Articles | Volume 31, issue 2
https://doi.org/10.5194/angeo-31-333-2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
https://doi.org/10.5194/angeo-31-333-2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
Regular paper
| 
27 Feb 2013
Regular paper |
| 27 Feb 2013
Response of polar mesosphere summer echoes to geomagnetic disturbances in the Southern and Northern Hemispheres: the importance of nitric oxide
S. Kirkwood
Swedish Institute of Space Physics, Box 812, 98128 Kiruna, Sweden
Graduate School of Space Technology, Luleå Technical University, Luleå, Sweden
E. Belova
Swedish Institute of Space Physics, Box 812, 98128 Kiruna, Sweden
Swedish Institute of Space Physics, Box 812, 98128 Kiruna, Sweden
M. Mihalikova
Swedish Institute of Space Physics, Box 812, 98128 Kiruna, Sweden
Graduate School of Space Technology, Luleå Technical University, Luleå, Sweden
D. Mikhaylova
Swedish Institute of Space Physics, Box 812, 98128 Kiruna, Sweden
D. Murtagh
Department of Radio and Space Science, Chalmers University of Technology, Horsalsvagen 11, 412 96 Gothenburg, Sweden
H. Nilsson
Swedish Institute of Space Physics, Box 812, 98128 Kiruna, Sweden
Graduate School of Space Technology, Luleå Technical University, Luleå, Sweden
K. Satheesan
Swedish Institute of Space Physics, Box 812, 98128 Kiruna, Sweden
now at: National Center for Antarctic and Ocean Research, Goa, India
J. Urban
Department of Radio and Space Science, Chalmers University of Technology, Horsalsvagen 11, 412 96 Gothenburg, Sweden
I. Wolf
Swedish Institute of Space Physics, Box 812, 98128 Kiruna, Sweden
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We compared 2 years of wind measurements by the Aeolus satellite with winds from two wind-profiler radars in Arctic Sweden and coastal Antarctica. Biases are similar in magnitude to results from other locations. They are smaller than in earlier studies due to more comparison points and improved criteria for data rejection. On the other hand, the standard deviation is somewhat higher because of degradation of the Aeolus lidar.
Evgenia Belova, Sheila Kirkwood, Peter Voelger, Sourav Chatterjee, Karathazhiyath Satheesan, Susanna Hagelin, Magnus Lindskog, and Heiner Körnich
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Wind measurements from two radars (ESRAD in Arctic Sweden and MARA at the Indian Antarctic station Maitri) are compared with lidar winds from the ESA satellite Aeolus, for July–December 2019. The aim is to check if Aeolus data processing is adequate for the sunlit conditions of polar summer. Agreement is generally good with bias in Aeolus winds < 1 m/s in most circumstances. The exception is a large bias (7 m/s) when the satellite has crossed a sunlit Antarctic ice cap before passing MARA.
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Atmos. Meas. Tech., 14, 2813–2825, https://doi.org/10.5194/amt-14-2813-2021, https://doi.org/10.5194/amt-14-2813-2021, 2021
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We validate horizontal wind measurements at altitudes of 0.5–14 km made with atmospheric radars: ESRAD located near Kiruna in the Swedish Arctic and MARA at the Indian research station Maitri in Antarctica, by comparison with radiosondes, the regional model HARMONIE-AROME and the ECMWF ERA5 reanalysis. Good agreement was found in general, and radar bias and uncertainty were estimated. These radars are planned to be used for validation of winds measured by lidar by the ESA satellite Aeolus.
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Ann. Geophys., 33, 789–804, https://doi.org/10.5194/angeo-33-789-2015, https://doi.org/10.5194/angeo-33-789-2015, 2015
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In December 1991, precipitation on the Glorieuses and Mayotte was more than 3 times the climatological mean and mean sunshine duration was less than 1.5h per day. The most likely explanation was low values of the Madden-Julian Oscillation index, which favours high rainfall. El Niño, eastward quasi-biennial oscillation and high solar activity may also have had an indirect effect. No effect of the Pinatubo volcanic eruption is indicated as the precipitation anomalies are only local.
