| 1. |
- Cai, Lei, et al.
(författare)
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GeospaceLAB : Python package for managing and visualizing data in space physics
- 2022
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Ingår i: Frontiers in Astronomy and Space Sciences. - : Frontiers Media SA. - 2296-987X. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- In the space physics community, processing and combining observational and modeling data from various sources is a demanding task because they often have different formats and use different coordinate systems. The Python package GeospaceLAB has been developed to provide a unified, standardized framework to process data. The package is composed of six core modules, including DataHub as the data manager, Visualization for generating publication quality figures, Express for higher-level interfaces of DataHub and Visualization, SpaceCoordinateSystem for coordinate system transformations, Toolbox for various utilities, and Configuration for preferences. The core modules form a standardized framework for downloading, storing, post-processing and visualizing data in space physics. The object-oriented design makes the core modules of GeospaceLAB easy to modify and extend. So far, GeospaceLAB can process more than twenty kinds of data products from nine databases, and the number will increase in the future. The data sources include, e.g., measurements by EISCAT incoherent scatter radars, DMSP, SWARM, and Grace satellites, OMNI solar wind data, and GITM simulations. In addition, the package provides an interface for the users to add their own data products. Hence, researchers can easily collect, combine, and view multiple kinds of data for their work using GeospaceLAB. Combining data from different sources will lead to a better understanding of the physics of the studied phenomena and may lead to new discoveries. GeospaceLAB is an open source software, which is hosted on GitHub. We welcome everyone in the community to contribute to its future development.
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| 2. |
- Pitkänen, Timo, 1979-, et al.
(författare)
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Asymmetry in the Earth's magnetotail neutral sheet rotation due to IMF B-y sign?
- 2021
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Ingår i: Geoscience Letters. - : Springer Nature. - 2196-4092. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Evidence suggests that a non-zero dawn-dusk interplanetary magnetic field (IMF B-y) can cause a rotation of the cross-tail current sheet/neutral sheet around its axis aligned with the Sun-Earth line in Earth's magnetotail. We use Geotail, THEMIS and Cluster data to statistically investigate how the rotation of the neutral sheet depends on the sign and magnitude of IMF B-y. In our dataset, we find that in the tail range of -30 < XGSM < -15 R-E, the degree of the neutral sheet rotation is clearly smaller, there appears no significant rotation or even, the rotation is clearly to an unexpected direction for negative IMF B-y, compared to positive IMF B-y. Comparison to a model by Tsyganenko et al. (2015, doi:10.5194/angeo-33-1-2015) suggests that this asymmetry in the neutral sheet rotation between positive and negative IMF B-y conditions is too large to be explained only by the currently known factors. The possible cause of the asymmetry remains unclear.
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| 3. |
- Blomberg, Lars G., et al.
(författare)
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EMMA - the electric and magnetic monitor of the aurora on Astrid-2
- 2004
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 22:1, s. 115-123
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Tidskriftsartikel (refereegranskat)abstract
- The Astrid-2 mission has dual primary objectives. First, it is an orbiting instrument platform for studying auroral electrodynamics. Second, it is a technology demonstration of the feasibility of using micro-satellites for innovative space plasma physics research. The EMMA instrument, which we discuss in the present paper, is designed to provide simultaneous sampling of two electric and three magnetic field components up to about 1 kHz. The spin plane components of the electric field are measured by two pairs of opposing probes extended by wire booms with a separation distance of 6.7 m. The probes have titanium nitride (TiN) surfaces. which has proved to be a material with excellent properties for providing good electrical contact between probe and plasma. The wire booms are of a new design in which the booms in the stowed position are wound around the exterior of the spacecraft body. The boom system was flown for the first time on this mission and worked flawlessly. The magnetic field is measured by a tri-axial fluxgate sensor located at the tip of a rigid. hinged boom extended along the spacecraft spin axis and facing away from the Sun. The new advanced-design fluxgate magnetometer uses digital signal processors for detection and feedback, thereby reducing the analogue circuitry to a minimum. The instrument characteristics as well as a brief review of the science accomplished and planned are presented.
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| 4. |
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| 5. |
- Cai, Lei, et al.
