Henrik Svensmark's research while affiliated with Technical University of Denmark and other places

Publications (74)

Article
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This study examines the relationship between cosmic rays and clouds during Forbush decreases (FDs) to understand the cause-effect relationships between cloud microphysics, cloud condensation nuclei (CCN), and ionisation in the atmosphere. The r e s u l t s of a Monte Carlo analysis of cloud parameters during FDs, which were obtained using newly cal...
Article
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Experiments on sulphuric acid nucleation in low oxygen atmospheres were done in order to investigate the role of nucleation in the Archean atmosphere. Nu-cleation initiated by photolysis of SO2 and subsequent reaction between atomic O and SO2 was measured with a PSM and a separate CPC. The parameters were <10 ppm O2 with varying levels of SO2 (4 le...
Article
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Plain Language Summary The study proposes a surprising link between the burial of organic matter in sediments and stellar processes. The paper has two components; the first component concerns empirical evidence: A close correlation between the fraction of organic matter buried in sediments and changes in supernovae frequency. This correlation is ev...
Article
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Atmospheric ionization produced by cosmic rays has been suspected to influence aerosols and clouds, but its actual importance has been questioned. If changes in atmospheric ionization have a substantial impact on clouds, one would expect to observe significant responses in Earth’s energy budget. Here it is shown that the average of the five stronge...
Article
Forest growth changes have been a matter of intense research efforts since the 1980s. Owing to the variety of their environmental causes - mainly atmospheric CO2 increase, atmospheric N deposition, changes in temperature and water availability, and their interactions - their interpretation has remained challenging. Recent isolated researches sugges...
Article
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Abstract The presence of small ions influences the growth dynamics of a size distribution of aerosols. Specifically, the often neglected mass of small ions influences the aerosol growth rate, which may be important for terrestrial cloud formation. To this end, we develop the Ion and Charged Aerosol Growth Enhancement (ION‐CAGE) code, a numerical mo...
Article
The nucleation of sulfuric acid-water clusters plays a significant role in the formation of aerosols. Based on a recently developed particle Monte Carlo (MC) Code, we analyze how the growth of sulfuric acid-water clusters is influenced by stochastic fluctuations. We here consider samples of H2SO4-H2O clusters at T = 200 K with a relative humidity o...
Preprint
The presence of small ions influences the growth dynamics of a size distribution of aerosols. Specifically the often neglected mass of small ions influences the aerosol growth rate, which may be important for terrestrial cloud formation. To this end, we develop a numerical model to calculate the growth of a species of aerosols in the presence of ch...
Article
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One hundred and ten direct measurements of aerosol nucleation rate at high ionization levels were performed in an 8 m³ reaction chamber. Neutral and ion-induced particle formation from sulfuric acid (H2SO4) was studied as a function of ionization and H2SO4 concentration. Other species that could have participated in the nucleation, such as NH3 or o...
Article
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The nucleation of sulphuric acid molecules plays a key role in the formation of aerosols. We here present a three dimensional particle Monte Carlo model to study the growth of sulphuric acid clusters as well as its dependence on the ambient temperature and the initial particle density. We initiate a swarm of sulphuric acid-water clusters with a siz...
Article
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Ions produced by cosmic rays have been thought to influence aerosols and clouds. In this study, the effect of ionization on the growth of aerosols into cloud condensation nuclei is investigated theoretically and experimentally. We show that the mass-flux of small ions can constitute an important addition to the growth caused by condensation of neut...
Article
Full-text available
One hundred and ten direct measurements of aerosol nucleation rate at high ionization levels were performed in an 8 m³ reaction chamber. Neutral and ion-induced particle formation from sulphuric acid (H2SO4) as a function of ionization and H2SO4 concentration was studied. Other species that could participate in the nucleation were not measured. The...
Article
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Here we combine observations of open clusters (OCs) with single- and binary population synthesis models and a Galactic potential to reconstruct the SN activity of these OCs during the past 35 Myr. We find that several OCs potentially hosting SN progenitors have passed within 100 pc of the Sun during the past 35 Myr. In particular we find that ASCC...
Article
Full-text available
The nucleation of sulphuric acid molecules plays a key role in the formation of aerosols. We here present a three dimensional particle Monte Carlo model to study the growth of sulphuric acid clusters as well as its dependence on the ambient temperature and the initial particle density.We initiate a swarm of sulphuric acid molecules with a size of 0...
Article
Full-text available
A method is developed to rank Forbush Decreases (FDs) in the galactic cosmic ray radiation according to their expected impact on the ionization of the lower atmosphere. Then a Monte Carlo bootstrap based statistical test is formulated to estimate the significance of the apparent response in physical and micro-physical cloud parameters to FDs. The t...