S. Kirkwood, A. Osepian, E. Belova, and Y.-S. Lee
Ann. Geophys., 33, 609–622, https://doi.org/10.5194/angeo-33-609-2015, https://doi.org/10.5194/angeo-33-609-2015, 2015
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It is well known that occasional eruptions of very high energy protons from the Sun directly impact the middle atmosphere in the polar regions. This paper shows that much more frequent high-speed streams in the plasma wind from the Sun can also modify the same parts of the atmosphere. Their effects are made "visible" by strong enhancement of radar echoes in polar winter and were found to affect half of the days when observations were made at Troll, Antarctica, in 2012 and 2013.
S. Kirkwood, A. Osepian, E. Belova, J. Urban, K. Pérot, and A. K. Sinha
Ann. Geophys., 33, 561–572, https://doi.org/10.5194/angeo-33-561-2015, https://doi.org/10.5194/angeo-33-561-2015, 2015
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High-speed streams of particles from the Sun can cause high-energy electrons to be precipitated into the Earth's middle atmosphere at polar latitudes. The paper develops and tests a model for how these particles can change the amount of a trace gas, nitric oxide, which has the potential to destroy stratospheric ozone. Model calculations agree well with observations by the Odin satellite of increased nitric oxide over Antarctica associated with high-speed solar wind streams.
A. Réchou, S. Kirkwood, J. Arnault, and P. Dalin
Atmos. Chem. Phys., 14, 6785–6799, https://doi.org/10.5194/acp-14-6785-2014, https://doi.org/10.5194/acp-14-6785-2014, 2014
E. Belova, S. Kirkwood, and T. Sergienko
Ann. Geophys., 31, 1177–1190, https://doi.org/10.5194/angeo-31-1177-2013, https://doi.org/10.5194/angeo-31-1177-2013, 2013
M. Mihalikova and S. Kirkwood
Ann. Geophys., 31, 591–598, https://doi.org/10.5194/angeo-31-591-2013, https://doi.org/10.5194/angeo-31-591-2013, 2013
A. Réchou, J. Arnault, P. Dalin, and S. Kirkwood
Ann. Geophys., 31, 239–250, https://doi.org/10.5194/angeo-31-239-2013, https://doi.org/10.5194/angeo-31-239-2013, 2013
Peter Dalin, Urban Brändström, Johan Kero, Peter Voelger, Takanori Nishiyama, Trond Trondsen, Devin Wyatt, Craig Unick, Vladimir Perminov, Nikolay Pertsev, and Jonas Hedin
Atmos. Meas. Tech., 17, 1561–1576, https://doi.org/10.5194/amt-17-1561-2024, https://doi.org/10.5194/amt-17-1561-2024, 2024
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A novel infrared imaging instrument (OH imager) was put into operation in November 2022 at the Swedish Institute of Space Physics in Kiruna (Sweden). The OH imager is dedicated to the study of nightglow emissions coming from the hydroxyl (OH) and molecular oxygen (O2) layers in the mesopause (80–100 km). Based on a brightness ratio of two OH emission lines, the neutral temperature is estimated at around 87 km. The average daily winter temperature for the period January–April 2023 is 203±10 K.
Florian Günzkofer, Dimitry Pokhotelov, Gunter Stober, Ingrid Mann, Sharon L. Vadas, Erich Becker, Anders Tjulin, Alexander Kozlovsky, Masaki Tsutsumi, Njål Gulbrandsen, Satonori Nozawa, Mark Lester, Evgenia Belova, Johan Kero, Nicholas J. Mitchell, and Claudia Borries
Ann. Geophys., 41, 409–428, https://doi.org/10.5194/angeo-41-409-2023, https://doi.org/10.5194/angeo-41-409-2023, 2023
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Gravity waves (GWs) are waves in Earth's atmosphere and can be observed as cloud ripples. Under certain conditions, these waves can propagate up into the ionosphere. Here, they can cause ripples in the ionosphere plasma, observable as oscillations of the plasma density. Therefore, GWs contribute to the ionospheric variability, making them relevant for space weather prediction. Additionally, the behavior of these waves allows us to draw conclusions about the atmosphere at these altitudes.
