JUICE lunar earth gravity assist

2026-08-14T08:08:53+02:00

Analysis of 3GM High Accuracy Accelerometer data collected during JUICE lunar earth gravity assist
Umberto De Filippis, Paolo Cappuccio, Mauro Di Benedetto, Ivan di Stefano, Daniele Durante, and Luciano Iess
Ann. Geophys., 44, 731–741, https://doi.org/10.5194/angeo-44-731-2026, 2026
The High Accuracy Accelerometer calibrated data collected during the JUICE (JUpiter ICy moons Explorer) Lunar Earth Gravity assist flyby was compared with predicted non-gravitational signals derived from analytical models, showing good agreement. Moon gravity gradient and thermoelastic displacement of solar array during the penumbra phases have been detected. High Accurate Accelerometer detected also unexpected signals such as instrument interference and outgassing event.

What is the neutral wind in height-integrated ionospheric electrodynamics?

2026-08-05T08:08:53+02:00

What is the neutral wind in height-integrated ionospheric electrodynamics?
Spencer Mark Hatch, Johnathan Burchill, Heikki Vanhamäki, Rafael Luiz Araujo de Mesquita, and Karl Magnus Laundal
Ann. Geophys., 44, 715–729, https://doi.org/10.5194/angeo-44-715-2026, 2026
Atmospheric winds at high altitudes (> 100 km) can play an important role in the electrodynamic processes that govern how ionospheric plasma interacts with Earth's neutral atmosphere. Here we investigate how a common idea in studies of ionospheric electrodynamics—that atmospheric winds can be ignored or represented via an average value—ignores the high variability of these winds. This variability forces a different formulation of the equations that govern ionosphere-thermosphere electrodynamics.

A numerical model for solving the linearized gravity-wave equations by a multilayer method

2026-07-28T08:08:53+02:00

A numerical model for solving the linearized gravity-wave equations by a multilayer method
Alexandru Doicu, Dmitry S. Efremenko, and Thomas Trautmann
Ann. Geophys., 44, 655–688, https://doi.org/10.5194/angeo-44-655-2026, 2026
We created a new computer model to study gravity waves, which are ripples in the atmosphere that affect weather and climate. Our research aimed to improve how these waves are simulated, as they play a key role in understanding atmospheric behavior. We developed a stable and efficient model that can model gravity waves in the atmosphere. Our method is fast and accurate, offering better tools for scientists to predict atmospheric changes.