New Challenges to Trajectory Design by the Use of Electric Propulsion and Other New Means of Wandering in the Solar System

The design of spacecraft trajectories is a crucial part of a space mission design. Often the mission goal is tightly related to the spacecraft trajectory. A geostationary orbit is indeed mandatory for a stationary equatorial position. Visiting a solar system planet implies that a proper trajectory is used to bring the spacecraft from Earth to the vicinity of the planet. The first planetary missions were based on conventional trajectories obtained with chemical engine rockets. The manoeuvres could be considered 'impulsive' and clear limitations to the possible missions were set by the energy required to reach certain orbits. The gravity-assist trajectories opened a new way of wandering through the solar system, by exploiting the gravitational field of some planets. The advent of other propulsion techniques, as electric or ion propulsion and solar sail, opened a new dimension to the planetary trajectory, while at the same time posing new challenges. These 'low thrust' propulsion techniques cannot be considered 'impulsive' anymore and require for their study mathematical techniques which are substantially different from before. The optimisation of such trajectories is also a new field of flight dynamics, which involves complex treatments especially in multi-revolution cases as in a lunar transfer trajectory. One advantage of these trajectories is that they allow to explore regions of space where different bodies gravitationally compete with each other. We can exploit therefore these gravitational perturbations to save fuel or reduce time of flight. The SMART-1 spacecraft, first European mission to the Moon, will test for the first time all these techniques. The paper is a summary report on various activities conducted by the project team in these areas.     

Changes in solar rotation due to the solar energy generation cycle of 11 years

It is suggested that the observed differences in the periods of variation of some solar phenomena (solar brightness, appearance of sunspot maximum and interplanetary sector structure) occurring close to 27 days are due to differences in the rotation periods of the solar regions in which these phenomena are originated. Changes in periods during the solar cycle can be attributed to changes in the solar energy generation. On the basis of these considerations changes in the sign of the gradient of the Sun's angular velocity can be expected.     

A logistic model for magnetic energy storage in solar active regions

Previous statistical analyses of a large number of SOHO/MDI full disk longitu-dinal magnetograms provided a result that demonstrated how responses of solar flares to photospheric magnetic properties can be fitted with sigmoid functions. A logistic model reveals that these fitted sigmoid functions might be related to the free energy storage process in solar active regions. Although this suggested model is rather simple, the free energy level of active regions can be estimated and the probability of a solar flare with importance over a threshold can be forecast within a given time window.     

Application of Spectroscopic Diagnostics to Early Observations with the SOHO Coronal Diagnostic Spectrometer

The Coronal Diagnostic Spectrometer (CDS) has as a scientific goal the determination of the physical parameters of the solar plasma using spectroscopic diagnostic techniques. Absolute intensities and intensity ratios of the EUV spectral emission lines can be used to obtain information on the electron density and temperature structure, element abundances, and dynamic nature of different features in the solar atmosphere. To ensure that these techniques are accurate it is necessary to interface solar analysis programs with the best available atomic data calculations. Progress is reported on this work in relation to CDS observations.     

A Manifestation of Negative Energy Waves in the Solar Atmosphere

Magnetosonic modes of magnetic structures of the solar atmosphere in the presence of inhomogeneous steady flows are considered. It is shown that, when the speed of the steady flow exceeds the phase speed of one of the modes, the mode has negative energy, and can be subject to an over-stability due to the negative energy wave instabilities. It is shown that registered steady flows in the solar atmosphere, with speeds below the threshold of the Kelvin–Helmholtz instability, can provide the existence of the magnetosonic negative energy wave phenomena. In particular, in isolated photospheric magnetic flux tubes, there are kink surface modes with negative energy, produced by the external granulation downflows. Dissipative instability of these modes due to finite thermal conductivity and explosive instability due to nonlinear coupling of these modes with Alfvén waves are discussed. For coronal loops, it is found that only very high-speed flows (>300 km s^-1) can produce negative energy slow body modes. In solar wind flow structures, both slow and fast body modes have negative energy and are unstable.     

