Publication archive

Publication archive

Observations of a Flux Transfer Event (FTE) signature at the dayside magnetopause are reported, which was consecutively observed on 4 January 2005 by both the Double Star/TC1 spacecraft and the Cluster quartet, while the spacecraft were traversing through the northern-dusk magnetopause. The event occurred as a magnetosheath FTE first at the Cluster spacecraft at about 07:13 UT on 4 January 2005 and crossed each of the others within 2 minutes. The spatial separations between the Cluster spacecraft were of the order of 200 km. The TC1 signature occurred about 108s after Cluster. All findings including magnetic fluxes, orientations and hot ion velocity distributions strongly suggest that Cluster and TC1 encountered the magnetosheath branch of the same flux tube at two different positions along its length and this is borne out by computation of the expected time delay. Four-spacecraft timing is used to obtain the velocity of FTE.
Published: 08 February 2007
Fifty-three substorms measured by Double Star/TC-1 in the near-Earth magnetotail from July to October, 2004 are studied. The main features of these events are: (a) Magnetic flux pileup characterized by continuous enhancement of Bz is observed, which starts almost simultaneously with aurora breakup within 1-3 minutes, indicating that substorm onset is in close relation to flux pileup. (b) Sudden plasma sheet expansion with sharp increases in ion temperature and density is seen in all events, which occurs typically ~11 minutes after the beginning of pileup. The plasma sheet expansion is shown to be in close relation with the primary substorm dipolarization and, hence, can be referred to as 'dipolarization-associated expansion'. (c) Evidence indicates that the substorm current wedge first forms earthward of TC-1 position and, hence, inward of the flow braking region, and then propagates tailward with an expansion in the Z-direction. Possible implications of these observations are briefly discussed.
Published: 03 February 2007
This article presents the fascinating ideas of Albert Einstein for a larger audience, not just in Bern, but in many stations all over the world and highlights some of the traces he continues to leave in our daily life.

