Articles | Volume 41, issue 1
https://doi.org/10.5194/angeo-41-1-2023
© Author(s) 2023. 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-41-1-2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Regular paper
| 
06 Jan 2023
Regular paper |
| 06 Jan 2023
| 06 Jan 2023
The altitude of green OI 557.7 nm and blue N2+ 427.8 nm aurora
School of Physics & Astronomy, University of Southampton, Southampton, UK
Noora Partamies
Department of Arctic Geophysics, University Centre in Svalbard (UNIS), Longyearbyen, Norway
Birkeland Centre for Space Science, University of Bergen, Bergen, Norway
Björn Gustavsson
Dept. of Physics and Technology, UiT The Arctic University of Norway, Tromsø, Norway
Kirsti Kauristie
Finnish Meteorological Institute, Helsinki, Finland
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Noora Partamies, Rowan Dayton-Oxland, Katie Herlingshaw, Ilkka Virtanen, Bea Gallardo-Lacourt, Mikko Syrjäsuo, Fred Sigernes, Takanori Nishiyama, Toshi Nishimura, Mathieu Barthelemy, Anasuya Aruliah, Daniel Whiter, Lena Mielke, Maxime Grandin, Eero Karvinen, Marjan Spijkers, and Vincent Ledvina
EGUsphere, https://doi.org/10.5194/egusphere-2024-3669, https://doi.org/10.5194/egusphere-2024-3669, 2024
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We studied the first broad band emissions, called continuum, in the dayside aurora. They are similar to STEVE with white, pale pink or mauve coloured light. But unlike STEVE, they follow the dayside aurora forming rays and other dynamic shapes. We used ground optical and radar observations and found evidence of heating and upwelling of both plasma and neutral air. This study provides new information on conditions for continuum emission, but its understanding will require further work.
Rowan Dayton-Oxland, Daniel K. Whiter, Hyomin Kim, and Betty Lanchester
EGUsphere, https://doi.org/10.22541/essoar.172641540.02035523/v1, https://doi.org/10.22541/essoar.172641540.02035523/v1, 2024
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It is typically thought that the protons which precipitate down from space to cause proton aurora are accelerated by a type of plasma wave called an EMIC wave. In this study we use ground-based observations of proton aurora and Pc1 waves (the ground signature of EMIC waves) to test whether this mechanism occurs in the high Arctic over Svalbard, on the Earth's day side. We did not find any link between the proton aurora and Pc1 pulsations, contrary to our expectations.
Anton Goertz, Noora Partamies, Daniel Whiter, and Lisa Baddeley
Ann. Geophys., 41, 115–128, https://doi.org/10.5194/angeo-41-115-2023, https://doi.org/10.5194/angeo-41-115-2023, 2023
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Poleward moving auroral forms (PMAFs) are specific types of aurora believed to be the signature of the connection of Earth's magnetic field to that of the sun. In this paper, we discuss the evolution of PMAFs with regard to their auroral morphology as observed in all-sky camera images. We interpret different aspects of this evolution in terms of the connection dynamics between the magnetic fields of Earth and the sun. This sheds more light on the magnetic interaction between the sun and Earth.
Noora Partamies, Daniel Whiter, Kirsti Kauristie, and Stefano Massetti
Ann. Geophys., 40, 605–618, https://doi.org/10.5194/angeo-40-605-2022, https://doi.org/10.5194/angeo-40-605-2022, 2022
Short summary
Short summary
We investigate the local time behaviour of auroral structures and emission height. Data are collected from the Fennoscandian Lapland and Svalbard latitutes from 7 identical auroral all-sky cameras over about 1 solar cycle. The typical peak emission height of the green aurora varies from 110 km on the nightside to about 118 km in the morning over Lapland but stays systematically higher over Svalbard. During fast solar wind, nightside emission heights are 5 km lower than during slow solar wind.
Fasil Tesema, Noora Partamies, Daniel K. Whiter, and Yasunobu Ogawa
Ann. Geophys., 40, 1–10, https://doi.org/10.5194/angeo-40-1-2022, https://doi.org/10.5194/angeo-40-1-2022, 2022
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In this study, we present the comparison between an auroral model and EISCAT radar electron densities during pulsating aurorae. We test whether an overpassing satellite measurement of the average energy spectrum is a reasonable estimate for pulsating aurora electron precipitation. When patchy pulsating aurora is dominant in the morning sector, the overpass-averaged spectrum is found to be a reasonable estimate – but not when there is a mix of pulsating aurora types in the post-midnight sector.
Daniel K. Whiter, Hanna Sundberg, Betty S. Lanchester, Joshua Dreyer, Noora Partamies, Nickolay Ivchenko, Marco Zaccaria Di Fraia, Rosie Oliver, Amanda Serpell-Stevens, Tiffany Shaw-Diaz, and Thomas Braunersreuther
Ann. Geophys., 39, 975–989, https://doi.org/10.5194/angeo-39-975-2021, https://doi.org/10.5194/angeo-39-975-2021, 2021
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This paper presents an analysis of high-resolution optical and radar observations of a phenomenon called fragmented aurora-like emissions (FAEs) observed close to aurora in the high Arctic. The observations suggest that FAEs are not caused by high-energy electrons or protons entering the atmosphere along Earth's magnetic field and are, therefore, not aurora. The speeds of the FAEs and their internal dynamics were measured and used to evaluate theories for how the FAEs are produced.