Gunter Stober, Sharon L. Vadas, Erich Becker, Alan Liu, Alexander Kozlovsky, Diego Janches, Zishun Qiao, Witali Krochin, Guochun Shi, Wen Yi, Jie Zeng, Peter Brown, Denis Vida, Neil Hindley, Christoph Jacobi, Damian Murphy, Ricardo Buriti, Vania Andrioli, Paulo Batista, John Marino, Scott Palo, Denise Thorsen, Masaki Tsutsumi, Njål Gulbrandsen, Satonori Nozawa, Mark Lester, Kathrin Baumgarten, Johan Kero, Evgenia Belova, Nicholas Mitchell, and Na Li
EGUsphere, https://doi.org/10.5194/egusphere-2023-1714, https://doi.org/10.5194/egusphere-2023-1714, 2023
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On 15th January 2022, the Hunga Tonga-Hunga Ha‘apai volcano exploded in a vigorous eruption causing many atmospheric phenomena reaching from the surface up to space. In this study, we investigate how the mesospheric winds were affected by the volcanic-caused gravity waves and estimated their propagation direction and speed. The interplay between model and observations permits us to gain new insights into the vertical coupling through atmospheric gravity waves.
Sheila Kirkwood, Evgenia Belova, Peter Voelger, Sourav Chatterjee, and Karathazhiyath Satheesan
Atmos. Meas. Tech., 16, 4215–4227, https://doi.org/10.5194/amt-16-4215-2023, https://doi.org/10.5194/amt-16-4215-2023, 2023
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We compared 2 years of wind measurements by the Aeolus satellite with winds from two wind-profiler radars in Arctic Sweden and coastal Antarctica. Biases are similar in magnitude to results from other locations. They are smaller than in earlier studies due to more comparison points and improved criteria for data rejection. On the other hand, the standard deviation is somewhat higher because of degradation of the Aeolus lidar.
Gunter Stober, Alan Liu, Alexander Kozlovsky, Zishun Qiao, Witali Krochin, Guochun Shi, Johan Kero, Masaki Tsutsumi, Njål Gulbrandsen, Satonori Nozawa, Mark Lester, Kathrin Baumgarten, Evgenia Belova, and Nicholas Mitchell
Ann. Geophys., 41, 197–208, https://doi.org/10.5194/angeo-41-197-2023, https://doi.org/10.5194/angeo-41-197-2023, 2023
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The Hunga Tonga–Hunga Ha‘apai volcanic eruption was one of the most vigorous volcanic explosions in the last centuries. The eruption launched many atmospheric waves traveling around the Earth. In this study, we identify these volcanic waves at the edge of space in the mesosphere/lower-thermosphere, leveraging wind observations conducted with multi-static meteor radars in northern Europe and with the Chilean Observation Network De Meteor Radars (CONDOR).
Tinna L. Gunnarsdottir, Arne Poggenpohl, Ingrid Mann, Alireza Mahmoudian, Peter Dalin, Ingemar Haeggstroem, and Michael Rietveld
Ann. Geophys., 41, 93–114, https://doi.org/10.5194/angeo-41-93-2023, https://doi.org/10.5194/angeo-41-93-2023, 2023
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Temperatures at 85 km around Earth's poles in summer can be so cold that small ice particles form. These can become charged, and, combined with turbulence at these altitudes, they can influence the many electrons present. This can cause large radar echoes called polar mesospheric summer echoes. We use radio waves to heat these echoes on and off when the sun is close to or below the horizon. This allows us to gain some insight into these ice particles and how the sun influences the echoes.
Tomas Karlsson, Henriette Trollvik, Savvas Raptis, Hans Nilsson, and Hadi Madanian
Ann. Geophys., 40, 687–699, https://doi.org/10.5194/angeo-40-687-2022, https://doi.org/10.5194/angeo-40-687-2022, 2022
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Magnetic holes are curious localized dropouts of magnetic field strength in the solar wind (the flow of ionized gas continuously streaming out from the sun). In this paper we show that these magnetic holes can cross the bow shock (where the solar wind brake down to subsonic velocity) and enter the region close to Earth’s magnetosphere. These structures may therefore represent a new type of non-uniform solar wind–magnetosphere interaction.
Gunter Stober, Alan Liu, Alexander Kozlovsky, Zishun Qiao, Ales Kuchar, Christoph Jacobi, Chris Meek, Diego Janches, Guiping Liu, Masaki Tsutsumi, Njål Gulbrandsen, Satonori Nozawa, Mark Lester, Evgenia Belova, Johan Kero, and Nicholas Mitchell
Atmos. Meas. Tech., 15, 5769–5792, https://doi.org/10.5194/amt-15-5769-2022, https://doi.org/10.5194/amt-15-5769-2022, 2022
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Precise and accurate measurements of vertical winds at the mesosphere and lower thermosphere are rare. Although meteor radars have been used for decades to observe horizontal winds, their ability to derive reliable vertical wind measurements was always questioned. In this article, we provide mathematical concepts to retrieve mathematically and physically consistent solutions, which are compared to the state-of-the-art non-hydrostatic model UA-ICON.
