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211.
The interplanetary magnetic field, geomagnetic variations, virtual ionosphere height h′F, and the critical frequency foF2 data during the geomagnetic storms are studied to demonstrate relationships between these phenomena. We study 5-min ionospheric variations using the first Western Pacific Ionosphere Campaign (1998–1999) observations, 5-min interplanetary magnetic field (IMF) and 5-min auroral electrojets data during a moderate geomagnetic storm. These data allowed us to demonstrate that the auroral and the equatorial ionospheric phenomena are developed practically simultaneously. Hourly average of the ionospheric foF2 and h′F variations at near equatorial stations during a similar storm show the same behavior. We suppose this is due to interaction between electric fields of the auroral and the equatorial ionosphere during geomagnetic storms. It is shown that the low-latitude ionosphere dynamics during these moderate storms was defined by the southward direction of the Bz-component of the interplanetary magnetic field. A southward IMF produces the Region I and Region II field-aligned currents (FAC) and polar electrojet current systems. We assume that the short-term ionospheric variations during geomagnetic storms can be explained mainly by the electric field of the FAC. The electric fields of the field-aligned currents can penetrate throughout the mid-latitude ionosphere to the equator and may serve as a coupling agent between the auroral and the equatorial ionosphere.  相似文献   
212.
    
We propose that the appropriate instability to trigger a substorm is a tailward meander (in the equatorial plane) of the strong current filament that develops during the growth phase. From this single assumption follows the entire sequence of events for a substorm. The main particle acceleration mechanism in the plasma sheet is curvature drift with a dawn-dusk electric field, leading to the production of auroral arcs. Eventually the curvature becomes so high that the ions cannot negotiate the sharp turn at the field-reversal region, locally, at a certain time. The particle motion becomes chaotic, causing a local outward meander of the cross-tail current. An induction electric field is produced by Lenz's law, Eind=–A/t. An outward meander with Bz>0 will cause E×B flow everywhere out from the disturbance; this reaction is a macroscopic instability which we designate the electromotive instability. The response of the plasma is through charge separation and a scalar potential, Ees=–. Both types of electric fields have components parallel to B in a realistic magnetic field. For MHD theory to hold the net E must be small; this usually seems to happen (because MHD often does hold), but not always. Part of the response is the formation of field-aligned currents producing the well-known substorm current diversion. This is a direct result of a strong Eind (the cause) needed to overcome the mirror force of the current carriers; this enables charge separation to produce an opposing electrostatic field Ees (the effect). Satellite data confirm the reality of a strong E in the plasma sheet by counter-streaming of electrons and ions, and by the inverse ion time dispersion, up to several 100 keV. The electron precipitation is associated with the westward traveling surge (WTS) and the ion with omega () bands, respectively. However, with zero curl, Ees cannot modify the emf =Edl=–dM/dt of the inductive electric field Eind (a property of vector fields); the charge separation that produces a reduction of E must enhance the transverse component E. The new plasma flow becomes a switch for access to the free energy of the stressed magnetotail. On the tailward side the dusk-dawn electric field with EJ<0 will cause tailward motion of the plasma and a plasmoid may be created; it will move in the direction of least magnetic pressure, tailward. On the earthward side the enhanced dawn-dusk induction electric field with EJ>0 will cause injection into the inner plasma sheet, repeatedly observed at moderate energies of 1–50 keV. This same electric field near the emerging X-line will accelerate particles non-adiabatically to moderate energies. With high magnetic moments in a weak magnetic field, electrons (ions) can benefit from gradient and curvature drift to attain high energies (by the ratio of the magnetic field magnitude) in seconds (minutes).  相似文献   
213.
This paper describes the results of studying the helium component of the solar-wind ion-flux measurement by the BMSW instrument on the Spektr-R satellite with a time resolution of 3 s. In contrast to most previous works that presented values averaged over large (hourly average or daily average) intervals, we have shown that the relative helium-ion abundance in the solar wind experiences considerable (by a few percent and even 10%) variations on such short intervals as 10 seconds or even several seconds.  相似文献   
214.
We investigate the north–south (N–S) asynchrony of the polar faculae and compare it with the hemispheric asynchrony of solar activity at low latitudes. We find that, (1) both the solar activity at high and low latitudes do not synchronously occur in the northern and southern hemispheres, there is phase shifts between the two hemispheres; (2) the N–S asynchrony of the polar faculae is a function of latitudes, implying that the asynchrony of the polar faculae between the two hemispheres is related to the hemispheric asymmetry and latitudinal distribution of the polar faculae.  相似文献   
215.