Joshua Dreyer, Noora Partamies, Daniel Whiter, Pål G. Ellingsen, Lisa Baddeley, and Stephan C. Buchert
Ann. Geophys., 39, 277–288, https://doi.org/10.5194/angeo-39-277-2021, https://doi.org/10.5194/angeo-39-277-2021, 2021
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Small-scale auroral features are still being discovered and are not well understood. Where aurorae are caused by particle precipitation, the newly reported fragmented aurora-like emissions (FAEs) seem to be locally generated in the ionosphere (hence,
aurora-like). We analyse data from multiple instruments located near Longyearbyen to derive their main characteristics. They seem to occur as two types in a narrow altitude region (individually or in regularly spaced groups).
Sam Tuttle, Betty Lanchester, Björn Gustavsson, Daniel Whiter, Nickolay Ivchenko, Robert Fear, and Mark Lester
Ann. Geophys., 38, 845–859, https://doi.org/10.5194/angeo-38-845-2020, https://doi.org/10.5194/angeo-38-845-2020, 2020
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Electric fields in the atmosphere near dynamic aurora are important in the physics of the electric circuit within the Earth's magnetic field. Oxygen ions emit light as they move under the influence of these electric fields; the flow of this emission is used to find the electric field at high temporal resolution. The solution needs two other simultaneous measurements of auroral emissions to give key parameters such as the auroral energy. The electric fields increase with brightness of the aurora.
Joshua M. Chadney and Daniel K. Whiter
Geosci. Instrum. Method. Data Syst., 7, 317–329, https://doi.org/10.5194/gi-7-317-2018, https://doi.org/10.5194/gi-7-317-2018, 2018
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We measure spectra of upper atmospheric emissions in optical wavelengths using the High Throughput Imaging Echelle Spectrograph (HiTIES) located on Svalbard. These spectra contain superposed emissions originating from different altitudes. In this paper, we describe a fitting method which allows us to separate the measured emissions, thus allowing us to measure neutral temperatures at different altitudes and the density of water vapour in the atmosphere above the instrument.
Hanna Dahlgren, Betty S. Lanchester, Nickolay Ivchenko, and Daniel K. Whiter
Ann. Geophys., 35, 493–503, https://doi.org/10.5194/angeo-35-493-2017, https://doi.org/10.5194/angeo-35-493-2017, 2017
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Pulsating aurora are ubiquitous events that constitute a large amount of energy transfer to the ionosphere. Still there are unsolved issues regarding their formation. Using high-resolution optical and radar data, we find that it is the flux of high-energy electrons that get reduced during the OFF period of the pulsations. We also report on dips in brightness at the transition between ON and OFF, and asymmetric rise and fall times, which may have implications for understanding the pulsations.
Joshua M. Chadney, Daniel K. Whiter, and Betty S. Lanchester
Ann. Geophys., 35, 481–491, https://doi.org/10.5194/angeo-35-481-2017, https://doi.org/10.5194/angeo-35-481-2017, 2017
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A layer of excited OH molecules in the upper atmosphere produces strong airglow emission from which it is possible to obtain the temperature of the layer. To obtain accurate temperatures values, one must take into account the absorption of OH emission by water vapour in the lower atmosphere before this emission is measured by instruments on the ground. This paper provides the amount of absorption suffered by each OH line due to water vapour and presents a method to estimate water concentrations.
Tuomas Savolainen, Daniel Keith Whiter, and Noora Partamies
Geosci. Instrum. Method. Data Syst., 5, 305–314, https://doi.org/10.5194/gi-5-305-2016, https://doi.org/10.5194/gi-5-305-2016, 2016
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In this paper we describe a new method for recognition of digits in seven-segment displays. The method is used for adding date and time information to a dataset consisting of about 7 million auroral all-sky images taken during the time period of 1973–1997 at camera stations centred around Sodankylä observatory in Northern Finland. In each image there is a clock display for the date and time together with the reflection of the whole night sky through a spherical mirror.
N. M. Schlatter, V. Belyey, B. Gustavsson, N. Ivchenko, D. Whiter, H. Dahlgren, S. Tuttle, and T. Grydeland
Ann. Geophys., 33, 837–844, https://doi.org/10.5194/angeo-33-837-2015, https://doi.org/10.5194/angeo-33-837-2015, 2015
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The high-latitude ionosphere is a dynamic region where particle precipitation leads to various phenomena including wave instability and turbulence. Anomalous echoes related to aurora are observed in ground-based radar observations of the ionosphere. These echoes indicate enhanced ion acoustic fluctuations. In this article, we show that the origin of the echo is located in or close to the region of particle precipitation and that the echo region itself is limited to hundreds of meters.
