The Evolving Sigmoid: Evidence for Magnetic Flux Ropes in the Corona Before, During, and After CMES

It is generally accepted that the energy that drives coronal mass ejections (CMEs) is magnetic in origin. Sheared and twisted coronal fields can store free magnetic energy which ultimately is released in the CME. We explore the possibility of the specific magnetic configuration of a magnetic flux rope of field lines that twist about an axial field line. The flux rope model predicts coronal observables, including heating along forward or inverse S-shaped, or sigmoid, topological surfaces. Therefore, studying the observed evolution of such sigmoids prior to, during, and after the CME gives us crucial insight into the physics of coronal storage and release of magnetic energy. In particular, we consider (1) soft-X-ray sigmoids, both transient and persistent; (2) The formation of a current sheet and cusp-shaped post-flare loops below the CME; (3) Reappearance of sigmoids after CMEs; (4) Partially erupting filaments; (5) Magnetic cloud observations of filament material.     

Mathematical modeling of heat transfer process in a variable domain

In this paper, a brief review and generalization of studies on the heat transfer and heat conduction problem in a variable domain are presented. The equations of the process, where the boundary displacement velocity is the control, are obtained taking into account heat inflow. This article was submitted by the authors in English.     

Chemical Composition of Rocks and Soils at the Pathfinder Site

As Viking Landers did not measure rock compositions, Pathfinder (PF) data are the first in this respect. This review gives no proof yet whether the PF rocks are igneous or sedimentary, but for petrogenetic reasons they could be igneous. We suggest a model in which Mars is covered by about 50% basaltic and 50% andesitic igneous rocks. The soils are a mixture of the two with addition of Mg-sulfate and -chloride plus iron compounds possibly derived from the hematite deposits.     

The local interstellar medium viewed through pickup ions, recent results and future perspectives

Over the last 10 years the experimental basis for the study of the very local interstellar medium (VLISM) has been substantially broadened by the direct detection of pickup ions and of neutral helium. The strength of these methods lies in the local measurement of the particles. By scanning the gravitational focusing cone of the interstellar wind, a consistent set of interstellar helium parameters, neutral density, temperature and relative velocity, has been derived. However, the accuracy of these parameters is still hampered by uncertainties in some of the crucial ionization rates and in the pickup ion transport. Recent observations have shown that the scattering mean free path of pickup ions is comparable with the large scale variation of the interplanetary magnetic field (IMF) in the inner heliosphere. This requires a substantial modification in the modeling of the ion distribution and more detailed measurements, tasks that can be addressed in the near future.     

Energetic Hydrogen and Oxygen Atoms Observed on the Nightside of Mars

We present measurements of energetic hydrogen and oxygen atoms (ENAs) on the nightside of Mars detected by the neutral particle detector (NPD) of ASPERA-3 on Mars Express. We focus on the observations for which the field-of-view of NPD was directed at the nightside of Mars or at the region around the limb, thus monitoring the flow of ENAs towards the nightside of the planet. We derive energy spectra and total fluxes, and have compiled maps of hydrogen ENA outflow. The hydrogen ENA intensities reach 10⁵ cm⁻² sr⁻¹ s⁻¹, but no oxygen ENA signals above the detection threshold of 10⁴ cm⁻² sr⁻¹ s⁻¹ are observed. These intensities are considerably lower than most theoretical predictions. We explain the discrepancy as due to an overestimation of the charge-exchange processes in the models for which too high an exospheric density was assumed. Recent UV limb emission measurements (Galli et al., this issue) point to a hydrogen exobase density of 10¹⁰ m⁻³ and a very hot hydrogen component, whereas the models were based on a hydrogen exobase density of 10¹² m⁻³ and a temperature of 200 K predicted by Krasnopolsky and Gladstone (1996). Finally, we estimate the global atmospheric loss rate of hydrogen and oxygen due to the production of ENAs.     

Comet Knudsen Layers

This paper reviews some important results about Knudsen layers obtained in theoretical gas kinetics research in the last few decades, focusing on the weak and strong evaporation problems in two-surface, half-space, and spherical geometries. Furthermore, the application of such results in cometary science is reviewed. In order to illustrate some properties of the half-space evaporation problem for water ice surfaces at temperatures relevant for active comets, a number of numerical Direct Simulation Monte Carlo calculations are presented.     

Aerosols within the world climate research programme

Based on the findings of the meeting of JSC experts on “Aerosol and Climate” (Geneva, 27–31 October 1980) the general research strategy consisting of three phases will be presented. The three phases are: Phase I: Sensitivity tests with available models Phase II: Improvement of climate models and data bases Phase III: Development of advanced climate models with internal aerosol generation and regulation processes. COSPAR's role within this research strategy is outlined.     

Properties of the neutral density and composition in the thermosphere

Measurements of the density and composition of the thermosphere between 150 and 500 km, which were obtained by the S3-1 satellite, have been compared with the Jacchia and MSIS models. The measurements of the densities of O, N₂, N and Ar show some differences from the current models which should be considered during the preparation of the next CIRA model. The Ar measurements are particularly useful in examining the response of the neutral atmosphere to geomagnetic heating. These results are useful in establishing the appropriate lower boundary conditions for modeling of the thermosphere.