| 1. |
- Blomberg, Lars, et al.
(författare)
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Atrid-2 : An advanced auroral microprobe
- 1999
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Astri-2 is an advanced auroral microprobe with dual primary mission objectives; to do high-quality in situ measurements of the physical processes behind the aurora, and to demonstrate the usefulness of microspacecraft as advanced research tools. Mission success will open up entirely new possibilities to carry out low-budget multipoint measurements in near-Earth space. This long-desired kind of in situ measurements are the next major step forward in experimental space physics. Astrid-2 has platform dimensions of 45×45×30 cm, a total mass of just below 30 kg, and carries scientific instruments for measuring local electric and magnetic fields, plasma density and density fluctuations, ions and electrons, as well as photometers for remote imaging of auroral emissions. Attitude determination is provided by a high-precision star imager. Some 250 Mbytes' worth of scientific data will be received each day at the two ground stations. Astrid-2 will be launched as a piggy-back on a Russian Kosmos-3M launcher into an 83 deg inclination circular orbit at 1000 km altitude. Nodal regression will give complete coverage of all local time sectors every 3.5 months. © 1999 Elsevier B.V. All rights reserved.
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| 2. |
- Escoubet, C P, et al.
(författare)
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Density in the magnetosphere inferred from ISEE 1 spacecraft potential
- 1997
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Ingår i: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS. - ROYAL INST TECHNOL,ALFVEN LAB,DIV PLASMA PHYS,S-10044 STOCKHOLM,SWEDEN.. ; 102:A8, s. 17595-17609
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Tidskriftsartikel (refereegranskat)abstract
- The potential of ISEE 1 spacecraft has been used to derive the plasma density in the magnetosphere and its environment. First, we show that using the equilibrium of currents flowing in and out of a spacecraft, we could numerically derive a relation between the spacecraft potential and the density of the surrounding plasma, After verifying: that this relation was in good agreement with the measurement of the density made by other instruments during selected periods of time, we apply this relation to the spacecraft potential measured continuously from 1977 to 1984 on ISEE 1, An image of the plasma density in the magnetosphere and its environment is obtained as a result, All principal magnetospheric regions are clearly identified: the solar wind with a density around 5 cm(-3) : the magnetosheath with a density around 50 cm(-3), the magnetosphere with a density around 1 cm(-3) the plasma sheet with a density around 0.5 cm(-3), and finally, the more tenuous tail lobes with a density below 0.1 cm(-3), The plasma density was observed slightly higher on the dawnside than on the duskside of the magnetosphere, In addition, the magnetosheath was closer to the Earth on the dawnside than on the duskside, When the magnetic activity increased (recorded by the AE index), the dayside magnetosphere was compressed/eroded by about 1 to 2 R-E, while the plasmasphere/inner magnetosphere became quite irregular and expanded in the dawn-midnight and in the dusk-noon sectors, In addition, during high magnetic activity, the plasma sheet at Y-GSM = 0 was thicker and slightly denser than at low-activity, On the other hand, the flanks of the plasma sheet were thinner and slightly less dense during high-activity than during low-activity.
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| 3. |
- Escoubet, C. P., et al.
(författare)
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Imaging the magnetosphere using ISEE-1 spacecraft potential
- 1996
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Ingår i: European Space Agency, (Special Publication) ESA SP. - 0379-6566. ; :392, s. 179-187
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Tidskriftsartikel (refereegranskat)abstract
- The potential of ISEE 1 spacecraft has been used to derived the plasma density in the magnetosphere and its environment. First we show that using the equilibrium of currents flowing in and out of a spacecraft, we could derive numerically a relation between the spacecraft potential and the density of the surrounding plasma. After verifying that this relation was in good agreement with the measurement of the density made by other instruments during selected periods of time, we apply this relation to the spacecraft potential measured continuously from 1977 to 1984 on ISEE-1. An image of the plasma density in the magnetosphere and its environment is obtained as a result. All principal magnetospheric regions are clearly identified, from the solar wind with a density around 5 cm-3 , the magnetosheath around 50 cm-3, the magnetosphere around 1 cm-3, the plasma sheet around 0.5 cm-3 and finally the more tenuous tail lobes below 0.1 cm-3. The plasma density was observed slightly higher on the dawnside than on the dusk side of the magnetosphere. In addition the magnetosheath was closer to the Earth on the dawnside than on the duskside. When the magnetic activity increased (recorded by the AE index), the dayside magnetosphere was compressed/eroded by about 1 to 2 RE while the plasmasphere/inner magnetosphere became quite irregular and expanded in the dawn-midnight and in the dusk-noon sectors. In addition, during high magnetic activity, the plasmasheet at Ygsm = 0 was thicker and denser than at low activity. On the other hand the flanks of the plasmasheet were thinner and less dense during high activity than during low activity.
