MPI fur Sonnensystemforschung

Lindau, Germany

MPI fur Sonnensystemforschung

Lindau, Germany

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Pouquet A.,NCAR | Baerenzung J.,NCAR | Pietarila Graham J.,MPI fur Sonnensystemforschung | Politano H.,Observatoire de la Cote dAzur | Ponty Y.,Observatoire de la Cote dAzur
Notes on Numerical Fluid Mechanics and Multidisciplinary Design | Year: 2010

We present two models for turbulent flows with periodic boundary conditions and with either rotation, or a magnetic field in the magnetohydrodynamics (MHD) limit. One model, based on Lagrangian averaging, can be viewed as an invariant-preserving filter, whereas the other model, based on spectral closures, generalizes the concepts of eddy viscosity and eddy noise. These models, when used separately or in conjunction, may lead to substantial savings for modeling high Reynolds number flows when checked against high resolution direct numerical simulations (DNS), the examples given here being run on grids of up to 15363 points. © 2010 Springer-Verlag Berlin Heidelberg.


Phillips T.G.,California Institute of Technology | Bergin E.A.,University of Michigan | Lis D.C.,California Institute of Technology | Neufeld D.A.,Johns Hopkins University | And 57 more authors.
Astronomy and Astrophysics | Year: 2010

We report a detection of the fundamental rotational transition of hydrogen fluoride in absorption towards Orion KL using Herschel/HIFI. After the removal of contaminating features associated with common molecules ("weeds"), the HF spectrum shows a P-Cygni profile, with weak redshifted emission and strong blue-shifted absorption, associated with the low-velocity molecular outflow. We derive an estimate of 2.9 × 1013 cm-2 for the HF column density responsible for the broad absorption component. Using our best estimate of the H2 column density within the low-velocity molecular outflow, we obtain a lower limit of ∼1.6 × 10-10 for the HF abundance relative to hydrogen nuclei, corresponding to ∼0.6% of the solar abundance of fluorine. This value is close to that inferred from previous ISO observations of HF J = 2-1 absorption towards Sgr B2, but is in sharp contrast to the lower limit of 6 × 10-9 derived by Neufeld et al. for cold, foreground clouds on the line of sight towards G10.6-0.4. © 2010 ESO.


Bergin E.A.,University of Michigan | Phillips T.G.,California Institute of Technology | Comito C.,Max Planck Institute for Radio Astronomy | Crockett N.R.,University of Michigan | And 61 more authors.
Astronomy and Astrophysics | Year: 2010

We present initial results from the Herschel GT key program: Herschel observations of EXtra-Ordinary Sources (HEXOS) and outline the promise and potential of spectral surveys with Herschel/HIFI. The HIFI instrument offers unprecedented sensitivity, as well as continuous spectral coverage across the gaps imposed by the atmosphere, opening up a largely unexplored wavelength regime to high-resolution spectroscopy. We show the spectrum of Orion KL between 480 and 560 GHz and from 1.06 to 1.115 THz. From these data, we confirm that HIFI separately measures the dust continuum and spectrally resolves emission lines in Orion KL. Based on this capability we demonstrate that the line contribution to the broad-band continuum in this molecule-rich source is ∼20-40% below 1 THz and declines to a few percent at higher frequencies. We also tentatively identify multiple transitions of HD18O in the spectra. The first detection of this rare isotopologue in the interstellar medium suggests that HDO emission is optically thick in the Orion hot core with HDO/H2O ∼ 0.02. We discuss the implications of this detection for the water D/H ratio in hot cores. © 2010 ESO.


