Hybrid Reconstruction to Derive 3D Height – Time Evolution for Coronal Mass Ejections

We present a hybrid combination of forward and inverse reconstruction methods using multiple observations of a coronal mass ejection (CME) to derive the three-dimensional (3D) “true” height?–?time plots for individual CME components. We apply this hybrid method to the components of the 31 December 2007 CME. This CME, observed clearly in both the STEREO A and STEREO B COR2 white-light coronagraphs, evolves asymmetrically across the 15-solar-radius field of view within a span of three hours. The method has two reconstruction steps. We fit a boundary envelope for the potential 3D CME shape using a flux-rope-type model oriented to best match the observations. Using this forward model as a constraining envelope, we then run an inverse reconstruction, solving for the simplest underlying 3D electron density distribution that can, when rendered, reproduce the observed coronagraph data frames. We produce plots for each segment to establish the 3D or “true” height?–?time plots for each center of mass as well as for the bulk CME motion, and we use these plots along with our derived density profiles to estimate the CME’s asymmetric expansion rate.     

“Real-time” evolution in Mira variables

After a brief review of our current understanding of Miras and their evolutionary status, three aspects of “real-time” evolution in these and related stars are examined: (i) Chemical changes (O-rich to C-rich) due to third dredge-up. (ii) Period changes due to the effects of the helium-shell flash. (iii) The existence of “fossil” dust and gas shells. Studies of resolved gas and dust shells are highlighted as particularly interesting. They will enable us to examine the mass-loss histories of many late-type stars over the last ten thousand years or so. Such observations have only recently become technically feasible and they are expected to provide important new insights into the late stages of stellar evolution.     

Submillimeter observations of the asteroid 10 hygiea

We report the first successful ground-based observations of any asteroid at submillimeter wave-lengths. Observations of the asteroid 10 Hygiea at 370 and 770 μm are combined with observations in the near and thermal infrared (2.2, 10.6, and 21 μm) to study the thermal properties of Hygiea's regolith. The “standard” (nonrotating) thermal model is consistent with the entire data set, although a rotating thermophysical model with a “lunarlike” thermal inertia cannot be ruled out.     

The Chemical Diversity of Comets: Synergies Between Space Exploration and Ground-based Radio Observations

A fundamental question in cometary science is whether the different dynamical classes of comets have different chemical compositions, which would reflect different initial conditions. From the ground or Earth orbit, radio and infrared spectroscopic observations of a now significant sample of comets indeed reveal deep differences in the relative abundances of cometary ices. However, no obvious correlation with dynamical classes is found. Further results come, or are expected, from space exploration. Such investigations, by nature limited to a small number of objects, are unfortunately focussed on short-period comets (mainly Jupiter-family). But these in situ studies provide “ground truth” for remote sensing. We discuss the chemical differences in comets from our database of spectroscopic radio observations, which has been recently enriched by several Jupiter-family and Halley-type comets.     

A refined “standard” thermal model for asteroids based on observations of 1 Ceres and 2 Pallas

We present ground-based thermal infrared observations of asteroids 1 Ceres and 2 Pallas made over a period of 2 years. By analysing these data in light of the recently determined occultation diameter of Ceres (933–945 km) and Pallas (538 km) and their known small-amplitude lightcurves, we have determined a new value for the infrared beaming parameter used in the “standard” thermal emission model for asteroids. The new value is significantly lower than that previously used, and when applied in the reduction of thermal infrared observations of other asteroids, should yield model diameters that are closer to actual diameters. In our formulation, we also incorporate the recently adopted IAU magnitude convention for asteroids, which uses the zero-phase magnitudes (including the opposition effect) the same as is used for satellites.     

From the Arrow of Time to the Arrow of Life

Astrobiology, like many (but not all) sciences, must take into account questions of the “Why?”, “Where?”, “How?” and “When?” type. In this introductory chapter, we explain why, in this book, we will only consider two of these questions that are, moreover, deeply interrelated. Chronology is by definition related to the “when?” question but as soon as we are interested in the history of Earth or the history of life, it is impossible to treat these questions and their answers without explicit references to the “how?” questions. We also present in this chapter the genesis and the aim of the book.     

