航天器太阳能电池阵驱动系统激扰因素辨识与扰动机理分析

建立了典型太阳能电池阵驱动系统(SADS)精细动力学模型，开展了扰动特性地面试验测试，讨论了产生扰动的必要条件，分析了直接激扰因素及其对应扰动的时频特点。结果表明：所建动力学模型分析结果与试验测试扰动数据吻合良好(误差<10%)；刚体转动角加速度和模态振动加速度不同时为零是引起驱动系统扰动的前提条件；细分驱动、电机磁场非线性、时变齿轮啮合参数等是驱动系统的主要内部激扰因素；扰动力矩一般均具有周期变化特点，扰动成分集中在激扰频率及其高倍频附近，扰动幅度随细分驱动步距、齿槽激扰幅度、电磁激扰幅度和啮合参数变化幅度的增大而提高。     

基于脉冲子结构的探测器结构动力学优化设计

针对传统结构优化设计中，精细化模型求解复杂结构动响应过于耗时的问题，引入保精度、高效的脉冲子结构方法，提出一种考虑结构动力学响应的优化设计流程，并对月球探测器太阳翼结构进行优化分析，获得了太阳翼结构设计参数，有效地提高了太阳翼动力学特性指标，改善了月球探测器关键位置处的动力学环境。结果表明，脉冲子结构方法可以有效应用于航天器结构动力学优化设计，提高优化设计效率，所得优化结果对实际结构设计具有一定指导意义。     

Solar polar magnetic field dependency of geomagnetic activity semiannual variation indicated in the Aa index

Three major hypotheses have been proposed to explain the well-known semiannual variation of geomagnetic activity, maxima at equinoxes and minima at solstices. This study examined whether the seasonal variation of equinoctial geomagnetic activity is different in periods of opposite solar magnetic polarity in order to understand the contribution of the interplanetary magnetic field (IMF) in the Sun-Earth connection. Solar magnetic polarity is parallel to the Earth’s polarity in solar minimum years of odd/even cycles but antiparallel in solar minimum years of even/odd cycles. The daily mean of the aa, Aa indices during each solar minimum was compared for periods when the solar magnetic polarity remained in opposite dipole conditions. The Aa index values were used for each of the three years surrounding the solar minimum years of the 14 solar cycles recorded since 1856. The Aa index reflects seasonal variation in geomagnetic activity, which is greater at the equinoxes than at the solstices. The Aa index reveals solar magnetic polarity dependency in which the geomagnetic activity is stronger in the antiparallel solar magnetic polarity condition than in the parallel one. The periodicity in semiannual variation of the Aa index is stronger in the antiparallel solar polar magnetic field period than in the parallel period. Additionally, we suggest the favorable IMF condition of the semiannual variation in geomagnetic activity. The orientation of IMF toward the Sun in spring and away from the Sun in fall mainly contributes to the semiannual variation of geomagnetic activity in both antiparallel and parallel solar minimum years.     

Characteristics of solar particle events at Mars relative to Earth

While not specifically designed to detect solar energetic particle radiation, the Electron Reflectometer onboard Mars Global Surveyor (MGS/ER) collected such data from January 1999 through October 2006. Energetic protons (?25 MeV) and other ions penetrated the MGS/ER shielding and registered counts within the instrument’s electronics. During solar particle events (SPE’s), prolonged enhancements in the particle background were observed at Mars with time intensity profiles similar to Earth based SPE observations. Throughout the lifespan of MGS/ER, 85 distinct SPE’s were observed. Basic characteristics of Mars based SPE observations and the frequency of SPE occurrences at Mars are compared to corresponding Earth based observations. Approximately 22% of SPE’s that occurred during MGS/ER operation were observed at Earth but not Mars. Similarly, 19% of SPE’s were observed at Mars but not Earth. Time intensity profiles at Earth and Mars match predictions provided in the literature, based on the physical location of the detector with respect to the motion of the interplanetary shock wave. Note: The work described herein was largely conducted as part of a doctoral dissertation produced by the author.     

Study of atmospheric air pollutants during the partial solar eclipse on 15 January 2010 over Udaipur: A semi-arid location in Western India

The paper describes behavior of surface ozone, its precursor gases, BC along with TOCC, TWVC, AOT1020 nm as well as UV and IR radiation intensities observed during the partial solar eclipse of 15th January, 2010 over Udaipur, where 52% solar disc is obscured due to the moon’s shadow. During the beginning to main eclipse phase, the deviation values of several air pollutants concentrations from eclipse to control day values vary in a small range from −9 to −2 ppb in case of surface ozone and −180 to −80 ppb for CO. The corresponding change in the values of BC observed from −3.3 to −.5 μg/m³. No significant change is found in NO₂, NO or in ratio of NO₂/NO values during the partial eclipse time. TOCC values decrease from 3 to 5 DU along with a reduction in UV radiation intensity from 20 to 35% from starting to the main eclipse phase. The AOT1020 nm values are found to increase from .2 to 1.0 along with a reduction in IR radiation intensity order of 50%. However, TWVC values decrease from .22 to .1 cm during the eclipse hours. The low level of dilution in surface ozone in eclipse period may be attributed with change in local atmospheric boundary layer dynamic conditions or limited air pollutants dispersion, in term of decreases in planetary boundary layer height, wind speed and hence ventilation coefficient in the same eclipse hours. Thus, present studies support the argument for the leading roles of photochemical reactions with its precursor gases under presence of solar radiation in surface ozone variability. Other possible controlling factors are advection of air pollutants from the polluted region as evident from backward wind trajectories and altering the local meteorological conditions.     