Article
With satellite altimetry data accumulating over the past two decades, the mean sea level (MSL) can now be measured to unprecedented accuracy. We search for physical processes which can explain the sea level variations and find that at least 70% of the variance in the annually smoothed detrended altimetry data can be explained as the combined effect...
Article
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We present analytical solutions to the steady state injection-condensation-coagulation equation of aerosols in the atmosphere. These solutions are appropriate under different limits but more general than previously derived analytical solutions. For example, we provide an analytic solution to the coagulation limit plus a condensation correction. Our...
Article
Observations of open star clusters in the solar neighborhood are used to calculate local supernova (SN) rates for the past 510 million years (Myr). Peaks in the SN rates match passages of the Sun through periods of locally increased cluster formation which could be caused by spiral arms of the Galaxy. A statistical analysis indicates that the Solar...
Article
Ion-induced nucleation has been studied in a deep underground ultra-low background radiation environment where the role of ions can be distinguished from alternative neutral aerosol nucleation mechanisms. Our results demonstrate that ions have a significant effect on the production of small sulfuric acid–water clusters over a range of sulfuric acid...
Article
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Based on density functional theory calculations we present a study of the gaseous oxidation of SO2 to SO3 by an anionic O3−(H2O)n cluster, n = 0–5. The configurations of the most relevant reactants, transition states, and products are discussed and compared to previous findings. Two different classes of transition states have been identified. One c...
Article
In experiments where ultraviolet light produces aerosols from trace amounts of ozone, sulphur dioxide, and water vapour, the number of additional small particles produced by ionization by gamma sources all grow up to diameters larger than 50 nm, appropriate for cloud condensation nuclei. This result contradicts both ion-free control experiments and...
Article
Sulphuric acid is an important factor in aerosol nucleation and growth. It has been shown that ions enhance the formation of sulphuric acid aerosols, but the exact mechanism has remained undetermined. Furthermore some studies have found a deficiency in the sulphuric acid budget, suggesting a missing source. In this study the production of sulphuric...
Article
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Using cloud data from MODIS we investigate the response of cloud microphysics to sudden decreases in galactic cosmic radiation - Forbush decreases - and find responses in effective emissivity, cloud fraction, liquid water content, and optical thickness above the 2-3 sigma level 6-9 days after the minimum in atmospheric ionization and less significa...
Article
Full-text available
Based on density functional theory calculations we present a study of the gaseous oxidation of SO2 to SO3 by an anionic O3-(H2On cluster, n=0-5. The configurations of the most relevant reactants, transition states, and products are discussed and compared to previous findings. Two different classes of transition states have been identified. One clas...
Article
Full-text available
An ab initio study of gaseous clusters of O2− and O3− with water is presented. Based on thorough scans of configurational space, we determine the thermodynamics of cluster growth. The results are in good agreement with benchmark computational methods and existing experimental data. We find that anionic O2−(H2O)n and O3−(H2O)n clusters are thermally...
Article
Full-text available
An ab initio study of gaseous clusters of O2- and O2- with water is presented. Based on thorough scans of configurational space, we determine the thermodynamics of cluster growth. The results are in good agreement with benchmark computational methods and existing experimental data. We find that anionic O2-(H2O)n and O3-(H2O)n clusters are thermally...
Article
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The effect of ions in aerosol nucleation is a subject where much remains to be discovered. That ions can enhance nucleation has been shown by theory, observations, and experiments. However, the exact mechanism still remains to be determined. One question is if the nature of the ionization affects the nucleation. This is an essential question since...
Article
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Atmospheric ions can enhance the nucleation of aerosols, as has been established by experiments, observation, and theory. In the clean marine atmosphere ionization is mainly caused by cosmic rays which in turn are controlled by the activity of the Sun, thus providing a potential link between solar activity and climate. In order to understand the ef...
Article
Changes in the intensity of galactic cosmic rays alter the Earth's cloudiness. A recent experiment has shown how electrons liberated by cosmic rays assist in making aerosols, the building blocks of cloud condensation nuclei, while sudden decreases in cosmic rays caused by coronal mass ejections from the Sun supports the link from ions to aerosols t...
Article
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Using kappa Ceti as a proxy for the young Sun we show that not only was the young Sun much more effective in protecting the Earth environment from galactic cosmic rays than the present day Sun; it also had flare and corona mass ejection rates up to three orders of magnitude larger than the present day Sun. The reduction in the galactic cosmic ray i...
Article
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In order to elucidate the effect of galactic cosmic rays on cloud formation, we investigate the optical response of marine aerosols to Forbush decreases – abrupt decreases in galactic cosmic rays – by means of modeling. We vary the nucleation rate of new aerosols, in a sectional coagulation and condensation model, according to changes in ionization...
