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971.
RATAN-600 multiwavelength observations of the Sun reveal sharp spectral inhomogeneities in the polarized radiation from active regions that produce intense flares. These events occur in a wide range of radio fluxes (0.05–10 s.f.u.) in a relatively narrow wavelength range (2–5 cm). They are detected on time scales from several hours to several days before and during an intense flare. We analyze the detected events and their relationship to the preliminary phase of intense flares. Significant statistical material was obtained in 2001. The new flare-plasma properties can be used to test existing solar-flare models and to develop new criteria of flaring activity. 相似文献
972.
We present the results of polarimetric and photometricobservations of split Comet C/2001 A2 (LINEAR), which wereobtained at
the 70-cm telescope of the Astronomical Observatoryof Kharkiv National University between 30 June and 31 July 2001.The brightest
fragment of the comet, nucleus B, was observed.Eight narrowband cometary filters in the continuum and in emissionbands and
a wideband red filter have been used. The comet wasobserved through apertures of 88, 33, and 19 arcsec. Polarizationphase
curves were obtained for the continuum and for the firsttime, for NH2(0, 7, 0) emission. The degree of polarization ofthe light scattered by the dust decreases with the increase ofaperture size.
An important temporal variation of the polarizationwith a rotation of the polarization plane was observed at twophase angles
(26.5° and 36.2°). Molecular column densities and production rates of CN, C2,C3, and NH2 species are calculated in the framework of theHaser model. A comparative analysis of the temporal variations ofthe visual
magnitudes, gas and dust production rates, dust colorand polarization are presented. 相似文献
973.
Hitoshi Hasegawa Takashi Ichikawa Shinsuke Abe Shiomo Hamamura Koji Ohnishi Jun-Ich Watanabe 《Earth, Moon, and Planets》1997,78(1-3):353-358
Near-infrared photometric and polarimetric observations of comet Hale-Bopp (1995 O1) using KONIC (Kiso Observatory Near-Infrared
Camera) are reported. Observations were carried out on March 18 UT and April 26 UT 1997, when the heliocentric distances of
the comet were 0.94 and 1.02 AU, and the phase angles were 48.5 deg and 32.9 deg, respectively. In the J, H, and K′ bands,
we obtained linear polarization of the near-nucleus region of 16.4 ± 1.2, 18.8 ± 1.3, and 15.1 ± 0.9 percent on March 18UT
and 7.1 ± 1.1, 8.9 ± 1.0, and 6.9 ± 0.6 percent on April 26, respectively. These values were higher than those observed for
1P/Halley. The maximum polarization was found at H band on both dates. Polarization maps showed higher polarization regions
toward the anti-solar direction in the J and H bands. No distinct correlation was found between high polarization regions
and bright regions. The projected expansion velocity of the arc structure of the dust jet was 375 ± 35.7 m/s on 17–19 March.
The periodicity was found to be 11.1 ± 2.8 hours.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
974.
975.
976.
977.
Composite interstellar grains 总被引:2,自引:0,他引:2
D. B. Vaidya Ranjan Gupta T. P. Snow 《Monthly notices of the Royal Astronomical Society》2007,379(2):791-800
978.
A number of studies have shown that the visibility of scattered broad emission lines in Seyfert 2 galaxies is strongly dependent on the IRAS flux ratio, where those Seyfert 2 galaxies with 'warm' IRAS colours show polarized broad line emission. It is now clear that this effect is owing to the increasing dominance of the galactic rather than the active galactic nucleus (AGN) emission at 60 μm in less-luminous 'cool' Seyfert 2 galaxies. However, we present evidence that the 25-μm emission is a good measure of the AGN luminosity for most Seyfert 2 galaxies. Using this result, we show that the visibility of scattered broad line emission has a dependence on the AGN luminosity. The observations can be interpreted self-consistently if the scaleheight of the scattering zone varies with central source luminosity whilst the scaleheight of the obscuring torus is approximately constant. 相似文献
979.
利用贵州威宁雪山X波段双偏振天气雷达一次冰雹过程观测资料,基于MATLAB软件对雷达观测数据进行数据质量控制基础上利用模糊逻辑算法对冰雹云中水成物粒子进行识别分类,主要结论如下:(1)采用综合小波去噪能够有效去除差分传播相位(ФDP)存才的脉动和毛刺,保证ФDP的连续性和平滑度,保留有效ФDP值,其用于雷达反射率因子衰减订正具有较好的效果。(2)冰雹形成与低密度霰(LDG)、高密度霰(HDG)以及过冷水(SCW)的增减演变较为对应,霰粒子是冰雹形成的关键粒子。(3)从霰粒子出现到识别出冰雹时间为26 min,约4个体扫时间,从识别出冰雹到地面观测到降雹32 min,约5个体扫时间。(4)冰雹识别结果与地面观测总体一致,所构建的识别参量阈值基本合理,研究所构建的粒子相态识别方法在贵州威宁具有普适性,可为冰雹早起识别、预警和人工防雹作业提供技术和理论支撑。 相似文献
980.
地基雷达观测可以提供太阳系天体目标的地形地貌、物理特征、轨道动力等信息。聚焦利用地基雷达天文技术开展月球观测的原理方法和科学意义,介绍了基于我国现有深空雷达上行装置、射电望远镜条件以及非相干散射雷达等系统,初步开展的特高频段(Ultra High Frequency,UHF)和X频段的地基雷达观测月球试验。通过月球反射回波的信号处理,获得了延迟、多普勒频移等参数,得到了一致的与近表层物质密度相关的月面雷达反射率,并得到了月球的左右旋圆极化率,反映了与波长同尺度的月球近表层结构。文章积累的数据处理经验将为我国的小行星预警、行星历表等地基雷达观测研究提供技术基础。 相似文献