This article is based on a multimedia presentation prepared by Rudolf von Steiger, Professor at the University of Bern and Director of the International Space Science Institute together with Thomas H. Zurbuchen, Associate Professor at the University of Michigan.
Published: 01 February 2007
We present space- and ground-based observations of the signatures of magnetic reconnection during an interval of duskward-oriented interplanetary magnetic field on 25 March 2004. In situ field and plasma measurements are drawn from the Double Star and Cluster satellites during traversals of the pre-noon sector dayside magnetopause at low and high latitudes, respectively. These reveal the typical signatures of flux transfer events (FTEs), namely bipolar perturbations in the magnetic field component normal to the local magnetopause, enhancements in the local magnetic field strength and mixing of magnetospheric and magnetosheath plasmas. Further evidence of magnetic reconnection is inferred from the ground-based signatures of pulsed ionospheric flow observed over an extended interval. In order to ascertain the location of the reconnection site responsible for the FTEs, a simple model of open flux tube motion over the surface of the magnetopause is employed. A comparison of the modelled and observed motion of open flux tubes (i.e. FTEs) and plasma flow in the magnetopause boundary layer indicates that the FTEs observed at both low and high latitudes were consistence with the existence of a tilted X-line passing through the sub-solar region, as suggested by the component reconnection paradigm. While a high latitude X-line (as predicted by the anti-parallel description of reconnection) may have been present, we find it unlikely that it could have been responsible for the FTEs observed in the pre-noon sector under the observed IMF conditions. Finally, we note that throughout the interval, the magnetosphere was bathed in ULF oscillations within the solar wind electric field. -- abstract truncated --
Published: 01 February 2007
Using Cluster multipoint magnetic and plasma measurements we analyze the spatial structure of plasma flow-associated turbulence on 26 September 2005. The fortunate relative configuration of the spacecraft and the plasma flow allowed for the first time to compare the scale evolution of statistical moments both at the boundary and in the central part of the flow at the same time. The simultaneous increase of skewness and kurtosis at the boundary of the plasma flow over the time scale of seconds provides evidence for the existence of nonlocal coupling in flow-associated turbulence in the Earth's plasma sheet.
Published: 01 February 2007
During the last 30 years, several magnetospheric missions have recorded the presence of narrow proton structures in the ring current region. These structures have been referred as "nose-like" structures, due to their appearance when represented in energy-time spectrograms, characterized by a flux value increase for a narrow energy range. Cluster's polar orbit, with a 4 RE perigee, samples the ring current region. The ion distribution functions obtained in-situ by the CIS experiment (for energies of ~5 eV/q to 40 keV/q) reveal the simultaneous presence of several (up to 3) narrow nose-like structures. A statistical study (over one year and a half of CIS data) reveals that double nose structures are preferentially observed in the post-midnight sector. Also, the characteristic energy of the nose (the one observed at the lower energy range when several noses occur simultaneously) reveals a clear MLT dependence during quiet events (Kp<2): a sharp transition in the energy range occurs in the pre-noon sector. Moreover, the multi-nose structures (up to 3 simultaneous noses) appear regardless of the magnetospheric activity level and/or the MLT sector crossed by the spacecraft. Numerical simulations of particles trajectories, using large-scale electric and magnetic field models are also presented. Most of the features have been accurately reproduced (namely the single and double noses), but the triple noses cannot be produced under these conditions and require to consider a more complex electric field model.
Published: 01 February 2007
We have used vector measurements of the electron drift velocity made by the Electron Drift Instrument (EDI) on Cluster between February 2001 and March 2006 to derive statistical maps of the high-latitude plasma convection. The EDI measurements, obtained at geocentric distances between ~4 and ~20 RE over both hemispheres, are mapped into the polar ionosphere, and sorted according to the clock-angle of the interplanetary magnetic field (IMF), measured at ACE and propagated to Earth, using best estimates of the orientation of the IMF variations. Only intervals of stable IMF are used, based on the magnitude of a "bias-vector" constructed from 30-min averages. The resulting data set consists of a total of 5862 h of EDI data. Contour maps of the electric potential in the polar ionosphere are subsequently derived from the mapped and averaged ionospheric drift vectors. Comparison with published statistical results based on Super Dual Auroral Radar Network (SuperDARN) radar and low-altitude satellite measurements shows excellent agreement between the average convection patterns, and in particular the lack of mirror-symmetry between the effects of positive and negative IMF By, the appearance of a duskward flow component for strongly southward IMF, and the general weakening of the average flows and potentials for northerly IMF directions. This agreement lends credence to the validity of the assumption underlying the mapping of the EDI data, namely that magnetic field lines are equipotentials. For strongly northward IMF the mapped EDI data show the clear emergence of two counter-rotating lobe cells with a channel of sunward flow between them. The total potential drops across the polar caps obtained from the mapped EDI data are intermediate between the radar and the low-altitude satellite results.
Published: 01 February 2007