D. K. Whiter, B. Gustavsson, N. Partamies, and L. Sangalli
Geosci. Instrum. Method. Data Syst., 2, 131–144, https://doi.org/10.5194/gi-2-131-2013, https://doi.org/10.5194/gi-2-131-2013, 2013
Noora Partamies, Rowan Dayton-Oxland, Katie Herlingshaw, Ilkka Virtanen, Bea Gallardo-Lacourt, Mikko Syrjäsuo, Fred Sigernes, Takanori Nishiyama, Toshi Nishimura, Mathieu Barthelemy, Anasuya Aruliah, Daniel Whiter, Lena Mielke, Maxime Grandin, Eero Karvinen, Marjan Spijkers, and Vincent Ledvina
EGUsphere, https://doi.org/10.5194/egusphere-2024-3669, https://doi.org/10.5194/egusphere-2024-3669, 2024
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We studied the first broad band emissions, called continuum, in the dayside aurora. They are similar to STEVE with white, pale pink or mauve coloured light. But unlike STEVE, they follow the dayside aurora forming rays and other dynamic shapes. We used ground optical and radar observations and found evidence of heating and upwelling of both plasma and neutral air. This study provides new information on conditions for continuum emission, but its understanding will require further work.
Rowan Dayton-Oxland, Daniel K. Whiter, Hyomin Kim, and Betty Lanchester
EGUsphere, https://doi.org/10.22541/essoar.172641540.02035523/v1, https://doi.org/10.22541/essoar.172641540.02035523/v1, 2024
Short summary
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It is typically thought that the protons which precipitate down from space to cause proton aurora are accelerated by a type of plasma wave called an EMIC wave. In this study we use ground-based observations of proton aurora and Pc1 waves (the ground signature of EMIC waves) to test whether this mechanism occurs in the high Arctic over Svalbard, on the Earth's day side. We did not find any link between the proton aurora and Pc1 pulsations, contrary to our expectations.
Yoshimasa Tanaka, Yasunobu Ogawa, Akira Kadokura, Takehiko Aso, Björn Gustavsson, Urban Brändström, Tima Sergienko, Genta Ueno, and Satoko Saita
Ann. Geophys., 42, 179–190, https://doi.org/10.5194/angeo-42-179-2024, https://doi.org/10.5194/angeo-42-179-2024, 2024
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We present via simulation how useful monochromatic images taken by a multi-point imager network are for auroral research in the EISCAT_3D project. We apply the generalized-aurora computed tomography (G-ACT) to modeled multiple auroral images and ionospheric electron density data. It is demonstrated that G-ACT provides better reconstruction results than the normal ACT and can interpolate ionospheric electron density at a much higher spatial resolution than observed by the EISCAT_3D radar.
Devin Huyghebaert, Björn Gustavsson, Juha Vierinen, Andreas Kvammen, Matthew Zettergren, John Swoboda, Ilkka Virtanen, Spencer Hatch, and Karl M. Laundal
EGUsphere, https://doi.org/10.5194/egusphere-2024-802, https://doi.org/10.5194/egusphere-2024-802, 2024
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The EISCAT_3D radar is a new ionospheric radar under construction in the Fennoscandia region. The radar will make measurements of plasma characteristics at altitudes above approximately 60 km. The capability of the system to make these measurements on spatial scales of less than 100 m using the multiple digitised signals from each of the radar antenna panels is highlighted. There are many ionospheric small-scale processes that will be further resolved using the techniques discussed here.
Theresa Rexer, Björn Gustavsson, Juha Vierinen, Andres Spicher, Devin Ray Huyghebaert, Andreas Kvammen, Robert Gillies, and Asti Bhatt
Geosci. Instrum. Method. Data Syst. Discuss., https://doi.org/10.5194/gi-2023-18, https://doi.org/10.5194/gi-2023-18, 2024
Preprint under review for GI
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We present a second-level calibration method for electron density measurements from multi-beam incoherent scatter radars. It is based on the well-known Flat field correction method used in imaging and photography. The methods improve data quality and useability as they account for unaccounted, and unpredictable variations in the radar system. This is valuable for studies where inter-beam calibration is important such as studies of polar cap patches, plasma irregularities and turbulence.
Thomas B. Leyser, Tima Sergienko, Urban Brändström, Björn Gustavsson, and Michael T. Rietveld
Ann. Geophys., 41, 589–600, https://doi.org/10.5194/angeo-41-589-2023, https://doi.org/10.5194/angeo-41-589-2023, 2023
Short summary
Short summary
Powerful radio waves transmitted into the ionosphere from the ground were used to study electron energization in the pumped ionospheric plasma turbulence, by detecting optical emissions from atomic oxygen. Our results obtained with the EISCAT (European Incoherent Scatter Scientific Association) facilities in northern Norway and optical detection with the ALIS (Auroral Large Imaging System) in northern Sweden suggest that long-wavelength upper hybrid waves are important in accelerating electrons.