Gunter Stober, Alexander Kozlovsky, Alan Liu, Zishun Qiao, Masaki Tsutsumi, Chris Hall, Satonori Nozawa, Mark Lester, Evgenia Belova, Johan Kero, Patrick J. Espy, Robert E. Hibbins, and Nicholas Mitchell
Atmos. Meas. Tech., 14, 6509–6532, https://doi.org/10.5194/amt-14-6509-2021, https://doi.org/10.5194/amt-14-6509-2021, 2021
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Wind observations at the edge to space, 70–110 km altitude, are challenging. Meteor radars have become a widely used instrument to obtain mean wind profiles above an instrument for these heights. We describe an advanced mathematical concept and present a tomographic analysis using several meteor radars located in Finland, Sweden and Norway, as well as Chile, to derive the three-dimensional flow field. We show an example of a gravity wave decelerating the mean flow.
Gunter Stober, Ales Kuchar, Dimitry Pokhotelov, Huixin Liu, Han-Li Liu, Hauke Schmidt, Christoph Jacobi, Kathrin Baumgarten, Peter Brown, Diego Janches, Damian Murphy, Alexander Kozlovsky, Mark Lester, Evgenia Belova, Johan Kero, and Nicholas Mitchell
Atmos. Chem. Phys., 21, 13855–13902, https://doi.org/10.5194/acp-21-13855-2021, https://doi.org/10.5194/acp-21-13855-2021, 2021
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Little is known about the climate change of wind systems in the mesosphere and lower thermosphere at the edge of space at altitudes from 70–110 km. Meteor radars represent a well-accepted remote sensing technique to measure winds at these altitudes. Here we present a state-of-the-art climatological interhemispheric comparison using continuous and long-lasting observations from worldwide distributed meteor radars from the Arctic to the Antarctic and sophisticated general circulation models.
Evgenia Belova, Sheila Kirkwood, Peter Voelger, Sourav Chatterjee, Karathazhiyath Satheesan, Susanna Hagelin, Magnus Lindskog, and Heiner Körnich
Atmos. Meas. Tech., 14, 5415–5428, https://doi.org/10.5194/amt-14-5415-2021, https://doi.org/10.5194/amt-14-5415-2021, 2021
Short summary
Short summary
Wind measurements from two radars (ESRAD in Arctic Sweden and MARA at the Indian Antarctic station Maitri) are compared with lidar winds from the ESA satellite Aeolus, for July–December 2019. The aim is to check if Aeolus data processing is adequate for the sunlit conditions of polar summer. Agreement is generally good with bias in Aeolus winds < 1 m/s in most circumstances. The exception is a large bias (7 m/s) when the satellite has crossed a sunlit Antarctic ice cap before passing MARA.
Peter Dalin, Hidehiko Suzuki, Nikolay Pertsev, Vladimir Perminov, Nikita Shevchuk, Egor Tsimerinov, Mark Zalcik, Jay Brausch, Tom McEwan, Iain McEachran, Martin Connors, Ian Schofield, Audrius Dubietis, Kazimieras Černis, Alexander Zadorozhny, Andrey Solodovnik, Daria Lifatova, Jesper Grønne, Ole Hansen, Holger Andersen, Dmitry Melnikov, Alexander Manevich, Nikolay Gusev, and Vitaly Romejko
Ann. Geophys. Discuss., https://doi.org/10.5194/angeo-2021-28, https://doi.org/10.5194/angeo-2021-28, 2021
Revised manuscript not accepted
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The 2020 summer season has revealed frequent occurrences of noctilucent clouds around the Northern hemisphere at middle latitudes (45–55° N). We have found that there has been a moderate decrease in the upper mesosphere temperature between 2016 and 2020 and no dramatic changes have been observed in temperature in the summer of 2020 at the middle latitude mesopause. At the same time, water vapor concentration has significantly increased in the zonal mean H2O value in the 2020 summer.