Article
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During a 4-week run in October–November 2006, a pilot experiment was performed at the CERN Proton Synchrotron in preparation for the CLOUD<sup>1</sup> experiment, whose aim is to study the possible influence of cosmic rays on clouds. The purpose of the pilot experiment was firstly to carry out exploratory measurements of the effect of ionising part...
Article
In order to elucidate the effect of galactic cosmic rays on cloud formation, we investigate the optical response of marine aerosols to Forbush decreases – abrupt decreases in galactic cosmic rays – by means of modeling. We vary the nucleation rate of new aerosols, in a sectional coagulation and condensation model, according to changes in ionization...
Article
1] Close passages of coronal mass ejections from the sun are signaled at the Earth's surface by Forbush decreases in cosmic ray counts. We find that low clouds contain less liquid water following Forbush decreases, and for the most influential events the liquid water in the oceanic atmosphere can diminish by as much as 7%. Cloud water content as ga...
Article
The role of ions in producing aerosols in Earth's atmosphere is an area of very active research. Atmospheric (Clarke et al. 1998) and experimental (Berndt et al. 2005) observations have shown that the nucleation of aerosol particles can occur under conditions that cannot be explained by classical nucleation theory. Several ideas have been put forwa...
Article
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Atmospheric aerosols affect climate and yet the reason for many observed events of new aerosol formation is not understood. One of the theories put forward to explain these events is that the presence of ions can enhance the formation of aerosols. The theory is called Ion Induced Nucleation and in this paper the state of observations, theory and ex...
Article
Experimental studies of aerosol nucleation in air, containing trace amounts of ozone, sulphur dioxide, and water vapor at concentrations relevant for the Earths atmosphere are reported. The production of new aerosol particles is found to be proportional to the negative ion density. These results suggest that ions are important for nucleation proces...
Article
Full-text available
Experimental studies of aerosol nucleation in air, containing trace amounts of ozone, sulphur dioxide and water vapour a concentrations relevant for the Earth's atmosphere, are reported. The production of new aerosol particles is found to be proportiona to the negative ion density and yields nucleation rates of the order of 0.1–1 cm−3 s−1. This sug...
Article
Changes in the intensity of galactic cosmic rays alter the Earth's cloudiness. A recent experiment has shown how electrons liberated by cosmic rays assist in making aerosols, the building blocks of cloud condensation nuclei, while anomalous climatic trends in Antarctica confirm the role of clouds in helping to drive climate change. Variations in th...
Article
It has been proposed that galactic cosmic rays may influence the Earth's climate by affecting cloud formation. If changes in cloudiness play a part in climate change, their effect changes sign in Antarctica. Satellite data from the Earth Radiation Budget Experiment (ERBE) are here used to calculate the changes in surface temperatures at all latitud...
Article
Variations in the flux of cosmic rays (CR) at Earth during the last 4.6 billion years are constructed from information about the star formation rate in the Milky Way and the evolution of the solar activity. The constructed CR signal is compared with variations in the Earths biological productivity as recorded in the isotope δ13C, which spans more t...
Article
A connection between climate and the Solar system's motion perpendicular to the Galactic plane during the last 200 Myr years is studied. An imprint of galactic dynamics is found in a long-term record of the Earth's climate that is consistent with variations in the Solar system oscillation around the Galactic midplane. From small modulations in the...
Article
Recent studies have shown that the Earth s cloud cover is strongly correlated with the galactic cosmic ray flux While this correlation is indicative of a possible physical connection there is until now no confirmation that a physical mechanism exists An experiment has therefore been set up in order to investigate the underlying microphysical proces...
Article
Nucleation in the presence of ions has been studied experimentally under conditions that prevail in the lower atmosphere. In order to observe the properties of nucleation processes below 3 nm, which cannot be detected using standard techniques for measuring atmospheric aerosol, the sub 3 nm aerosols were grown via the condensation of sulphuric acid...
Article
Experimental studies of ultra-fine aerosol nucleation in clean atmospheric air, containing trace amounts of ozone, sulphur dioxide, and water vapour suggest that the production rate of critical clusters is sensitive to ionisation. To assess this sensitivity numerical simulations of the initial stages of particle coagulation and condensation have be...
Article
Resent studies have shown that the Earth's cloud cover is strongly correlated with the galactic cosmic ray flux. While this correlation is indicative of a possible physical connection, there is until now no confirmation that a physical mechanism exists. An experiment has therefore been set up in order to investigate the underlying microphysical pro...
Article
An experiment has been set up in order to investigate the role of ionization in Earth's climate. We have chosen to start our investigation at the smallest scales, namely by studying the effect of cosmic ray produced ions on atmospheric aerosol nucleation and growth processes. This experiment is conducted at the Danish National Space Center, Center...