Mizuki Fukizawa, Yoshimasa Tanaka, Yasunobu Ogawa, Keisuke Hosokawa, Tero Raita, and Kirsti Kauristie
Ann. Geophys., 41, 511–528, https://doi.org/10.5194/angeo-41-511-2023, https://doi.org/10.5194/angeo-41-511-2023, 2023
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We use computed tomography to reconstruct the three-dimensional distributions of the Hall and Pedersen conductivities of pulsating auroras, a key research target for understanding the magnetosphere–ionosphere coupling process. It is suggested that the high-energy electron precipitation associated with pulsating auroras may have a greater impact on the closure of field-aligned currents in the ionosphere than has been previously reported.
Liisa Juusola, Ari Viljanen, Noora Partamies, Heikki Vanhamäki, Mirjam Kellinsalmi, and Simon Walker
Ann. Geophys., 41, 483–510, https://doi.org/10.5194/angeo-41-483-2023, https://doi.org/10.5194/angeo-41-483-2023, 2023
Short summary
Short summary
At times when auroras erupt on the sky, the magnetic field surrounding the Earth undergoes rapid changes. On the ground, these changes can induce harmful electric currents in technological conductor networks, such as powerlines. We have used magnetic field observations from northern Europe during 28 such events and found consistent behavior that can help to understand, and thus predict, the processes that drive auroras and geomagnetically induced currents.
Anton Goertz, Noora Partamies, Daniel Whiter, and Lisa Baddeley
Ann. Geophys., 41, 115–128, https://doi.org/10.5194/angeo-41-115-2023, https://doi.org/10.5194/angeo-41-115-2023, 2023
Short summary
Short summary
Poleward moving auroral forms (PMAFs) are specific types of aurora believed to be the signature of the connection of Earth's magnetic field to that of the sun. In this paper, we discuss the evolution of PMAFs with regard to their auroral morphology as observed in all-sky camera images. We interpret different aspects of this evolution in terms of the connection dynamics between the magnetic fields of Earth and the sun. This sheds more light on the magnetic interaction between the sun and Earth.
Johann Stamm, Juha Vierinen, Björn Gustavsson, and Andres Spicher
Ann. Geophys., 41, 55–67, https://doi.org/10.5194/angeo-41-55-2023, https://doi.org/10.5194/angeo-41-55-2023, 2023
Short summary
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The study of some ionospheric events benefit from the knowledge of how the physics varies over a volume and over time. Examples are studies of aurora or energy deposition. With EISCAT3D, measurements of ion velocity vectors in a volume will be possible for the first time. We present a technique that uses a set of such measurements to estimate electric field and neutral wind. The technique relies on adding restrictions to the estimates. We successfully consider restrictions based on physics.
Noora Partamies, Daniel Whiter, Kirsti Kauristie, and Stefano Massetti
Ann. Geophys., 40, 605–618, https://doi.org/10.5194/angeo-40-605-2022, https://doi.org/10.5194/angeo-40-605-2022, 2022
Short summary
Short summary
We investigate the local time behaviour of auroral structures and emission height. Data are collected from the Fennoscandian Lapland and Svalbard latitutes from 7 identical auroral all-sky cameras over about 1 solar cycle. The typical peak emission height of the green aurora varies from 110 km on the nightside to about 118 km in the morning over Lapland but stays systematically higher over Svalbard. During fast solar wind, nightside emission heights are 5 km lower than during slow solar wind.
Mizuki Fukizawa, Takeshi Sakanoi, Yoshimasa Tanaka, Yasunobu Ogawa, Keisuke Hosokawa, Björn Gustavsson, Kirsti Kauristie, Alexander Kozlovsky, Tero Raita, Urban Brändström, and Tima Sergienko
Ann. Geophys., 40, 475–484, https://doi.org/10.5194/angeo-40-475-2022, https://doi.org/10.5194/angeo-40-475-2022, 2022
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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.
Sebastian Käki, Ari Viljanen, Liisa Juusola, and Kirsti Kauristie
Ann. Geophys., 40, 107–119, https://doi.org/10.5194/angeo-40-107-2022, https://doi.org/10.5194/angeo-40-107-2022, 2022
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During auroral substorms, the ionospheric electric currents change rapidly, and a large amount of energy is dissipated. We combine ionospheric current data derived from the Swarm satellite mission with the substorm database from the SuperMAG ground magnetometer network. We obtain statistics of the strength and location of the currents relative to the substorm onset. Our results show that low-earth orbit satellites give a coherent picture of the main features in the substorm current system.
Derek McKay, Juha Vierinen, Antti Kero, and Noora Partamies
Geosci. Instrum. Method. Data Syst., 11, 25–35, https://doi.org/10.5194/gi-11-25-2022, https://doi.org/10.5194/gi-11-25-2022, 2022
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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.