Charlotte Goetz, Herbert Gunell, Fredrik Johansson, Kristie LLera, Hans Nilsson, Karl-Heinz Glassmeier, and Matthew G. G. T. Taylor
Ann. Geophys., 39, 379–396, https://doi.org/10.5194/angeo-39-379-2021, https://doi.org/10.5194/angeo-39-379-2021, 2021
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Boundaries in the plasma around comet 67P separate regions with different properties. Many have been identified, including a new boundary called an infant bow shock. Here, we investigate how the plasma and fields behave at this boundary and where it can be found. The main result is that the infant bow shock occurs at intermediate activity and intermediate distances to the comet. Most plasma parameters behave as expected; however, some inconsistencies indicate that the boundary is non-stationary.
Evgenia Belova, Peter Voelger, Sheila Kirkwood, Susanna Hagelin, Magnus Lindskog, Heiner Körnich, Sourav Chatterjee, and Karathazhiyath Satheesan
Atmos. Meas. Tech., 14, 2813–2825, https://doi.org/10.5194/amt-14-2813-2021, https://doi.org/10.5194/amt-14-2813-2021, 2021
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We validate horizontal wind measurements at altitudes of 0.5–14 km made with atmospheric radars: ESRAD located near Kiruna in the Swedish Arctic and MARA at the Indian research station Maitri in Antarctica, by comparison with radiosondes, the regional model HARMONIE-AROME and the ECMWF ERA5 reanalysis. Good agreement was found in general, and radar bias and uncertainty were estimated. These radars are planned to be used for validation of winds measured by lidar by the ESA satellite Aeolus.
Herbert Gunell, Charlotte Goetz, Elias Odelstad, Arnaud Beth, Maria Hamrin, Pierre Henri, Fredrik L. Johansson, Hans Nilsson, and Gabriella Stenberg Wieser
Ann. Geophys., 39, 53–68, https://doi.org/10.5194/angeo-39-53-2021, https://doi.org/10.5194/angeo-39-53-2021, 2021
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When the magnetised solar wind meets the plasma surrounding a comet, the magnetic field is enhanced in front of the comet, and the field lines are draped around it. This happens because electric currents are induced in the plasma. When these currents flow through the plasma, they can generate waves. In this article we present observations of ion acoustic waves, which is a kind of sound wave in the plasma, detected by instruments on the Rosetta spacecraft near comet 67P/Churyumov–Gerasimenko.
Audrey Schillings, Herbert Gunell, Hans Nilsson, Alexandre De Spiegeleer, Yusuke Ebihara, Lars G. Westerberg, Masatoshi Yamauchi, and Rikard Slapak
Ann. Geophys., 38, 645–656, https://doi.org/10.5194/angeo-38-645-2020, https://doi.org/10.5194/angeo-38-645-2020, 2020
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The Earth's atmosphere is constantly losing molecules and charged particles, amongst them oxygen ions or O+. Quantifying this loss provides information about the evolution of the atmosphere on geological timescales. In this study, we investigate the final destination of O+ observed with Cluster satellites in a high-altitude magnetospheric region (plasma mantle) by tracing the particles forward in time using simulations. We find that approximately 98 % of O+ escapes the Earth's magnetosphere.
Peter Dalin, Nikolay Pertsev, Vladimir Perminov, Denis Efremov, and Vitaly Romejko
Ann. Geophys., 38, 61–71, https://doi.org/10.5194/angeo-38-61-2020, https://doi.org/10.5194/angeo-38-61-2020, 2020
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A unique stratospheric balloon-borne observation of noctilucent clouds (NLCs) was performed at night on 5–6 July 2018. A sounding balloon, carrying the NLC camera, reached 20.4 km altitude. NLCs were observed from the stratosphere at large scales (100–1500 km) for the first time. Propagations of gravity waves of various scales were registered. This experiment is rather simple and can be reproduced by the broad geoscience community and amateurs, providing a new technique in NLC observations.
Audrey Schillings, Hans Nilsson, Rikard Slapak, Masatoshi Yamauchi, and Lars-Göran Westerberg
Ann. Geophys., 35, 1341–1352, https://doi.org/10.5194/angeo-35-1341-2017, https://doi.org/10.5194/angeo-35-1341-2017, 2017
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The Earth's atmosphere is constantly losing ions and in particular oxygen ions. This phenomenon is important to understand the atmospheric evolution on a large timescale. In this study, the O+ outflow is estimated during six extreme geomagnetic storms using the European Cluster mission data. These estimations are compared with average magnetospheric conditions and show that during those six extreme storms, the O+ outflow is approximately 2 orders of magnitude higher.
