Trace — The transition region and coronal explorer

TRACE is a single-instrument solar mission that will be put into a Sunsynchronous polar orbit and will obtain continuous solar observations for about 8 months per year. It will collect images of solar plasmas at temperatures from 10⁴ to 10⁷ K, with 1-arcsec spatial resolution and excellent temporal resolution and continuity. With such data, we expect to gain a new understanding of many solar and stellar problems ranging from coronal heating to impulsive magnetohydrodynamic phenomena.     

Investigation of the composition of solar and interstellar matter using solar wind and pickup ion measurements with SWICS and SWIMS on the ACE spacecraft

The Solar Wind Ion Composition Spectrometer (SWICS) and the Solar Wind Ions Mass Spectrometer (SWIMS) on ACE are instruments optimized for measurements of the chemical and isotopic composition of solar and interstellar matter. SWICS determines uniquely the chemical and ionic-charge composition of the solar wind, the thermal and mean speeds of all major solar wind ions from H through Fe at all solar wind speeds above 300 km s−1 (protons) and 170 km s−1 (Fe+16), and resolves H and He isotopes of both solar and interstellar sources. SWICS will measure the distribution functions of both the interstellar cloud and dust cloud pickup ions up to energies of 100 keV e−1. SWIMS will measure the chemical, isotopic and charge state composition of the solar wind for every element between He and Ni. Each of the two instruments uses electrostatic analysis followed by a time-of-flight and, as required, an energy measurement. The observations made with SWICS and SWIMS will make valuable contributions to the ISTP objectives by providing information regarding the composition and energy distribution of matter entering the magnetosphere. In addition, SWICS and SWIMS results will have an impact on many areas of solar and heliospheric physics, in particular providing important and unique information on: (i) conditions and processes in the region of the corona where the solar wind is accelerated; (ii) the location of the source regions of the solar wind in the corona; (iii) coronal heating processes; (iv) the extent and causes of variations in the composition of the solar atmosphere; (v) plasma processes in the solar wind; (vi) the acceleration of particles in the solar wind; (vii) the physics of the pickup process of interstellar He in the solar wind; and (viii) the spatial distribution and characteristics of sources of neutral matter in the inner heliosphere. This revised version was published online in June 2006 with corrections to the Cover Date.     

Global Solar Wind Structure from Solar Minimum to Solar Maximum: Sources and Evolution

During the past few years, significant progress has been made in identifying the coronal sources of structures observed in the solar wind. This recent work has been facilitated by the relative simplicity and stability of structures during solar minimum. The challenge now is to continue to use coordinated coronal/solar wind observations to study the far more complicated and time-evolving structures of solar maximum. In this paper I will review analyses that use a wide range of observations to map out the global heliosphere and connect the corona to the solar wind. In particular, I will review some of the solar minimum studies done for the first Whole Sun Month campaign (WSM1), and briefly consider work in progress modeling the ascending phase time period of the second Whole Sun Fortnight campaign (WSF) and SPARTAN 201-05 observations, and the solar maximum third Whole Sun Month campaign (WSM3). In so doing I hope to demonstrate the increase in complexity of the connections between corona and heliosphere with solar cycle, and highlight the issues that need to be addressed in modeling solar maximum connections. This revised version was published online in August 2006 with corrections to the Cover Date.     

Probing Solar Subsurface Magnetic Fields

Helioseismology uses solar p-mode oscillations to probe the structure of the solar interior. The modifications of p-mode properties due to the presence of solar magnetic fields provide information on the magnetic fields in the solar interior. Here we review some of results in helioseismology on the magnetic fields in the solar convection zone. We will also discuss a recent result on the magnetic fields at the base of the convection zone. This revised version was published online in August 2006 with corrections to the Cover Date.     

新型太阳能利用装置的研究

对目前太阳能的几种常见的应用领域及相关装置进行了分析和研究,并在此基础上,结合相关理论,设计了利用太阳能的新型装置,如:太阳能房、太阳能热发电装置、聚光式太阳能电池发电装置等,这些装置将为更好地利用太阳能开辟新的途径.太阳能作为一种新兴的可再生能源有着不可限量的发展前景.     

