海尔—波普彗星球状喷出物的光变曲线

研究了海尔－波普彗星１９９６年９月的光变曲线,发现其在９月１０日至１１日发生了一次爆发,爆发时核Ｖ星等增亮２．１＾ｍ,相应地,在ＣＣＤ图像上也出现爆发时彗核抛出的２个球状凝聚物。     

1998年4月15日微波爆发观测

北京天文台１ ．０２ ．０ＧＨｚ 太阳射电频谱仪从１９９４ 年开始观测至１９９８ 年９ 月记录到太阳射电爆发１７１ 个,２ ．６３ ．８ＧＨｚ 太阳射电频谱仪１９９６ 年９ 月投入观测至１９９８ 年９ 月,记录到１４６ 个太阳射电爆发。１９９８ 年４ 月１５ 日太阳射电爆发同时在这两台频谱仪上记录到。这个事件在时间和频率上显示了丰富的幅度和结构的变化。发现了微波Ⅲ型爆发对群,并存在着丰富的快速活动现象。取得了高时间分辨率、高质量的动态谱资料,为研究耀斑各种尺度的时间及空间演化过程提供了丰富的信息。     

Hale-Bopp彗星的一次爆发观测

使用上海天文台的１．５６ｍ望远镜和Ｓｅｒｉｅｓ２００ＣＣＤ照相机发现ＨａｌｅＢｏｐｐ彗星于１９９６年４月２１日至４月２３日期间有一次爆发,４月２２日彗星星等比前一天增亮了０２等,但一天后其亮度又大致恢复原来的亮度．这段时间内,彗头的半强度处的直径也有相应的变化．     

Hale—Bopp彗星的一次爆发观测

使用上海天台的１．５６ｍ望远镜和Ｓｅｒｉｅｓ２００ＣＣＤ照相机发现Ｈａｌｅ－Ｂｏｐｐ彗星于１９９６年４月２１日于４月２３日期间有一次爆发,４月２２彗星星等比前一天增亮了０．２等,但一天后其亮度又致恢复原来的亮度,这段时间内,彗头的半强度处的直径也相应的变化。     

1997年3月9日的日冕偏振CCD观测

给出１９９７年３月９日日全食时所作的日冕偏振ＣＣＤ观测资料的处理结果,包括太阳赤道东西和两极等十二个方向的中冕（１．６－３．２Ｒ）绝对亮度分布和偏振度分布。     

1997年3月9日的日冕偏振CCD观测

给出１９９７年３月９日日全食时所作的日冕偏振ＣＣＤ观测资料的处理结果,包括太阳赤道东西和两极等十二个方向的中冕（１．６￣３．２Ｒ⊙）绝对亮度分布和偏振度分布。     

1.0—2.0GHz,2.6—3.8GHz微波爆发与共生的HXR爆发的统计关系

利用日本ＹＯＨＫＯＨ卫星ＨＸＴ提供的ＨＸＲ爆发资料,和中国科学院北京天台的大亨是射电宽频带动态频谱仪（１．０－２．０ＧＨｚ,２．６－３．８ＧＨｚ）提供的微波爆发资料,对共生事件进行了初步统计分析,并对其中两例典型事件：１９９７年１１月２８日０５０３ＵＴ事件及１９９８年５月９日０３４０ＵＴ事件与共生的ＨＸＲ爆发进行了详细比较,给出了几点有意义的结果及理论解释。     

DALSA 1024T CCD检验

１９９６年９月２日至９月６日云南天文台ＣＣＤ实验室对北京天文台太阳气球望远镜主探测器ＤＡＬＳＡＣＡ－Ｄ７－１０２４Ｔ ＣＣＤ相机各种主要参数进行了检测,测试结果令人满意。     

DALSA 1024T CCD检测

１９９６年９月２日至９月６日云南天文台ＣＣＤ实验室对北京天文台太阳气球望远镜主探测器ＤＡＬＳＡＣＡ－Ｄ７－１０２４ＴＣＣＤ相机各种主要参数进行了检测,测试结果令人满意。     

