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181.
New one-axis magnetic attitude control is proposed. Only one attitude sensor providing any inertial direction measurements is necessary, magnetometer is not used. The control may be used as a backup capability in case main actuators or some attitude sensors fail. Sun pointing is achievable using only three-axis Sun sensor, so the control may be used to lower the power consumption during battery charging. Asymptotic stability of different equilibria depending on the satellite inertia tensor is summarized. In-flight results from “Chibis-M” microsatellite are provided proving general control performance.  相似文献   
182.
Lagrangian points L4 and L5 lie at 60° ahead of and behind the Moon in its orbit with respect to the Earth. Each one of them is a third point of an equilateral triangle with the base of the line defined by those two bodies. These Lagrangian points are stable for the Earth–Moon mass ratio. As so, these Lagrangian points represent remarkable positions to host astronomical observatories or space stations. However, this same distance characteristic may be a challenge for periodic servicing mission. This paper studies elliptic trajectories from an Earth circular parking orbit to reach the Moon’s sphere of influence and apply a swing-by maneuver in order to re-direct the path of a spacecraft to a vicinity of the Lagrangian points L4 and L5. Once the geocentric transfer orbit and the initial impulsive thrust have been determined, the goal is to establish the angle at which the geocentric trajectory crosses the lunar sphere of influence in such a way that when the spacecraft leaves the Moon’s gravitational field, its trajectory and velocity with respect to the Earth change in order to the spacecraft arrives at L4 and L5. In this work, the planar Circular Restricted Three Body Problem approximation is used and in order to avoid solving a two boundary problem, the patched-conic approximation is considered.  相似文献   
183.
The responses of the ionospheric F region using GPS–TEC measurements during two moderate geomagnetic storms at equatorial, low-, and mid-latitude regions over the South American and African sectors in May 2010, during the ascending phase of solar cycle 24, are investigated. The first moderate geomagnetic storm studied reached a minimum Dst value of −64 nT at 1500 UT on 02 May 2010 and the second moderate geomagnetic storm reached a minimum Dst value of −85 nT at 1400 UT on 29 May 2010. In this paper, we present vertical total electron content (VTEC) and phase fluctuations (in TECU/min) from Global Positioning System (GPS) observations from the equatorial to mid-latitude regions in the South American and African sectors. Our results obtained during these two moderate geomagnetic storms from both sectors show significant positive ionospheric storms during daytime hours at the equatorial, low-, and mid-latitude regions during the main and recovery phases of the storms. The thermospheric wind circulation change towards the equator is a strong indicator that suggests an important mechanism is responsible for these positive phases at these regions. A pre-storm event that was observed in the African sector from low- to the mid-latitude regions on 01 May 2010 was absent in the South American sector. This study also showed that there was no generation or suppression of ionospheric irregularities by storm events. Therefore, knowledge about the suppression and generation of ionospheric irregularities during moderate geomagnetic storms is still unclear.  相似文献   
184.
Diffusive shock acceleration is the theory of particle acceleration through multiple shock crossings. In order for this process to proceed at a rate that can be reconciled with observations of high-energy electrons in the vicinity of the shock, and for cosmic rays protons to be accelerated to energies up to observed galactic values, significant magnetic field amplification is required. In this review we will discuss various theories on how magnetic field amplification can proceed in the presence of a cosmic ray population. On both short and long length scales, cosmic ray streaming can induce instabilities that act to amplify the magnetic field. Developments in this area that have occurred over the past decade are the main focus of this paper.  相似文献   
185.
In this paper an analysis of data coordinate systems from selenographic catalogues and space missions was carried out. The lunar macrorelief models were made on basis of the software package ASNI USTU using method of the spherical harmonic expansion. These models accurately describe the global features of the lunar figure. To construct these models the following sources of topographic information were used: “Clementine” and “KАGUYА” (Selena, Japan mission) missions, “KSC-1162” (Kazan selenocentric catalogue), “Kiev” (selenodesic catalogue), “SAI” (Chuikova (1975)), “Bills, Ferrari”, “ULCN” (The Unified Lunar Control Network 2005). Direct comparison hypsometric information “KSС-1162” catalogue data with “Clementine” mission was carried out. These researches confirmed a good agreement of the hypsometric information of compared systems. The normalized coefficients were obtained on basis of the hypsometric information expansion for eight sources. The displacement of the lunar center of mass (LCM) relatively to the lunar center of figure (LCF) was obtained by using topographic data selenodetical catalogues and space missions.  相似文献   
186.