Extrasolar space exploration by a solar sail accelerated via thermal desorption of coating

For extrasolar space exploration it might be very convenient to take advantage of space environmental effects such as solar radiation heating to accelerate a solar sail coated by materials that undergo thermal desorption at a particular temperature. Thermal desorption can provide additional thrust as heating liberates atoms, embedded on the surface of the solar sail. We are considering orbital dynamics of a solar sail coated with materials that undergo thermal desorption at a specific temperature, as a result of heating by solar radiation at a particular heliocentric distance, and focus on two scenarios that only differ in the way the sail approaches the Sun. For each scenario once the perihelion is reached, the sail coat undergoes thermal desorption. When the desorption process ends, the sail then escapes the Solar System having the conventional acceleration due to solar radiation pressure. We study the dependence of a cruise speed of a solar sail on perihelion of the orbit where the solar sail is deployed. The following scenarios are considered and analyzed: (1) Hohmann transfer plus thermal desorption. In this scenario the sail would be carried as a payload to the perihelion with a conventional propulsion system by a Hohmann transfer from Earth’s orbit to an orbit very close to the Sun and then be deployed. Our calculations show that the cruise speed of the solar sail varies from 173?km/s to 325?km/s that corresponds to perihelion 0.3?AU and 0.1 AU, respectively. (2) Elliptical transfer plus Slingshot plus thermal desorption. In this scenario the transfer occurs from Earth’s orbit to Jupiter’s orbit; then a Jupiter’s fly-by leads to the orbit close to the Sun, where the sail is deployed and thermal desorption comes active. In this case the cruise speed of the solar sail varies from 187?km/s to 331?km/s depending on the perihelion of the orbit. Our study analyses and compares the different scenarios in which thermal desorption comes beside traditional propulsion systems for extrasolar space exploration.     

Adjustable box-wing model for solar radiation pressure impacting GPS satellites

One of the major uncertainty sources affecting Global Positioning System (GPS) satellite orbits is the direct solar radiation pressure. In this paper a new model for the solar radiation pressure on GPS satellites is presented that is based on a box-wing satellite model, and assumes nominal attitude. The box-wing model is based on the physical interaction between solar radiation and satellite surfaces, and can be adjusted to fit the GPS tracking data.     

Predicting indices of the ionosphere response to solar activity for the ascending phase of the 25th solar cycle

The international reference ionosphere, IRI, and its extension to plasmasphere, IRI-Plas, models require reliable prediction of solar and ionospheric proxy indices of solar activity for nowcasting and forecasting of the ionosphere parameters. It is shown that IRI prediction errors could increase for the F2 layer critical frequency foF2 and the peak height hmF2 due to erroneous predictions of the ionospheric global IG index and the international sunspot number SSN1 index on which IRI and IRI-Plas models are built. Regression relation is introduced to produce daily SSN1 proxy index from new time series SSN2 index provided from June 2015, after recalibration of sunspots data. To avoid extra errors of the ionosphere model a new solar activity prediction (SAP) model for the ascending part of the solar cycle SC25 is proposed which expresses analytically the SSN1 proxy index and the 10.7-cm radio flux F10.7 index in terms of the phase of the solar cycle, Φ. SAP model is based on monthly indices observed during the descending part of SC24 complemented with forecast of time and amplitude for SC25 peak. The strength of SC25 is predicted to be less than that of SC24 as shown with their amplitudes for eight types of indices driving IRI-Plas model.     

Temporal variation and asymmetry of sunspot and solar plage types from 1930 to 1936

Using the recently converted to digital format heliophysics catalogues of the Ebro Observatory published in the 1930s, we analyse simultaneously the temporal variation and asymmetry of two different solar structures located at different layers of the solar atmosphere: sunspots and solar plages. In particular, we do the research for all the types of sunspots and plages, including the daily and relative frequencies over the solar cycle. The data were catalogued using the sunspot Cortie classification and a solar plage classification scheme proposed by the Ebro Observatory, which group the phenomena by size and shape. For all types of both sunspots and plages, we observe a decrease in their frequency up to the end of solar cycle 16 and an increase over the beginning of solar cycle 17. Furthermore, we note that small sunspot groups are more likely to happen than bigger groups, although single big spots dominate near the solar minimum. The daily frequency of solar plage occurrences shows that there is not a dominance of compact or scattered solar plages. The North-South occurrence distribution of every type in both sunspots and solar plages shows an asymmetry during the solar cycle: in its declining phase, such asymmetry is directed to the north, while in the beginning of a new cycle is directed to the south.     

Flaring loop parameters estimated from solar decimeter type U-like and type J-like fine structures

This work presents the analysis of five fine structures in the solar radio emission, observed between June 2000 and October 2001 by the Brazilian Solar Spectroscope (BSS), in the decimeter frequency band of 950–2500 MHz. Based on their morphological characteristics identified in the dynamic spectra, the fine structures had been classified as type U-like or type J-like bursts. Such emissions are variants of the type III bursts. They support the hypothesis of generation by plasma emission mechanism, from interaction of electron beams accelerated during solar flares, propagating along closed magnetic structures, within the trapped plasma of the solar corona. The spectral and temporal characteristics of the five fine structures had been obtained from the dynamic spectra and the parameters of the agent and the emitting source have been determined, assuming both fundamental and harmonic emissions. The analysis revealed the flux density of the structures is less than 20–80 s.f.u. For assumption of harmonic emission, the interval of values for the source parameters estimated are: the loop size is (0.3–5.1) × 10¹⁰ cm; the electron beam velocity is in the range of 0.16–0.53 c; the temperature of coronal loop top is of the order of (0.25–1.55) × 10⁷ K; and the low limit for the magnetic field is of 7–26 G. These results are in agreement with previous determinations reported in the literature.