WP8 includes eight Competence Centres (CCs) that work on establishing infrastructures to support ... more WP8 includes eight Competence Centres (CCs) that work on establishing infrastructures to support users in coping with the data deluge in various compute intensive data analysis scenarios. This document provides the final report about the CC activities and informs readers about the use cases the CCs worked on, the implementations they reached in the past 3 years with the use of EOSC-hub and other EOSC-related services. The document also covers the impact of this work on the various research infrastructures and scientific communities that are linked to the CCs, and outlines future work for after EOSC-hub, based on the reported achievements.
Additional file 1. The first paragraph of the Additional file 1 provides more details on the calc... more Additional file 1. The first paragraph of the Additional file 1 provides more details on the calculations of the Vasyliunas et al. formula used in Figs. 4 and 5. The equations are fully described. The second part provides additional information on the geomagnetic activity (Kp) compared with the solar wind dynamic pressure and the photoionisation flux.
Electric currents in the cusp region are reviewed from viewpoints of history and energy conversio... more 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 sys ...
Ion outflow at Earth is studied since several decades and is important for the global atmospheric... more Ion outflow at Earth is studied since several decades and is important for the global atmospheric evolution. Over the years, spacecraft and technology improved leading to new studies and breakthrou ...
This thesis is composed of three articles, which have the common denominator that they are studie... more This thesis is composed of three articles, which have the common denominator that they are studies of heating of oxygen ions in the high altitude cusp and mantle in the terrestrial magnetosphere. A ...
Atmospheric outflow from the terrestrial magnetosphere : implications forescape on evolutionary t... more Atmospheric outflow from the terrestrial magnetosphere : implications forescape on evolutionary time scales
The Earth and its atmosphere are embedded in the magnetosphere, a region in space dominated by th... more The Earth and its atmosphere are embedded in the magnetosphere, a region in space dominated by the geomagnetic field, shielding our planet as it acts to deflect the energetic solar wind. Even thoug ...
Corrigendum to Atmospheric loss from the dayside open polar region and its dependence on geomagne... more Corrigendum to Atmospheric loss from the dayside open polar region and its dependence on geomagnetic activity : Implications for atmospheric escape on evolutionary time scales, published in Ann. Geophys., 35, 721–731,2017
Ion escape is of particular interest for studying the evolution of the atmosphere on geological t... more 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 (K p 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.
By conserving momentum during the mixing of fast solar wind flow and slow planetary ion flow in a... more 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 (K) is sufficient to explain the cusp FACs, and that K depends only on the solar wind velocity accessing the mass-loading region (u sw) and the total mass flux of the escaping ions into this region (m load F load), as K ∼ −m load F load u 2 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 u 0 ∝ Kp+1.2 and F load ∝ exp(0.45Kp) for Kp = 1-7, where u 0 is the solar wind velocity upstream of the bow shock, K becomes a simple function of Kp as log 10 (K) = 0.2 • Kp + 2 • log 10 (Kp + 1.2) + constant. The major contribution of this nearly linear increase is the F load term, i.e. positive feedback between the increase of ion escaping rate F load through the increased energy consumption in the ionosphere for high Kp, and subsequent extraction of more kinetic energy K from the solar wind to the current system by the increased F load. Since F load 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 = 9. This raises a possibility that the ion escape has substantially contributed to the evolution of the Earth's atmosphere.