Scaling relations governing magnetospheric energy transfer

The functional dependence on solar wind parameters of the rate of energy transfer from the solar wind into the magnetosphere is subject to constraints imposed by dimensional analysis. The form and extent of the constraints depend on assumption about the energy coupling mechanisms, specifically on the relative importance of electromagnetic coupling (MHD flows effects), ionospheric conductivity effects (through Birkeland currents), and the viscous coupling. The effective viscosity coefficient scales in a well-defined manner with solar wind parameters, and its effect is dimensionally the same as that of more general finite-gyroradius mechanisms. We obtain the general form of the expression for energy transfer which takes all these effects into account and which can then be specialized to specific assumptions about the coupling mechanism. We point out the needed changes in energy transfer formulas previously used in the littrature, which make them conform to the requirements of dimensional analysis. Electromagnetic coupling yields the most restrictive formulas for energy transfer, although a unique expression cannot be obtained either on solely dimensional grounds or from presently available theory. Modifications required by the addition of viscous or finite-gyroradius effects are well defined but small and likely to be difficult to detect in practice. Assumptions of energy transfer by solar wind plasma entry leads to expressions equivalent, as far as dimensional arguments go, to those based on assumptions of electromagnetic or viscous coupling. Ionospheric conductivity effects are likely to be minor since Joule heating in the ionosphere is a relatively small fraction of the magnetospheric energy budget. All energy transfer formulas discussed presuppose a well-defined set of solar wind parameters and hence can be valid only on time scales longer than the solar wind flow time past the magnetosphere, which is also the expected time scale for energy storage (if any) in the magnetotail.     

A theoretically derived energy coupling function for the magnetosphere

The energy coupling function between the solar wind and the magnetosphere can be obtained for two extreme situations, in which the magnetospheric geometry is determined primarily by either (i) the interplanetary magnetic field, or (ii) the solar wind pressure. In this paper, we obtained an expression for the energy coupling function by assuming a simple interpermeation of the interplanetary and geomagnetic fields. Two important quantities in this case are the potential difference between the two neutral points and the amount of open flux. From these two overall quantities, the voltage and the current of the magnetospheric dynamo are calculated. The dynamo power output represents the rate at which energy is transferred from the solar wind to the magnetosphere. The derived functional dependence on the interplanetary conditions provides a theoretical basis for the energy coupling function previously deduced from observations.     

Certain problems of solar and heliospheric physics in the light of novel satellite data

Recent satellite data have given a better insight into the possible nature of extremely strong disturbances on the Sun and in the heliosphere by relating them to processes in the solar interior. The energy, momentum, and mass transfer on various spatiotemporal scales are organized in the Sun into a hierarchy of coupled nonlinear processes. Confirmation has been given to the fact that coronal mass ejections and solar flares are not linked causally but merely reflect the existence of two channels of free-energy dissipation in the solar atmosphere in the form of plasma motion and plasma emission; their relative role can be described by a corresponding nondimensional parameter. Information on the global asymmetry of the solar emission and active processes has been gained. A great diversity in the geometry of eruptive events (not necessarily associated with magnetic reconnection) has been revealed. In our opinion, the basic unresolved problems in the investigation of solar activity dictate the necessity of carrying out more accurate, absolutely calibrated measurements of the whitelight solar emission at appropriately high spatiotemporal resolutions. The development of direct and indirect techniques of measuring the electric fields and currents with the aim of reconstructing the solar and heliospheric current system remains a challenging task.     

Digital enhancement of solar X-ray space photography

Digital enhancement techniques are applied to digitized solar X-ray photography. Two-dimensional Fourier filtering, intensity thresholding, and histogram equalization techniques are described, and their effects on the X-ray image are compared and analyzed. Possible applications of these digital techniques to solar photography interpretation are suggested.P.O. Box 92957.     

Stopping power of matter and energy losses of solar neutrinos

The effects of neutrino mass and oscillations are investigated in the calculations of energy losses of solar neutrinos. In these calculations, we take into account the full energy dependence of the stopping power of matter for neutrinos. The case of Majorana neutrinos are also investigated. It is found that the total losses of energy of solar neutrinos are too small to account for the solar neutrino problem.     

Automatic Solar Flare Detection Using MLP,RBF, and SVM

The focus of automatic solar-flare detection is on the development of efficient feature-based classifiers. The three principal techniques used in this work are multi-layer perceptron (MLP), radial basis function (RBF), and support vector machine (SVM) classifiers. We have experimented and compared these three methods for solar-flare detection on solar H images obtained from the Big Bear Solar Observatory in California. The preprocessing step is to obtain nine principal features of the solar flares for the classifiers. Experimental results show that by using SVM we can obtain the best classification rate of the solar flares. We believe our work will lead to real-time solar-flare detection using advanced pattern recognition techniques.     

