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Pekka Janhunen Annika Olsson Christopher T. Russell Harri Laakso 《Space Science Reviews》2006,122(1-4):89-95
Auroral emission caused by electron precipitation (Hardy et al., 1987, J. Geophys. Res. 92, 12275–12294) is powered by magnetospheric driving processes. It is not yet fully understood how the energy transfer mechanisms
are responsible for the electron precipitation. It has been proposed (Hasegawa, 1976, J. Geophys. Res. 81, 5083–5090) that Alfvén waves coming from the magnetosphere play some role in powering the aurora (Wygant et al., 2000, J. Geophys. Res. 105, 18675–18692, Keiling et al., 2003, Science
299, 383–386). Alfvén-wave-induced electron acceleration is shown to be confined in a rather narrow radial distance range of
4–5 R
E
(Earth radii) and its importance, relative to other electron acceleration mechanisms, depends strongly on the magnetic disturbance
level so that it represents 10% of all electron precipitation power during quiet conditions and increased to 40% during disturbed
conditions. Our observations suggest that an electron Landau resonance mechanism operating in the “Alfvén resonosphere” is
responsible for the energy transfer. 相似文献
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The FIELDS Instrument Suite on MMS: Scientific Objectives,Measurements, and Data Products 总被引:1,自引:0,他引:1
R. B. Torbert C. T. Russell W. Magnes R. E. Ergun P.-A. Lindqvist O. LeContel H. Vaith J. Macri S. Myers D. Rau J. Needell B. King M. Granoff M. Chutter I. Dors G. Olsson Y. V. Khotyaintsev A. Eriksson C. A. Kletzing S. Bounds B. Anderson W. Baumjohann M. Steller K. Bromund Guan Le R. Nakamura R. J. Strangeway H. K. Leinweber S. Tucker J. Westfall D. Fischer F. Plaschke J. Porter K. Lappalainen 《Space Science Reviews》2016,199(1-4):105-135
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O.?Le?ContelEmail author P.?Leroy A.?Roux C.?Coillot D.?Alison A.?Bouabdellah L.?Mirioni L.?Meslier A.?Galic M.?C.?Vassal R.?B.?Torbert J.?Needell D.?Rau I.?Dors R.?E.?Ergun J.?Westfall D.?Summers J.?Wallace W.?Magnes A.?Valavanoglou G.?Olsson M.?Chutter J.?Macri S.?Myers S.?Turco J.?Nolin D.?Bodet K.?Rowe M.?Tanguy B.?de?la?Porte 《Space Science Reviews》2016,199(1-4):257-282
The tri-axial search-coil magnetometer (SCM) belongs to the FIELDS instrumentation suite on the Magnetospheric Multiscale (MMS) mission (Torbert et al. in Space Sci. Rev. (2014), this issue). It provides the three magnetic components of the waves from 1 Hz to 6 kHz in particular in the key regions of the Earth’s magnetosphere namely the subsolar region and the magnetotail. Magnetospheric plasmas being collisionless, such a measurement is crucial as the electromagnetic waves are thought to provide a way to ensure the conversion from magnetic to thermal and kinetic energies allowing local or global reconfigurations of the Earth’s magnetic field. The analog waveforms provided by the SCM are digitized and processed inside the digital signal processor (DSP), within the Central Electronics Box (CEB), together with the electric field data provided by the spin-plane double probe (SDP) and the axial double probe (ADP). On-board calibration signal provided by DSP allows the verification of the SCM transfer function once per orbit. Magnetic waveforms and on-board spectra computed by DSP are available at different time resolution depending on the selected mode. The SCM design is described in details as well as the different steps of the ground and in-flight calibrations. 相似文献
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K. Olsson 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(11):161-164
The relationship between canopy cover and spectral characteristics of the corresponding areas was studied in a semi-arid savannah environment in Kordofan, The Sudan.The canopy cover was measured in 32 test plots through air photo interpretation. Achieved values were correlated with multitemporal Landsat MSS raw data and manipulated data.The highest correlation coefficients in general were obtained between crown cover and spectral data recorded during the dry season.The inverse relationship between amount of woody vegetation and nIR reflectance (MSS 6, MSS 7) was striking. This implied that other factors than a healthy foliage characterized the spectral responses.Destructive measurements of woody biomass were carried out to establish a relationship between woody wet weight and crown diameter for future biomass studies. 相似文献
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