We have investigated the oxygen escape-to-capture ratio from the high altitude cusp regions for v... more We have investigated the oxygen escape-to-capture ratio from the high altitude cusp regions for various geomagnetic activity levels by combining EDI and CODIF measurements from the Cluster spacecraft. Using Tsyganenko model, we traced the observed oxygen ions to one of three regions: plasma sheet, solar wind beyond distant X-line or dayside magnetosheath. Our results indicate that 69 % of high altitude oxygen escapes the magnetosphere, from which most escape beyond the distant X-line (50% of total oxygen flux). Convection of oxygen to the plasma sheet shows a strong dependence on geomagnetic activity. We used the Dst index as a proxy for geomagnetic storms and separated data into quiet conditions (Dst > 0 nT), moderate conditions (0 > Dst > −20 nT), and active conditions (Dst < −20 nT). For quiet magnetospheric conditions we found increased escape due to low convection. For active magnetospheric conditions we found an increase in both parallel velocities and convection velocities, but the increase in convection velocities is higher, and thus most of oxygen flux gets convected into plasma sheet (73 %). The convected oxygen ions reach the plasma sheet in the distant tail, mostly beyond 50 R E .
Atmospheric loss and ion outflow play an important role in the magnetospheric dynamics and in the... more Atmospheric loss and ion outflow 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 + outflow [ s −1 ] through the plasma mantle and its dependency on several solar wind parameters. 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 field 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 field (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 flux which does not have a significant influence 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 approximately 10 11 W.
The rate of ion outflow from the polar ionosphere is known to vary by orders of magnitude, depend... more The rate of ion outflow from the polar ionosphere is known to vary by orders of magnitude, depending on the geomagnetic activity. However, the upper limit of the outflow rate during the largest geomagnetic storms is not well constrained due to poor spatial coverage during storm events. In this paper, we analyse six major geomagnetic storms between 2001 and 2004 using Cluster data. The six major storms fulfil the criteria of Dst < −100 nT or Kp > 7+. Since the shape of the magnetospheric regions (plasma mantle, lobe and inner magnetosphere) are distorted during large magnetic storms, we use both plasma beta (β) and ion characteristics to define a spatial box where the upward O + flux scaled to an ionospheric reference altitude for the extreme event is observed. The relative enhancement of the scaled outflow in the spatial boxes as compared to the data from the full year when the storm occurred is estimated. Only O + data were used because H + may have a solar wind origin. The storm time data for most cases showed up as a clearly distinguishable separate peak in the distribution toward the largest fluxes observed. The relative enhancement in the outflow region during storm time is 1 to 2 orders of magnitude higher compared to less disturbed time. The largest relative scaled outflow enhancement is 83 (7 November 2004) and the highest scaled O + outflow observed is 2 × 10 14 m −2 s −1
The presence or absence of a magnetic field determines the nature of how a planet interacts with ... more The presence or absence of a magnetic field determines the nature of how a planet interacts with the solar wind and what paths are available for atmospheric escape. Magnetospheres form both around magnetised planets, such as Earth, and unmagnetised planets, like Mars and Venus, but it has been suggested that magnetised planets are better protected against atmospheric loss. However, the observed mass escape rates from these three planets are similar (in the approximate (0.5–2) kg s−1 range), putting this latter hypothesis into question. Modelling the effects of a planetary magnetic field on the major atmospheric escape processes, we show that the escape rate can be higher for magnetised planets over a wide range of magnetisations due to escape of ions through the polar caps and cusps. Therefore, contrary to what has previously been believed, magnetisation is not a sufficient condition for protecting a planet from atmospheric loss. Estimates of the atmospheric escape rates from exopla...
We have investigated the consequences of extreme space weather on ion outflow from the polar iono... more We have investigated the consequences of extreme space weather on ion outflow from the polar ionosphere by analyzing the solar storm that occurred early September 2017, causing a severe geomagnetic storm. Several X-flares and coronal mass ejections were observed between 4 and 10 September. The first shock-likely associated with a coronal mass ejection-hit the Earth late on 6 September, produced a storm sudden commencement, and began the initial phase of the storm. It was followed by a second shock, approximately 24 hr later, that initiated the main phase and simultaneously the Dst index dropped to Dst = −142 nT and Kp index reached Kp = 8. Using COmposition DIstribution Function data on board Cluster satellite 4, we estimated the ionospheric O + outflow before and after the second shock. We found an enhancement in the polar cap by a factor of 3 for an unusually high ionospheric O + outflow (mapped to an ionospheric reference altitude) of 10 13 m −2 s −1. We suggest that this high ionospheric O + outflow is due to a preheating of the ionosphere by the multiple X-flares. Finally, we briefly discuss the space weather consequences on the magnetosphere as a whole and the enhanced O + outflow in connection with enhanced satellite drag.