The role of suprathermal particle measurements in CrossScale studies of collisionless plasma processes

The CrossScale mission will advance our understanding of fundamental plasma processes in collisionless plasmas. It will exploit the excellent natural plasma laboratory provided by the Earth’s magnetosphere and the near-Earth solar wind and, in particular, carry out multi-scale studies that will strongly complement plasma studies in ground-based laboratories. Previous studies of collisionless plasmas in space environments across the solar system have shown the ubiquitous nature of suprathermal particles and that these particles exhibit a power-law energy spectrum. In this paper we discuss the great significance of these suprathermal particles for CrossScale studies. We show that the presence of these particles is a natural consequence of the collisionless regime as they can propagate across the heliosphere with little spectral change and are not thermalised by collisions. They are a key indicator of the non-equilibrium nature of collisionless plasmas and an important source of free energy that can drive plasma processes. We discuss how these suprathermal particles influence the overall properties of the plasma. In particular, the energy distribution of particles follows a Kappa, rather than Maxwellian, distribution and thus the plasma does not have a single thermodynamic temperature. We also discuss the importance of the suprathermal tail as a tool to diagnose the processes responsible for particle energisation in collisionless plasmas. Such energisation is a common feature in collisionless plasmas, especially in terms of the primary science targets for CrossScale: reconnection, shocks and turbulence. Finally we also touch on the value of using CrossScale studies to provide ground truth measurements for a number of astrophysical techniques that exploit the effects of energetic electrons in the distant universe. Throughout the paper, we stress that suprathermal (30 keV-1 MeV) measurements are essential to fully characterise particle distributions. We show that such measurements will benefit greatly from the improved spatial and temporal resolution (compared to Cluster) that is proposed for the HEP instrument on CrossScale.     

Energy and nuclear charge dependence of abundance enhancements of solar cosmic ray heavy ions in three large solar events

The differential flux and energy spectra of solar cosmic ray heavy ions of He, C, O, Ne, Mg, Si, and Fe were determined in the energy interval E = 3–30 MeV amu^-1 for two large solar events of January 24, 1971 and September 1, 1971 in rocket flights made from Ft. Churchill. From these data the relative abundances and the abundance enhancement factors, ξ, relative to photospheric abundances were obtained for these elements. Similar results were obtained for a third event on August 4, 1972 from the available published data. Characteristic features of ξ vs nuclear charge dependences were deduced for five energy intervals. The energy dependence of ξ for He shows a moderate change by a factor of about 3, whereas for Fe, ξ shows a very dramatic decrease by a factor of 10–20 with increasing energy. It is inferred that these abundance enhancements of solar cosmic ray heavy ions at low energies seem to be related to their ionization states (Z ^*) and hence studies of Z ^* can give information on the important parameters such as temperature and density in the accelerating region in the Sun.     

Turbulence In The Solar Atmosphere: Manifestations And Diagnostics Via Solar Image Processing

Intermittent magnetohydrodynamical turbulence is most likely at work in the magnetized solar atmosphere. As a result, an array of scaling and multi-scaling image-processing techniques can be used to measure the expected self-organization of solar magnetic fields. While these techniques advance our understanding of the physical system at work, it is unclear whether they can be used to predict solar eruptions, thus obtaining a practical significance for space weather. We address part of this problem by focusing on solar active regions and by investigating the usefulness of scaling and multi-scaling image-processing techniques in solar flare prediction. Since solar flares exhibit spatial and temporal intermittency, we suggest that they are the products of instabilities subject to a critical threshold in a turbulent magnetic configuration. The identification of this threshold in scaling and multi-scaling spectra would then contribute meaningfully to the prediction of solar flares. We find that the fractal dimension of solar magnetic fields and their multi-fractal spectrum of generalized correlation dimensions do not have significant predictive ability. The respective multi-fractal structure functions and their inertial-range scaling exponents, however, probably provide some statistical distinguishing features between flaring and non-flaring active regions. More importantly, the temporal evolution of the above scaling exponents in flaring active regions probably shows a distinct behavior starting a few hours prior to a flare and therefore this temporal behavior may be practically useful in flare prediction. The results of this study need to be validated by more comprehensive works over a large number of solar active regions. Sufficient statistics may also establish critical thresholds in the values of the multi-fractal structure functions and/or their scaling exponents above which a flare may be predicted with a high level of confidence. Based on the author's contributed talk “Manifestations and Diagnostics of Turbulence in the Solar Atmosphere”, presented at the Solar Image Processing Workshop II, Annapolis, Maryland, USA, 3–5 November 2004.     

The relation of energetic solar X-rays (hν>60 keV) and high frequency microwaves deduced from the periodic bursts of August 8, 1968 flare

Correlated sixteen-second periodic bursts were observed during the flash phase of a class 2b solar flare in energetic X-rays, microwaves, and EUV ionizing radiation. The observations of the periodic structures in the various X-ray energy channels indicate that the structures are predominantly a phenomenon of high energy electrons, E>80 keV. In view of the fact that the periodic X-ray structures were correlated extensively in microwave and EUV frequencies, a plausible conclusion is that these three types of radiation have a common energy source. The acceleration of the energetic electrons must occur deep in the chromosphere where there are sufficient solar constituents that can be ionized to produce the correlated periodic EUV radiation.     