(författare)
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DMSP Observations of High-Latitude Dayside Aurora (HiLDA)
- 2021
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Ingår i: Journal of Geophysical Research - Space Physics. - : AMER GEOPHYSICAL UNION. - 2169-9380 .- 2169-9402. ; 126:4
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Tidskriftsartikel (refereegranskat)abstract
- We report two events of high-latitude dayside aurora (HiLDA), a large-scale aurora in the dayside polar cap, observed by the Defense Meteorological Satellite Program (DMSP) spacecraft in the northern and southern hemispheres, respectively. While HiLDA in the northern hemisphere was reported before under interplanetary magnetic field (IMF) positive By conditions, we show for the first time a HiLDA event in the southern hemisphere when the IMF negative By component was dominant. Our observations also show that HiLDA is highly dynamical: change in its forms, size, location, and development of fine structures during its long lifetime of hours. The co-occurrence of HiLDA and the duskside oval-aligned transpolar aurora (TPA) may be a common feature during IMF By dominant conditions. Both are associated with the high-latitude reconnection and the cusp. Based on the linear Knight relation, we estimate the distribution of the electron density in the magnetospheric source region of HiLDA. These results indicate that HiLDA maps most probably to the high-latitude lobe tailward of the cusp, where the electron density is down to 0.03-3 cm(-3). The lobe electrons are accelerated by the field-aligned potential drop (up to 10 kV) set up in the poleward part of upward Region 0 field-aligned current (FAC). The total energy flux of HiLDA electrons can be up to 50 mW/m(2), indicating HiLDA precipitation as a potential energy source that impacts the polar ionosphere-thermosphere system.
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| 6. |
- Carter, J. A., et al.
(författare)
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Dayside reconnection under interplanetary magnetic field B-y-dominated conditions : The formation and movement of bending arcs
- 2015
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Ingår i: Journal of Geophysical Research - Space Physics. - 2169-9380 .- 2169-9402. ; 120:4, s. 2967-2978
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Tidskriftsartikel (refereegranskat)abstract
- Based upon a survey of global auroral images collected by the Polar Ultraviolet Imager, Kullen etal. (2002) subdivided polar cap auroral arcs into a number of categories, including that of bending arcs. We are concerned with those bending arcs that appear as a bifurcation of the dayside auroral oval and which subsequently form a spur intruding into the polar cap. Once formed, the spur moves poleward and antisunward over the lifetime of the arc. We propose that dayside bending arcs are ionospheric signatures of pulses of dayside reconnection and are therefore part of a group of transient phenomena associated with flux transfer events. We observe the formation and subsequent motion of a bending arc across the polar cap during a 30 min interval on 8 January 1999, and we show that this example is consistent with the proposed model. We quantify the motion of the arc and find it to be commensurate with the convection flows observed by both ground-based radar observations and space-based particle flow measurements. In addition, precipitating particles coincident with the arc appear to occur along open field lines, lending further support to the model.
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| 7. |
- Chong, Ghai Siung, et al.
(författare)
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Dawn-Dusk Ion Flow Asymmetry in the Plasma Sheet : Interplanetary Magnetic Field B-y Versus Distance With Respect to the Neutral Sheet
- 2022
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Ingår i: Journal of Geophysical Research - Space Physics. - : American Geophysical Union (AGU). - 2169-9380 .- 2169-9402. ; 127:4
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies have shown that the average dawn-dusk component of the perpendicular plasma flow in the plasma sheet (V-perpendicular to) can vary depending on the distance relative to the neutral sheet and the dawn-dusk component of the interplanetary magnetic field (IMF B-y). In this study, we combined 33 years of data from the Geotail, Time History of Events and Macroscale Interactions during Substorms, Cluster, and magnetospheric multiscale missions to study the slow (<200 km/s) ion flows perpendicular to the magnetic field. We find that IMF B-y has a hemispheric dependent influence on both the tail B-y and tail V-perpendicular to. Particularly, the influence is more prominent in the midnight sector (compared to both the pre- and post-midnight sectors) and at distances far from the neutral sheet (compared to the distances close to the neutral sheet). However, at distances close to the neutral sheet, there is an increased dominance of duskward flows which dominates over the systematic influence of IMF B-y on tail V-perpendicular to. Our results indicate that IMF B-y has a major influence on the magnetic flux transport in the magnetotail, mainly at distances far from the neutral sheet. The influence is weaker at distances close to the neutral sheet.
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| 8. |
- Cumnock, Judy A., et al.