ON THE FUTURE PROSPECTS OF METEOR DETECTIONS (INVITED REVIEW)

The successful application of modern observing techniques for Leonid storm observations show that meteor (shower) detections will have a bright future if the field will pursue difficult but important questions. How to forecast a satellite threatening meteor storm? What happens to the organic matter in meteors and can this be an important source of prebiotic molecules? What range of variations in composition and morphology exists among cometary grains and what does this tell us about the origin of the solar system? What long-period comets approach Earth orbit and can meteoroid streams provide early warning for giant impacts? What are the sources of interstellar and interplanetary grains? Just to mention a few. To answer these questions will need new technologies and facilities, some of which are being developed for other use. This may include NASA’s Stratospheric Observatory For Infrared and sub-millimeter Astronomy (SOFIA). In addition, big-science space missions can drive the field if meteor detections are an integral part. Special events, such as meteor outbursts and the “artificial meteor” from the reentry of sample return capsules from interplanetary space, can mobilize observing and theoretical efforts. These and other future opportunities are briefly discussed.     

Estimating the Parameters of Collisions between Fractal Dust Clusters in a Gas–Dust Protoplanetary Disk

Studying the origin and evolution of the Solar system is among the fundamental problems of modern natural science. This problem is interdisciplinary and requires the development of mathematical models for the physical structure and evolution of a gas–dust accretion disk from the initial stages of its formation to the formation of a planetary system. One of the key problems is the formation and growth of bodies in a protoplanetary disk, the basis for which is a study of the collisional processes of the solidbody component. We have performed a parametric analysis of the cluster–cluster collision processes occurring in a protoplanetary disk within the model of permeable particles being developed by us. The outcome of such collisions is shown to be affected significantly by the topological properties of colliding dust clusters with a fractal internal structure. The results of our parametric analysis show that for sufficiently “dense” fractal dust clusters, at low relative collision velocities, there exists a range in which the colliding clusters bounce. At the same time, for “porous” fractal clusters the bounce is impossible for any sets of collision parameters. As the relative collision velocities increase, the cluster coalescence processes begin to dominate due to a rearrangement of the fractal structure in the contact zone. However, as the kinetic energy of collisions increases further, a critical threshold is reached beyond which the collision energy exceeds the particle binding energy in clusters and the fractal dust cluster destruction processes are switched on during collisions. Thus, our parametric analysis imposes quite definite constraints on the dynamics and chronology of the evolution processes during the formation of primordial solid bodies and planetesimals. The proposed approach and the results obtained are fairly realistic and open prospects for more comprehensive model studies of the initial evolutionary phase of a protoplanetary disk.     

Measuring the Magnetic-Field Strength of the Quiet Solar Corona Using “EIT Waves”

Variations in the propagation of globally propagating disturbances (commonly called “EIT waves”) through the low solar corona offer a unique opportunity to probe the plasma parameters of the solar atmosphere. Here, high-cadence observations of two “EIT wave” events taken using the Atmospheric Imaging Assembly (AIA) instrument onboard the Solar Dynamics Observatory (SDO) are combined with spectroscopic measurements from the Extreme ultraviolet Imaging Spectrometer (EIS) onboard the Hinode spacecraft and used to examine the variability of the quiet coronal magnetic-field strength. The combination of pulse kinematics from SDO/AIA and plasma density from Hinode/EIS is used to show that the magnetic-field strength is in the range ≈?2?–?6 G in the quiet corona. The magnetic-field estimates are then used to determine the height of the pulse, allowing a direct comparison with theoretical values obtained from magnetic-field measurements from the Helioseismic and Magnetic Imager (HMI) onboard SDO using global-scale PFSS and local-scale extrapolations. While local-scale extrapolations predict heights inconsistent with prior measurements, the agreement between observations and the PFSS model indicates that “EIT waves” are a global phenomenon influenced by global-scale magnetic field.     

