An extensive variety of instruments were continuously monitoring the dayside mag- netosphere and ... more An extensive variety of instruments were continuously monitoring the dayside mag- netosphere and ionosphere for several hours, and the location of the instruments pro- vides an excellent opportunity to study the direct coupling between the solar wind, the magnetosphere, and the ionosphere. Flux transfer events were observed by Geo- tail on the dawn magnetopause as the spacecraft passed from the
An extensive variety of instruments were continuously monitoring the dayside mag- netosphere and ... more An extensive variety of instruments were continuously monitoring the dayside mag- netosphere and ionosphere for several hours, and the location of the instruments pro- vides an excellent opportunity to study the direct coupling between the solar wind, the magnetosphere, and the ionosphere. Flux transfer events were observed by Geo- tail on the dawn magnetopause as the spacecraft passed from the
X-ray emission from charge exchange recombination between the highly ionized solar wind and neutr... more X-ray emission from charge exchange recombination between the highly ionized solar wind and neutral material in Earth's magnetosheath has complicated x-ray observations of celestial objects with x-ray observatories including ROSAT, Chandra, XMM-Newton, and Suzaku. However, the charge-exchange emission can also be used as an important diagnostic of the solar-wind interacting with the magnetosheath. Soft x-ray observations from low-earth orbit or even the highly eccentric orbits of Chandra and XMM-Newton are likely superpositions of the celestial object of interest, the true extra-solar soft x-ray background, geospheric charge exchange, and heliospheric charge exchange. We show that with a small x-ray telescope placed either on the moon, in a similar vein as the Apollo ALSEP instruments, or in a stable orbit at a similar distance from the earth, we can begin to disentangle the complicated emission structure in the soft x-ray band. Here we present initial results of a feasibility study recently funded by NASA to place a small x-ray telescope on the lunar surface. The telescope operates during lunar night to observe charge exchange interactions between the solar wind and magnetosphic neutrals, between the solar wind and the lunar atmosphere, and an unobstructed view of the soft x-ray background without the geospheric component.
Planetary plasma and magnetic field environments can be studied in two complementary ways—by in s... more Planetary plasma and magnetic field environments can be studied in two complementary ways—by in situ measurements, or by remote sensing. While the former provide precise information about plasma behaviour, instabilities and dynamics on local scales, the latter offers the global view necessary to understand the overall interaction of the magnetospheric plasma with the solar wind. Some parts of the Earth’s magnetosphere have been remotely sensed, but the majority remains unexplored by this type of measurements. Here we propose a novel and more elegant approach employing remote X-ray imaging techniques, which are now possible thanks to the relatively recent discovery of solar wind charge exchange X-ray emissions in the vicinity of the Earth’s magnetosphere. In this article we describe how an appropriately designed and located X-ray telescope, supported by simultaneous in situ measurements of the solar wind, can be used to image the dayside magnetosphere, magnetosheath and bow shock, with a temporal and spatial resolution sufficient to address several key outstanding questions concerning how the solar wind interacts with the Earth’s magnetosphere on a global level. Global images of the dayside magnetospheric boundaries require vantage points well outside the magnetosphere. Our studies have led us to propose ‘AXIOM: Advanced X-ray Imaging of the Magnetosphere’, a concept mission using a Vega launcher with a LISA Pathfinder-type Propulsion Module to place the spacecraft in a Lissajous orbit around the Earth–Moon L1 point. The model payload consists of an X-ray Wide Field Imager, capable of both imaging and spectroscopy, and an in situ plasma and magnetic field measurement package. This package comprises a Proton-Alpha Sensor, designed to measure the bulk properties of the solar wind, an Ion Composition Analyser, to characterise the minor ion populations in the solar wind that cause charge exchange emission, and a Magnetometer, designed to measure the strength and direction of the solar wind magnetic field. We also show simulations that demonstrate how the proposed X-ray telescope design is capable of imaging the predicted emission from the dayside magnetosphere with the sensitivity and cadence required to achieve the science goals of the mission.
