The IBEX-Lo Sensor

The IBEX-Lo sensor covers the low-energy heliospheric neutral atom spectrum from 0.01 to 2 keV. It shares significant energy overlap and an overall design philosophy with the IBEX-Hi sensor. Both sensors are large geometric factor, single pixel cameras that maximize the relatively weak heliospheric neutral signal while effectively eliminating ion, electron, and UV background sources. The IBEX-Lo sensor is divided into four major subsystems. The entrance subsystem includes an annular collimator that collimates neutrals to approximately 7°×7° in three 90° sectors and approximately 3.5°×3.5° in the fourth 90° sector (called the high angular resolution sector). A fraction of the interstellar neutrals and heliospheric neutrals that pass through the collimator are converted to negative ions in the ENA to ion conversion subsystem. The neutrals are converted on a high yield, inert, diamond-like carbon conversion surface. Negative ions from the conversion surface are accelerated into an electrostatic analyzer (ESA), which sets the energy passband for the sensor. Finally, negative ions exit the ESA, are post-accelerated to 16 kV, and then are analyzed in a time-of-flight (TOF) mass spectrometer. This triple-coincidence, TOF subsystem effectively rejects random background while maintaining high detection efficiency for negative ions. Mass analysis distinguishes heliospheric hydrogen from interstellar helium and oxygen. In normal sensor operations, eight energy steps are sampled on a 2-spin per energy step cadence so that the full energy range is covered in 16 spacecraft spins. Each year in the spring and fall, the sensor is operated in a special interstellar oxygen and helium mode during part of the spacecraft spin. In the spring, this mode includes electrostatic shutoff of the low resolution (7°×7°) quadrants of the collimator so that the interstellar neutrals are detected with 3.5°×3.5° angular resolution. These high angular resolution data are combined with star positions determined from a dedicated star sensor to measure the relative flow difference between filtered and unfiltered interstellar oxygen. At the end of 6 months of operation, full sky maps of heliospheric neutral hydrogen from 0.01 to 2 keV in 8 energy steps are accumulated. These data, similar sky maps from IBEX-Hi, and the first observations of interstellar neutral oxygen will answer the four key science questions of the IBEX mission.     

Electric field measurements in the solar wind,bow shock,magnetosheath, magnetopause,and magnetosphere

Electric field measurements are reported at 11 magnetopause crossings that occurred during a single in-bound ISEE-1 satellite pass near a local time of 1030. In combination with magnetic field data, these measurements show the existence of electric field components tangential to the actual magnetopause in the frame of rest of the magnetopause on every crossing of the current carrying layers associated with the 11 magnetopause traversals. These tangential electric field components were oriented with respect to the magnetopause sheet currents such that there was an electrical power dissipation of between 30 and 110 W km^-2 on 10 of the 11 crossings. These results are in agreement with requirements of reconnection theories. Histograms of the normal electric field components and of the orientation, velocity, and thickness of the current carrying layer are presented. Suggestions of the existence of a parallel electric field in the magnetosheath near the magnetopause and of propagation of large amplitude waves along the magnetopause are also made.     

Saturn kilometric radiation as a monitor for the solar wind?

Since the Voyager mission it is known that Saturn Kilometric Radiation (SKR) is strongly influenced by external forces, i.e., the solar wind and in particular the solar wind ram pressure. Recent studies using Cassini data essentially confirmed these findings for particular periods during the first Cassini orbit of Saturn. The data coverage of SKR by the Cassini/RPWS experiment for the period of six months prior to Saturn Orbit Insertion (July 1, 2004) is rather continuous, whereas there are gaps in the solar wind plasma data. The strong correlation of SKR with the solar wind may provide an indication on the variations of the solar wind plasma, specifically during the gap periods. These periods lacking solar wind data are substituted by Ulysses solar wind data which have been propagated over ∼4 AU, applying magnetohydrodynamic propagation models. Cross correlation studies showed that Ulysses solar wind data can be taken as a substitute for missing Cassini data. The use of SKR as monitor for solar wind variations is discussed. With the present set of observations the SKR proxy lacks significant reliability.     