Fasil Tesema, Noora Partamies, Daniel K. Whiter, and Yasunobu Ogawa
Ann. Geophys., 40, 1–10, https://doi.org/10.5194/angeo-40-1-2022, https://doi.org/10.5194/angeo-40-1-2022, 2022
Short summary
Short summary
In this study, we present the comparison between an auroral model and EISCAT radar electron densities during pulsating aurorae. We test whether an overpassing satellite measurement of the average energy spectrum is a reasonable estimate for pulsating aurora electron precipitation. When patchy pulsating aurora is dominant in the morning sector, the overpass-averaged spectrum is found to be a reasonable estimate – but not when there is a mix of pulsating aurora types in the post-midnight sector.
Daniel K. Whiter, Hanna Sundberg, Betty S. Lanchester, Joshua Dreyer, Noora Partamies, Nickolay Ivchenko, Marco Zaccaria Di Fraia, Rosie Oliver, Amanda Serpell-Stevens, Tiffany Shaw-Diaz, and Thomas Braunersreuther
Ann. Geophys., 39, 975–989, https://doi.org/10.5194/angeo-39-975-2021, https://doi.org/10.5194/angeo-39-975-2021, 2021
Short summary
Short summary
This paper presents an analysis of high-resolution optical and radar observations of a phenomenon called fragmented aurora-like emissions (FAEs) observed close to aurora in the high Arctic. The observations suggest that FAEs are not caused by high-energy electrons or protons entering the atmosphere along Earth's magnetic field and are, therefore, not aurora. The speeds of the FAEs and their internal dynamics were measured and used to evaluate theories for how the FAEs are produced.
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.
Florine Enengl, Noora Partamies, Nickolay Ivchenko, and Lisa Baddeley
Ann. Geophys., 39, 795–809, https://doi.org/10.5194/angeo-39-795-2021, https://doi.org/10.5194/angeo-39-795-2021, 2021
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Energetic particle precipitation has the potential to change the neutral atmospheric temperature at the bottom of the ionosphere. We have searched for events and investigated a possible correlation between lower-ionosphere electron density enhancements and simultaneous neutral temperature changes. Six of the 10 analysed events are associated with a temperature decrease of 10–20K. The events change the chemical composition in the mesosphere, and the temperatures are probed at lower altitudes.
Torbjørn Tveito, Juha Vierinen, Björn Gustavsson, and Viswanathan Lakshmi Narayanan
Ann. Geophys., 39, 427–438, https://doi.org/10.5194/angeo-39-427-2021, https://doi.org/10.5194/angeo-39-427-2021, 2021
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This work explores the role of EISCAT 3D as a tool for planetary mapping. Due to the challenges inherent in detecting the signals reflected from faraway bodies, we have concluded that only the Moon is a viable mapping target. We estimate the impact of the ionosphere on lunar mapping, concluding that its distorting effects should be easily manageable. EISCAT 3D will be useful for mapping the lunar nearside due to its previously unused frequency (233 MHz) and its interferometric capabilities.
Joshua Dreyer, Noora Partamies, Daniel Whiter, Pål G. Ellingsen, Lisa Baddeley, and Stephan C. Buchert
Ann. Geophys., 39, 277–288, https://doi.org/10.5194/angeo-39-277-2021, https://doi.org/10.5194/angeo-39-277-2021, 2021
Short summary
Short summary
Small-scale auroral features are still being discovered and are not well understood. Where aurorae are caused by particle precipitation, the newly reported fragmented aurora-like emissions (FAEs) seem to be locally generated in the ionosphere (hence,
aurora-like). We analyse data from multiple instruments located near Longyearbyen to derive their main characteristics. They seem to occur as two types in a narrow altitude region (individually or in regularly spaced groups).
Johann Stamm, Juha Vierinen, Juan M. Urco, Björn Gustavsson, and Jorge L. Chau
Ann. Geophys., 39, 119–134, https://doi.org/10.5194/angeo-39-119-2021, https://doi.org/10.5194/angeo-39-119-2021, 2021
Sam Tuttle, Betty Lanchester, Björn Gustavsson, Daniel Whiter, Nickolay Ivchenko, Robert Fear, and Mark Lester
Ann. Geophys., 38, 845–859, https://doi.org/10.5194/angeo-38-845-2020, https://doi.org/10.5194/angeo-38-845-2020, 2020
Short summary
Short summary
Electric fields in the atmosphere near dynamic aurora are important in the physics of the electric circuit within the Earth's magnetic field. Oxygen ions emit light as they move under the influence of these electric fields; the flow of this emission is used to find the electric field at high temporal resolution. The solution needs two other simultaneous measurements of auroral emissions to give key parameters such as the auroral energy. The electric fields increase with brightness of the aurora.
Thomas B. Leyser, Björn Gustavsson, Theresa Rexer, and Michael T. Rietveld
Ann. Geophys., 38, 297–307, https://doi.org/10.5194/angeo-38-297-2020, https://doi.org/10.5194/angeo-38-297-2020, 2020
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Powerful radio waves transmitted into the ionosphere give the strongest turbulence effects in geomagnetic zenith, antiparallel to the magnetic field in the Northern Hemisphere. Our results obtained with the EISCAT (European Incoherent SCATter association) Heating facility in Norway and the EISCAT UHF incoherent scatter radar together with modelling suggest that the pump wave propagates in the L mode, rather than in the O mode that is usually assumed to be involved in such experiments.