Rikard Slapak, Maria Hamrin, Timo Pitkänen, Masatoshi Yamauchi, Hans Nilsson, Tomas Karlsson, and Audrey Schillings
Ann. Geophys., 35, 869–877, https://doi.org/10.5194/angeo-35-869-2017, https://doi.org/10.5194/angeo-35-869-2017, 2017
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The ion total transports in the near-Earth plasma sheet have been investigated and quantified. Specifically, the net O+ transport is about 1024 s−1 in the earthward direction, which is 1 order of magnitude smaller than the typical O+ ionospheric outflows, strongly indicating that most outflow will eventually escape, leading to significant atmospheric loss. The study also shows that low-velocity flows (< 100 km s−1) dominate the mass transport in the near-Earth plasma sheet.
Rikard Slapak, Audrey Schillings, Hans Nilsson, Masatoshi Yamauchi, Lars-Göran Westerberg, and Iannis Dandouras
Ann. Geophys., 35, 721–731, https://doi.org/10.5194/angeo-35-721-2017, https://doi.org/10.5194/angeo-35-721-2017, 2017
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In this study, we have used Cluster satellite data to quantify the ionospheric oxygen ion (O+) escape into the solar wind and its dependence on geomagnetic activity. During times of high activity, the escape may be 2 orders of magnitude higher than under quiet conditions, strongly suggesting that the escape rate was much higher when the Sun was young. The results are important for future studies regarding atmospheric loss over geological timescales.
M. Volwerk, I. Richter, B. Tsurutani, C. Götz, K. Altwegg, T. Broiles, J. Burch, C. Carr, E. Cupido, M. Delva, M. Dósa, N. J. T. Edberg, A. Eriksson, P. Henri, C. Koenders, J.-P. Lebreton, K. E. Mandt, H. Nilsson, A. Opitz, M. Rubin, K. Schwingenschuh, G. Stenberg Wieser, K. Szegö, C. Vallat, X. Vallieres, and K.-H. Glassmeier
Ann. Geophys., 34, 1–15, https://doi.org/10.5194/angeo-34-1-2016, https://doi.org/10.5194/angeo-34-1-2016, 2016
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The solar wind magnetic field drapes around the active nucleus of comet 67P/CG, creating a magnetosphere. The solar wind density increases and with that the pressure, which compresses the magnetosphere, increasing the magnetic field strength near Rosetta. The higher solar wind density also creates more ionization through collisions with the gas from the comet. The new ions are picked-up by the magnetic field and generate mirror-mode waves, creating low-field high-density "bottles" near 67P/CG.
I. Richter, C. Koenders, H.-U. Auster, D. Frühauff, C. Götz, P. Heinisch, C. Perschke, U. Motschmann, B. Stoll, K. Altwegg, J. Burch, C. Carr, E. Cupido, A. Eriksson, P. Henri, R. Goldstein, J.-P. Lebreton, P. Mokashi, Z. Nemeth, H. Nilsson, M. Rubin, K. Szegö, B. T. Tsurutani, C. Vallat, M. Volwerk, and K.-H. Glassmeier
Ann. Geophys., 33, 1031–1036, https://doi.org/10.5194/angeo-33-1031-2015, https://doi.org/10.5194/angeo-33-1031-2015, 2015
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We present a first report on magnetic field measurements made in the coma of comet 67P/C-G in its low-activity state. The plasma environment is dominated by quasi-coherent, large-amplitude, compressional magnetic field oscillations around 40mHz, differing from the observations at strongly active comets where waves at the cometary ion gyro-frequencies are the main feature. We propose a cross-field current instability associated with the newborn cometary ions as a possible source mechanism.
A. Réchou and S. Kirkwood
Ann. Geophys., 33, 789–804, https://doi.org/10.5194/angeo-33-789-2015, https://doi.org/10.5194/angeo-33-789-2015, 2015
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In December 1991, precipitation on the Glorieuses and Mayotte was more than 3 times the climatological mean and mean sunshine duration was less than 1.5h per day. The most likely explanation was low values of the Madden-Julian Oscillation index, which favours high rainfall. El Niño, eastward quasi-biennial oscillation and high solar activity may also have had an indirect effect. No effect of the Pinatubo volcanic eruption is indicated as the precipitation anomalies are only local.