Spatial Distribution of Solar Energetic Particles in the Inner Heliosphere

We study the spatial distribution of solar energetic particles (SEPs) throughout the inner heliosphere during six large SEP events from the period 1977 through 1979, as deduced from observations on the Helios 1 and 2, IMP 7 and 8, ISEE 3, and Voyager 1 and 2 spacecraft. Evidence of intensity maxima associated with the expanding shock wave is commonly seen along its central and western flanks, although the region of peak acceleration or “nose” of the shock is sometimes highly localized in longitude. In one event (1 January 1978) a sharp peak in 20?–?30 MeV proton intensities is seen more strongly by Voyager at ～?2 AU than it is by spacecraft at nearby longitudes at ～?1 AU. Large spatial regions, or “reservoirs,” often exist behind the shocks with spatially uniform SEP intensities and invariant spectra that decrease adiabatically with time as their containment volume expands. Reservoirs are seen to sweep past 0.3 AU and can extend out many AU. Boundaries of the reservoirs can vary with time and with particle velocity, rather than rigidity. In one case, a second shock wave from the Sun reaccelerates protons that retain the same hard spectrum as protons in the reservoir from the preceding SEP event. Thus reservoirs can provide not only seed particles but also a “seed spectrum” with a spectral shape that is unchanged by a weaker second shock.     

Radial velocity and line-profile variations in the sdBV star PG 1325+101

Historically, any newly discovered object needed to be “confirmed” with optical observations. Catalogs were published, such as the PKS (Parkes Catalog), with stamp-sized photographs that allowed us to “see” what was just found. This is still somewhat true, although far less than in the past. We are probably reaching an information overload with more efficient instruments, larger detectors, multiple wavelength coverage and an increasing number of ground and space-based facilities. At the same time, information technology is catching up and is allowing us to use the data regardless of where they reside. An increasing need of multi-wavelength observations to understand the underlying physics of the observed phenomena and the challenge to mine petabyte databases is leading to a federation of archives and cooperation among computer scientists and astronomers. These are the seeds of a virtual observatory, a cyberspace entity where the data are ready to be found and analyzed. In the United States, the National Science Foundation (NSF) and the National Aeronautics and Space Administration (NASA) are funding initiatives that will lead to the creation of this entity. This paper describes these projects.     

UVES Abundances of Stars in Nearby Dwarf Spheroidal Galaxies

It is a truth universally acknowledged, that a galaxy in possession of a good quantity of gas must want to form stars. It is the details of how and why that baffle us all. The simplest theories either would have this process a carefully self-regulated affair, or one that goes completely out of control and is capable of wrecking the galaxy which hosts it. Of course the majority of galaxies seem to amble along somewhere between these two extremes, and the mean properties tend to favour a quiescent self-regulated evolutionary scenario. But there area variety of observations which require us to invoke transitory ‘bursts’ of star-formation at one time or another in most galaxy types. Several nearby dwarf spheroidal galaxies have clearly determined star-formation histories with apparent periods of zero star formation followed by periods of fairly active star formation. If we are able to understand what separated these bursts we would understand several important phenomena in galaxy evolution. Were these galaxies able to clear out their gas reservoir in a burst of star formation? How did this gas return? or did it? Have these galaxies receieved gas from the IGM instead? Could stars from these types of galaxy contribute significantly to the halo population in our Galaxy? To answer these questions we need to combine accurate stellar photometry and Colour-Magnitude Diagram interpretation with detailed metal abundances to combine a star-formation rate versus time with a range of element abundances with time. Different elements trace different evolutionary process (e.g., relative contributions of type I and II supernovae). We often aren't even sure of the abundance spread in these galaxies. We have collected detailed high resolution UVES spectra of four nearby dwarf spheroidal galaxies (Sculptor, Fornax, Leo I &; Carina) to begin to answer these questions. This is a precursor study to a more complete study with FLAMES. We presented at this meeting the initial results for the Sculptor and Fornax dwarf spheroidal galaxies which have been previously had single element (low resolution) calcium abundance studies (Tolstoy et al., 2001). See Figures 1 and 2.     

Architectures for science: Intelligent agent technology

I review the current architecture of the HTN and make three suggestions for the future. (i) We should retain the expertise split between agents which deal with the science programmes and those which deal with telescope constraints. This makes it easy to add new programmes or new telescopes. (ii) We should develop “look ahead” schedulers which attempt to schedule a whole night at once. This will give reliable calculations for the chance an observation will be carried out, and give a better chance that high priority time critical observations are successfully scheduled. (iii)We should strive to attract more science programmes to the HTN, in particular time critical observations spread over many nights, and non‐time critical work which can benefit from access to databases and the literature. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Long-term oscillations of sunspots and a special class of artifacts in SOHO/MDI and SDO/HMI data