Journal of Geophysical Research: Space Physics, 2016
We have used Cluster spacecraft data from the years 2001 to 2005 to study how oxygen ions respond... more We have used Cluster spacecraft data from the years 2001 to 2005 to study how oxygen ions respond to bursty bulk flows (BBFs) as identified from proton data. We here define bursty bulk flows as periods of proton perpendicular velocities more than 100 km/s and a peak perpendicular velocity in the structure of more than 200 km/s, observed in a region with plasma beta above 1 in the near-Earth central tail region. We find that during proton BBFs only a minor increase in the O + velocity is seen. The different behavior of the two ion species is further shown by statistics of H + and O + flow also outside BBFs: For perpendicular earthward velocities of H + above about 100 km/s, the O + perpendicular velocity is consistently lower, most commonly being a few tens of kilometers per second earthward. In summary, O + ions in the plasma sheet experience less acceleration than H + ions and are not fully frozen in to the magnetic field. Therefore, H + and O + motion is decoupled, and O + ions have a slower earthward motion. This is particularly clear during BBFs. This may add further to the increased relative abundance of O + ions in the plasma sheet during magnetic storms. The data indicate that O + is typically less accelerated in association with plasma sheet X lines as compared to H + .
Recent studies strongly suggest that a majority of the observed O + cusp outflows will eventually... more 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 10 26 and 10 24 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 × 10 25 s −1 , which can be considered as a lower limit of the nightside auroral region O + outflow. Lower velocity flows (< 100 km s −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.
We have investigated the total O + escape rate from the dayside open polar region and its depende... more 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 ∼ 3.9×10 24 exp(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 × 10 26 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 10 27-28 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.
WP8 includes eight Competence Centres (CCs) that work on establishing infrastructures to support ... more WP8 includes eight Competence Centres (CCs) that work on establishing infrastructures to support users in coping with the data deluge in various compute intensive data analysis scenarios. This document provides the final report about the CC activities and informs readers about the use cases the CCs worked on, the implementations they reached in the past 3 years with the use of EOSC-hub and other EOSC-related services. The document also covers the impact of this work on the various research infrastructures and scientific communities that are linked to the CCs, and outlines future work for after EOSC-hub, based on the reported achievements.
Additional file 1. The first paragraph of the Additional file 1 provides more details on the calc... more Additional file 1. The first paragraph of the Additional file 1 provides more details on the calculations of the Vasyliunas et al. formula used in Figs. 4 and 5. The equations are fully described. The second part provides additional information on the geomagnetic activity (Kp) compared with the solar wind dynamic pressure and the photoionisation flux.
Electric currents in the cusp region are reviewed from viewpoints of history and energy conversio... more 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 sys ...
Ion outflow at Earth is studied since several decades and is important for the global atmospheric... more Ion outflow at Earth is studied since several decades and is important for the global atmospheric evolution. Over the years, spacecraft and technology improved leading to new studies and breakthrou ...
This thesis is composed of three articles, which have the common denominator that they are studie... more This thesis is composed of three articles, which have the common denominator that they are studies of heating of oxygen ions in the high altitude cusp and mantle in the terrestrial magnetosphere. A ...
Atmospheric outflow from the terrestrial magnetosphere : implications forescape on evolutionary t... more Atmospheric outflow from the terrestrial magnetosphere : implications forescape on evolutionary time scales
The Earth and its atmosphere are embedded in the magnetosphere, a region in space dominated by th... more The Earth and its atmosphere are embedded in the magnetosphere, a region in space dominated by the geomagnetic field, shielding our planet as it acts to deflect the energetic solar wind. Even thoug ...
