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| 2. |
- Schillings, Audrey, et al.
(författare)
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Earth atmospheric loss through the plasma mantle and its dependence on solar wind parameters
- 2019
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Ingår i: Earth Planets and Space. - : Springer. - 1343-8832 .- 1880-5981. ; 71:70
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric loss and ion outfow play an important role in the magnetospheric dynamics and in the evolution of the atmosphere on geological timescales—an evolution which is also dependent on the solar activity. In this paper, we investigate the total O+ outfow [s−1 ] through the plasma mantle and its dependency on several solar wind param‑ eters. The oxygen ion data come from the CODIF instrument on board the spacecraft Cluster 4 and solar wind data from the OMNIWeb database for a period of 5 years (2001–2005). We study the distribution of the dynamic pressure and the interplanetary magnetic feld for time periods with available O+ observations in the plasma mantle. We then divided the data into suitably sized intervals. Additionally, we analyse the extreme ultraviolet radiation (EUV) data from the TIMED mission. We estimate the O+ escape rate [ions/s] as a function of the solar wind dynamic pressure, the interplanetary magnetic feld (IMF) and EUV. Our analysis shows that the O+ escape rate in the plasma mantle increases with increased solar wind dynamic pressure. Consistently, it was found that the southward IMF also plays an important role in the O+ escape rate in contrast to the EUV fux which does not have a signifcant infuence for the plasma mantle region. Finally, the relation between the O+ escape rate and the solar wind energy transferred into the magnetosphere shows a nonlinear response. The O+ escape rate starts increasing with an energy input of approxi‑ mately 1011W.
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| 3. |
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| 4. |
- Schillings, Audrey, et al.
(författare)
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The fate of O+ ions observed in the plasma mantle: particle tracing modelling and cluster observations
- 2020
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Ingår i: Annales Geophysicae. - : Copernicus Publications. - 0992-7689 .- 1432-0576. ; 38:3, s. 645-656
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Tidskriftsartikel (refereegranskat)abstract
- Ion escape is of particular interest for studying the evolution of the atmosphere on geological timescales. Previously, using Cluster-CODIF data, we investigated the oxygen ion outflow from the plasma mantle for different solar wind conditions and geomagnetic activity. We found significant correlations between solar wind parameters, geomagnetic activity (Kp index), and the O+ outflow. From these studies, we suggested that O+ ions observed in the plasma mantle and cusp have enough energy and velocity to escape the magnetosphere and be lost into the solar wind or in the distant magnetotail. Thus, this study aims to investigate where the ions observed in the plasma mantle end up. In order to answer this question, we numerically calculate the trajectories of O+ ions using a tracing code to further test this assumption and determine the fate of the observed ions. Our code consists of a magnetic field model (Tsyganenko T96) and an ionospheric potential model (Weimer 2001) in which particles initiated in the plasma mantle region are launched and traced forward in time. We analysed 131 observations of plasma mantle events in Cluster data between 2001 and 2007, and for each event 200 O+ particles were launched with an initial thermal and parallel bulk velocity corresponding to the velocities observed by Cluster. After the tracing, we found that 98 % of the particles are lost into the solar wind or in the distant tail. Out of these 98 %, 20 % escape via the dayside magnetosphere.
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| 5. |
- Slapak, Rikard, et al.
(författare)
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Atmospheric loss from the dayside open polar region and its dependence on geomagnetic activity: implications for atmospheric escape on evolutionary timescales
- 2017
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Ingår i: Annales Geophysicae. - : Copernicus Publications. - 0992-7689 .- 1432-0576. ; 35:3, s. 721-731
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the total O+ escape rate from the dayside open polar region and its dependence on geomagnetic activity, specifically Kp. Two different escape routes of magnetospheric plasma into the solar wind, the plasma mantle, and the high-latitude dayside magnetosheath have been investigated separately. The flux of O+ in the plasma mantle is sufficiently fast to subsequently escape further down the magnetotail passing the neutral point, and it is nearly 3 times larger than that in the dayside magnetosheath. The contribution from the plasma mantle route is estimated as ∼ 3. 9 × 1024exp(0. 45 Kp) [s−1] with a 1 to 2 order of magnitude range for a given geomagnetic activity condition. The extrapolation of this result, including escape via the dayside magnetosheath, indicates an average O+ escape of 3 × 1026 s−1 for the most extreme geomagnetic storms. Assuming that the range is mainly caused by the solar EUV level, which was also larger in the past, the average O+ escape could have reached 1027–28 s−1 a few billion years ago. Integration over time suggests a total oxygen escape from ancient times until the present roughly equal to the atmospheric oxygen content today.
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| 7. |
- Nilsson, Hans, et al.
(författare)
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Birth of a comet magnetosphere : A spring of water ions
- 2015
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 347:6220
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Tidskriftsartikel (refereegranskat)abstract
- The Rosetta mission shall accompany comet 67P/Churyumov-Gerasimenko from a heliocentric distance of >3.6 astronomical units through perihelion passage at 1.25 astronomical units, spanning low and maximum activity levels. Initially, the solar wind permeates the thin comet atmosphere formed from sublimation, until the size and plasma pressure of the ionized atmosphere define its boundaries: A magnetosphere is born. Using the Rosetta Plasma Consortium ion composition analyzer, we trace the evolution from the first detection of water ions to when the atmosphere begins repelling the solar wind (~3.3 astronomical units), and we report the spatial structure of this early interaction. The near-comet water population comprises accelerated ions (
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| 8. |
- Slapak, Rikard, et al.