(författare)
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Small-scale characteristics of extremely high latitude aurora
- 2009
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 27:9, s. 3335-3347
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Tidskriftsartikel (refereegranskat)abstract
- We examine 14 cases of an interesting type of extremely high latitude aurora as identified in the precipitating particles measured by the DMSP F13 satellite. In particular we investigate structures within large-scale arcs for which the particle signatures are made up of a group of multiple distinct thin arcs. These cases are chosen without regard to IMF orientation and are part of a group of 87 events where DMSP F13 SSJ/4 measures emissions which occur near the noon-midnight meridian and are spatially separated from both the dawnside and duskside auroral ovals by wide regions with precipitating particles typical of the polar cap. For 73 of these events the high-latitude aurora consists of a continuous region of precipitating particles. We focus on the remaining 14 of these events where the particle signatures show multiple distinct thin arcs. These events occur during northward or weakly southward IMF conditions and follow a change in IMF B-y. Correlations are seen between the field-aligned currents and plasma flows associated with the arcs, implying local closure of the FACs. Strong correlations are seen only in the sunlit hemisphere. The convection associated with the multiple thin arcs is localized and has little influence on the large-scale convection. This also implies that the sunward flow along the arcs is unrelated to the overall ionospheric convection.
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| 9. |
- Fryer, L. J., et al.
(författare)
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3D GUMICS Simulations of Northward IMF Magnetotail Structure
- 2023
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Ingår i: Journal of Geophysical Research - Space Physics. - : American Geophysical Union (AGU). - 2169-9380 .- 2169-9402. ; 128:8
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Tidskriftsartikel (refereegranskat)abstract
- This study presents a re-evaluation of the Kullen and Janhunen (2004, https://doi.org/10.5194/angeo-22-951-2004) global northward interplanetary magnetic field (IMF) simulation, using the Grand Unified Magnetosphere–Ionosphere Coupling Simulation version 4 (GUMICS-4), a global MHD model. We investigate the dynamic coupling between northward IMF conditions and the Earth’s magnetotail and compare the results to observation-based mechanisms for the formation of transpolar arcs. The results of this study reveal that under northward IMF conditions (and northward IMF initialization), a large closed field line region forms in the magnetotail, with similarities to transpolar arc structures observed from spacecraft data. This interpretation is supported by the simultaneous increase of closed flux measured in the magnetotail. However, the reconnection configuration differs in several respects from previously theorized magnetotail structures that have been inferred from both observations and simulations results and associated with transpolar arcs. We observe that dawn–dusk lobe regions form as a result of high-latitude reconnection during the initialization stages, which later come into contact as the change in the IMF By component causes the magnetotail to twist. We conclude that in the GUMICS simulation, transpolar arc-like structures are formed as a result of reconnection in the magnetotail, rather than high-latitude reconnection or due to the mapping of the plasma sheet through a twisted magnetotail as interpreted from previous analysis of GUMICS simulations.
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| 10. |
- Golovchanskaya, I. V., et al.
(författare)
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Ballooning instability at the plasma sheet-lobe interface and its implications for polar arc formation
- 2006
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 111:A11, s. A11216-
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Tidskriftsartikel (refereegranskat)abstract
- Huang et al. ( 1987, 1989) reported hot filaments of plasma sheet origin filling the magnetospheric lobes during northward interplanetary magnetic field ( IMF). On the other hand, cold plasma transients of presumably lobe origin are often observed in the plasma sheet. These features can be interpreted in terms of plasma exchange at the plasma sheet - lobe interface (PSLI) proceeding in a filamentary manner. We present a description of this process within ballooning destabilizing of the near-Earth curved segment of the PSLI. Although the basic ballooning instability condition is not typically met inside the plasma sheet, it is satisfied at this segment. The PSLI always separates the cold lobe population from the hot plasma sheet, thus providing a pressure gradient favorable for the instability; its near-Earth part has a nonnegligible magnetic curvature. A solution for the least stable ballooning harmonics is found, which satisfies the finite conductivity boundary condition in the ionosphere and the outgoing Alfven wave condition at the tailward end of the near-Earth curved segment of the plasma sheet boundary. We show that this part of the PSLI may be a generator region launching filamentation. The background convection is imposed on the ballooning motions. The large-scale convection associated with southward IMF B-z suppresses hot filament progression into the lobes, while promoting penetration of lobe transients into the plasma sheet. However, during northward IMF, the convection favors at certain magnetic local times the extension of plasma sheet filaments into the lobes and their subsequent protrusion toward noon. This process is signified in the ionosphere by the occurrence of nightside originating polar arcs. Several polar arc events are shown that develop from the nightside oval boundary into the polar cap on timescales of approximately 10 - 15 min, consistent with the growth rates of the studied instability.
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