Joshua M. Chadney and Daniel K. Whiter
Geosci. Instrum. Method. Data Syst., 7, 317–329, https://doi.org/10.5194/gi-7-317-2018, https://doi.org/10.5194/gi-7-317-2018, 2018
Short summary
Short summary
We measure spectra of upper atmospheric emissions in optical wavelengths using the High Throughput Imaging Echelle Spectrograph (HiTIES) located on Svalbard. These spectra contain superposed emissions originating from different altitudes. In this paper, we describe a fitting method which allows us to separate the measured emissions, thus allowing us to measure neutral temperatures at different altitudes and the density of water vapour in the atmosphere above the instrument.
Thomas B. Leyser, H. Gordon James, Björn Gustavsson, and Michael T. Rietveld
Ann. Geophys., 36, 243–251, https://doi.org/10.5194/angeo-36-243-2018, https://doi.org/10.5194/angeo-36-243-2018, 2018
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Transmission of powerful radio waves into the overhead ionosphere is used to study plasma turbulence processes. It is well known that the ionospheric response to radio waves is the strongest in the direction of the geomagnetic field. We have found evidence that the transmitted radio wave can propagate in a mode that enables the wave to propagate much higher in altitude and deeper into the ionosphere than what is usually expected, which may account for the strong plasma response observed.
Hanna Dahlgren, Betty S. Lanchester, Nickolay Ivchenko, and Daniel K. Whiter
Ann. Geophys., 35, 493–503, https://doi.org/10.5194/angeo-35-493-2017, https://doi.org/10.5194/angeo-35-493-2017, 2017
Short summary
Short summary
Pulsating aurora are ubiquitous events that constitute a large amount of energy transfer to the ionosphere. Still there are unsolved issues regarding their formation. Using high-resolution optical and radar data, we find that it is the flux of high-energy electrons that get reduced during the OFF period of the pulsations. We also report on dips in brightness at the transition between ON and OFF, and asymmetric rise and fall times, which may have implications for understanding the pulsations.
Joshua M. Chadney, Daniel K. Whiter, and Betty S. Lanchester
Ann. Geophys., 35, 481–491, https://doi.org/10.5194/angeo-35-481-2017, https://doi.org/10.5194/angeo-35-481-2017, 2017
Short summary
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A layer of excited OH molecules in the upper atmosphere produces strong airglow emission from which it is possible to obtain the temperature of the layer. To obtain accurate temperatures values, one must take into account the absorption of OH emission by water vapour in the lower atmosphere before this emission is measured by instruments on the ground. This paper provides the amount of absorption suffered by each OH line due to water vapour and presents a method to estimate water concentrations.
Tuomas Savolainen, Daniel Keith Whiter, and Noora Partamies
Geosci. Instrum. Method. Data Syst., 5, 305–314, https://doi.org/10.5194/gi-5-305-2016, https://doi.org/10.5194/gi-5-305-2016, 2016
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In this paper we describe a new method for recognition of digits in seven-segment displays. The method is used for adding date and time information to a dataset consisting of about 7 million auroral all-sky images taken during the time period of 1973–1997 at camera stations centred around Sodankylä observatory in Northern Finland. In each image there is a clock display for the date and time together with the reflection of the whole night sky through a spherical mirror.
Johannes Norberg, Lassi Roininen, Antti Kero, Tero Raita, Thomas Ulich, Markku Markkanen, Liisa Juusola, and Kirsti Kauristie
Geosci. Instrum. Method. Data Syst., 5, 263–270, https://doi.org/10.5194/gi-5-263-2016, https://doi.org/10.5194/gi-5-263-2016, 2016
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The Sodankylä Geophysical Observatory has been producing ionospheric tomography data since 2003. Based on these data, one solar cycle of ionospheric vertical total electron content (VTEC) estimates is constructed. The measurements are compared against the IRI-2012 model, F10.7 solar flux index and sunspot number data. Qualitatively the tomographic VTEC estimate corresponds to reference data very well, but the IRI-2012 model are on average 40 % higher of that of the tomographic results.
Kirsti Kauristie, Minna Myllys, Noora Partamies, Ari Viljanen, Pyry Peitso, Liisa Juusola, Shabana Ahmadzai, Vikramjit Singh, Ralf Keil, Unai Martinez, Alexej Luginin, Alexi Glover, Vicente Navarro, and Tero Raita
Geosci. Instrum. Method. Data Syst., 5, 253–262, https://doi.org/10.5194/gi-5-253-2016, https://doi.org/10.5194/gi-5-253-2016, 2016
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We use the connection between auroras and geomagnetic field variations in a concept for a Regional Auroral Forecast (RAF) service. RAF is based on statistical relationships between alerts by the NOAA Space Weather Prediction Center and magnetic time derivatives measured by five MIRACLE magnetometer stations located in the surroundings of the Sodankylä research station. As an improvement to previous similar services RAF yields knowledge on typical auroral storm durations at different latitudes.
