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911.
912.
913.
We calculate the conditions of pickup protons inside the termination shock. Outside 50 AU the partial pressure of pickup protons is greater than the magnetic pressure by a factor of > 10, and greater than the partial pressure of solar wind protons by a factor of > 100. Thus, pickup protons have a significant dynamical influence on the structures of the solar wind in the outer heliosphere. 相似文献
914.
Lohr D. A. Zanetti L. J. Anderson B. J. Potemra T. A. Hayes J. R. Gold R. E. Henshaw R. M. Mobley F. F. Holland D. B. Acuña M. H. Scheifele J. L. 《Space Science Reviews》1997,82(1-2):255-281
The primary objective of the investigation is the search for a body-wide magnetic field of the near Earth asteroid Eros. The Near Earth Asteroid Rendezvous (NEAR) 3-axis fluxgate magnetometer includes a sensor mounted on the high-gain antenna feed structure. The NEAR Magnetic Facility Instrument (MFI) is a joint hardware effort between GSFC and APL. The design and magnetics approach achieved by the NEAR MFI effort entailed low-cost, up-front attention to engineering solutions which did not impact the schedule. The goal of the magnetometer is reliable magnetic field measurements within 5 nT, which necessitates the use of an extensive spacecraft magnetic interference model but is achievable with the full year's orbital data set. Such a goal has been shown viable with recent in-flight calibration data and comparisons to the WIND magnetometer data. The NEAR MFI effort has succeeded in providing magnetic field measurements for the first flight in NASA's Discovery line. 相似文献
915.
916.
N.U. Crooker J.T. Gosling V. Bothmer R.J. Forsyth P.R. Gazis A. Hewish T.S. Horbury D.S. Intriligator J.R. Jokipii J. Kóta A.J. Lazarus M.A. Lee E. Lucek E. Marsch A. Posner I.G. Richardson E.C. Roelof J.M. Schmidt G.L. Siscoe B.T. Tsurutani R.F. Wimmer-Schweingruber 《Space Science Reviews》1999,89(1-2):179-220
Corotating interaction regions (CIRs) in the middle heliosphere have distinct morphological features and associated patterns
of turbulence and energetic particles. This report summarizes current understanding of those features and patterns, discusses
how they can vary from case to case and with distance from the Sun and possible causes of those variations, presents an analytical
model of the morphological features found in earlier qualitative models and numerical simulations, and identifies aspects
of the features and patterns that have yet to be resolved.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
917.
918.
A global view of the ring current ions is presented using data acquired by the instrument MICS onboard the CRRES satellite during solar maximum. The variations of differential intensities, energy spectra, radial profile of the energetic particles and the origin of the magnetic local time (MLT) asymmetry of the ring current have been investigated in detail. O+ ions are an important contributor to the storm time ring current. Its abundance in terms of number density increases with increasing geomagnetic activity as well as its energy density. However, a saturation value for the energy density of O+ ions has been found. The low-energy H+ ions show a dramatic intensification and a rapid decay. However, its density ratio during the storm maximum is almost constant. On the other hand, high-energy H+ ions first exhibit a flux decrease followed by a delayed increase. Its density ratio shows an anti-correlation with the storm intensity. Both the positions of the maximum flux of O+ and He+ depend on storm activity: they move to lower altitudes in the early stage of a storm and move back to higher L-values during the recovery phase. Whereas the position of H+ and He++ show almost no dependence on the Dst index. The energy density distributions in radial distance and magnetic local time show drastic differences for different ion species. It demonstrates that the ring current asymmetry mainly comes from oxygen and helium ions, but not from protons. The outward motion of O+ around local noon may have some implications for oxygen bursts in the magnetosheath during IMF Bz negative conditions as observed by GEOTAIL. 相似文献
919.
The ACE Magnetic Fields Experiment 总被引:2,自引:0,他引:2
Smith C.W. L'Heureux J. Ness N.F. Acuña M.H. Burlaga L.F. Scheifele J. 《Space Science Reviews》1998,86(1-4):613-632
The magnetic field experiment on ACE provides continuous measurements of the local magnetic field in the interplanetary medium.
These measurements are essential in the interpretation of simultaneous ACE observations of energetic and thermal particles
distributions. The experiment consists of a pair of twin, boom- mounted, triaxial fluxgate sensors which are located 165 inches
(=4.19 m) from the center of the spacecraft on opposing solar panels. The electronics and digital processing unit (DPU) is
mounted on the top deck of the spacecraft. The two triaxial sensors provide a balanced, fully redundant vector instrument
and permit some enhanced assessment of the spacecraft's magnetic field. The instrument provides data for Browse and high-level
products with between 3 and 6 vector s−1 resolution for continuous coverage of the interplanetary magnetic field. Two high-resolution
snapshot buffers each hold 297 s of 24 vector s−1 data while on- board Fast Fourier Transforms extend the continuous data
to 12 Hz resolution. Real-time observations with 1-s resolution are provided continuously to the Space Environmental Center
(SEC) of the National Oceanographic and Atmospheric Association (NOAA) for near- instantaneous, world-wide dissemination in
service to space weather studies. As has been our team's tradition, high instrument reliability is obtained by the use of
fully redundant systems and extremely conservative designs. We plan studies of the interplanetary medium in support of the
fundamental goals of the ACE mission and cooperative studies with other ACE investigators using the combined ACE dataset as
well as other ISTP spacecraft involved in the general program of Sun-Earth Connections.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
920.
IMMPDAF for radar management and tracking benchmark with ECM 总被引:2,自引:0,他引:2
Kirubarajan T. Bar-Shalom Y. Blair W.D. Watson G.A. 《IEEE transactions on aerospace and electronic systems》1998,34(4):1115-1134
A framework is presented for controlling a phased array radar for tracking highly maneuvering targets in the presence of false alarms (FAs) and electronic countermeasures (ECMs). Algorithms are presented for track formation and maintenance; adaptive selection of target revisit interval, waveform and detection threshold; and neutralizing techniques for ECM, namely, against a standoff jammer (SOJ) and range gate pull off (RGPO). The interacting multiple model (IMM) estimator in combination with the probabilistic data association (PDA) technique is used for tracking. A constant false alarm rate (CFAR) approach is used to adaptively select the detection threshold and radar waveform, countering the effect of jammer-induced false measurements. The revisit interval is selected adaptively, based on the predicted angular innovation standard deviations. This tracker/radar-resource-allocator provides a complete solution to the benchmark problem for target tracking and radar control. Simulation results show an average sampling interval of about 2.5 s while maintaining a track loss less than the maximum allowed 4% 相似文献