A specific type of artifacts (named as “p2p”), that originate due to displacement of the image of a moving object along the digital (pixel) matrix of receiver are analyzed in detail. The criteria of appearance and the influence of these artifacts on the study of long-term oscillations of sunspots are deduced. The obtained criteria suggest us methods for reduction or even elimination of these artifacts. It is shown that the use of integral parameters can be very effective against the “p2p” artifact distortions. The simultaneous observations of sunspot magnetic field and ultraviolet intensity of the umbra have given the same periods for the long-term oscillations. In this way the real physical nature of the oscillatory process, which is independent of the artifacts have been confirmed again. A number of examples considered here confirm the dependence between the periods of main mode of the sunspot magnetic field long-term oscillations and its strength. The dependence was derived earlier from both the observations and the theoretical model of the shallow sunspot. The anti-phase behavior of time variations of sunspot umbra area and magnetic field of the sunspot demonstrates that the umbra of sunspot moves in long-term oscillations as a whole: all its points oscillate with the same phase.     

Multiverses of the past

More than 2000 years ago, Epicurus taught that there are an infinite number of other worlds, both like and unlike ours, and Aristotle taught that there are none. Neither hypothesis can currently be falsified, and some versions of current multiverses perhaps never can be, which has contributed to occasional claims that “this isn't science!” (a common complaint about cosmology for centuries). Define “cosmos”, or “world”, or “universe” to mean the largest structure of which you and the majority of knowledgeable contemporaries will admit to being a part. This begins with the small, earth‐centered worlds of ancient Egyptian paintings, Greek mythology, and Genesis, which a god could circumnavigate in a day and humans in a generation. These tend to expand and become helio‐rather than geo‐centric (not quite monotonically in time) and are succeeded by various assemblages of sun‐like stars with planets of their own. Finite vs. infinite assemblages are debated and then the issue of whether the Milky Way is unique (so that “island universes” made sense, even if you were against the idea) for a couple of centuries. Today one thinks as a rule of the entire 4‐dimensional space‐time we might in principle communicate with and all its contents. Beyond are the modern multi‐verses, sequential (cyclic or oscillating), hierarchical, or non‐communicating entities in more than four dimensions. Each of these has older analogues, and, in every milieu where the ideas have been discussed, there have been firm supporters and firm opponents, some of whose ideas are explored here. Because astronomical observations have firmly settled some earlier disputes in favor of very many galaxies and very many stars with planets, “other worlds” can now refer only to other planets like Earth or to other universes. The focus is on the latter (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Scheduling the EChO survey with known exoplanets

The Exoplanet Characterization Observatory (EChO) is a concept of a dedicated space telescope optimized for low-resolution transit and occultation spectroscopy to study the exoplanet diversity through the composition of their atmospheres. The scope of this paper is to answer the following question: Can we schedule a nominal EChO mission, with targets known today (in mid 2013), given the science requirements, realistic performances and operational constraints? We examine this issue from the point of view of duration of the mission and the scheduling restrictions with a sample of exoplanet systems known nowadays. We choose different scheduling algorithms taking into account the science and operational constraints and we verified that it is fairly straightforward to schedule a mission scenario over the lifetime of EChO compliant with the science requirements. We identified agility as a critical constraint that reduces significantly the efficiency of the survey. We conclude that even with known targets today the EChO science objectives can be reached in the 4.5 years duration of the mission. We also show that it is possible to use gaps between exoplanet observations, to fit the required calibration observations, data downlinks and station keeping operations or even to observe more exoplanet targets to be discovered in the coming years.     

Photometric Calibration of the LASCO-C2 Coronagraph over 14 Years (1996 – 2009)

We present a photometric calibration of the SOHO/LASCO-C2 coronagraph based on the analysis of all stars down to magnitude V=8 that transited its field of view during the past 14 years of operation (1996?–?2009), extending the previous work of Llebaria, Lamy, and Danjard (Icarus 182, 281, 2006). The pre-processing of the images incorporates the most recent determination of the evolution of the LASCO-C2 performances. The automatic procedure then analyzes some 260?000 images to detect, locate, and measure those stars. Aperture photometry is performed using four different aperture sizes, and the zero points (ZPs) of the photometric transformations between the LASCO-C2 magnitudes for its orange filter and the standard V magnitudes are determined after introducing a correction for the color of the stars. A new statistical method (“bootstrap”) is introduced to assess the confidence intervals of the mean yearly value of the ZPs. The correction for finite aperture required to derive the calibration coefficient for the surface photometry of extended sources is based on the reconstructed image of bright saturated stars and a robust model for the growth curve. The global temporal evolution of the sensitivity of LASCO-C2 is compatible with a continuous decrease at a rate of ≈?0.56 % per year. However, it is better described by two separate linear variations with a discontinuity at the time of the loss of SOHO. After the resumption of normal operations in 1999, the linear decrease of the sensitivity amounts to ≈?0.35 % per year.     