Johannes Norberg, Ilkka I. Virtanen, Lassi Roininen, Juha Vierinen, Mikko Orispää, Kirsti Kauristie, and Markku S. Lehtinen
Atmos. Meas. Tech., 9, 1859–1869, https://doi.org/10.5194/amt-9-1859-2016, https://doi.org/10.5194/amt-9-1859-2016, 2016
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We validate 2-D ionospheric tomography reconstructions against EISCAT incoherent scatter radar measurements. The method is based on Bayesian statistical inversion. We employ ionosonde measurements for the choice of the prior distribution parameters and use a sparse matrix approximation for the computations. This results in a computationally efficient tomography algorithm with clear probabilistic interpretation. We find that ionosonde measurements improve the reconstruction significantly.
K. Kauristie, M. V. Uspensky, N. G. Kleimenova, O. V. Kozyreva, M. M. J. L. Van De Kamp, S. V. Dubyagin, and S. Massetti
Ann. Geophys., 34, 379–392, https://doi.org/10.5194/angeo-34-379-2016, https://doi.org/10.5194/angeo-34-379-2016, 2016
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This study presents some example events in which sudden changes in the auroral activity at midnight sector seem to have an impact on the intensity of morning-sector magnetic pulsations. Mechanisms which could link these two separate regions are discussed in the paper. Sudden changes in the solar wind properties and fast westward-propagating electrons are suggested to explain the coupling between midnight-sector and morning-sector phenomena.
N. M. Schlatter, V. Belyey, B. Gustavsson, N. Ivchenko, D. Whiter, H. Dahlgren, S. Tuttle, and T. Grydeland
Ann. Geophys., 33, 837–844, https://doi.org/10.5194/angeo-33-837-2015, https://doi.org/10.5194/angeo-33-837-2015, 2015
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The high-latitude ionosphere is a dynamic region where particle precipitation leads to various phenomena including wave instability and turbulence. Anomalous echoes related to aurora are observed in ground-based radar observations of the ionosphere. These echoes indicate enhanced ion acoustic fluctuations. In this article, we show that the origin of the echo is located in or close to the region of particle precipitation and that the echo region itself is limited to hundreds of meters.
P. T. Verronen, M. E. Andersson, A. Kero, C.-F. Enell, J. M. Wissing, E. R. Talaat, K. Kauristie, M. Palmroth, T. E. Sarris, and E. Armandillo
Ann. Geophys., 33, 381–394, https://doi.org/10.5194/angeo-33-381-2015, https://doi.org/10.5194/angeo-33-381-2015, 2015
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Electron concentrations observed by EISCAT radars can be reasonable well represented using AIMOS v1.2 satellite-data-based ionization model and SIC D-region ion chemistry model. SIC-EISCAT difference varies from event to event, probably because the statistical nature of AIMOS ionization is not capturing all the spatio-temporal fine structure of electron precipitation. Below 90km, AIMOS overestimates electron ionization because of proton contamination of the satellite electron detectors.
M. van de Kamp, D. Pokhotelov, and K. Kauristie
Ann. Geophys., 32, 1511–1532, https://doi.org/10.5194/angeo-32-1511-2014, https://doi.org/10.5194/angeo-32-1511-2014, 2014
N. M. Schlatter, N. Ivchenko, B. Gustavsson, T. Leyser, and M. Rietveld
Ann. Geophys., 31, 1103–1108, https://doi.org/10.5194/angeo-31-1103-2013, https://doi.org/10.5194/angeo-31-1103-2013, 2013
D. K. Whiter, B. Gustavsson, N. Partamies, and L. Sangalli
Geosci. Instrum. Method. Data Syst., 2, 131–144, https://doi.org/10.5194/gi-2-131-2013, https://doi.org/10.5194/gi-2-131-2013, 2013
N. Partamies, L. Juusola, E. Tanskanen, and K. Kauristie
Ann. Geophys., 31, 349–358, https://doi.org/10.5194/angeo-31-349-2013, https://doi.org/10.5194/angeo-31-349-2013, 2013
Related subject area
Subject: Earth's ionosphere & aeronomy | Keywords: Auroral ionosphere
Application of generalized aurora computed tomography to the EISCAT_3D project
Auroral breakup detection in all-sky images by unsupervised learning
Three-dimensional ionospheric conductivity associated with pulsating auroral patches: reconstruction from ground-based optical observations
Reconstruction of precipitating electrons and three-dimensional structure of a pulsating auroral patch from monochromatic auroral images obtained from multiple observation points
Spatio-temporal development of large-scale auroral electrojet currents relative to substorm onsets
Validation of SSUSI-derived auroral electron densities: comparisons to EISCAT data
Observations of sunlit N2+ aurora at high altitudes during the RENU2 flight
Yoshimasa Tanaka, Yasunobu Ogawa, Akira Kadokura, Takehiko Aso, Björn Gustavsson, Urban Brändström, Tima Sergienko, Genta Ueno, and Satoko Saita
Ann. Geophys., 42, 179–190, https://doi.org/10.5194/angeo-42-179-2024, https://doi.org/10.5194/angeo-42-179-2024, 2024
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We present via simulation how useful monochromatic images taken by a multi-point imager network are for auroral research in the EISCAT_3D project. We apply the generalized-aurora computed tomography (G-ACT) to modeled multiple auroral images and ionospheric electron density data. It is demonstrated that G-ACT provides better reconstruction results than the normal ACT and can interpolate ionospheric electron density at a much higher spatial resolution than observed by the EISCAT_3D radar.