An extensive variety of instruments, including Geotail, DMSP F11, SuperDARN, and IMP-8, were moni... more An extensive variety of instruments, including Geotail, DMSP F11, SuperDARN, and IMP-8, were monitoring the dayside magnetosphere and ionosphere between 14:00 and 18:00 UT on 18 January 1999. The location of the instruments provided an excellent opportunity to study in detail the direct coupling between the solar wind, the magnetosphere, and the ionosphere. Flux transfer events were observed by Geotail near the magnetopause in the dawn side magnetosheath at about 4 magnetic local time during exclusively northward interplanetary magnetic field conditions. Excellent coverage of the entire dayside high-latitude ionosphere was achieved by the Northern Hemisphere Su-perDARN radars. On the large scale, temporally and spatially, the dayside magnetosphere convection remained directly driven by the interplanetary magnetic field, despite the highly variable interplanetary magnetic field conditions, including long periods of northward field. The SuperDARN radars in the dawn sector also measured small-scale temporally varying convection velocities, which are indicative of flux transfer event activity, in the vicinity of the magnetic footprint of Geotail. DMSP F11 in the Southern Hemisphere measured typical cusp precipitation simultaneously with and magnetically conjugate to a single flux transfer event signature detected by Geotail. A study of the characteristics of the DMSP ion spectrogram revealed that the source plasma from the reconnection site originated downstream of the subsolar point. Detailed analyses of locally optimised coordinate systems for individual flux transfer events at Geotail are consistent with a series of flux tubes protruding from the magnetopause, and originating from a high-latitude reconnection site in the Southern Hemisphere. This high-latitude reconnection site agrees with plasma injected away from the sub-Correspondence to: K. A. McWilliams ([email protected]) solar point. This is the first simultaneous and independent determination from ionospheric and space-based data of the location of magnetic reconnection.
The ion foreshock is a dynamic region with many linear and nonlinear plasma processes which lead ... more The ion foreshock is a dynamic region with many linear and nonlinear plasma processes which lead to a variety of observables such as ion beams, ULF waves and cavity structures. Local spacecraft observations and theory/simulation studies have investigated many individual processes in the foreshock. Global hybrid (kinetic ions, fluid electrons) simulations of the bow shock and associated foreshock provide a
Magnetopause depletion layer MDL is characterized by the decreased density and increased magnetic... more Magnetopause depletion layer MDL is characterized by the decreased density and increased magnetic field strength Decreased plasma pressure in the depletion layer is balanced with the increased magnetic field pressure Although MDL is reported to occur during other IMF orientations as well it is most clearly observed when the IMF is strongly northward We have studied the energetic particle events
ABSTRACT High flux of energetic particles causes depressed magnetic field and density regions in ... more ABSTRACT High flux of energetic particles causes depressed magnetic field and density regions in the foreshock which are called cavities. These cavities are suggested to be swept into the magnetosheath with the solar wind. In this work, we used one year of CDAWeb Cluster energetic particle data and found very clear examples of these cavities in the magnetosheath. Case examples show that the magnetosheath density and the magnetic fields are decreased during these high energetic particle flux events as in the foreshock region. While temperature in the magnetosheath shows very slight increase, velocity decreases during these times as well. We studied the effects of these high energetic fluxes on the magnetopause motion. Our preliminary findings indicate that the magnetopause moves outward by 2 Re on the average compared to the distance found by using ACE data at L1 point. We will investigate the IMF and solar wind plasma dependence of our events. We will present our case examples and statistical results by emphasizing on the importance of these events from the magnetosheath and magnetospheric interaction.
ABSTRACT As the inner boundary of the magnetosheath, the magnetopause is the location for energy,... more ABSTRACT As the inner boundary of the magnetosheath, the magnetopause is the location for energy, mass, and momentum transfer between the solar wind and the magnetosphere. The location of the magnetopause as well as its dependence on solar wind and geophysical conditions is critical for solar wind-magnetosphere interaction and global magnetosphere dynamics. Since the first theoretical solution of the shape and size of the magnetopause, many models have been proposed for magnetopause location. However, none of these models make use of new magnetopause crossings with much better coverage of high-latitude magnetopause and the cusps, as well as solar wind conditions. Previous studies also usually mandated analytical descriptions of magnetopause shape, which were then fit to subsets of crossings. This leaves much room for improvement, especially for unusual upstream conditions. In this study, we use the biggest magnetopause crossing database ever used by magnetopause modeling, including both older magnetopause crossings mainly from Space Physics Data Facility (SPDF) and earlier studies, and new magnetopause crossings from Cluster, THEMIS, Wind, Geotail, Polar, and Interball-1 with better high-latitude magnetopause and cusp coverage and corresponding solar wind conditions. Advanced machine learning technique, Support Vector Regression Machine (SVRM), and machine learning tool, MineTool, are used in this study to explore this big database for the control of the magnetopause locations by various solar wind and geophysical factors, including Earth's dipole tilt, the vector solar wind velocity, and the vector IMF, solar wind dynamic pressure, Beta, and Alfven Mach number. Comparison of our new magnetopause model with some leading earlier models shows that the new model has the smallest error, very well captures the subsolar magnetopause, high-latitude magnetopause, and cusps. Behavior of the new magnetopause model, including its asymmetry, magnetopause and cusp locations, is further studied under various typical solar wind conditions.