CME Projection Effects Studied with STEREO/COR and SOHO/LASCO

Based on a set of 11 CME events we study the impact of projection effects by tracking CME leading edge features in the plane of sky (traditional CME tracking) from combined STEREO-SECCHI and SOHO-LASCO observations up to 20R _⊙. By using CME observations from two vantage points and applying triangulation techniques, the source region location of the CME on the solar surface was determined (heliospheric longitude and latitude) to correct for projection effects. With this information, the directivity and “true” speed of a CME can be estimated in a simple way. The comparison of the results obtained from the spacecraft pairs SOHO-LASCO/STEREO-A and SOHO-LASCO/STEREO-B allows us to study the reliability of the method. The determined CME source region is generally coincident within ?10°.     

Orbit determination of satellite “Tance 1” with VLBI data

The satellite “Tance 1” of the “Double-Star Program” is the first truly scientific experimentation satellite of China. Its orbit is the farthest so far launched in China, with a geocentric apogee reaching 78 thousand kilometers. The tracking of “Tance 1” and of more distant space targets, such as the lunar exploration craft, can be realized with the VLBI technique of radio astronomy. In order to test and verify the role which the VLBI technique plays in the lunar exploration program of China, Shanghai Astronomical Observatory organized the only 3 tracking stations in China (located at Shanghai, Urumqi and Kunming), to carry out test tracking of “Tance 1,” and used the time delay data obtained to determine the orbit of “Tance 1” over a two-day period, so providing a preliminary assessment of the possibility of VLBI orbit determination. The fitting error of the orbit so obtained is about 5.5 m in the time delay and about 2 cm/s in the delay rate (this for checking only), much better than is provided by the preliminary orbit (used merely for ensuring tracking) in which the corresponding figures are around 2 km and 15 cm/s. Further, if the orbit is determined by using both the time delay and time delay rate data (with weights according to their internal accuracies), then the residuals are 5.5 m in the time delay and 2 cm/s in the delay rate. For an appreciation of the true accuracy of the VLBI orbit determination, we used simulation data (of the observed two-day VLBI data) and found the results depended greatly on the error in the dynamic model of the satellite which, however, is difficult to assess, while the formal residuals are of the order of 1 kin in the delay and of cm/s in the delay rate. The simulation computation also indicates that a joint determination using both VLBI and USB data will have an improved accuracy.     

Intricacies of the fine structure of the eclipse corona

The inner white-light corona (up to 2 solar radii) can only be observed during total solar eclipses. New mathematical methods of the corona image processing and digital photo cameras or CCD cameras allow us to detect very faint structures (of a few arcseconds) in this part of the corona, even from images taken with relatively small telescopes (1–2 meters in the focal length). In the present paper we will discuss such structures as observed during the last few solar eclipses, mainly those of 2001 and 2006. Obtained results show that the white-light corona is highly structured not only in the sense of a variety of different types of its classical “objects”, e.g., polar plumes, helmet streamers, threadlike streamers, etc, but also within these objects themselves. Voids, loops, radial and non-radial threads, and other yet-undefined dark structures (“empty space”?) are well visible especially inside helmet streamers. This strongly indicates that the classical picture of the corona characterized by a hydrostatic distribution of density and temperature is no longer a sufficient assumption. It is magnetic forces that play a dominant role in shaping and structuring this part the corona. Given a remarkable similarity between the EUV corona as observed by SOHO and the white-light corona observed by us during the above-mentioned eclipses up to two solar radii. We suggest that the “missing” observations of the white-light corona should be replaced by those of the EUV one. Moreover, the last eclipse’s observations also indicate that the knots of some prominences extend well into the white-light corona. So, the next total eclipses of the Sun, of 1 August 2008 and 22 July 2009, offer an excellent opportunity for preparing joint observations for space-borne and ground-based eclipse teams.