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Calisto M.,International Space Science Institute ISSI | Usoskin I.,University of Oulu | Rozanov E.,World Radiation Center | Rozanov E.,ETH Zurich
Environmental Research Letters | Year: 2013

This study investigates the influence of a major solar proton event (SPE) similar to the Carrington event of 1-2 September 1859 by means of the 3D chemistry climate model (CCM) SOCOL v2.0. Ionization rates were parameterized according to CRAC:CRII (Cosmic Ray-induced Atmospheric Cascade: Application for Cosmic Ray Induced Ionization), a detailed state-of-the-art model describing the effects of SPEs in the entire altitude range of the CCM from 0 to 80 km. This is the first study of the atmospheric effect of such an extreme event that considers all the effects of energetic particles, including the variability of galactic cosmic rays, in the entire atmosphere. We assumed two scenarios for the event, namely with a hard (as for the SPE of February 1956) and soft (as for the SPE of August 1972) spectrum of solar particles. We have placed such an event in the year 2020 in order to analyze the impact on a near future atmosphere. We find statistically significant effects on NOx, HO x, ozone, temperature and zonal wind. The results show an increase of NOx of up to 80 ppb in the northern polar region and an increase of up to 70 ppb in the southern polar region. HOx shows an increase of up to 4000%. Due to the NOx and HOx enhancements, ozone reduces by up to 60% in the mesosphere and by up to 20% in the stratosphere for several weeks after the event started. Total ozone shows a decrease of more than 20 DU in the northern hemisphere and up to 20 DU in the southern hemisphere. The model also identifies SPE induced statistically significant changes in the surface air temperature, with warming in the eastern part of Europe and Russia of up to 7 K for January. © 2013 IOP Publishing Ltd.


Wilkinson D.M.,Liverpool John Moores University | Wilkinson D.M.,Swiss Federal Institute of forest | Wilkinson D.M.,Ecole Polytechnique Federale de Lausanne | Koumoutsaris S.,International Space Science Institute ISSI | And 4 more authors.
Journal of Biogeography | Year: 2012

Aim We investigate the long-standing question of whether the small size of microbes allows most microbial species to colonize all suitable sites around the globe or whether their ranges are limited by opportunities for dispersal. In this study we use a modelling approach to investigate the effect of size on the probability of between-continent dispersal using virtual microorganisms in a global model of the Earth's atmosphere. Location Global. Methods We use a computer model of global atmospheric circulation to investigate the effect of microbe size (effective diameters of 9, 20, 40 and 60μm) on the probability of aerial dispersal. Results We found that for smaller microbes, once airborne, dispersal is remarkably successful over a 1-year period. The most striking results are the extensive within-hemisphere distribution of virtual microbes of 9 and 20μm diameter and the lack of dispersal between the Northern and Southern Hemispheres during the year-long time-scale of our simulations. Main conclusions Above a diameter of 20μm wind dispersal of virtual microbes between continents becomes increasingly unlikely, and it does not occur at all (within our simulated 1-year period) for those of 60μm diameter. Within our simulation, the success of small microbes in long-distance dispersal is due both to their greater abundance and to their longer time in the atmosphere - once airborne - compared with larger microbes. © 2011 Blackwell Publishing Ltd.


Bozzo E.,University of Geneva | Pavan L.,University of Geneva | Ferrigno C.,University of Geneva | Falanga M.,International Space Science Institute ISSI | And 4 more authors.
Astronomy and Astrophysics | Year: 2012

We present the results of the XMM-Newton observations of five hard X-ray emitters: IGR J08262-3736, IGR J17354-3255, IGR J16328-4726, SAX J1818.6-1703, and IGR J17348-2045. The first source is a confirmed supergiant high mass X-ray binary, the following two are candidates supergiant fast X-ray transients, SAX J1818.6-1703 is a confirmed supergiant fast X-ray transient and IGR J17348-2045 is one of the still unidentified objects discovered with INTEGRAL. The XMM-Newton observations permitted the first detailed soft X-ray spectral and timing study of IGR J08262-3736 and provided further support in favor of the association of IGR J17354-3255 and IGR J16328-4726 with the supergiant fast X-ray transients. SAX J1818.6-1703 was not detected by XMM-Newton, thus supporting the idea that this source reaches its lowest X-ray luminosity (≈ 10 32 erg s -1) around apastron. For IGR J17348-2045 we identified for the first time the soft X-ray counterpart and proposed the association with a close-by radio object, suggestive of an extragalactic origin. © 2012 ESO.


Calisto M.,International Space Science Institute ISSI | Verronen P.T.,Finnish Meteorological Institute | Rozanov E.,World Radiation Center | Rozanov E.,ETH Zurich | Peter T.,ETH Zurich
Atmospheric Chemistry and Physics | Year: 2012

We have modeled the atmospheric impact of a major solar energetic particle event similar in intensity to what is thought of the Carrington Event of 1-2 September 1859. Ionization rates for the August 1972 solar proton event, which had an energy spectrum comparable to the Carrington Event, were scaled up in proportion to the fluence estimated for both events. We have assumed such an event to take place in the year 2020 in order to investigate the impact on the modern, near future atmosphere. Effects on atmospheric chemistry, temperature and dynamics were investigated using the 3-D Chemistry Climate Model SOCOL v2.0. We find significant responses of NOx, HOx, ozone, temperature and zonal wind. Ozone and NOx have in common an unusually strong and long-lived response to this solar proton event. The model suggests a 3-fold increase of NOx generated in the upper stratosphere lasting until the end of November, and an up to 10-fold increase in upper mesospheric HOx. Due to the NOx and HOx enhancements, ozone reduces by up to 60-80% in the mesosphere during the days after the event, and by up to 20-40% in the middle stratosphere lasting for several months after the event. Total ozone is reduced by up to 20 DU in the Northern Hemisphere and up to 10 DU in the Southern Hemisphere. Free tropospheric and surface air temperatures show a significant cooling of more than 3 K and zonal winds change significantly by 3-5 m sĝ̂'1 in the UTLS region. In conclusion, a solar proton event, if it took place in the near future with an intensity similar to that ascribed to of the Carrington Event of 1859, must be expected to have a major impact on atmospheric composition throughout the middle atmosphere, resulting in significant and persistent decrease in total ozone. © 2012 Author(s).


Bini D.,CNR Institute of Neuroscience | Bini D.,University of Rome La Sapienza | Falanga M.,International Space Science Institute ISSI | Geralico A.,University of Rome La Sapienza | Stella L.,National institute for astrophysics
Classical and Quantum Gravity | Year: 2012

The motion of matter immersed in a radiation field is affected by a radiation drag, as a result of scattering or absorption and re-emission. The resulting friction-like drag, also known as the Poynting-Robertson effect, has been recently studied in the general relativistic background of the Schwarzschild and Kerr metric, under the assumption that all photons in the radiation field possess the same angular momentum. We calculate here the signal produced by an emitting point-like specific source moving in a Schwarzschild spacetime under the influence of such a radiation field. We derive the flux, redshift factor and solid angle of the hot spot as a function of (coordinate) time, as well as the time-integrated image of the hot spot as seen by an observer at infinity. The results are then compared with those for a spot moving on a circular geodesic in a Schwarzschild metric. © 2012 IOP Publishing Ltd.

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