The STAFF-SC observations complemented by the data from other instruments on Cluster spacecraft were used to study the main properties of magnetospheric lion roars: sporadic bursts of whistler emissions at f~0.1-0.2fe where fe is the electron gyrofrequency. Magnetospheric lion roars are shown to be similar to the emissions in the magnetosheath while the conditions for their generation are much less favorable: the growth rate of the cyclotron temperature anisotropy instability is much smaller due to a smaller number of the resonant electrons. This implies a nonlinear mechanism of generation of the observed wave emissions. It is shown that the observed whistler turbulence, in reality, consists of many nearly monochromatic wave packets. It is suggested that these structures are nonlinear Gendrin's whistler solitary waves. Properties of these waves are widely discussed. Since the group velocity of Gendrin's waves is aligned with the magnetic field, these well guided wave packets can propagate through many magnetic "bottles" associated with mirror structures, without being trapped.
Published: 01 February 2007
We present space- and ground-based observations of the signatures of magnetic reconnection during an interval of duskward-oriented interplanetary magnetic field on 25 March 2004. In situ field and plasma measurements are drawn from the Double Star and Cluster satellites during traversals of the pre-noon sector dayside magnetopause at low and high latitudes, respectively. These reveal the typical signatures of flux transfer events (FTEs), namely bipolar perturbations in the magnetic field component normal to the local magnetopause, enhancements in the local magnetic field strength and mixing of magnetospheric and magnetosheath plasmas. Further evidence of magnetic reconnection is inferred from the ground-based signatures of pulsed ionospheric flow observed over an extended interval. In order to ascertain the location of the reconnection site responsible for the FTEs, a simple model of open flux tube motion over the surface of the magnetopause is employed. A comparison of the modelled and observed motion of open flux tubes (i.e. FTEs) and plasma flow in the magnetopause boundary layer indicates that the FTEs observed at both low and high latitudes were consistence with the existence of a tilted X-line passing through the sub-solar region, as suggested by the component reconnection paradigm. While a high latitude X-line (as predicted by the anti-parallel description of reconnection) may have been present, we find it unlikely that it could have been responsible for the FTEs observed in the pre-noon sector under the observed IMF conditions. Finally, we note that throughout the interval, the magnetosphere was bathed in ULF oscillations within the solar wind electric field.
--- abstract truncated ---
Published: 01 February 2007
The project science team has revisited the science case for LISA Pathfinder and produced this document on the scientific and technological goals of the mission. Abstract: LISA Pathfinder is an experiment to demonstrate Einstein's geodesic motion in space more than two orders of magnitude better than any past, present, or planned experiment, except for LISA. The concept that a particle falling under the influence of gravity alone follows a geodesic in spacetime is at the foundation of general relativity, our best model of gravitation, yet. LISA Pathfinder's experiment concept is to prove geodesic motion by tracking two test-masses nominally in free-fall through laser interferometry with picometre distance resolution. LISA Pathfinder will show that the relative parasitic acceleration between the masses, at frequencies around 1 mHz, is at least two orders of magnitude smaller than the value demonstrated so far or to be demonstrated by any planned mission. LISA Pathfinder hardware has been designed to be transferred directly to LISA. However, it is obvious that many other possibilities are opened by the results of LISA Pathfinder. LISA Pathfinder is a mission both in general relativity and in precision metrology and will open the ground for an entirely new generation of missions not just in general relativity, but in fundamental physics at large and in Earth observation.
Published: 23 January 2007
We report strong repeated magnetic reconnection pulses that occurred deep inside closed plasma sheet flux tubes at r <= 14Re. They have been observed with a fortuitous spacecraft constellation during three consecutive turbulent magnetic dipolarizations, accompanied by localized auroral brightenings near the equatorward edge of a wide auroral oval. The reconnection separatrix was mapped to ~64° CGLat in the ionosphere, where a very energetic and narrow energy-dispersed ion injection with unusually steep dispersion slope was observed. Reconstruction of the reconnection rate from magnetic waveforms at Cluster provided a reconnection pulse duration (~1 min) and peak strength (ER ~ 8 mV/m) consistent with direct observations in the reconnection outflow region. The magnetic activity was rather weak, although the concurrent solar wind flow pressure was above the norm. We suggest that near-Earth reconnection events may be a phenomenon more frequent than generally thought. We also confirm that reconnection and the growth of strong turbulence in the near tail are strongly coupled together in near-Earth reconnection events.
Published: 20 January 2007
We report strong repeated magnetic reconnection pulses that occurred deep inside closed plasma sheet flux tubes at r <= 14Re. They have been observed with a fortuitous spacecraft constellation during three consecutive turbulent magnetic dipolarizations, accompanied by localized auroral brightenings near the equatorward edge of a wide auroral oval. The reconnection separatrix was mapped to ~64° CGLat in the ionosphere, where a very energetic and narrow energy-dispersed ion injection with unusually steep dispersion slope was observed. Reconstruction of the reconnection rate from magnetic waveforms at Cluster provided a reconnection pulse duration (~1 min) and peak strength (ER ~ 8 mV/m) consistent with direct observations in the reconnection outflow region. The magnetic activity was rather weak, although the concurrent solar wind flow pressure was above the norm. We suggest that near-Earth reconnection events may be a phenomenon more frequent than generally thought. We also confirm that reconnection and the growth of strong turbulence in the near tail are strongly coupled together in near-Earth reconnection events.
Published: 20 January 2007
Over the last few years, due to a diminishing purchasing power and difficulties in increasing the available budget, cost effectiveness has become a great concern within ESA. Indeed, missions cost have noticeably increased (especially for science missions) and many initiatives have been undertaken to control and limit the expenditure by streamlining processes and resources, especially in order to implement a mission within a more restrictive budget.