Dubinin E.,MPI fur Sonnensystemforschung | Fraenz M.,MPI fur Sonnensystemforschung | Woch J.,MPI fur Sonnensystemforschung | Modolo R.,French National Center for Scientific Research | And 5 more authors.
Earth, Planets and Space | Year: 2012

The measurements carried out by the ASPERA-3 and MARSIS experiments on board the Mars Express (MEX) spacecraft show that the upper Martian ionosphere (h ≥ 400 km) is strongly azimuthally asymmetrical. There are several factors, e.g., the crustal magnetization on Mars and the orientation of the interplanetary magnetic field (IMF) which can give rise to formation of ionospheric swells and valleys. It is shown that expansion of the ionospheric plasma along the magnetic field lines of crustal origin can produce bulges in the plasma density. The absense of a magnetometer on MEX makes the retrieval of an asymmetry caused by the IMF more difficult. However hybrid simulations give a hint that the ionosphere in the hemisphere (E-) to which the motional electric field is pointed occurs more inflated than the ionosphere in the opposite (E+) hemisphere. Copyright © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS).


Lockwood M.,University of Reading | Lockwood M.,Rutherford Appleton Laboratory | Harrison R.G.,University of Reading | Woollings T.,University of Reading | And 2 more authors.
Environmental Research Letters | Year: 2010

Solar activity during the current sunspot minimum has fallen to levels unknown since the start of the 20th century. The Maunder minimum (about 1650-1700) was a prolonged episode of low solar activity which coincided with more severe winters in the United Kingdom and continental Europe. Motivated by recent relatively cold winters in the UK, we investigate the possible connection with solar activity. We identify regionally anomalous cold winters by detrending the Central England temperature (CET) record using reconstructions of the northern hemisphere mean temperature. We show that cold winter excursions from the hemispheric trend occur more commonly in the UK during low solar activity, consistent with the solar influence on the occurrence of persistent blocking events in the eastern Atlantic. We stress that this is a regional and seasonal effect relating to European winters and not a global effect. Average solar activity has declined rapidly since 1985 and cosmogenic isotopes suggest an 8% chance of a return to Maunder minimum conditions within the next 50 years (Lockwood 2010 Proc. R. Soc. A 466 303-29): the results presented here indicate that, despite hemispheric warming, the UK and Europe could experience more cold winters than during recent decades. © 2010 IOP Publishing Ltd.


Christensen U.R.,MPI fur Sonnensystemforschung
Space Science Reviews | Year: 2010

A didactic introduction to current thinking on some aspects of the solar dynamo is given for geophysicists and planetary scientists. © 2010 Springer Science+Business Media B.V.


Dubinin E.,MPI fur Sonnensystemforschung | Fraenz M.,MPI fur Sonnensystemforschung | Fedorov A.,CNRS Institute for research in astrophysics and planetology | Lundin R.,Swedish Institute of Space Physics | And 3 more authors.
Space Science Reviews | Year: 2011

Mars and Venus do not have a global magnetic field and as a result solar wind interacts directly with their ionospheres and upper atmospheres. Neutral atoms ionized by solar UV, charge exchange and electron impact, are extracted and scavenged by solar wind providing a significant loss of planetary volatiles. There are different channels and routes through which the ionized planetary matter escapes from the planets. Processes of ion energization driven by direct solar wind forcing and their escape are intimately related. Forces responsible for ion energization in different channels are different and, correspondingly, the effectiveness of escape is also different. Classification of the energization processes and escape channels on Mars and Venus and also their variability with solar wind parameters is the main topic of our review. We will distinguish between classical pickup and 'mass-loaded' pickup processes, energization in boundary layer and plasma sheet, polar winds on unmagnetized planets with magnetized ionospheres and enhanced escape flows from localized auroral regions in the regions filled by strong crustal magnetic fields. © 2011 Springer Science+Business Media B.V.


Cernicharo J.,CSIC - National Institute of Aerospace Technology | Goicoechea J.R.,CSIC - National Institute of Aerospace Technology | Daniel F.,CSIC - National Institute of Aerospace Technology | Agundez M.,CSIC - National Institute of Aerospace Technology | And 9 more authors.
Astronomy and Astrophysics | Year: 2010