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| 4. |
- Feldstein, Y I, et al.
(författare)
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Electromagnetic characteristics of the high-latitude ionosphere during the various phases of magnetic substorms
- 1996
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 101:A9, s. 19921-19936
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Tidskriftsartikel (refereegranskat)abstract
- Model calculations of the electrodynamics of the high-latitude ionosphere are compared to measurements made by the Viking satellite during July-August 1986. The model calculations are based on the IZMEM procedure, where the electric field and currents in the ionosphere are given as functions of the interplanetary magnetic field. The events chosen correspond to the growth, the expansion, and the recovery phases of substorms. During the growth and expansion phases the correlation between the model results and the satellite data is rather good. During recovery phase the correlation is not as good. The correlation between modeled and observed quantities suggest that during growth and expansion phase the magnetosphere is mainly directly driven by the solar wind, whereas during recovery phase it is mainly driven by internal processes, i.e., loading-unloading. Best fit is obtained when averaging the measured quantities over a few minutes, which means adjusting the spatial resolution of the measurements to the resolution of the model. Different time delays between the interplanetary magnetic field observations and those of Viking were examined. Best agreement was obtained, not surprisingly, for time delays corresponding to the estimated information transit time from the solar wind spacecraft to the ionosphere.
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| 5. |
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| 6. |
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| 7. |
- Feldstein, Yakov I., et al.
(författare)
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To directly driven and loading-unloading processes during substorm
- 1996
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Ingår i: European Space Agency, (Special Publication) ESA SP. - 0379-6566. ; :389, s. 69-74
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Tidskriftsartikel (refereegranskat)abstract
- Model calculations of the electric fields in the high-latitude ionosphere are compared to measurements made by the Viking satellite during August 3, 1986 pass. The model calculations are based on the IZMEM procedure, where the electric field and currents in the ionosphere are given as functions of the interplanetary magnetic field (IMF). The event chosen correspond to the growth phase of substorm. The correlation between the model results and the satellite data is high, which assumes directly driven of the magnetosphere by the solar wind. Similar high correlation exists between the electric field in the solar wind (V*Bs) and AL magnetic activity indices, if time delays between the V*Bs observations in space and magnetic activity above the Earth's ground are taken into account. It is concluded, that the directly driven response of the magnetosphere to highly variable solar wind electric field is the main feature of geomagnetic activity at high latitudes.
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| 8. |
- Gustafsson, G, et al.
(författare)
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The electric field and wave experiment for the Cluster mission
- 1997
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Ingår i: Space Science Reviews. - 0038-6308 .- 1572-9672. ; 79, s. 137-156
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Tidskriftsartikel (refereegranskat)abstract
- The electric-field and wave experiment (EFW) on Cluster is designed to measure the electric-field and density fluctuations with sampling rates up to 36 000 samples s(-1). Langmuir probe sweeps can also be made to determine the electron density and temperature. The instrument has several important capabilities. These include (1) measurements of quasi-static electric fields of amplitudes lip to 700 mV m(-1) with high amplitude and time resolution, (2) measurements over short periods of time of up to five simualtaneous waveforms (two electric signals and three magnetic signals from the seach coil magnetometer sensors) of a bandwidth of 4 kHz with high time resolution, (3) measurements of density fluctuations in four points with high time resolution. Among the more interesting scientific objectives of the experiment are studies of nonlinear wave phenomena that result in acceleration of plasma as well as large- and small-scale interferometric measurements. By using four spacecraft for large-scale differential measurements and several Langmuir probes on one spacecraft for small-scale interferometry, it will be possible to study motion and shape of plasma structures on a wide range of spatial and temporal scales. This paper describes the primary scientific objectives of the EFW experiment and the technical capabilities of the instrument.
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