The Ultra-Low-Energy Isotope Spectrometer (ULEIS) for the ACE spacecraft

The Ultra Low Energy Isotope Spectrometer (ULEIS) on the ACE spacecraft is an ultra high resolution mass spectrometer designed to measure particle composition and energy spectra of elements He-Ni with energies from ∼45 keV nucl−1 to a few MeV nucl−1. ULEIS will investigate particles accelerated in solar energetic particle events, interplanetary shocks, and at the solar wind termination shock. By determining energy spectra, mass composition, and their temporal variations in conjunction with other ACE instruments, ULEIS will greatly improve our knowledge of solar abundances, as well as other reservoirs such as the local interstellar medium. ULEIS is designed to combine the high sensitivity required to measure low particle fluxes, along with the capability to operate in the largest solar particle or interplanetary shock events. In addition to detailed information for individual ions, ULEIS features a wide range of count rates for different ions and energies that will allow accurate determination of particle fluxes and anisotropies over short (∼few minutes) time scales. This revised version was published online in June 2006 with corrections to the Cover Date.     

Solar Neutrinos

The current status of solar neutrino experiments is reviewed. All the experimental measurements show deficits of solar neutrinos. Non monotonic suppression indicates that the problem may naturally be explained by neutrino oscillations, but not by modifying solar models. A new experiment shows very promising results. We hope that a definite answer to the question of whether solar neutrinos are oscillating will be obtained in the very near future. This revised version was published online in June 2006 with corrections to the Cover Date.     

Solar cosmic rays

The first observations of solar cosmic rays were made simultaneously by many investigators at worldwide cosmic-ray stations in the periods of powerful chromospheric flares on February 28 and March 7, 1942. The discovery of these and the investigation of cosmic-ray solar-daily variations with maximum time near noon led some authors (Richtmyer and Teller, 1948; Alfvén, 1949, 1950) to a model of apparent cosmic-ray solar origin. We present here the results of the properties of solar cosmic rays from ground events (experimental and theoretical investigations). We also discuss important information from solar experimental data relating to these ground events observed in September and October 1989 and May 1990. Some experimental evidence of acceleration processes in associated phenomena with flares and long-term (solar cycle) variation of the average flux of solar cosmic rays is discussed as also cornal and interplanetary propagation, and that in the terrestrial magnetosphere. Note that the energy spectrum of solar cosmic rays varied very strongly from one flare to another. What are the causes of these phenomena? What is the nature of chemical and isotopic contents of solar cosmic rays? How can its changes occur in the energy spectrum and chemical contents of solar cosmic rays in the process of propagation? Is it possible to recalculate these parameters to the source? What makes solar cosmic rays rich in heavy nucleus and³He? The important data about electrons, positrons, gamma-quanta and neutrons from flares will be discussed in a subsequent paper (Dorman and Venkatesan, 1992). The question is: What main acceleration mechanism of solar flare and associated phenomena are reliable? These problems are connected with the more general problem on solar flare origin and its energetics. In Dorman and Venkatesan (1993) we will consider these problems as well as the problem of prediction of radiation hazard from solar cosmic rays (not only in space, but also in the Earth's atmosphere too).     

Structural dynamic responses of a stripped solar sail subjected to solar radiation pressure

The stripped solar sail whose membrane is divided into separate narrow membrane strips is believed to have the best structural efficiency. In this paper, the stripped solar sail structure is regarded as an assembly made by connecting a number of boom-strip components in sequence. Considering the coupling effects between booms and membrane strips, an exact and semi-analytical method to calculate structural dynamic responses of the stripped solar sail subjected to solar radiation pressure is established. The case study of a 100 m stripped solar sail shows that the stripped architecture helps to reduce the static deflections and amplitudes of the steady-state dynamic response. Larger prestress of the membrane strips will decrease stiffness of the sail and increase amplitudes of the steady-state dynamic response. Increasing thickness of the boom will benefit to stability of the sail and reduce the resonant amplitudes. This proposed semi-analytical method provides an efficient analysis tool for structure design and attitude control of the stripped solar sail.     