An extensive variety of instruments were continuously monitoring the dayside mag- netosphere and ... more An extensive variety of instruments were continuously monitoring the dayside mag- netosphere and ionosphere for several hours, and the location of the instruments pro- vides an excellent opportunity to study the direct coupling between the solar wind, the magnetosphere, and the ionosphere. Flux transfer events were observed by Geo- tail on the dawn magnetopause as the spacecraft passed from the
An extensive variety of instruments were continuously monitoring the dayside mag- netosphere and ... more An extensive variety of instruments were continuously monitoring the dayside mag- netosphere and ionosphere for several hours, and the location of the instruments pro- vides an excellent opportunity to study the direct coupling between the solar wind, the magnetosphere, and the ionosphere. Flux transfer events were observed by Geo- tail on the dawn magnetopause as the spacecraft passed from the
X-ray emission from charge exchange recombination between the highly ionized solar wind and neutr... more X-ray emission from charge exchange recombination between the highly ionized solar wind and neutral material in Earth's magnetosheath has complicated x-ray observations of celestial objects with x-ray observatories including ROSAT, Chandra, XMM-Newton, and Suzaku. However, the charge-exchange emission can also be used as an important diagnostic of the solar-wind interacting with the magnetosheath. Soft x-ray observations from low-earth orbit or even the highly eccentric orbits of Chandra and XMM-Newton are likely superpositions of the celestial object of interest, the true extra-solar soft x-ray background, geospheric charge exchange, and heliospheric charge exchange. We show that with a small x-ray telescope placed either on the moon, in a similar vein as the Apollo ALSEP instruments, or in a stable orbit at a similar distance from the earth, we can begin to disentangle the complicated emission structure in the soft x-ray band. Here we present initial results of a feasibility study recently funded by NASA to place a small x-ray telescope on the lunar surface. The telescope operates during lunar night to observe charge exchange interactions between the solar wind and magnetosphic neutrals, between the solar wind and the lunar atmosphere, and an unobstructed view of the soft x-ray background without the geospheric component.
Planetary plasma and magnetic field environments can be studied in two complementary ways—by in s... more Planetary plasma and magnetic field environments can be studied in two complementary ways—by in situ measurements, or by remote sensing. While the former provide precise information about plasma behaviour, instabilities and dynamics on local scales, the latter offers the global view necessary to understand the overall interaction of the magnetospheric plasma with the solar wind. Some parts of the Earth’s magnetosphere have been remotely sensed, but the majority remains unexplored by this type of measurements. Here we propose a novel and more elegant approach employing remote X-ray imaging techniques, which are now possible thanks to the relatively recent discovery of solar wind charge exchange X-ray emissions in the vicinity of the Earth’s magnetosphere. In this article we describe how an appropriately designed and located X-ray telescope, supported by simultaneous in situ measurements of the solar wind, can be used to image the dayside magnetosphere, magnetosheath and bow shock, with a temporal and spatial resolution sufficient to address several key outstanding questions concerning how the solar wind interacts with the Earth’s magnetosphere on a global level. Global images of the dayside magnetospheric boundaries require vantage points well outside the magnetosphere. Our studies have led us to propose ‘AXIOM: Advanced X-ray Imaging of the Magnetosphere’, a concept mission using a Vega launcher with a LISA Pathfinder-type Propulsion Module to place the spacecraft in a Lissajous orbit around the Earth–Moon L1 point. The model payload consists of an X-ray Wide Field Imager, capable of both imaging and spectroscopy, and an in situ plasma and magnetic field measurement package. This package comprises a Proton-Alpha Sensor, designed to measure the bulk properties of the solar wind, an Ion Composition Analyser, to characterise the minor ion populations in the solar wind that cause charge exchange emission, and a Magnetometer, designed to measure the strength and direction of the solar wind magnetic field. We also show simulations that demonstrate how the proposed X-ray telescope design is capable of imaging the predicted emission from the dayside magnetosphere with the sensitivity and cadence required to achieve the science goals of the mission.
