A5004413087- Stellar, planetary, and galactic studies
- Solar and Space Plasma Dynamics
- Astronomy and Astrophysical Research
- Atmospheric Ozone and Climate
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Solar Radiation and Photovoltaics
- Calibration and Measurement Techniques
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Atmospheric and Environmental Gas Dynamics
- Atmospheric chemistry and aerosols
- Climate variability and models
- Geophysics and Gravity Measurements
- Ionosphere and magnetosphere dynamics
- Gamma-ray bursts and supernovae
- Spacecraft Design and Technology
- Adaptive optics and wavefront sensing
- History and Developments in Astronomy
- Spacecraft and Cryogenic Technologies
- CCD and CMOS Imaging Sensors
- Geomagnetism and Paleomagnetism Studies
- Galaxies: Formation, Evolution, Phenomena
- Pulsars and Gravitational Waves Research
- Planetary Science and Exploration
Physikalisch-Meteorologisches Observatorium Davos
2015-2024
Laboratoire d’Astrophysique de Marseille
2017
World Meteorological Organization
2003-2015
ETH Zurich
1984-2012
International Space Science Institute
2012
Kiel University
1987-2006
École Polytechnique Fédérale de Lausanne
1999
Institute of Astronomy
1994
Board of the Swiss Federal Institutes of Technology
1992
University of Colorado System
1990-1991
The variable Sun is the most likely candidate for natural forcing of past climate change on time scales 50 to 1000 years. Evidence this understanding that terrestrial correlates positively with solar activity. During 10,000 years, has experienced substantial variations in activity and there have been numerous attempts reconstruct irradiance. While general agreement how varied during last several hundred years --- all reconstructions are proportional scientific controversy magnitude forcing....
The lack of long and reliable time series solar spectral irradiance (SSI) measurements makes an accurate quantification contributions to recent climate change difficult. Whereas earlier SSI observations models provided a qualitatively consistent picture the variability, by SORCE satellite suggest significantly stronger variability in ultraviolet (UV) range changes visible near-infrared (NIR) bands anti-phase with cycle. A number chemistry-climate model (CCM) simulations have shown that this...
Context. The Extreme Ultraviolet Imager (EUI) is part of the remote sensing instrument package ESA/NASA Solar Orbiter mission that will explore inner heliosphere and observe Sun from vantage points close to out ecliptic. advance “connection science” between solar activity heliosphere. Aims. With EUI we aim improve our understanding structure dynamics atmosphere, globally as well at high resolution, latitude perspectives. Methods. consists three telescopes, Full two High Resolution Imagers,...
Abstract. The pre-industrial millennium is among the periods selected by Paleoclimate Model Intercomparison Project (PMIP) for experiments contributing to sixth phase of Coupled (CMIP6) and fourth PMIP (PMIP4). past1000 transient simulations serve investigate response (mainly) natural forcing under background conditions not too different from today, discriminate between forced internally generated variability on interannual centennial timescales. This paper describes motivation experimental...
ABSTRACT In this brief communication we provide the rationale for and outcome of International Astronomical Union (IAU) resolution vote at XXIXth General Assembly in Honolulu, Hawaii, 2015, on recommended nominal conversion constants selected solar planetary properties. The problem addressed by is a lack established between values SI units: missing standard has caused proliferation (e.g., radius, irradiance, luminosity, effective temperature, mass parameter) literature, with cited typically...
The uninterrupted measurement of the total solar irradiance during last three cycles and an increasing amount spectral measurements as well imaging observations (magnetograms photometric data) have stimulated development models attributing variations to surface magnetism. Here we review current status modelling efforts based on photospheric magnetic fields. Thereby restrict ourselves study from days cycle. Phenomenological atmosphere in combination with electromagnetic radiation field...
The Spectral Imaging of the Coronal Environment (SPICE) instrument is a high-resolution imaging spectrometer operating at extreme ultraviolet (EUV) wavelengths. In this paper, we present concept, design, and pre-launch performance facility on ESA/NASA Solar Orbiter mission. goal paper to give prospective users better understanding possible types observations, data acquisition, sources that contribute instrument's signal. discusses science objectives, with focus SPICE-specific aspects, before...
The Sun and stars with low magnetic activity levels, become photometrically brighter when their increases. Magnetically more active display the opposite behaviour get fainter We reproduce observed photometric trends in stellar variations a model that treats as hypothetical Suns coverage by features different from of Sun. presented attributes variability spectra to imbalance between contributions components solar atmosphere, such dark starspots bright faculae. A spectrum is calculated...
This paper represents a collective effort to provide an extensive electronic database useful for the interpretation of spectra and evolution galaxies. A broad variety empirical theoretical data are discussed here, made fully available in AAS CD-ROM Series, Vo. 7. Several stellar libraries part this database. They cover ultraviolet spectral range observed with IUE, optical from different ground-based telescopes, infrared data. Spectral type coverage depends on wavelength, but it is mostly...
We discuss the problem of assigning an effective temperature to models stellar evolution in Wolf-Rayet stage. conclude that it is best use with different velocity laws depending on temperature. follow most simple approach and propose a standard law Beta = 1 for cooler 2 hotter stars. present energy distributions from non-LTE model calculations law. The new together published results based allow one synthesize realistic spectra starburst regions. flux tables are available digital form authors.