Noora Partamies, Bas Dol, Vincent Teissier, Liisa Juusola, Mikko Syrjäsuo, and Hjalmar Mulders
Ann. Geophys., 42, 103–115, https://doi.org/10.5194/angeo-42-103-2024, https://doi.org/10.5194/angeo-42-103-2024, 2024
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Auroral imaging produces large amounts of image data that can no longer be analyzed by visual inspection. Thus, every step towards automatic analysis tools is crucial. Previously supervised learning methods have been used in auroral physics, with a human expert providing ground truth. However, this ground truth is debatable. We present an unsupervised learning method, which shows promising results in detecting auroral breakups in the all-sky image data.
Mizuki Fukizawa, Yoshimasa Tanaka, Yasunobu Ogawa, Keisuke Hosokawa, Tero Raita, and Kirsti Kauristie
Ann. Geophys., 41, 511–528, https://doi.org/10.5194/angeo-41-511-2023, https://doi.org/10.5194/angeo-41-511-2023, 2023
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We use computed tomography to reconstruct the three-dimensional distributions of the Hall and Pedersen conductivities of pulsating auroras, a key research target for understanding the magnetosphere–ionosphere coupling process. It is suggested that the high-energy electron precipitation associated with pulsating auroras may have a greater impact on the closure of field-aligned currents in the ionosphere than has been previously reported.
Mizuki Fukizawa, Takeshi Sakanoi, Yoshimasa Tanaka, Yasunobu Ogawa, Keisuke Hosokawa, Björn Gustavsson, Kirsti Kauristie, Alexander Kozlovsky, Tero Raita, Urban Brändström, and Tima Sergienko
Ann. Geophys., 40, 475–484, https://doi.org/10.5194/angeo-40-475-2022, https://doi.org/10.5194/angeo-40-475-2022, 2022
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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.
Sebastian Käki, Ari Viljanen, Liisa Juusola, and Kirsti Kauristie
Ann. Geophys., 40, 107–119, https://doi.org/10.5194/angeo-40-107-2022, https://doi.org/10.5194/angeo-40-107-2022, 2022
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During auroral substorms, the ionospheric electric currents change rapidly, and a large amount of energy is dissipated. We combine ionospheric current data derived from the Swarm satellite mission with the substorm database from the SuperMAG ground magnetometer network. We obtain statistics of the strength and location of the currents relative to the substorm onset. Our results show that low-earth orbit satellites give a coherent picture of the main features in the substorm current system.
Stefan Bender, Patrick J. Espy, and Larry J. Paxton
Ann. Geophys., 39, 899–910, https://doi.org/10.5194/angeo-39-899-2021, https://doi.org/10.5194/angeo-39-899-2021, 2021
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The coupling of the atmosphere to the space environment has become recognized as an important driver of atmospheric chemistry and dynamics. We have validated the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) products for average electron energy and electron energy flux by comparison to EISCAT electron density profiles. The good agreement shows that SSUSI far-UV observations can be used to provide ionization rate profiles throughout the auroral region.
Pål Gunnar Ellingsen, Dag Lorentzen, David Kenward, James H. Hecht, J. Scott Evans, Fred Sigernes, and Marc Lessard
Ann. Geophys., 39, 849–859, https://doi.org/10.5194/angeo-39-849-2021, https://doi.org/10.5194/angeo-39-849-2021, 2021
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Using the RENU2 rocket and ground-based instruments, we show that significant parts of the blue aurora above Svalbard at the time of launch were sunlit aurora. A sunlit aurora occurs when nitrogen molecules are ionised by extreme UV sunlight and subsequently hit by electrons from the Sun, resulting in blue and violet emissions. Understanding the source of an auroral emission gives insight into the interaction between the Sun and the Earth's upper atmosphere.
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Short summary
We measured the height of green and blue aurorae using thousands of camera images recorded over a 7-year period. Both colours are typically brightest at about 114 km altitude. When they peak at higher altitudes the blue aurora is usually higher than the green aurora. This information will help other studies which need an estimate of the auroral height. We used a computer model to explain our observations and to investigate how the green aurora is produced.
We measured the height of green and blue aurorae using thousands of camera images recorded over...
