Articles | Volume 44, issue 2
https://doi.org/10.5194/angeo-44-903-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/angeo-44-903-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Regular paper
| 
04 Sep 2026
Regular paper |
| 04 Sep 2026
| 04 Sep 2026
Estimating the source altitude of auroral precipitation from dispersed Alfvén waves in the dayside ionosphere
Department of Physics and Technology, UiT The Arctic University of Norway, Tromsø, Norway
Andres Spicher
Department of Physics and Technology, UiT The Arctic University of Norway, Tromsø, Norway
Björn Gustavsson
Department of Physics and Technology, UiT The Arctic University of Norway, Tromsø, Norway
Juha Vierinen
Department of Physics and Technology, UiT The Arctic University of Norway, Tromsø, Norway
James Clemmons
Department of Physics and Astronomy, University of New Hampshire, Durham, NH, USA
Robert Pfaff
NASA Goddard Space Flight Center, Greenbelt, MD, USA
Douglas Rowland
NASA Goddard Space Flight Center, Greenbelt, MD, USA
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Margaretha Myrvang and Björn Gustavsson
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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.
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The rapid changes in ion composition during auroral are dynamically modeled by integrating the coupled continuity equations for 15 ionospheric species. The effect of the ionospheric variation on the inversion of incoherent scatter radar (ISR) electron density profiles to differential energy spectra of precipitating electrons is studied. A systematic overestimation at high electron energies can be removed using a dynamic model. Comparisons are made with static and steady-state ionospheric models.
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Knowledge of the charged environment in the upper atmosphere is essential for understanding space weather effects on satellites and radio communication. This environment is difficult to estimate at high latitudes, where aurora cause strong variability. We developed an artificial intelligence model to estimate this environment continuously. Our results show that the model provides reliable estimates even during auroral activity, improving monitoring of the polar upper atmosphere.
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Auroral precipitation refers to energetic particles that come down into the upper part of our atmosphere, the ionosphere. There, they collide with atoms and molecules and transfer some of their energy, causing aurora. The most rapid time-variation of this energy deposition and its consequences on the ionosphere are not fully understood. We show here that one can use a new model to study auroral precipitation on sub-second timescales and advance our understanding about small-scale dynamic aurora.
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Sensors capable of measuring rapid fluctuations are important to improve our understanding of environmental processes. Many sensors are unable to do this, due to their reliance on the transfer of the measured property, for instance a gas, across a semi-permeable barrier. We have developed a mathematical tool which enables the retrieval of fast-response signals from sensors with this type of sensor design.
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The Arecibo radar was used to probe free electrons of the ionized atmosphere between 70 and 100 km altitude. This is also the altitude region were meteors evaporate and form secondary particulate matter, the so-called meteor smoke particles (MSPs). Free electrons attach to these MSPs when the sun is below the horizon and cause a drop in the number of free electrons, which are the subject of these measurements. We also identified a different number of free electrons during sunset and sunrise.
Mizuki Fukizawa, Takeshi Sakanoi, Yoshimasa Tanaka, Yasunobu Ogawa, Keisuke Hosokawa, Björn Gustavsson, Kirsti Kauristie, Alexander Kozlovsky, Tero Raita, Urban Brändström, and Tima Sergienko
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The pulsating auroral generation mechanism has been investigated by observing precipitating electrons using rockets or satellites. However, it is difficult for such observations to distinguish temporal changes from spatial ones. In this study, we reconstructed the horizontal 2-D distribution of precipitating electrons using only auroral images. The 3-D aurora structure was also reconstructed. We found that there were both spatial and temporal changes in the precipitating electron energy.
Derek McKay, Juha Vierinen, Antti Kero, and Noora Partamies
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When radio waves from our galaxy enter the Earth's atmosphere, they are absorbed by electrons in the upper atmosphere. It was thought that by measuring the amount of absorption, it would allow the height of these electrons in the atmosphere to be determined. If so, this would have significance for future instrument design. However, this paper demonstrates that it is not possible to do this, but it does explain how multiple-frequency measurements can nevertheless be useful.
Ryan Volz, Jorge L. Chau, Philip J. Erickson, Juha P. Vierinen, J. Miguel Urco, and Matthias Clahsen
Atmos. Meas. Tech., 14, 7199–7219, https://doi.org/10.5194/amt-14-7199-2021, https://doi.org/10.5194/amt-14-7199-2021, 2021
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We introduce a new way of estimating winds in the upper atmosphere (about 80 to 100 km in altitude) from the observed Doppler shift of meteor trails using a statistical method called Gaussian process regression. Wind estimates and, critically, the uncertainty of those estimates can be evaluated smoothly (i.e., not gridded) in space and time. The effective resolution is set by provided parameters, which are limited in practice by the number density of the observed meteors.
Johann Stamm, Juha Vierinen, and Björn Gustavsson
Ann. Geophys., 39, 961–974, https://doi.org/10.5194/angeo-39-961-2021, https://doi.org/10.5194/angeo-39-961-2021, 2021
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Measurements of the electric field and neutral wind in the ionosphere are important for understanding energy flows or electric currents. With incoherent scatter radars (ISRs), we can measure the velocity of the ions, which depends on both the electrical field and the neutral wind. In this paper, we investigate methods to use ISR data to find reasonable values for both parameters. We find that electric field can be well measured down to 125 km height and neutral wind below this height.
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Short summary
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.
Auroras are caused by energetic electrons entering the upper atmosphere. For the smallest and...