Study of the seasonal ozone variations at European high latitudes

The geographic area at high latitudes beyond the polar circle is characterized with long darkness during the winter (polar night) and with a long summertime insolation (polar day). Consequentially, the polar vortex is formed and the surrounding strong polar jet is characterized by a strong potential vorticity gradient representing a horizontal transport barrier. The ozone dynamics of the lower and middle stratosphere is controlled both by chemical destruction processes and transport processes.     

Elemental Abundances in the Solar Upper Atmosphere Derived by Spectroscopic Means

The composition of the solar photosphere is believed to be uniform. Indeed a quantity that does not vary with solar surface location or with a particular solar feature, i.e., no observational evidence is available to indicate that the photospheric composition near the solar equator is different from the photospheric composition near the solar poles or that the photospheric composition in quiet regions is different from the composition in active regions. In contrast, the composition of the solar upper atmosphere is not well defined. Solar composition work in recent decades has brought the recognition that there are systematic differences between the composition of the corona and the photosphere and revealed evidence for spatial and time variability in the composition of various coronal features. We review the spectroscopic techniques used and the progress that was made in recent years in deriving the plasma compositions of various solar upper atmosphere structures. This revised version was published online in August 2006 with corrections to the Cover Date.     

Outflow Velocities at the Base of a Polar Coronal Hole During the 1998 Total Eclipse

Polar coronal holes represent the most convincing site from which the high-speed solar wind originates. Here we report high-accuracy Doppler shifts measured in the O VI (1037.6 Å) line obtained by SUMER on SOHO inside an interplume region within the south polar coronal hole. We infer limits on the outflow velocity and draw hints about the flow geometry.     

Results of impact simulation for the GIOTTO mission

The European Space Agency (ESA) has decided to carry out a fly-by mission to the comet Halley. The spacecraft will be launched by an ARIANE II and intercept the retrograde Halley orbit on 13 March, 1986. One group of experiments is designed to obtain data on size, mass and composition of the dust in the cometary tail. Because of the very high relative velocity during fly-by (69 km/s) laboratory experiments are necessary to develop and calibrate the experiments. These experiments are presently under way in the laboratory of the Lehrstuhl für Raumfahrttechnik of the Technische Universität München. First results have been obtained for both the Dust Impact Detection System (DIDSY) and the P?articulate Impact Analyzer (PIA). These results are compared with the theoretical models for hypervelocity impact craters. The agreement is good at impact velocities around 15 km/s.     

基于生产成本的作业调度

提出了一个基于净现值的调度指标，该指标充分考虑到影响调度决策的各项费用．如在制品库存费用、机床工时费、直接工人的工资、工件提前或拖期完工造成的损失等。然后以遗传算法为工具，研究了作业调度问题，设计了一种很实用的算法。该算法采用基于工序的编码方法把调度编码成染色体，并通过遗传操作来搜索最佳染色体。解码算法根据工序在染色体中的次序和最短加工时间一紧迫度规则得到调度。仿真结果表明该方法是可行的。并有一定的优越性。     

Old tail lobes effect on the solar-wind – Magnetosphere energy transport for the 27 August 2001 substorm

The magnetic flux of tail lobes Ψ is divided in two parts of comparable values Ψ₁ and Ψ₀₂, with the first that appears during substorm and the second, observed before substorm start. The first was named “new magnetic flux”, the second – “old magnetic flux”. The first, Ψ₁, is known to play a definitive role in the energy transport from the solar wind into the magnetosphere-ionosphere-atmosphere system, but the role of Ψ₀₂ in this transport is not well known. From the 27 August 2001 substorm data we study the involvement in the above transport process of the old flux Ψ₀₂. This involvement is observed in the polar cap (PC) area, which existed prior to the substorm and is called respectively “the old PC”. In this study, as distinct from earlier works, we use the balance equation of the energy stored in magnetosphere and energy consumed. Activation of the old PC magnetic flux Ψ₀₂ was found to increase the energy input by ∼85% in the event under consideration.