Corrigendum to Atmospheric loss from the dayside open polar region and its dependence on geomagne... more Corrigendum to Atmospheric loss from the dayside open polar region and its dependence on geomagnetic activity : Implications for atmospheric escape on evolutionary time scales, published in Ann. Geophys., 35, 721–731,2017
Ion escape is of particular interest for studying the evolution of the atmosphere on geological t... more 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 (K p 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.
By conserving momentum during the mixing of fast solar wind flow and slow planetary ion flow in a... more 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 (K) is sufficient to explain the cusp FACs, and that K depends only on the solar wind velocity accessing the mass-loading region (u sw) and the total mass flux of the escaping ions into this region (m load F load), as K ∼ −m load F load u 2 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 u 0 ∝ Kp+1.2 and F load ∝ exp(0.45Kp) for Kp = 1-7, where u 0 is the solar wind velocity upstream of the bow shock, K becomes a simple function of Kp as log 10 (K) = 0.2 • Kp + 2 • log 10 (Kp + 1.2) + constant. The major contribution of this nearly linear increase is the F load term, i.e. positive feedback between the increase of ion escaping rate F load through the increased energy consumption in the ionosphere for high Kp, and subsequent extraction of more kinetic energy K from the solar wind to the current system by the increased F load. Since F load 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 = 9. This raises a possibility that the ion escape has substantially contributed to the evolution of the Earth's atmosphere.
We have investigated the oxygen escape-to-capture ratio from the high altitude cusp regions for v... more We have investigated the oxygen escape-to-capture ratio from the high altitude cusp regions for various geomagnetic activity levels by combining EDI and CODIF measurements from the Cluster spacecraft. Using Tsyganenko model, we traced the observed oxygen ions to one of three regions: plasma sheet, solar wind beyond distant X-line or dayside magnetosheath. Our results indicate that 69 % of high altitude oxygen escapes the magnetosphere, from which most escape beyond the distant X-line (50% of total oxygen flux). Convection of oxygen to the plasma sheet shows a strong dependence on geomagnetic activity. We used the Dst index as a proxy for geomagnetic storms and separated data into quiet conditions (Dst > 0 nT), moderate conditions (0 > Dst > −20 nT), and active conditions (Dst < −20 nT). For quiet magnetospheric conditions we found increased escape due to low convection. For active magnetospheric conditions we found an increase in both parallel velocities and convection velocities, but the increase in convection velocities is higher, and thus most of oxygen flux gets convected into plasma sheet (73 %). The convected oxygen ions reach the plasma sheet in the distant tail, mostly beyond 50 R E .
Atmospheric loss and ion outflow play an important role in the magnetospheric dynamics and in the... more Atmospheric loss and ion outflow 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 + outflow [ s −1 ] through the plasma mantle and its dependency on several solar wind parameters. 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 field 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 field (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 flux which does not have a significant influence 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 approximately 10 11 W.