In addition, the scientific community requirements are more and more challenging: demanding mission objectives lead to more complex mission concepts. Moreover, a quicker response time from approval to launch would be desirable, whilst keeping a very high overall level of reliability.

The main objective of this study is to review the application of recurring service modules as a potential answer to the challenges listed above.

Published: 19 January 2007
CDF Study Report: CDF-46(A)

The ESA Concurrent Design Facility (CDF) was requested and financed by ESA/ESTEC/SCIAM to carry out a feasibility study for an optical-near-infrared wide field imager (WFI). Such a mission would search for Type Ia supernovae over a given redshift range with optical and near infrared wavelength coverage. The overall aim of the mission would be to use supernova observations to model the changing rate of expansion of the universe and to determine the contributions of decelerating and accelerating energies such as the mass density and dark energy density. This model could be constructed using a Hubble diagram (redshift vs. magnitude) populated with supernovae measurements. This study is the first step in the feasibility assessment of a technology reference mission and a follow-on phase-A industrial study is foreseen for the payload, where most of the technology development is needed.

Published: 16 October 2006
In: Reconnection of Magnetic Fields, ed. by J. Birn and E. R. Priest, Cambridge University Press, Cambridge, ISBN-13: 978-0-521-85420-7
Published: 15 January 2007
Cluster observations are used to illustrate the reconfiguration of an auroral potential structure encountered at the poleward boundary of the central plasma sheet within the Southern Hemisphere premidnight auroral oval. The reconfiguration from a symmetric U shape to an asymmetric S shape takes place between two consecutive crossings by Cluster spacecraft 1 and 2, moving along roughly the same orbits and separated in time by 16 minutes. During this time the plasma conditions poleward of the boundary changed dramatically. The fluxes of energetic electrons decreased, as did the intensities of the associated small-scale field-aligned currents (FACs) and the ambient plasma density. These changes were particularly pronounced in a narrow region adjacent to the boundary. The reconfiguration of the potential structure, and of the associated FAC system consistent with this, are consistent with the predictions by Marklund et al. (2004).
Published: 13 January 2007
E-print arXiv:astro-ph/0612311, for ApJS COSMOS Special Issue, 2007 in press

We present the first set of XMM-Newton EPIC observations in the 2 square degree COSMOS field. The strength of the COSMOS project is the unprecedented combination of a large solid angle and sensitivity over the whole multiwavelength spectrum. The XMM-Newton observations are very efficient in localizing and identifying active galactic nuclei (AGN) and clusters as well as groups of galaxies. One of the primary goals of the XMM-Newton Cosmos survey is to study the co-evolution of active galactic nuclei as a function of their environment in the Cosmic web. Here we present the log of observations, images and a summary of first research highlights for the first pass of 25 XMM-Newton pointings across the field. In the existing dataset we have detected 1416 new X-ray sources in the 0.5-2, 2-4.5 and 4.5-10 keV bands to an equivalent 0.5-2 keV flux limit of 7x10-16 erg cm-2 s-1. The number of sources is expected to grow to almost 2000 in the final coverage of the survey. From an X-ray color color analysis we identify a population of heavily obscured, partially leaky or reflecting absorbers, most of which are likely to be nearby, Compton-thick AGN.

Published: 12 December 2006

Chronology is the key to understanding climatically and tectonically driven changes on Mars. The objective of the present proposal was to assess the potential of in-situ Martian sediment dating using luminescence techniques. The work was divided into two parts:

    a) Work package 1 : Review and optimisation of appropriate techniques and instrumentation
    b) Work package 2 : Laboratory measurements and proposals for instrumentation.

Published: 02 May 2006

The aim of the activity was to develop and test an Instrumented Mole System (IMS) - i.e. a system able to deploy a mobile penetrometer carrying a payload of sensors for sub-surface measurements - to be mounted on a Planetary Lander.

This IMS could potentially be used on future planetary missions such as those for the exploration of the surface of Mercury or on other planets.

Published: 29 March 2006
4-Dec-2020 23:35 UT

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