Employing Atmsophere Explorer-C measurements made in 1974, just prior to solar minimum, Brace and Theis /1/ demonstrated that a remarkably consistent inverse relationship existed between the electron density Ne and temperature Te in the F-region. In this paper we use later data from AE-C, taken when solar activity was rising (1975–1978), and Dynamics Explorer-2 data taken at solar maximum (1981), to examine how the temperature and density relationship changes with solar activity. We find that the solar maximum Te is a factor of two larger than the solar minimum Te for the same values of Ne. Te does not necessarily increase with solar activity, however, because Ne increases enough to approximately cancel the effect of higher solar extreme ultraviolet heating. We find that the effect of solar activity can be accounted for by a simple function of the F10.7 cm index that multiplies the solar minimum equation of Brace and Theis /1/. 相似文献
The allowed cosmic radiation flux accessible to an earth-orbiting spacecraft is a complex function of the satellite position and the geomagnetic cutoff characteristics at each zenith and azimuth angle at each position. We have determined cosmic ray exposure factors for the galactic cosmic ray spectrum for typical shuttle altitudes and inclinations up to 50 degrees. We have utilized d world grid of trajectory-derived cutoff rigidity calculations at 400 km altitude to determine geomagnetic transmission functions that permit a simple and direct calculation of the allowed cosmic ray spectrum to a 400 km satellite orbit. If the interplanetary cosmic ray spectrum is multiplied by the orbit-averaged geomagnetic transmission function the result is the allowed cosmic ray spectrum at the spacecraft. 相似文献
The early phases of three flares, observed by the Nobeyama Radio Heliograph, are studied. Nonthermal and thermal radio sources are identified by comparison with soft X-ray images taken by the Soft X-ray Telescope onboard the Yohkoh satellite. Two of the flares are mainly of nonthermal origin and their location coincides with one of the footpoints of soft X-ray loops. Another flare has both thermal and nonthermal components which start to brighten simultaneously. This suggests that particle acceleration and plasma compression develop simultaneously. 相似文献
In this paper we intend to enlarge the fof2 long-term prediction accuracy taking into account the systematic variations of the hysteresis and secular-time phenomena. 相似文献
The question of attitude control and elastic mode stabilization of a spacecraft (orbiter) with beam-tip-mass-type payloads is considered. A three-axis moment control law is derived to control the attitude of the spacecraft. The derivation of the control moments acting on the spacecraft does not require any information on the system dynamics. The control law includes a reference model and a dynamic compensator in the feedback path. For damping out the elastic motion excited by the slewing maneuver, an elastic mode stabilizer is designed. The stabilization is achieved by modal velocity feedback using force and torque actuators located at the payload end of the elastic beam. Collocated actuators and sensors provide robust stabilization. Simulation results are presented to show that rotational maneuvers and vibration stabilization can be accomplished in the closed-loop systems despite the presence of model uncertainty and disturbance torque in the system 相似文献
An ultraviolet sounding rocket telescope/spectrograph experiment observed Comet Halley on 26 February 1986, 17 days after perihelion. From the long-slit spectra, the production rates of O, C, and CO are calculated. The derived water production rate is a lower limit of 5.0 × 1029s−1 and the volume mixing ratio of CO to H2O is 21%. The predicted brightness distribution from a radial outflow model with H2O and CO as parent molecules are in accordance with the measured spatial profiles of OI and CO emissions. The ratio of the production rates of CO to C is 2.7 which is consistent with the carbon source being the photodissociation of CO. However, the radial outflow model which best fits the CO data predicts significantly weaker CI emissions than was observed. A better fit to the carbon data is found when an inner coma source of C at a rate of 3% of the water production rate is included in the model. 相似文献
On February 4, 1986 Halley passed through inferior conjunction with Venus but was at high latitudes. Not all data for this time period have been received. However, the data that are available suggest that at most only weak effects associated with Halley were seen at Pioneer Venus. The data during this time, however, are useful for correlating with the behavior of the plasma tail. 相似文献
Pleurodeles waltl, an Urodele amphibian is proposed as a model for space biology studies. Our laboratory is developing three types of experiments in space using this animal: 1) in vivo fertilization and development ("FERTILE" project); 2) influence of microgravity and space radiation on the organization and preservation of specialized structures in the neurons and muscle cells (in vitro; "CELIMENE" PROJECT); 3) influence of microgravity on tissue regeneration (muscle, bone, epidermis and spinal cord). 相似文献
Since 1988 high sensitivity semiconductor dosimeter-radiometer “Liulin” worked on board of MIR space station. Device measured the absorbed dose rate and the flux of penetrating particles. The analysis of the data hows the following new results:
In October 1989 and after March 24, 1991, two additional stable maximums in flux channel were observed in the southern-eastern part of South Atlantic Anomaly (SAA). These two maximums existed at least several months and seem to be due to trapped high energy electron and proton fluxes. In April 1991 additional maximums were localized in the following geographical coordinates regions: LATITUDE = (−35 °)–(−50 °) LONGITUDE = 332 ° − 16 ° and lat.(−46 °)–(−52 °) long. 360 ° − 60 °. Additional maximums diffusion occurs inside radiation belt. Appearance of these maximums seems to be closely connected with preceding powerful solar proton events and associated geomagnetic dynamics of new belt disturbances. After the series of solar proton events in June 1991 we observed significant enhancement of this new radiation belt formation. To achieve sufficient accuracy of dose rate predictions in low Earth orbits the structure and dynamics of new belt should be carefully analyzed to be included in a new environment model.
From the inter comparison of the data from “Liulin” and French developed tissue equivalent LET spectrometer NAUSICAA in the time period August–November 1992 we come to the following conclusions: Mainly there is good agreement between both data sets for absorbed dose in the region of SAA; Different situation of the instruments on the station can explain the cases when differences up to 2 times are observed; At high latitudes usually the tissue equivalent absorbed dose observations are 2 times larger than “Liulin” doses. 相似文献