微U型爆发及微波精细结构

我们用新的时间分辨率短至８ｍｓ 的２ ．６ ～３ ．８ＧＨｚ 微波动态频谱仪在１９９８ 年４ 月１５ 日爆发和１９９７ 年１１ 月３ 日爆发中发现了微Ｕ 型爆发。其顶部频率为３ ．２ ～３ ．４ＧＨｚ（ 相应的等离子体密度：基波：１ ．２ ×１０１１ － １ ．４ ×１０１１／ｃｍ ３ ,二次谐波：３ ．２ ×１０１０ － ３ ．５ ×１０１０／ｃｍ ３） ;根部频率为３ ．４ ～３ ．６ＧＨｚ;单个Ｕ 型爆发的频率范围为６０ ～２２０ ＭＨｚ ;上升段频漂率为７ ～２８ＧＨｚ／ｓ;上升段持续时间为８ ～２４ｍｓ;寿命为１６ ～４８ｍｓ;偏振度大于８０ ％ 。在活动区为偶极子磁场的假设下,估计源区高度约为１ ．３ ×１０４ 公里,单一环的高度为２５０ ～８００ 公里。由此得出结论：１ ．由于高频漂率和高偏振度,似乎发现的微Ｕ 型爆发不是Ⅲ型爆发形成,而是尖峰辐射（Ｓｐｉｋｅ） 形成。２ ．我们发现的是小尺度的微磁环,其尺度与Ｓｐｉｋｅ 辐射的寿命相当。我们在１９９７ 年１１ 月２ 日的爆发中发现平均周期为数十ｍｓ 的准周期振荡群。在高密度流管的磁声波ＭＨＤ 振荡条件下,可取得磁环半径约９０ 公里的结果。由此可以得到微磁环物理尺度的图象     

Non-equilibrium of a cylindrical magnetic arcade

A cylindrically-symmetric magnetic arcade with its axis on the photosphere is perturbed by means of an alteration in the pressure along the base. The perturbation is examined with a view to finding equilibrium configurations close to the original equilibrium. It is found that equilibria can only be found when the integral of the excess pressure along the base is zero. In other cases no equilibria can be found and the arcade is likely either to collapse or, in the case of a coronal mass ejection, to erupt. For an initial arcade whose field increases linearly with radial distance from the axis, the neighbouring equilibria have been found.     

Rarefied gas flow near an asymmetric plane stagnation point

The probability of pulsars and supernovae being found close to each other on the celestial sphere by chance is calculated. It is found that this corresponds to the number of pulsars found close to supernovae in recent investigations. Thus, we conclude that, given also the inaccuracy of distances involved, the apparent spatial coincidence of pulsars and supernovae does not generally imply generic associations.     

Degradation of mid-latitude craters on Mars

Recent geomorphic, remote sensing, and atmospheric modeling studies have shown evidence for abundant ground ice deposits in the martian mid-latitudes. Numerous potential water/ice-rich flow features have been identified in craters in these regions, including arcuate ridges, gullies, and small flow lobes. Previous studies (such as in Newton Basin) have shown that arcuate ridges and gullies are mainly found in small craters (∼2-30 km in diameter). These features are located on both pole-facing and equator-facing crater walls, and their orientations have been found to be dependent on latitude. We have conducted surveys of craters >20 km in diameter in two mid-latitude regions, one in the northern hemisphere in Arabia Terra, and one in the southern hemisphere east of Hellas basin. In these regions, prominent lobes, potentially ice-rich, are commonly found on the walls of craters with diameters between ∼20-100 km. Additional water/ice-rich features such as channels, valleys, alcoves, and debris aprons have also been found in association with crater walls. In the eastern Hellas study region, channels were found to be located primarily on pole-facing walls, whereas valleys and alcoves were found primarily on equator-facing walls. In the Arabia Terra study region, these preferences are less distinct. In both study regions, lobate flows, gullies, and arcuate ridges were found to have pole-facing orientation preferences at latitudes below 45° and equator-facing orientation preferences above 45°, similar to preferences previously found for gullies and arcuate ridges in smaller craters. Interrelations between the features suggest they all formed from the mobilization of accumulated ice-rich materials. The dependencies of orientations on latitude suggest a relationship to differences in total solar insolation along the crater walls. Differences in slope of the crater wall, differences in total solar insolation with respect to wall orientation, and variations in topography along the crater rim can explain the variability in morphology of the features studied. The formation and evolution of these landforms may best be explained by multiple cycles of deposition of ice-rich material during periods of high obliquity and subsequent modification and transport of these materials down crater walls.     

Herbig Ae/Be Stars with the IRAS Low-Resolution Spectra

IRAS low-resolution spectra are presented for 36 HAEBE stars. It is found that silicate dust is common material in the circumstellar disks or/and shells of HAEBE stars. It is also found that the PAH feature often appears as well. In addition, the correlation between the dust features and spectral type, and infrared excesses can be found for most HAEBE stars. This revised version was published online in July 2006 with corrections to the Cover Date.     

