Chromospheric dynamics

This review focuses on dynamics of the solar chromosphere, which serves as a good proxy for understanding processes in stellar chromospheres as well. In the quiet chromosphere it is useful to distinguish between the magnetic network on the boundaries of supergranulation cells, where strong magnetic fields are organized in mainly vertical magnetic flux tubes, and internetwork regions in the cell interior, where magnetic fields are weaker and dynamically less important. Recently, some progress has been made in understanding the physics of the non-magnetic chromosphere. On the other hand, the physical processes that heat the magnetic network have not been fully identified. Is the network heated by wave dissipation and if so, what are their physical characteristics? These and other aspects relating to the dynamics and energy transport mechanisms will be discussed in detail. In addition, some of the outstanding problems in the field such the driving mechanism for spicules and the nature of internetwork magnetic fields will also be highlighted. Furthermore, a critical assessment will be made on the challenges facing theory and the direction for future investigations, particularly in the light of the new space experiments, will be highlighted.     

Low-latitude geomagnetic response to the interplanetary conditions during very intense magnetic storms

The variations in the horizontal and declination components of the geomagnetic field in response to the interplanetary shocks driven by fast halo coronal mass ejections, fast solar wind streams from the coronal hole regions and the dynamic pressure pulses associated with these events are studied. Close association between the field-aligned current density (j_∥) and the fluctuations in the declination component (ΔD_ABG) at Alibag is found for intense storm conditions. Increase in the dawn-dusk interplanetary electric field (E_y) and ΔD_ABG are generally in phase. However, when the magnetospheric electric field is directed from dusk to dawn direction, a prominent scatter occurs between the two. It is suggested that low-latitude ground magnetic data may serve as a proxy for the interplanetary conditions in the solar wind.     

帕金森大鼠模型的影像特性

利用影像技术对帕金森病（Parkinsondisease，PD）大鼠模型的脑形态与功能信息进行了系统研究。利用磁共振（Magneticresonance imaging。MRI）及磁共振血管成像（Magneticresonanceangiography，MRA）获取PD大鼠脑部形态影像资料，利用质子磁共振波谱（1H—magneticreso—nancespectroscopy，1H—MRS）及CT灌注（CTperfusion，CTP）成像获取波谱及血流变化等功能影像学资料。研究结果表明PD大鼠在形态上影像无特征性异常，在功能影像学纹状体存在局部脑血流降低和波谱变化。     

Preliminary Study on Magnetic Induction Intensity Induced by Plasma During Hypervelocity Impact

An experimental system has been built to produce and measure the magnetic field in the backward ejected matter during hypervelocity impact. The designs of measurement system and coil, the choice of associated equipment, and the system calibration are also described in detail. The measurement of magnetic induction intensity for different given coil positions and azimuth angles are performed with two-stage light-gas gun. On condition that impact velocities are approximately equal and incidence angles are 45°, 60° and 90° respectively, the relationship between average magnetic induction intensity and impact angle at different time spans is obtained. Experimental results show that the average magnetic induction intensity with incidence angle of 90° is larger than those with incidence angles of 45°and 60°.     

The detection of “magnetic element” – Why we need a one-meter Space Solar Telescope

The nature of a magnetic element, the elemental structure of the solar magnetic field, is one of the most important mysteries in solar physics. In this paper, we will discuss the requirements of magnetic element detection, such as spatial resolution and magnetic sensitivity. By these discussions, we conclude that it is almost impossible to detect magnetic element with currently used ground-based telescopes and techniques. The proposed Space Solar Telescope, a one-meter Chinese space project, can match these requirements.     

7T磁共振seipin鼠活体无损显型

因遗传突变作用引起皮下脂肪组织缺失可导致脂肪萎缩。本文利用7T小动物磁共振仪对seipin鼠进行了活体无损显型的研究。通过伪彩及加权图像融合技术对采集的seipin鼠和野生鼠图像的处理，可清楚观察到seipin组老鼠的脂肪组织明显少于野生组。同时利用自行开发的7T小动物三维可视化系统中的stroke—based分类方法可方便提取感兴趣组织。为了对两组老鼠的脂肪组织进行定量比较，利用t检验对两组老鼠总的脂肪组织、皮下脂肪及内脏脂肪占总体积的比例进行统计。统计结果表明，seipin组老鼠的脂肪组织及皮下脂肪明显少于野生组，但在本次实验中没有发现两组鼠在内脏组织中脂肪含量存在明显差异。7T小动物磁共振仪为活体研究seipin鼠的显型提供了可靠的手段。     

数字高程模型在航线分析中的应用

航路分析的主体是飘降分析与供氧分析,是高原航路开辟前所必须做的性能分析工作。传统方法在确定航迹下方特定宽度范围内的地形剖面时,存在巨大的手工地图作业,工作量巨大且不能保证精度要求。以地理信息系统数字高程模型为基础,通过建立航线分析自动化软件系统,对实际高原航线下方的地形剖面进行搜索计算,解决了这类问题。作为算例,进行了几种情况下的成都拉萨航线地形剖面的对比分析。     

A MHD-turbulence model for solar corona

The disposition of energy in the solar corona has always been a problem of great interest. It remains an open question how the low temperature photosphere supports the occurence of solar extreme phenomena. In this work, a turbulent heating mechanism for the solar corona through the framework of reduced magnetohydrodynamics (RMHD) is proposed. Two-dimensional incompressible long time simulations of the average energy disposition have been carried out with the aim to reveal the characteristics of the long time statistical behavior of a two-dimensional cross-section of a coronal loop and the importance of the photospheric time scales in the understanding of the underlying mechanisms. It was found that for a slow, shear type photospheric driving the magnetic field in the loop self-organizes at large scales via an inverse MHD cascade. The system undergoes three distinct evolutionary phases. The initial forcing conditions are quickly “forgotten” giving way to an inverse cascade accompanied with and ending up to electric current dissipation. Scaling laws are being proposed in order to quantify the nonlinearity of the system response which seems to become more impulsive for decreasing resistivity. It is also shown that few, if any, qualitative changes in the above results occur by increasing spatial resolution.     

Geosynchronous magnetic field response to the large and fast solar wind dynamic pressure change

We present a comparison of large and sharp solar wind dynamic pressure changes, observed by several spacecraft, with fast disturbances in the magnetospheric magnetic field measured by the GOES-8, 9 and 10 geosynchronous satellites. Almost 400 solar wind pressure changes in the period 1996–2003 were selected for this study. Using the large statistics we confirmed that increases (decreases) in the dynamic pressure always results in increases (decreases) in the magnitude of geosynchronous B_z component. The amplitude of the geosynchronous B_z response strongly depends on the location of observer relative to the noon meridian, from the value of solar wind pressure before the disturbance arriving and firstly – from the amplitude of the pressure change.