The rate of ion outflow from the polar ionosphere is known to vary by orders of magnitude, depend... more The rate of ion outflow from the polar ionosphere is known to vary by orders of magnitude, depending on the geomagnetic activity. However, the upper limit of the outflow rate during the largest geomagnetic storms is not well constrained due to poor spatial coverage during storm events. In this paper, we analyse six major geomagnetic storms between 2001 and 2004 using Cluster data. The six major storms fulfil the criteria of Dst < −100 nT or Kp > 7+. Since the shape of the magnetospheric regions (plasma mantle, lobe and inner magnetosphere) are distorted during large magnetic storms, we use both plasma beta (β) and ion characteristics to define a spatial box where the upward O + flux scaled to an ionospheric reference altitude for the extreme event is observed. The relative enhancement of the scaled outflow in the spatial boxes as compared to the data from the full year when the storm occurred is estimated. Only O + data were used because H + may have a solar wind origin. The storm time data for most cases showed up as a clearly distinguishable separate peak in the distribution toward the largest fluxes observed. The relative enhancement in the outflow region during storm time is 1 to 2 orders of magnitude higher compared to less disturbed time. The largest relative scaled outflow enhancement is 83 (7 November 2004) and the highest scaled O + outflow observed is 2 × 10 14 m −2 s −1
The presence or absence of a magnetic field determines the nature of how a planet interacts with ... more The presence or absence of a magnetic field determines the nature of how a planet interacts with the solar wind and what paths are available for atmospheric escape. Magnetospheres form both around magnetised planets, such as Earth, and unmagnetised planets, like Mars and Venus, but it has been suggested that magnetised planets are better protected against atmospheric loss. However, the observed mass escape rates from these three planets are similar (in the approximate (0.5–2) kg s−1 range), putting this latter hypothesis into question. Modelling the effects of a planetary magnetic field on the major atmospheric escape processes, we show that the escape rate can be higher for magnetised planets over a wide range of magnetisations due to escape of ions through the polar caps and cusps. Therefore, contrary to what has previously been believed, magnetisation is not a sufficient condition for protecting a planet from atmospheric loss. Estimates of the atmospheric escape rates from exopla...
We have investigated the consequences of extreme space weather on ion outflow from the polar iono... more We have investigated the consequences of extreme space weather on ion outflow from the polar ionosphere by analyzing the solar storm that occurred early September 2017, causing a severe geomagnetic storm. Several X-flares and coronal mass ejections were observed between 4 and 10 September. The first shock-likely associated with a coronal mass ejection-hit the Earth late on 6 September, produced a storm sudden commencement, and began the initial phase of the storm. It was followed by a second shock, approximately 24 hr later, that initiated the main phase and simultaneously the Dst index dropped to Dst = −142 nT and Kp index reached Kp = 8. Using COmposition DIstribution Function data on board Cluster satellite 4, we estimated the ionospheric O + outflow before and after the second shock. We found an enhancement in the polar cap by a factor of 3 for an unusually high ionospheric O + outflow (mapped to an ionospheric reference altitude) of 10 13 m −2 s −1. We suggest that this high ionospheric O + outflow is due to a preheating of the ionosphere by the multiple X-flares. Finally, we briefly discuss the space weather consequences on the magnetosphere as a whole and the enhanced O + outflow in connection with enhanced satellite drag.
Journal of Geophysical Research: Space Physics, 2016
We have used Cluster spacecraft data from the years 2001 to 2005 to study how oxygen ions respond... more We have used Cluster spacecraft data from the years 2001 to 2005 to study how oxygen ions respond to bursty bulk flows (BBFs) as identified from proton data. We here define bursty bulk flows as periods of proton perpendicular velocities more than 100 km/s and a peak perpendicular velocity in the structure of more than 200 km/s, observed in a region with plasma beta above 1 in the near-Earth central tail region. We find that during proton BBFs only a minor increase in the O + velocity is seen. The different behavior of the two ion species is further shown by statistics of H + and O + flow also outside BBFs: For perpendicular earthward velocities of H + above about 100 km/s, the O + perpendicular velocity is consistently lower, most commonly being a few tens of kilometers per second earthward. In summary, O + ions in the plasma sheet experience less acceleration than H + ions and are not fully frozen in to the magnetic field. Therefore, H + and O + motion is decoupled, and O + ions have a slower earthward motion. This is particularly clear during BBFs. This may add further to the increased relative abundance of O + ions in the plasma sheet during magnetic storms. The data indicate that O + is typically less accelerated in association with plasma sheet X lines as compared to H + .
Recent studies strongly suggest that a majority of the observed O + cusp outflows will eventually... more 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 10 26 and 10 24 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 × 10 25 s −1 , which can be considered as a lower limit of the nightside auroral region O + outflow. Lower velocity flows (< 100 km s −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.
We have investigated the total O + escape rate from the dayside open polar region and its depende... more 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 ∼ 3.9×10 24 exp(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 × 10 26 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 10 27-28 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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Papers by Rikard Slapak