Two-dimensional steady-state pressure structure in a coronal loop

By expressing the magnetic field and fluid velocity in terms of two Chandrasekhar-Kendall functions (n = 0, m = 0; n = 1, m = 0) we investigated the steady-state pressure profile inside a solar coronal loop. For constant density loops, we found a two-dimensional (radial and axial) structure of pressure. This work is the modified version of the work of Krishan (1985). At the base of the loop, the pressure is found to increase steeply outwards along the radius, whereas at the apex it decreases slowly. The radial variation of pressure is found to be minimum around L/5, where L is the length of the loop measured from one foot to another one. But Krishan (1985) found that the rate of increase of pressure at the base was nearly equal to the rate of decrease of pressure at the apex, and the pressure was found nearly constant at L/4. For axial variation, we found that along the loop axis the pressure increases from the base up to z = 3L/8 and then decreases up to the apex, whereas at the surface, the pressure decreases from the base up to the apex. Krishan (1985), however, found the axial variation to be linear.     

Asymmetric eigenmodes in a simple model plasmasphere

A theoretical plasma is supposed to be contained between two perfectly conducting cylinders. A magnetic field from a hypothetical line pole is postulated because the metric coefficients have similar properties to those of a dipole field. It is found, as expected, that the asymmetric hydromagnetic eigenmodes involve coupling of torsion and compression. Nevertheless the behaviour is found to be still roughly like that of a uniform field model. The modes are found to be either roughly torsional or roughly compressional, and the roughly torsional eigenfrequencies are found to be insensitive to the eigenmode structure across the field lines. It is therefore suggested that estimates of micropulsation spectra from the axisymmetric toroidal mode in the dipole field may be fairly valid whatever the true longitude distribution of the micropulsations.     

The causality between the rapid rotation of a sunspot and an X3.4 flare

Using multi-wavelength data of Hinode, the rapid rotation of a sunspot in ac-tive region NOAA 10930 is studied in detail. We found extraordinary counterclockwise rotation of the sunspot with positive polarity before an X3.4 flare. From a series of vector magnetograms, it is found that magnetic force lines are highly sheared along the neu-tral line accompanying the sunspot rotation. Furthermore, it is also found that sheared loops and an inverse S-shaped magnetic loop in the corona formed gradually after the sunspot rotation. The X3.4 flare can be reasonably regarded as a result of this movement. A detailed analysis provides evidence that sunspot rotation leads to magnetic field linestwisting in the photosphere. The twist is then transported into the corona and triggers flares.     

Granulation deformation near and in sunspot regions

High-resolution white-light pictures are analyzed to study the differences between the granular size near sunspot penumbrae and in light-bridges presenting granular structure and that of the quiet photosphere. No difference is found between the mean granular diameter in light-bridges and the quiet photosphere. The dispersion found in the results corresponding to different zones around the sunspots indicates that the size of the granulation may vary from place to place near the sunspots, its mean value not differing significantly from that of the quiet photosphere. A possible systematic bias in the selection of the granules by Macris (1979) is found.     

Search for Phobos and Deimos gas/dust tori using in situ observations from Mars Global Surveyor MAG/ER

More than 490 elliptical aerobraking and science phasing orbits made by Mars Global Surveyor (MGS) in 1997 and 1998 provide unprecedented coverage of the solar wind in the vicinity of the orbits of the martian moons Phobos and Deimos. We have performed a comprehensive survey of magnetic field perturbations in the solar wind to search for possible signatures of solar wind interaction with dust or gas escaping from the moons. A total of 1246 solar wind disturbance events were identified and their distribution was examined relative to Phobos, the Phobos orbit, and the Deimos orbit. We find that the spatial distribution of solar wind perturbations does not increase near or downstream of Phobos, Phobos’ orbit, or Deimos’ orbit, which would have been expected if there is significant outgassing or dust escape from the martian moons. Of the 1246 magnetic field perturbation events found in the MGS data set, 11 events were found within 2000 km of the Phobos orbit, while three events were found within 2000 km of the Deimos orbit. These events were analyzed in detail and found to likely have other causes than outgassing/dust escape from the martian moons. Thus we conclude that the amount of gas/dust escaping the martian moons is not significant enough to induce detectable magnetic field perturbations in the solar wind. In essence we have not found any clear evidence in the MGS magnetic field data for outgassing or dust escape from the martian moons.     

Quantum gravitomagnetic clock effect in Kerr gravitational field

We have found an approximate solution of Dirac equation using Foldy-Wouthuysen-Tani Hamiltonian of a Dirac particle in the Kerr gravitational field. We have solved the equation approximately using time-independent perturbation theory for the positive energy states. We have found frequencies by which these states oscillate. Difference of the periods of any of these two states has an identical form of the classical gravitomagnetic clock effect where the terms are quantized. So that, we have found a quantum version of the gravitomagnetic clock effect of a Dirac fermion in the Kerr gravitational field.