An extensive variety of instruments, including Geotail, DMSP F11, SuperDARN, and IMP-8, were moni... more An extensive variety of instruments, including Geotail, DMSP F11, SuperDARN, and IMP-8, were monitoring the dayside magnetosphere and ionosphere between 14:00 and 18:00 UT on 18 January 1999. The location of the instruments provided an excellent opportunity to study in detail the direct coupling between the solar wind, the magnetosphere, and the ionosphere. Flux transfer events were observed by Geotail near the magnetopause in the dawn side magnetosheath at about 4 magnetic local time during exclusively northward interplanetary magnetic field conditions. Excellent coverage of the entire dayside high-latitude ionosphere was achieved by the Northern Hemisphere Su-perDARN radars. On the large scale, temporally and spatially, the dayside magnetosphere convection remained directly driven by the interplanetary magnetic field, despite the highly variable interplanetary magnetic field conditions, including long periods of northward field. The SuperDARN radars in the dawn sector also measured small-scale temporally varying convection velocities, which are indicative of flux transfer event activity, in the vicinity of the magnetic footprint of Geotail. DMSP F11 in the Southern Hemisphere measured typical cusp precipitation simultaneously with and magnetically conjugate to a single flux transfer event signature detected by Geotail. A study of the characteristics of the DMSP ion spectrogram revealed that the source plasma from the reconnection site originated downstream of the subsolar point. Detailed analyses of locally optimised coordinate systems for individual flux transfer events at Geotail are consistent with a series of flux tubes protruding from the magnetopause, and originating from a high-latitude reconnection site in the Southern Hemisphere. This high-latitude reconnection site agrees with plasma injected away from the sub-Correspondence to: K. A. McWilliams ([email protected]) solar point. This is the first simultaneous and independent determination from ionospheric and space-based data of the location of magnetic reconnection.
The ion foreshock is a dynamic region with many linear and nonlinear plasma processes which lead ... more The ion foreshock is a dynamic region with many linear and nonlinear plasma processes which lead to a variety of observables such as ion beams, ULF waves and cavity structures. Local spacecraft observations and theory/simulation studies have investigated many individual processes in the foreshock. Global hybrid (kinetic ions, fluid electrons) simulations of the bow shock and associated foreshock provide a
Magnetopause depletion layer MDL is characterized by the decreased density and increased magnetic... more Magnetopause depletion layer MDL is characterized by the decreased density and increased magnetic field strength Decreased plasma pressure in the depletion layer is balanced with the increased magnetic field pressure Although MDL is reported to occur during other IMF orientations as well it is most clearly observed when the IMF is strongly northward We have studied the energetic particle events
ABSTRACT High flux of energetic particles causes depressed magnetic field and density regions in ... more ABSTRACT High flux of energetic particles causes depressed magnetic field and density regions in the foreshock which are called cavities. These cavities are suggested to be swept into the magnetosheath with the solar wind. In this work, we used one year of CDAWeb Cluster energetic particle data and found very clear examples of these cavities in the magnetosheath. Case examples show that the magnetosheath density and the magnetic fields are decreased during these high energetic particle flux events as in the foreshock region. While temperature in the magnetosheath shows very slight increase, velocity decreases during these times as well. We studied the effects of these high energetic fluxes on the magnetopause motion. Our preliminary findings indicate that the magnetopause moves outward by 2 Re on the average compared to the distance found by using ACE data at L1 point. We will investigate the IMF and solar wind plasma dependence of our events. We will present our case examples and statistical results by emphasizing on the importance of these events from the magnetosheath and magnetospheric interaction.
ABSTRACT As the inner boundary of the magnetosheath, the magnetopause is the location for energy,... more ABSTRACT As the inner boundary of the magnetosheath, the magnetopause is the location for energy, mass, and momentum transfer between the solar wind and the magnetosphere. The location of the magnetopause as well as its dependence on solar wind and geophysical conditions is critical for solar wind-magnetosphere interaction and global magnetosphere dynamics. Since the first theoretical solution of the shape and size of the magnetopause, many models have been proposed for magnetopause location. However, none of these models make use of new magnetopause crossings with much better coverage of high-latitude magnetopause and the cusps, as well as solar wind conditions. Previous studies also usually mandated analytical descriptions of magnetopause shape, which were then fit to subsets of crossings. This leaves much room for improvement, especially for unusual upstream conditions. In this study, we use the biggest magnetopause crossing database ever used by magnetopause modeling, including both older magnetopause crossings mainly from Space Physics Data Facility (SPDF) and earlier studies, and new magnetopause crossings from Cluster, THEMIS, Wind, Geotail, Polar, and Interball-1 with better high-latitude magnetopause and cusp coverage and corresponding solar wind conditions. Advanced machine learning technique, Support Vector Regression Machine (SVRM), and machine learning tool, MineTool, are used in this study to explore this big database for the control of the magnetopause locations by various solar wind and geophysical factors, including Earth's dipole tilt, the vector solar wind velocity, and the vector IMF, solar wind dynamic pressure, Beta, and Alfven Mach number. Comparison of our new magnetopause model with some leading earlier models shows that the new model has the smallest error, very well captures the subsolar magnetopause, high-latitude magnetopause, and cusps. Behavior of the new magnetopause model, including its asymmetry, magnetopause and cusp locations, is further studied under various typical solar wind conditions.
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Papers by David Sibeck