We report on the detection with the HIFI instrument on board the Herschel satellite of the two hydrogen chloride isotopologues, H35Cl and H37Cl, towards the massive star-forming region W3 A. The J = 1-0 line of both species was observed with receiver 1b of the HIFI instrument at ∼625.9 and ∼624.9 GHz. The different hyperfine components were resolved. The observations were modeled with a non-local, non-LTE radiative transfer model that includes hyperfine line overlap and radiative pumping by dust. Both effects are found to play an important role in the emerging intensity from the different hyperfine components. The inferred H35Cl column density (a few times ∼1014 cm-2), and fractional abundance relative to H nuclei (∼7.5 × 10-10), supports an upper limit to the gas phase chlorine depletion of ≈ 200. Our best-fit model estimate of the H35Cl/H37Cl abundance ratio is ≈ 2.1 ± 0.5, slightly lower, but still compatible with the solar isotopic abundance ratio (≈ 3.1). Since both species were observed simultaneously, this is the first accurate estimation of the [35Cl] /[ 37Cl] isotopic ratio in molecular clouds. Our models indicate that even for large line opacities and possible hyperfine intensity anomalies, the H35Cl and H37Cl J = 1-0 integrated line-intensity ratio provides a good estimate of the 35Cl/37Cl isotopic abundance ratio. © 2010 ESO.


Cernicharo J.,CSIC - National Institute of Aerospace Technology | Goicoechea J.R.,CSIC - National Institute of Aerospace Technology | Daniel F.,CSIC - National Institute of Aerospace Technology | Agundez M.,CSIC - National Institute of Aerospace Technology | And 9 more authors.
Astronomy and Astrophysics | Year: 2010

We report on the detection with the HIFI instrument on board the Herschel satellite of the two hydrogen chloride isotopologues, H35Cl and H37Cl, towards the massive star-forming region W3 A. The J = 1-0 line of both species was observed with receiver 1b of the HIFI instrument at ∼625.9 and ∼624.9 GHz. The different hyperfine components were resolved. The observations were modeled with a non-local, non-LTE radiative transfer model that includes hyperfine line overlap and radiative pumping by dust. Both effects are found to play an important role in the emerging intensity from the different hyperfine components. The inferred H35Cl column density (a few times ∼1014 cm-2), and fractional abundance relative to H nuclei (∼7.5 × 10-10), supports an upper limit to the gas phase chlorine depletion of ≈ 200. Our best-fit model estimate of the H35Cl/H37Cl abundance ratio is ≈ 2.1 ± 0.5, slightly lower, but still compatible with the solar isotopic abundance ratio (≈ 3.1). Since both species were observed simultaneously, this is the first accurate estimation of the [35Cl]/[37Cl] isotopic ratio in molecular clouds. Our models indicate that even for large line opacities and possible hyperfine intensity anomalies, the H35Cl and H37Cl J = 1-0 integrated line-intensity ratio provides a good estimate of the 35Cl/37Cl isotopic abundance ratio. © 2010 ESO.


A'Hearn M.F.,University of Maryland University College | Feaga L.M.,University of Maryland University College | Bertaux J.-L.,Service dAeronomie | Feldman P.D.,Johns Hopkins University | And 8 more authors.
Planetary and Space Science | Year: 2010

During Rosetta's flyby of the asteroid (2867) Šteins in 2008, we used the ALICE instrument to measure the first far-ultraviolet (FUV) reflectivity spectrum of an asteroid (8502000 ). It is very dark in the FUV, ∼4%, compared to its very high reflectivity (40%) at optical wavelengths. The FUV albedo does not exhibit a systematic color trend across the spectral range, but there is a broad absorption feature, not yet identified with a specific mineral, with maximum depth near 1650 Å. The shape of this feature implies a very low abundance of Fe2 ions in the surface minerals. The FUV brightness exhibits a significant opposition surge at phases below 10°. The visible/FUV color gets much redder with increasing phase angle inside the opposition surge and gets gradually redder at larger phase angles. We also conducted a deep search for an exosphere of atoms sputtered from the surface and set upper limits on any column densities of oxygen and hydrogen atoms at the time of our observations. The upper limit for H is comparable to that predicted by the only theoretical prediction of which we are aware, while that for O is higher than predicted by about an order of magnitude. © 2010 Elsevier Ltd. 2010 Elsevier Ltd. All rights reserved.

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