An electric-current description of solar flares

The presently prevailing theories of solar flares rely on the hypothetical presence of magnetic flux tubes beneath the photosphere and the two subsequent hypotheses, their emergence above the photosphere and explosive magnetic reconnection, converting magnetic energy carried by the flux tubes to solar flare energy. In this paper, we discuss solar flares from an entirely different point of view, namely in terms of power supply by a dynamo process in the photosphere. By this process, electric currents flowing along the magnetic field lines are generated and the familiar ‘force-free’ fields or the ‘sheared’ magnetic fields are produced. Upward field-aligned currents thus generated are carried by downward streaming electrons; these electrons can excite hydrogen atoms in the chromosphere, causing the optical Hα flares or ‘low temperature flares’. It is thus argued that as the ‘force-free’ fields are being built up for the magnetic energy storage, a flare must already be in progress.     

How is the sun working?

I assume that at the solar core finite amplitude flows are generated by some process for which a candidate can be the planetary tides. I assume also that there are some local magnetic flux bundles at the solar core with a strength larger than 10³ G. The aim of this paper is to show that these assumptions involve an electric field generation which then produces local thermonuclear runaways which shoot up convective cells to the outer layers. Within certain conditions these primal convective cells erupt in the subphotospheric layers which phenomenon can produce high-energy particle beams which when injected into magnetic flux tubes appear as flares. I suggest these processes for solving the neutrino problem, and also to interpret the spiky character of the solar neutrino flux and the correlation of the energy production of the Sun with its atmospheric activity.     

Global Energy Transfer from Pick-up Ions to Solar Wind Protons

It has been known for years now that pick-up ions (PUIs) are produced by ionization of interstellar neutral atoms in the heliosphere and are then convected outwards with the solar wind flow as a separate suprathermal ion fluid. Only poorly known is the thermal behaviour of these pick-ups while being convected outwards. On the one hand they drive waves since their distribution function is unstable with respect to wave growth, on the other hand they also experience Fermi-2 energizations by nonlinear wave-particle interactions with convected wave turbulences. Here we will show that this complicated network of interwoven processes can quantitatively be balanced when adequate use is made of transport-kinetic results according to which pick-up ions essentially behave isothermally at their convection to large solar distances. We derive the adequate heat source necessary to maintain this pick-up ion isothermy and use the negative of that source to formulate the enthalpy flow conservation for solar wind protons (SWPs). This takes care of a consistent PUI-induced heat source guaranteeing that the net energy balance in the SWP–PUI two-fluid plasma is satisfied. With this PUI-induced heat input to SWPs we not only obtain the well-observed SWP polytropy, but we can also derive an expression for the percentage of intitial pick-up energy fed into the thermal proton energy. By a first-order evaluation of this expression we then can estimate that, dependent on the actual PUI temperature, about 40 to 50% of the initial pick-up energy is globally passed to solar protons within the inner heliosphere.     

对金斯定则的几点认识

用物理学基本定律可导出金斯经验定则,它似应称为金斯定则,该定则的速度、高度或能量等表述完全等效,可随意选用,用能量观点更容易解释此定则,满足金斯定则只是给定的粒子成为具有稠密大气的行星或卫星的主要大气成分的必要条件,该定则的适应范围可用方程或其图像表示,也能用诺模图确定,它适用于太阳系内的行星,卫星,小行星,流星体和像柯伊伯带天体与半人马族星这样的外太阳系天体,此定则现在仍有普遍的现实意义。     

The emission and propagation of ∼ 40keV solar flare electrons

Observations of prompt 40 keV solar flare electron events by the IMP series of satellites in the period August, 1966 to December, 1967 are tabulated along with prompt energetic solar proton events in the period 1964–1967. The interrelationship of the various types of energetic particle emission by the sun, including relativistic energy electrons reported by Cline and McDonald (1968) are investigated. Relativistic energy electron emission is found to occur only during proton events. The solar optical, radio and X-ray emission associated with these various energetic particle emissions as well as the propagation characteristics of each particle species are examined in order to study the particle acceleration and emission mechanisms in a solar flare. Evidence is presented for two separate particle acceleration and/or emission mechanisms, one of which produces 40 keV electrons and the other of which produces solar proton and possibly relativistic energy electrons. It is found that solar flares can be divided into three categories depending on their energetic particle emission: (1) small flares with no accompanying energetic phenomena either in particles, radio or X-ray emission; (2) small flares which produce low energy electrons and which are accompanied by type III and microwave radio bursts and energetic ( 20 keV) X-ray bursts; and (3) major solar flare eruptions characterized by energetic solar proton production and type II and IV radio bursts and accompanied by intense microwave and X-ray emission and relativistic energy electrons.