(författare)
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Quantification of the total ion transport in the near-Earth plasma sheet
- 2017
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 35:4, s. 869-877
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies strongly suggest that a majority of the observed O+ cusp outflows will eventually escape into the solar wind, rather than be transported to the plasma sheet. Therefore, an investigation of plasma sheet flows will add to these studies and give a more complete picture of magnetospheric ion dynamics. Specifically, it will provide a greater understanding of atmospheric loss. We have used Cluster spacecraft 4 to quantify the H+ and O+ total transports in the near-Earth plasma sheet, using data covering 2001-2005. The results show that both H+ and O+ have earthward net fluxes of the orders of 1026 and 1024 s -1, respectively. The O+ plasma sheet return flux is 1 order of magnitude smaller than the O+ outflows observed in the cusps, strengthening the view that most ionospheric O+ outflows do escape. The H+ return flux is approximately the same as the ionospheric outflow, suggesting a stable budget of H+ in the magnetosphere. However, low-energy H+, not detectable by the ion spectrometer, is not considered in our study, leaving the complete magnetospheric H+ circulation an open question. Studying tailward flows separately reveals a total tailward O+ flux of about 0. 5 × 1025 s -1, which can be considered as a lower limit of the nightside auroral region O+ outflow. Lower velocity flows ( < 100kms -1) contribute most to the total transports, whereas the high-velocity flows contribute very little, suggesting that bursty bulk flows are not dominant in plasma sheet mass transport.
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| 9. |
- Yamauchi, Masatoshi, et al.
(författare)
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Cusp Current System : An Energy Source View
- 2018
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Ingår i: Electric Currents in Geospace and Beyond. - Hoboken, N.J. : John Wiley & Sons. - 9781119324492 - 9781119324522 ; , s. 339-358
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Bokkapitel (refereegranskat)abstract
- Electric currents in the cusp region are reviewed from viewpoints of history and energy conversion. During late 1980s and early 1990s, there were debates on the cause of the cusp region current system (cusp Region 0 field‐aligned current [FAC] and cusp Region 1 FAC, and relevant ionospheric current). The major debates were whether the cusp part Region 1 FAC is an extension of the non‐cusp‐part dayside Region 1 FAC or whether they are generated in different regions independently. The independency of the cusp current system, which was demonstrated by many observations, suggests additional extraction of energy from the magnetosheath‐like flow (e.g., deceleration) inside the polar magnetosphere. An extra deceleration is theoretically possible by adding a substantial local obstacle such as the outflowing ionospheric ions through the mass‐loading effect, which conserves momentum but not kinetic energy. Thus, two different dynamo (J · E < 0) mechanisms most likely exist between the dayside Region 1 and 2 FACs and cusp Region 1 and 0 FACs, forming “double openness,” which was introduced by Vasyliunas [1995]. The other debates (e.g., roles of mesoscale FACs, mapping to high latitude, and current carriers problems) are also reviewed in the light of new observational knowledge after Cluster.
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| 10. |
- Yamauchi, Masatoshi, et al.
(författare)
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Energy conversion through mass loading of escaping ionospheric ions for different Kp values
- 2018
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 36:1, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- By conserving momentum during the mixing of fast solar wind flow and slow planetary ion flow in an inelastic way, mass loading converts kinetic energy to other forms-e.g. first to electrical energy through charge separation and then to thermal energy (randomness) through gyromotion of the newly born cold ions for the comet and Mars cases. Here, we consider the Earth's exterior cusp and plasma mantle, where the ionospheric origin escaping ions with finite temperatures are loaded into the decelerated solar wind flow. Due to direct connectivity to the ionosphere through the geomagnetic field, a large part of this electrical energy is consumed to maintain field-aligned currents (FACs) toward the ionosphere, in a similar manner as the solar wind-driven ionospheric convection in the open geomagnetic field region. We show that the energy extraction rate by the mass loading of escaping ions (δK) is sufficient to explain the cusp FACs, and that 1K depends only on the solar wind velocity accessing the mass-loading region (usw) and the total mass flux of the escaping ions into this region (mloadFload), as δK ∼-mloadFloadu2 sw=4. The expected distribution of the separated charges by this process also predicts the observed flowing directions of the cusp FACs for different interplanetary magnetic field (IMF) orientations if we include the deflection of the solar wind flow directions in the exterior cusp. Using empirical relations of μ 0α KpC1:2 and Fload/exp.0:45Kp/for Kp D 1-7, where u0 is the solar wind velocity upstream of the bow shock, δK becomes a simple function of Kp as log10.δK/log10 0:2 &dw=elta;KpC 2 log10.KpC1:2)+Cconstant. The major contribution of this nearly linear increase is the Fload term, i.e. positive feedback between the increase of ion escaping rate Fload through the increased energy consumption in the ionosphere for high Kp, and subsequent extraction of more kinetic energy 1K from the solar wind to the current system by the increased Fload. Since Fload significantly increases for increased flux of extreme ultraviolet (EUV) radiation, high EUV flux may significantly enhance this positive feedback. Therefore, the ion escape rate and the energy extraction by mass loading during ancient Earth, when the Sun is believed to have emitted much higher EUV flux than at present, could have been even higher than the currently available highest values based on Kp D 9. This raises a possibility that the ion escape has substantially contributed to the evolution of the Earth's atmosphere.
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