The wide variety of geophysical plasmas that will be investigated by the Cluster mission contain waves with a frequency range from DC to over 100 kHz with both magnetic and electric components. The characteristic duration of these waves extends from a few milliseconds to minutes and a dynamic range of over 90 dB is desired. All of these factors make it essential that the on-board control system for the Wave-Experiment Consortium (WEC) instruments be flexible so as to make effective use of the limited spacecraft resources of power and telemetry-information bandwidth. The Digital Wave Processing Experiment, (DWP), will be flown on Cluster satellites as a component of the WEC. DWP will coordinate WEC measurements as well as perform particle correlations in order to permit the direct study of wave/particle interactions. The DWP instrument employs a novel architecture based on the use of transputers with parallel processing and re-allocatable tasks to provide a high-reliability system. Members of the DWP team are also providing sophisticated electrical ground support equipment, for use during development and testing by the WEC. This is described further in Pedersen et al. (this issue). 相似文献
Despite 20 years of total solar irradiance measurements from space, the lack of high precision spatially resolved observations limits definitive answers to even simple questions like ``Are the solar irradiance changes caused solely by magnetic fields perturbing the radiative flux at the photosphere?" More subtle questions like how the aspheric structure of the sun changes with the magnetic cycle are only now beginning to be addressed with new tools like p-mode helioseismology. Solar 5-min oscillation studies have yielded precise information on the mean radial interior solar structure and some knowledge about the rotational and thermal solar asphericity. Unfortunately this progress has not been enough to generate a self-consistent theory for why the solar irradiance and luminosity vary with the magnetic cycle. We need sharper tools to describe and understand the sun's global aspheric response to its internal dynamo, and we need to be able to measure the solar cycle manifestation of the magnetic cycle on entropy transport from the interior to the photosphere in much the same way that we study the fundamentally more complex problem of magnetic flux transport from the solar interior. A space experiment called the Solar Physics Explorer for Radius, Irradiance and Shape (SPHERIS) and in particular its Astrometric and Photometric Telescope (APT) component will accomplish these goals.
A procedure based on the envelope concept of differential geometry is described that permits the reconstruction of the contour of a smooth, moving, conducting target, satisfying the geometrical optics approximation. The target reflections are assumed to be specular in nature with either one reflection point or multiple resolvable reflection points. The time variation of the range to the reflection point of the target (assumed derivable from a high-resolution radar) and the general motion of the target (assumed derivable from tracking or trajectory information) are employed to reconstruct the contour of that portion of the assumed target surface that is illuminated by the radar. The reconstruction is accomplished by the simultaneous solution of two nonlinear differential equations which are derived using the envelope concept of differential geometry. Several reconstruction examples based on computer analysis are presented which indicate the results obtainable using this method. 相似文献
We have developed a 2D semi-empirical model (Sittler and Guhathakurta 1999) of the corona and the interplanetary medium using
the time independent MHD equations and assuming azimuthal symmetry, utilizing the SOHO, Spartan and Ulysses observations.
The model uses as inputs (1) an empirically derived global electron density distribution using LASCO, Mark III and Spartan
white light observations and in situ observations of the Ulysses spacecraft, and (2) an empirical model of the coronal magnetic
field topology using SOHO/LASCO and EIT observations. The model requires an estimate of solar wind velocity as a function
of latitude at 1 AU and the radial component of the magnetic field at 1 AU, for which we use Ulysses plasma and magnetic field
data results respectively. The model makes estimates as a function of radial distance and latitude of various fluid parameters
of the plasma such as flow velocity V, temperature Teff, and heat flux Qeff which are derived from the equations of conservation of mass, momentum and energy, respectively, in the rotating frame of
the Sun. The term "effective" indicates possible wave contributions. The model can be used as a planning tool for such missions
as Solar Probe and provide an empirical framework for theoretical models of the solar corona and solar wind.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
Corotating interaction regions (CIRs) in the middle heliosphere have distinct morphological features and associated patterns
of turbulence and energetic particles. This report summarizes current understanding of those features and patterns, discusses
how they can vary from case to case and with distance from the Sun and possible causes of those variations, presents an analytical
model of the morphological features found in earlier qualitative models and numerical simulations, and identifies aspects
of the features and patterns that have yet to be resolved.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
In January 2000, the Ulysses spacecraft observed an ICME event at 43° S heliographic latitude and ∼ 4.1 AU. We use electron (Ee>38 keV) observations to trace the topology of the IMF embedded within the ICME. The still controversial issue of whether
ICMEs have been detached from the solar corona or are still magnetically anchored to it when they arrive at the spacecraft
is tackled. An in ecliptic ICME event is also presented.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
On day 49 of 1999 a strong interplanetary shock was observed by the ACE spacecraft located at 1 AU from the Sun. This shock
was followed 10 hours later by a magnetic cloud (MC). A large solar energetic particle (SEP) event was observed in association
with the arrival of the shock and the MC at ACE. The Ulysses spacecraft, located at 22° S heliolatitude and nearly the same
ecliptic longitude as ACE, observed a large SEP event beginning on day 54 that peaked with the arrival of a solar wind and
magnetic field disturbance on day 61. A magnetic cloud was observed by Ulysses on days 63–64. We suggest a scenario in which both spacecraft intercepted the same MC, although sampling different regions
of it. We describe the effects that the MC produced on the streaming of energetic particles at both spacecraft.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
We present and compare observations of energetic protons during the two first transits of the Ulysses spacecraft from low to high latitudes in the southern heliosphere. Protons in the energy range 1.8–3.8 MeV from the COSPIN
experiment are studied for global trends and in relation to some ambient structures in the solar wind (corotating interaction
region, forward/reverse shock). The global trends show the large dependence on the heliospheric condition and solar activity,
including indications of a larger ambient particle population during the rising phase of solar activity and more efficient
solar wind particle accelerators during the declining phase. More enhancements in the proton flux intensity are time associated
with forward shocks than reverse contrary to first pass. Recurrent structures are found even during the second transit. Some
latitude dependent periodicities are observed that could relate to the differential solar rotation.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献