Time filter

Source Type

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. Source

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. Source

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. Source

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. Source

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). Source

Discover hidden collaborations