  总被引:1,自引:0,他引:1  
We have used several transport codes to calculate dose and dose equivalent values as well as the particle spectra behind a slab or inside a spherical shell shielding in typical space radiation environments. Two deterministic codes, HZETRN and UPROP, and two Monte Carlo codes, FLUKA and Geant4, are included. A soft solar particle event, a hard solar particle event, and a solar minimum galactic cosmic rays environment are considered; and the shielding material is either aluminum or polyethylene. We find that the dose values and particle spectra from HZETRN are in general rather consistent with Geant4 except for neutrons. The dose equivalent values from HZETRN and Geant4 are not far from each other, but the HZETRN values behind shielding are often lower than the Geant4 values. Results from FLUKA and Geant4 are mostly consistent for considered cases. However, results from the legacy code UPROP are often quite different from the other transport codes, partly due to its non-consideration of neutrons. Comparisons for the spherical shell geometry exhibit the same qualitative features as for the slab geometry. In addition, results from both deterministic and Monte Carlo transport codes show that the dose equivalent inside the spherical shell decreases from the center to the inner surface and this decrease is large for solar particle events; consistent with an earlier study based on deterministic radiation transport results. This study demonstrates both the consistency and inconsistency among these transport models in their typical space radiation predictions; further studies will be required to pinpoint the exact physics modules in these models that cause the differences and thus may be improved.  相似文献   
216.
A large coronal transient took place on 8 May 1981. The transient was related to an M7.7/2B flare and was associated with at least two coronal type II bursts. The velocities of the type II bursts were in the range 1100–1800 kms?1, in excess of the transient velocity of 500–1000 kms?1. Two dimensional positions of the type II radio sources are available from both the Clark Lake and the Culgoora Radio Observatories. We carry out two dimensional MHD simulations of the event, taking into account the observed velocity, position, and size of the type II bursts. We simulate the multiple shocks observed during the event and their interaction, and discuss some results of the simulation.  相似文献   
217.
This paper presents the observational results of space energetic particles obtained by the Cosmic Ray Composition Monitor (CRCM) onboard the Chinese satellite, Fengyun-1(B). These results, including those of a few solar proton events, the geomagnetically trapped particles and the anomalous cosmic ray components, were obtained from 3 September 1990 to 15 February 1991. The observed elements include H, He, C, N, O and Fe of energies from 4-23 MeV/u. It was found that the proton fluxes of the inner Radiation Belt (IRB) increased obviously during the period of solar proton event (SPE). A few kinds of heavy ions (Z > or = 6) were also detected in the IRB. As to the anomalous cosmic ray component (ACRC), in addition to C, N and O, anomalous iron particles were also recorded.  相似文献   
218.
A short history of the application of space images to geology and mineral exploration in the U.S.S.R. is given with special emphasis to circular features observed on small scale and low-resolution pictures within the Precambrian terrain. These features are believed to correspond to the oldest basins of volcano-sedimentary deposition or, in other words, to primary cells of basic proto-crust. Metallogenic significance of circular features is also discussed. Remote sensing in oil-gas field exploration and in the study of recent tectonics are also dealt with.  相似文献   
219.
The GPS (Global Positioning System) signal contains information which, when properly combined with information from INS and other sensors, provides exceptionally high accuracy position, velocity, attitude, and time measurements. These ten elements of information (three each in position, velocity, and attitude, and one in time) are common, in various combinations, to most avionics functions. When viewed from a system perspective, this high-precision information can be thought of as an integration basis, or a reference set, which offers opportunities for reconfiguration of the offensive, defensive, communication, navigation, and other sensors. Various integration architectures for fusion of these sensors can inherently enhance, enable, or severely limit these potential mission capabilities. The choice of integration architecture, can directly and profoundly affect performance, cost of integration, cost of ownership, and exploitation of much greater mission capability. This is illustrated by an example  相似文献   
220.
The rocket experiment ZARNITZA-2 on artificial electron beam injection in the ionosphere was carried out on September 11, 1975. Great attention was paid to the study of phenomena occurring in the near-rocket region. The results of the experiment are discussed in terms of a beam plasma discharge.  相似文献   
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