Synoptic observations of coronal transients and their interplanetary consequences

A small coronagraph has been placed in orbit to monitor the sun's outer corona from 2.5 to 10.0 solar radii, and five years of nearly continuous synoptic observations have now been completed. Rapid and sensitive image processing techniques have been developed to screen the data for transient phenomena, particularly coronal mass ejections (CMEs). About 50,000 coronal images have been examined, out of a five-year total of 68,000, and a standardized listing of more than 1,200 coronal transients for the period 1979–1982 has been prepared. These data have been analysed in the light of other available information, particularly on conditions in the interplanetary plasma. The dynamical characteristics of the active corona, as they are beginning to emerge from the data, are presented. We find that coronal mass ejections exercise significant influence on the interplanetary solar wind. They are the source of disturbances that are frequent and energetic, that tend to be somewhat focussed, that often reach shock intensity, and that propagate to large heliocentric distances, sometimes causing major geomagnetic storms.     

COSAC onboard Rosetta: a bioastronomy experiment for the short-period comet 67P/Churyumov-Gerasimenko

The COSAC (Cometary Sampling and Composition Experiment) onboard the Rosetta mission is a combined gas chromatograph (GC)-mass spectrometer (MS). It is situated on Philae, the lander of the mission, which is intended to land on the nucleus of comet 67P/Churyumov- Gerasimenko. The purpose of the experiment is to analyze the volatile fraction of soil samples retrieved by a drill. For investigation, the samples will be pyrolysed, and the emanating gases fed into a GC, into an MS, or the combination of both. In the first part of this paper, the bioastronomical relevance of such measurements is outlined. In the second part the details of the hardware and its performance are described.     

THE CLUSTER ION SPECTROMETRY (CIS) EXPERIMENT

The Cluster Ion Spectrometry (CIS) experiment is a comprehensive ionic plasma spectrometry package on-board the four Cluster spacecraft capable of obtaining full three-dimensional ion distributions with good time resolution (one spacecraft spin) with mass per charge composition determination. The requirements to cover the scientific objectives cannot be met with a single instrument. The CIS package therefore consists of two different instruments, a Hot Ion Analyser (HIA) and a time-of-flight ion COmposition and DIstribution Function analyser (CODIF), plus a sophisticated dual-processor-based instrument-control and Data-Processing System (DPS), which permits extensive on-board data-processing. Both analysers use symmetric optics resulting in continuous, uniform, and well-characterised phase space coverage. CODIF measures the distributions of the major ions (H⁺, He⁺, He⁺⁺, and O⁺) with energies from ~0 to 40 keV/e with medium (22.5°) angular resolution and two different sensitivities. HIA does not offer mass resolution but, also having two different sensitivities, increases the dynamic range, and has an angular resolution capability (5.6° × 5.6°) adequate for ion-beam and solar-wind measurements.     

Dynamics of magnetospheric ion Composition as observed by the GEOS mass spectrometer

After one year of operation the GEOS-1 Ion Composition Experiment has surveyed plasma composition at all local times in the L range 3 8 and the energy per charge range from thermal to 16 keV/e. From measurements made in the keV range during eleven magnetic storms we find that the percentage of heavy (M/Q > 1) ions present in the outer magnetosphere increases by a factor of 3 to 10 during disturbances. We conclude that two independent sources (solar wind, characterized by ⁴He²⁺, and ionosphere, characterized by O⁺) give on the average comparable contributions to injected populations, although in a single event one or the other source may dominate. However, in magnetically quiet periods protons are the dominant species with a few percent of heavy ions. With the help of special satellite manoeuvres magnetic field aligned fluxes of 0.05-3 keV/e H⁺, He⁺, O⁺ with traces of O²⁺ have been observed which may be related to ion beams found previously at lower altitudes in the auroral zone. At still lower energies ( 1 eV/e) the thermal plasma population is found to be made up of six ion species, three of which, D⁺, He²⁺ and O²⁺, were unknown in the magnetosphere prior to the GEOS-1 measurements. We present here a study of the evolution of doubly charged ions and their parent populations over four consecutive days. Various production mechanisms for doubly charged ions are discussed. We argue that ionization of singly charged ions by UV and energetic electrons and protons is the dominant process for plasmasphere production. Furthermore, the observed high concentrations of O²⁺ at high altitudes are a result of production in the upper ionosphere and plasmasphere combined with upward transport by thermal diffusion. Throughout the 1 year lifetime of GEOS-1 the ICE functioned perfectly and, because of its novel design, a short review of technical performance is included here.     

The Toroidal Imaging Mass-Angle Spectrograph (TIMAS) for the polar mission

The science objectives of the Toroidal Imaging Mass-Angle Spectrograph (TIMAS) are to investigate the transfer of solar wind energy and momentum to the magnetosphere, the interaction between the magnetosphere and the ionosphere, the transport processes that distribute plasma and energy throughout the magnetosphere, and the interactions that occur as plasma of different origins and histories mix and interact. In order to meet these objectives the TIMAS instrument measures virtually the full three-dimensional velocity distribution functions of all major magnetospheric ion species with one-half spin period time resolution. The TIMAS is a first-order double focusing (angle and energy), imaging spectrograph that simultaneously measures all mass per charge components from 1 AMU e^–1 to greater than 32 AMU e^–1 over a nearly 360° by 10° instantaneous field-of-view. Mass per charge is dispersed radially on an annular microchannel plate detector and the azimuthal position on the detector is a map of the instantaneous 360° field of view. With the rotation of the spacecraft, the TIMAS sweeps out very nearly a 4 solid angle image in a half spin period. The energy per charge range from 15 eV e^–1 to 32 keV e^–1 is covered in 28 non-contiguous steps spaced approximately logarithmically with adjacent steps separated by about 30%. Each energy step is sampled for approximately 20 ms;14 step (odd or even) energy sweeps are completed 16 times per spin. In order to handle the large volume of data within the telemetry limitations the distributions are compressed to varying degrees in angle and energy, log-count compressed and then further compressed by a lossless technique. This data processing task is supported by two SA3300 microprocessors. The voltages (up to 5 kV) for the tandem toroidal electrostatic analyzers and preacceleration sections are supplied from fixed high voltage supplies using optically controlled series-shunt regulators.     