S. Kirkwood, A. Osepian, E. Belova, and Y.-S. Lee
Ann. Geophys., 33, 609–622, https://doi.org/10.5194/angeo-33-609-2015, https://doi.org/10.5194/angeo-33-609-2015, 2015
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It is well known that occasional eruptions of very high energy protons from the Sun directly impact the middle atmosphere in the polar regions. This paper shows that much more frequent high-speed streams in the plasma wind from the Sun can also modify the same parts of the atmosphere. Their effects are made "visible" by strong enhancement of radar echoes in polar winter and were found to affect half of the days when observations were made at Troll, Antarctica, in 2012 and 2013.
S. Kirkwood, A. Osepian, E. Belova, J. Urban, K. Pérot, and A. K. Sinha
Ann. Geophys., 33, 561–572, https://doi.org/10.5194/angeo-33-561-2015, https://doi.org/10.5194/angeo-33-561-2015, 2015
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High-speed streams of particles from the Sun can cause high-energy electrons to be precipitated into the Earth's middle atmosphere at polar latitudes. The paper develops and tests a model for how these particles can change the amount of a trace gas, nitric oxide, which has the potential to destroy stratospheric ozone. Model calculations agree well with observations by the Odin satellite of increased nitric oxide over Antarctica associated with high-speed solar wind streams.
R. Slapak, H. Nilsson, L. G. Westerberg, and R. Larsson
Ann. Geophys., 33, 301–307, https://doi.org/10.5194/angeo-33-301-2015, https://doi.org/10.5194/angeo-33-301-2015, 2015
T. Pitkänen, M. Hamrin, P. Norqvist, T. Karlsson, H. Nilsson, A. Kullen, S. M. Imber, and S. E. Milan
Ann. Geophys., 33, 245–255, https://doi.org/10.5194/angeo-33-245-2015, https://doi.org/10.5194/angeo-33-245-2015, 2015
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An azimuthal velocity shear with a reversal within an earthward magnetotail fast flow is studied using Cluster observations. In addition, ionospheric SuperDARN data and different magnetospheric models (T96 and TF04) are utilized when interpreting the Cluster observations. Untwisting of twisted tail B field lines is a good candidate to explain the observations.
I. A. Barghouthi, H. Nilsson, and S. H. Ghithan
Ann. Geophys., 32, 1043–1057, https://doi.org/10.5194/angeo-32-1043-2014, https://doi.org/10.5194/angeo-32-1043-2014, 2014
A. Réchou, S. Kirkwood, J. Arnault, and P. Dalin
Atmos. Chem. Phys., 14, 6785–6799, https://doi.org/10.5194/acp-14-6785-2014, https://doi.org/10.5194/acp-14-6785-2014, 2014
K. Axelsson, T. Sergienko, H. Nilsson, U. Brändström, K. Asamura, and T. Sakanoi
Ann. Geophys., 32, 499–506, https://doi.org/10.5194/angeo-32-499-2014, https://doi.org/10.5194/angeo-32-499-2014, 2014
V. Barabash, A. Osepian, and P. Dalin
Ann. Geophys., 32, 207–222, https://doi.org/10.5194/angeo-32-207-2014, https://doi.org/10.5194/angeo-32-207-2014, 2014
E. Belova, S. Kirkwood, and T. Sergienko
Ann. Geophys., 31, 1177–1190, https://doi.org/10.5194/angeo-31-1177-2013, https://doi.org/10.5194/angeo-31-1177-2013, 2013
R. Slapak, H. Nilsson, and L. G. Westerberg
Ann. Geophys., 31, 1005–1010, https://doi.org/10.5194/angeo-31-1005-2013, https://doi.org/10.5194/angeo-31-1005-2013, 2013
M. Mihalikova and S. Kirkwood
Ann. Geophys., 31, 591–598, https://doi.org/10.5194/angeo-31-591-2013, https://doi.org/10.5194/angeo-31-591-2013, 2013
A. Réchou, J. Arnault, P. Dalin, and S. Kirkwood
Ann. Geophys., 31, 239–250, https://doi.org/10.5194/angeo-31-239-2013, https://doi.org/10.5194/angeo-31-239-2013, 2013
K. Axelsson, T. Sergienko, H. Nilsson, U. Brändström, Y. Ebihara, K. Asamura, and M. Hirahara
Ann. Geophys., 30, 1693–1701, https://doi.org/10.5194/angeo-30-1693-2012, https://doi.org/10.5194/angeo-30-1693-2012, 2012