Abstract. We describe version 2.0 of the chemistry-climate model (CCM) SOCOL. The new includes fundamental changes transport scheme such as transporting all chemical species individually and applying a family-based correction for mass conservation nitrogen, chlorine bromine groups, revised ozone, furthermore more detailed halogen reaction deposition schemes, cirrus parameterisation in tropical tropopause region. By means these manages to overcome or considerably reduce deficiencies recently...
Two methods are used to observationally determine the solar radius: One is observation of intensity profile at limb; other one uses f-mode frequencies derive a "seismic" radius which then corrected optical depth unity. The two inconsistent and lead difference in ~0.3 Mm. Because geometrical extension photosphere increased path lengths tangential rays Sun appears be larger an observer who measures extent disk. Based on radiative transfer calculations we show that this discrepancy can...
Abstract Sporadic solar energetic particle (SEP) events affect the Earth’s atmosphere and environment, in particular leading to depletion of protective ozone layer atmosphere, pose potential technological even life hazards. The greatest SEP storm known for last 11 millennia (the Holocene) occurred 774–775 AD, serving as a likely worst-case scenario being 40–50 times stronger than any directly observed one. Here we present systematic analysis impact such an extreme event can have on...
Regular spaceborne measurements have revealed that solar brightness varies on multiple timescales, variations timescales greater than a day being attributed to surface magnetic field. Independently, ground-based and suggest Sun-like stars show similar, but significantly broader pattern of photometric variability. To understand whether the stellar is consistent with paradigm we assess relative contributions faculae spots magnetically-driven We investigate how variability as well its facular...
Context. There is no consensus on the amplitude of historical solar forcing. The estimated magnitude total irradiance difference between Maunder minimum and present time ranges from 0.1 to 6 W/m2 making uncertain simulation past future climate. One reason for this disagreement applied evolution quiet Sun brightness in reconstruction models. This work addresses role model choice updated magnetic activity proxies forcing reconstruction. Aims. We aim establish a plausible range variability...
Abstract. The newly developed atmosphere–ocean–chemistry–climate model SOCOL-MPIOM is presented by demonstrating the influence of chemistry–climate interactions on climate state and variability. Therefore, we compare pre-industrial control simulations with (CHEM) without (NOCHEM) interactive chemistry. In general, chemistry mean variability small mainly restricted to stratosphere mesosphere. atmospheric dynamics differ in polar regions, slightly stronger vortices austral boreal winter,...
The correlation between the averaged reconstructed March temperature record for Kyoto, Japan, and Total Solar Irradiance (TSI) over 660 years from 1230 to 1890 gives evidence with 98% probability that Little Ice Age four cold periods is forced by variations of TSI. If restricted period 1650–1890, two in 17th 19th century which independent records are available, solar forcing increases 99.99%. As irradiance have a global effect there has be climatic impact. However, how much were lower during...
Atmospheric effects of the solar irradiance variations during 11‐year cycle are investigated using a chemistry‐climate model. The model is enhanced by more detailed parameterization oxygen and ozone UV heating rates. simulated response to imposed forcing shows positive correlation in tropical stratosphere negative mesosphere, agreement with theoretical expectation. suggests an acceleration polar night jets both hemispheres dipole structure temperature changes at high latitudes. results also...
Abstract. In this paper we document "SOCOL", a new chemistry-climate model, which has been ported for regular PCs and shows good wall-clock performance. An extensive validation of the model results against present-day climate data obtained from observations assimilation sets that describes climatological state atmosphere late 1990s with reasonable accuracy. The significant temperature bias only in upper stratosphere near tropopause at high latitudes. latter is result rather low vertical...
PREMOS on the French satellite PICARD is first spaceborne absolute radiometer measuring Total Solar Irradiance that has been irradiance-calibrated in vacuum with SI-traceability. The measurements of at light July 27, 2010, yield a TSI value 1360.9±0.4 W/m2 (k=1). This agrees measured by TIM/SORCE for this date within their combined uncertainties, and it differs more than ten sigma from other space experiments, e.g. VIRGO/SOHO. thus establish SI-traceability to solar constant 1361 W/m2.
Context. The solar irradiance is known to change on time scales of minutes decades, and it suspected that its substantial fluctua- tions are partially responsible for climate variations. Aims. We developing a atmosphere code allows the physical modeling entire spectrum composed quiet Sun active regions. This tool variability understanding influence Earth. Methods. exploit further development radiative transfer COSI now incorporates calculation molecular lines. validated under conditions...
We report observations of quasi-periodic pulsations (QPPs) during the X2.2 flare 2011 February 15, observed simultaneously in several wavebands. focus on fluctuations timescale 1–30 s and find different time lags between During impulsive phase, Reuven Ramaty High Energy Solar Spectroscopic Imager channels range 25–100 keV lead all other channels. They are followed by Nobeyama RadioPolarimeters at 9 17 GHz extreme-ultraviolet (EUV) Euv SpectroPhotometer (ESP) board Dynamic Observatory. The...
Abstract. The aim of this work is to elucidate the impact changes in solar irradiance and energetic particles versus volcanic eruptions on tropospheric global climate during Dalton Minimum (DM, AD 1780–1840). Separate variations (i) UV-C with wavelengths λ < 250 nm, (ii) at > (iii) particle spectrum, (iv) aerosol forcing were analyzed separately, (v) combination, by means small ensemble calculations using a coupled atmosphere–ocean chemistry–climate model. Global hemispheric mean...