Conception of the 'Chirality-Experiment' on ESA's mission ROSETTA to comet P46/Wirtanen.

In the last years extraterrestrial scenarios for the origin of homochirality in biological structures received considerable attention in the topical literature: Rubenstein and Bonner postulated a rapidly rotating neutron star emitting circularly polarised synchrotron radiation responsible for the first asymmetric synthesis; the group of Bailey published the observation of circular polarisation caused by Mie scattering from aligned dust grains in the Orion OMC-1 star-formation region that might provide an enantioselective effect on prochiral or racemic organic molecules. Rikken and Raupach observed a magnetochiral effect and considered extraterrestrial magnetic fields of sufficient strengths to introduce biomoleculars parity violation. With the aim to investigate these hypotheses among other theories describing the origin of biological asymmetry, our laboratory participates in the conception and development of ROSETTA's COSAC Experiment, that is designed to identify organic molecules in the cometary matter in situ. Within COSAC's 'Chirality Module' enantiomers will be separated gas chromatographically with the help of capillary columns coated with chirally active liquid films. This technique will allow the separation of specific chiral organic compounds out of the analysed cometary matter into their enantiomeric constituents. Both thermo conductivity and mass spectrometric detectors will be used to determine each enantiomer's amount and therefore the corresponding enantiomeric excesses. As a consequence of COSAC's 'Chirality-Experiment' far-reaching results are expected to investigate the various hypotheses about the first asymmetric synthesis.     

Recent results on the parameters of the interstellar helium from the ULYSSES/GAS experiment

Velocity and direction of the flow of the interstellar helium and its temperature and density have been determined from the measurements of the ULYSSES/GAS experiment for two different epochs: during the in-ecliptic path of ULYSSES, representing solar maximum conditions, and during the south to the north pole transition (11/94-6/95), close to the solar minimum conditions. Within the improved error bars the values are consistent with results published earlier.The determination of the density n of the interstellar helium at the heliospheric boundary from observations in the inner solar system requires knowledge about the loss processes experienced by the particles on their way to the observer. The simultaneous observation of the helium particles arriving on direct and indirect orbits at the observer provides a tool to directly determine the effects of the loss processes assumed to be predominantly photoionization and — for particles travelling close to the Sun — electron impact ionization by high-energy solar wind electrons.Such observations were obtained with the ULYSSES/GAS instrument in February 1995, before the spaceprobe passed its perihelion. From these measurements values for the loss rates and the interstellar density could be derived. Assuming photoionization to be the only loss process reasonable fits to the observations were obtained for an ionization rate = 1.1 · 10^–7 s^–1 and a density n 1.7 · 10^–2 cm^–3. Including, in addition, electron impact ionization, a photoionization = 0.6 · 10^–7 s^–1 was sufficient to fit both observations, resulting in a density n 1.4 · 10^–2 cm^–3.On leave from Space Research Centre, Warsaw, Poland.     

The Rosetta Lander (“Philae”) Investigations

The paper describes the Rosetta Lander named Philae and introduces its complement of scientific instruments. Philae was launched aboard the European Space Agency Rosetta spacecraft on 02 March 2004 and is expected to land and operate on the nucleus of 67P/Churyumov-Gerasimenko at a distance of about 3 AU from the Sun. Its overall mass is ~98 kg (plus the support systems remaining on the Orbiter), including its scientific payload of ~27 kg. It will operate autonomously, using the Rosetta Orbiter as a communication relay to Earth. The scientific goals of its experiments focus on elemental, isotopic, molecular and mineralogical composition of the cometary material, the characterization of physical properties of the surface and subsurface material, the large-scale structure and the magnetic and plasma environment of the nucleus. In particular, surface and sub-surface samples will be acquired and sequentially analyzed by a suite of instruments. Measurements will be performed primarily during descent and along the first five days following touch-down. Philae is designed to also operate on a long time-scale, to monitor the evolution of the nucleus properties. Philae is a very integrated project at system, science and management levels, provided by an international consortium. The Philae experiments have the potential of providing unique scientific outcomes, complementing by in situ ground truth the Rosetta Orbiter investigations. Philae team members are listed in the acknowledgements     

Unusually Distant Bow Shock Encounters at Mars: Analysis of March 24, 1989 Event

Detailed analysis of disturbances observed on 24 March, 1989 far upstream of the usual Martian bow shock position was completed with the use of the planetary obstacle and bow shock models relevant for the period of Phobos 2 observations and for low Mach numbers, respectively. It is proven that the system of discontinuities observed in the solar wind between 18:42 and 19:36 UT was the consequence of unusually distant planetary bow shock excursions. The cause was unusually small ρV ² and M _a values in the solar wind flow.