The Genesis Discovery Mission: Return of Solar Matter to Earth

The Genesis Discovery mission will return samples of solar matter for analysis of isotopic and elemental compositions in terrestrial laboratories. This is accomplished by exposing ultra-pure materials to the solar wind at the L1 Lagrangian point and returning the materials to Earth. Solar wind collection will continue until April 2004 with Earth return in Sept. 2004. The general science objectives of Genesis are to (1) to obtain solar isotopic abundances to the level of precision required for the interpretation of planetary science data, (2) to significantly improve knowledge of solar elemental abundances, (3) to measure the composition of the different solar wind regimes, and (4) to provide a reservoir of solar matter to serve the needs of planetary science in the 21st century. The Genesis flight system is a sun-pointed spinner, consisting of a spacecraft deck and a sample return capsule (SRC). The SRC houses a canister which contains the collector materials. The lid of the SRC and a cover to the canister were opened to begin solar wind collection on November 30, 2001. To obtain samples of O and N ions of higher fluence relative to background levels in the target materials, an electrostatic mirror (‘concentrator’) is used which focuses the incoming ions over a diameter of about 20 cm onto a 6 cm diameter set of target materials. Solar wind electron and ion monitors (electrostatic analyzers) determine the solar wind regime present at the spacecraft and control the deployment of separate arrays of collector materials to provide the independent regime samples. This revised version was published online in August 2006 with corrections to the Cover Date.     

Miniskirt for Dancing Spinner

An idea for use of skirts made of optical solar reflectors to concentrate solar energy on the solar cell array of geosynchronous spinning spacecraft is presented. From theoretical consideration it is predicted that the practical realization of this concept will allow significant overall cost and weight reduction of such spacecrafts.     

太阳帆航天器在绕地轨道中的热诱发振动

太阳帆航天器在绕地轨道中将会周期性地进出地球阴影，经历热环境的剧烈变化，在热辐射冲击作用下，太阳帆这种大柔性空间结构的热致响应值得研究。以方形有桅杆式太阳帆为研究对象，考虑热辐射等非线性因素，建立了太阳帆的热-结构耦合动力学模型，分析了太阳帆桅杆-薄膜结构热诱发振动的特点和影响因素。分析结果表明：太阳帆由地球阴影区进入光照区将会发生明显的热诱发振动；随着热流入射角的增大，太阳帆桅杆截面的摄动温度减小，热诱发振动减弱，频率不变；太阳帆桅杆刚度的增大有利于抑制结构热诱发振动的发生；帆膜预应力将会影响太阳帆的热诱发振动，随着桅杆轴力增大，热诱发振动的振幅增大，频率减小，当轴力增大至一定程度，太阳帆的热诱发振动将会发散。     

Solar Wind Sources and Their Variations Over the Solar Cycle

In this paper I will briefly summarize the present status of our knowledge on the four different sorts of solar wind, their sources and their short- and long-term variations. First: the fast solar wind in high-speed streams that emerges from coronal hole regions. Second: the slow solar wind emerging from the non-active Sun near the global heliospheric current sheet above helmet streamers and underlying active regions. Third: the slow solar wind filling most of the heliosphere during high solar activity, emerging above active regions in a highly turbulent state, and fourth: the plasma expelled from the Sun during coronal mass ejections. The coronal sources of these different flows vary dramatically with the solar activity cycle.     

The Solar Isotope Spectrometer for the Advanced Composition Explorer

The Solar Isotope Spectrometer (SIS), one of nine instruments on the Advanced Composition Explorer (ACE), is designed to provide high- resolution measurements of the isotopic composition of energetic nuclei from He to Zn (Z=2 to 30) over the energy range from ∼10 to ∼100 MeV nucl−1. During large solar events SIS will measure the isotopic abundances of solar energetic particles to determine directly the composition of the solar corona and to study particle acceleration processes. During solar quiet times SIS will measure the isotopes of low-energy cosmic rays from the Galaxy and isotopes of the anomalous cosmic-ray component, which originates in the nearby interstellar medium. SIS has two telescopes composed of silicon solid-state detectors that provide measurements of the nuclear charge, mass, and kinetic energy of incident nuclei. Within each telescope, particle trajectories are measured with a pair of two-dimensional silicon-strip detectors instrumented with custom, very large-scale integrated (VLSI) electronics to provide both position and energy-loss measurements. SIS was especially designed to achieve excellent mass resolution under the extreme, high flux conditions encountered in large solar particle events. It provides a geometry factor of ∼40 cm2 sr, significantly greater than earlier solar particle isotope spectrometers. A microprocessor controls the instrument operation, sorts events into prioritized buffers on the basis of their charge, range, angle of incidence, and quality of trajectory determination, and formats data for readout by the spacecraft. This paper describes the design and operation of SIS and the scientific objectives that the instrument will address. This revised version was published online in June 2006 with corrections to the Cover Date.     