We present an observational study of magnetospheric and ionospheric disturbances during the December 2006 intense magnetic storm associated with the 4В/Х3.4 class solar flare. To perform the study we utilize the ground data from North–East Asian ionospheric and magnetic observatories (60–72°N, 88–152°E) and in situ measurements from LANL, GOES, Geotail and ACE satellites. The comparative analysis of ionospheric, magnetospheric and heliospheric disturbances shows that the interaction of the magnetosphere with heavily compressed solar wind and interplanetary magnetic field caused the initial phase of the magnetic storm. It was accompanied by the intense sporadic E and F2 layers and the total black-out in the nocturnal subauroral ionosphere. During the storm main phase, LANL-97A, LANL 1994_084, LANL 1989-046 and GOES_11 satellites registered a compression of the dayside magnetosphere up to their orbits. In the morning–noon sector the compression was accompanied by an absence of reflections from ionosphere over subauroral ionospheric station Zhigansk (66.8°N, 123.3°E), and a drastic decrease in the F2 layer critical frequency (foF2) up to 54% of the quite one over subauroral Yakutsk station (62°N, 129.7°E). At the end of the main phase, these stations registered a sharp foF2 increase in the afternoon sector. At Yakutsk the peak foF2 was 1.9 time higher than the undisturbed one. The mentioned ionospheric disturbances occurred simultaneously with changes in the temperature, density and temperature anisotropy of particles at geosynchronous orbit, registered by the LANL-97A satellite nearby the meridian of ionospheric and magnetic measurements. The whole complex of disturbances may be caused by radial displacement of the main magnetospheric domains (magnetopause, cusp/cleft, plasma sheet) with respect to the observation points, caused by changes in the solar wind dynamic pressure, the field of magnetospheric convection, and rotation of the Earth.  相似文献   
187.
The application of the optimized dispersion relation preserving scheme (DRP-scheme) in combination with the explicit optimized two-layer Runge-Kutta scheme is presented to solve a system of one-dimensional and quasi-one-dimensional Euler equations using as an example the solution of four test problems, namely, discontinuity disintegration in a tube (Sod’s problem); transfer of the lowamplitude Gaussian pulse; acoustic wave propagation through the transonic nozzle; acoustic wave-shock interaction. Also given are the comparison of the calculation results using different schemes: DRP, CABARET, CE-SE and the standard Lax-Wendroff schemes as well as the solutions obtained with the use of software packages.  相似文献   
188.
The results of measurements of fluxes and spectra carried out using the RELEC (relativistic electrons) equipment onboard the VERNOV satellite in the second half of 2014 are presented. The VERNOV satellite was launched on July 8, 2014 in a sun-synchronous orbit with an altitude from 640 to 830 km and an inclination of 98.4°. Scientific information from the satellite was first received on July 20, 2014. The comparative analysis of electron fluxes using data from RELEC and using experimental data on the electron detection by satellites Elektro-L (positioned at a geostationary orbit) and Meteor-M no. 2 (positioned at a circular polar orbit at an altitude of about 800 km as the VERNOV satellite) will make it possible to study the spatial distribution pattern of energetic electrons in near-Earth space in more detail.  相似文献   
189.
Solar wind is probably the best laboratory to study turbulence in astrophysical plasmas. In addition to the presence of magnetic field, the differences with neutral fluid isotropic turbulence are: (i) weakness of collisional dissipation and (ii) presence of several characteristic space and time scales. In this paper we discuss observational properties of solar wind turbulence in a large range from the MHD to the electron scales. At MHD scales, within the inertial range, turbulence cascade of magnetic fluctuations develops mostly in the plane perpendicular to the mean field, with the Kolmogorov scaling $k_{\perp}^{-5/3}$ for the perpendicular cascade and $k_{\|}^{-2}$ for the parallel one. Solar wind turbulence is compressible in nature: density fluctuations at MHD scales have the Kolmogorov spectrum. Velocity fluctuations do not follow magnetic field ones: their spectrum is a power-law with a ?3/2 spectral index. Probability distribution functions of different plasma parameters are not Gaussian, indicating presence of intermittency. At the moment there is no global model taking into account all these observed properties of the inertial range. At ion scales, turbulent spectra have a break, compressibility increases and the density fluctuation spectrum has a local flattening. Around ion scales, magnetic spectra are variable and ion instabilities occur as a function of the local plasma parameters. Between ion and electron scales, a small scale turbulent cascade seems to be established. It is characterized by a well defined power-law spectrum in magnetic and density fluctuations with a spectral index close to ?2.8. Approaching electron scales, the fluctuations are no more self-similar: an exponential cut-off is usually observed (for time intervals without quasi-parallel whistlers) indicating an onset of dissipation. The small scale inertial range between ion and electron scales and the electron dissipation range can be together described by $\sim k_{\perp}^{-\alpha}\exp(-k_{\perp}\ell_{d})$ , with α?8/3 and the dissipation scale ? d close to the electron Larmor radius ? d ?ρ e . The nature of this small scale cascade and a possible dissipation mechanism are still under debate.  相似文献   
190.
A very strong interplanetary and magnetospheric disturbance observed on 7–13 November 2004 can be regarded as one of the strongest events during the entire period of space observations. In this paper we report on the studies of cosmic ray cutoff rigidity variations during 7–13 November 2004 showing how storm conditions can affect the direct cosmic ray access to the inner magnetosphere. Effective cutoff rigidities have been calculated for selected points on the ground by tracing trajectories of cosmic ray particles through the magnetospheric magnetic field of the “storm-oriented” Tsyganenko 2003 model. Cutoff rigidity variations have also been determined by the spectrographic global survey method on the basis of experimental data of the neutron monitor network. Relations between the calculated and experimental cutoff rigidities and the geomagnetic Dst-index and interplanetary parameters have been investigated. Correlation coefficients between the cutoff rigidities obtained by the trajectory tracing method and the spectrographic global survey method have been found to be in the limits 0.76–0.89 for all stations except the low-latitude station Tokyo (0.35). The most pronounced correlation has been revealed between the cutoff rigidities that exhibited a very large variation of ∼1–1.5 GV during the magnetic storm and the Dst index.  相似文献   
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