银膜的原子氧剥蚀效应及其防护的试验研究

 空间太阳电池板作为空间飞行器电源系统的重要组成部分,它的正常工作对飞行器的运行起着非常重要的作用,而作为互连片的银材料,可能会与空间环境中的原子氧发生反应,生成不导电的氧化物,从而影响空间太阳电池板的有效寿命。本文在原子氧效应地面模拟试验设备中,对银以及镀有不同防护层的银膜进行了原子氧效应地面模拟试验研究,对试验前后试样的外观、质量进行了比较,获得了银在设备中的反应特点,同时对不同防护镀层的有效性进行了验证,为银互连片在空间太阳电池板上的应用及其防护提供了设计依据。     

The solar WIND and suprathermal ion composition investigation on the WIND spacecraft

The Solar Wind and Suprathermal Ion Composition Experiment (SMS) on WIND is designed to determine uniquely the elemental, isotopic, and ionic-charge composition of the solar wind, the temperatures and mean speeds of all major solar-wind ions, from H through Fe, at solar wind speeds ranging from 175 kms^–1 (protons) to 1280 kms^–1 (Fe⁺⁸), and the composition, charge states as well as the 3-dimensional distribution functions of suprathermal ions, including interstellar pick-up He⁺, of energies up to 230 keV/e. The experiment consists of three instruments with a common Data Processing Unit. Each of the three instruments uses electrostatic analysis followed by a time-of-flight and, as required, an energy measurement. The observations made by SMS will make valuable contributions to the ISTP objectives by providing information regarding the composition and energy distribution of matter entering the magnetosphere. In addition SMS results will have an impact on many areas of solar and heliospheric physics, in particular providing important and unique information on: (i) conditions and processes in the region of the corona where the solar wind is accelerated; (ii) the location of the source regions of the solar wind in the corona; (iii) coronal heating processes; (iv) the extent and causes of variations in the composition of the solar atmosphere; (v) plasma processes in the solar wind; (vi) the acceleration of particles in the solar wind; and (vii) the physics of the pick-up process of interstellar He as well as lunar particles in the solar wind, and the isotopic composition of interstellar helium.     

The Solar Wind - Inner Heliosphere

The solar wind in the inner heliosphere, inside ~ 5 AU, has been almost fully characterized by the addition of the high heliographic latitude Ulysses mission to the many low latitude inner heliosphere missions that preceded it. The two major omissions are the high latitude solar wind at solar maximum, which will be measured during the second Ulysses polar passages, and the solar wind near the Sun, which could be analyzed by a Solar Probe mission. Here, existing knowledge of the global solar wind in the inner heliosphere is summarized in the context of the new results from Ulysses.     

On the Slow Solar Wind

A theory for the origin of the slow solar wind is described. Recent papers have demonstrated that magnetic flux moves across coronal holes as a result of the interplay between the differential rotation of the photosphere and the non-radial expansion of the solar wind in more rigidly rotating coronal holes. This flux will be deposited at low latitudes and should reconnect with closed magnetic loops, thereby releasing material from the loops to form the slow solar wind. It is pointed out that this mechanism provides a natural explanation for the charge states of elements observed in the slow solar wind, and for the presence of the First-Ionization Potential, or FIP, effect in the slow wind and its absence in fast wind. Comments are also provided on the role that the ACE mission should have in understanding the slow solar wind. This revised version was published online in June 2006 with corrections to the Cover Date.     

Sources of Solar Wind at Solar Minimum: Constraints from Composition Data

In this discussion of observational constraints on the source regions and acceleration processes of solar wind, we will focus on the ionic composition of the solar wind and the distribution of charge states of heavy elements such as oxygen and iron. We first focus on the now well-known bi-modal nature of solar wind, which dominates the heliosphere at solar minimum: Compositionally cool solar wind from polar coronal holes over-expands, filling a much larger solid angle than the coronal holes on the Sun. We use a series of remote and in-situ characteristics to derive a global geometric expansion factor of?～5. Slower, streamer-associated wind is located near the heliospheric current sheet with a width of 10–20°, but in a well-defined band with a geometrically small transition width. We then compute charge states under the assumption of thermal electron distributions and temperature, velocity, and density profiles predicted by a recent solar wind model, and conclude that the solar wind originates from a hot source at around 1 million?K, characteristic of the closed corona.