Article
Variations in the flux of Galactic Cosmic Rays (GCR) at Earth during the last 4.6 billion years are constructed from information about the Star Formation Rate (SFR) in the Milky Way and the evolution of solar activity. The variations of GCR show a remarkable resemblance to changes in Earth's climate during the period considered, suggesting that Ear...
Article
The recently reported correlation between clouds and galactic cosmic rays (GCR) implies the existence of a previously unknown process linking solar variability and climate. An analysis of the interannual variability of International Satellite Cloud Climatology Project D2 (ISCCP-D2) low-cloud properties over the period July 1983 to August 1994 sugge...
Article
An increasing number of studies indicate that variations in solar activity have had a significant influence on Earth's climate. However, the mechanisms responsible for a solar influence are still not known. One possibility is that atmospheric transparency is influenced by changing cloud properties via cosmic ray ionisation (the latter being modulat...
Article
Variations in Earth's climate suggest that the atmosphere is capable of amplifying small changes in solar activity. One possibility is to influence the atmospheric trans- parency by changing cloud properties via cosmic ray ionisation (the latter is modulated by solar activity). Support for this idea is found from satellite observations of cloud cov...
Article
The recently reported correlation between clouds and galactic cosmic rays (GCR) implies the existence of a previously unknown process linking solar variability and climate. An analysis of the interannual variability of ISCCP-D2 low cloud proper- ties suggests that low clouds are statistically related to two processes, a) GCR and b) ENSO, with GCR e...
Article
The recently reported correlation between Galactic Cosmic Rays (GCR) and low cloud properties raises the possibility of a new mechanism linking solar variability to cli- mate. However, GCR are negatively correlated with Total Solar Irradiance (TSI), and with the current lack of experimental evidence to confirm or otherwise the role of ion- isation...
Article
The influence of solar variability on climate is currently uncertain. Recent observations have indicated a possible mechanism via the influence of solar modulated cosmic rays on global cloud cover. Surprisingly the influence of solar variability is strongest in low clouds (</=3 km), which points to a microphysical mechanism involving aerosol format...
Article
A correlation between a global average of low cloud cover and the flux of cosmic rays incident in the atmosphere has been observed during the last solar cycle. The ionising potential of Earth bound cosmic rays are modulated by the state of the heliosphere, while clouds play an important role in the Earth''s radiation budget through trapping outgoin...
Article
During the last solar cycle the Earth's cloud cover underwent a modulation in phase with the cosmic ray flux. Assuming that there is a causal relationship between the two, it is expected and found that the Earth's temperature follows more closely decade variations in cosmic ray flux than other solar activity parameters. If the relationship is real...
Article
During the last solar cycle Earth's cloud cover underwent a modulation more closely in phase with the galactic cosmic ray flux than with other solar activity parameters. Further it is found that Earth's temperature follows more closely decade variations in galactic cosmic ray flux and solar cycle length, than other solar activity parameters. The ma...
Article
The Earth's climate has always been changing. This is documented in historical as well as in geological records. The reasons for these changes, however, have always been subject to discussions and are still not well understood. In addition to natural climate changes the risk of human influence on climate has recently been seriously considered by th...
Article
In the search for a physical mechanism that could account for reported correlations between solar activity parameters and climate, we have investigated the global cloud cover observed by satellites. We find that the observed variation of 3–4% of the global cloud cover during the recent solar cycle is strongly correlated with the cosmic ray flux. Th...
Article
Gennem de sidste hundred ar er Jordens overflade-temperatur steget med ca. 0.7 • C. Samtidig har af-braendingen af fossile braendstoffer fået koncentrationen af drivhusgasser, isaer kuldioxid (CO 2), til at stige i at-mosfaeren. Dette har affødt en bekymring for, at den registrerede klimaaendring er skabt af mennesker. Men Jordens klima har altid v...

Citations

... We found little relationship between WCH drift and months with fewer data from one sensor or with ENSO (not shown), but found a curious correspondence between total solar irradiance and Terra-Aqua WCH difference, primarily during daytime (Figures S14 and S15 in Supporting Information S1). Some evidence suggests a measurable solar effect on the tropical upper atmosphere (e.g., Misios et al., 2019) or indirectly on high clouds (Svensmark et al., 2021), but any effect on diurnal WCH differences necessary to cause Aqua-Terra divergence is entirely speculative. Another possibility is related to differences in the thermal environment experienced by the instruments either due to changes in solar heating, or as they enter and exit umbra at high latitudes. ...
... Considering only the unhydrated process of Reaction (R3), the rate constant is 4-5 orders of magnitude lower than the rate constant obtained for the SO 2 + O − 3 → SO − 3 + O 2 reaction (Fehsenfeld and Ferguson, 1974;Bork et al., 2012). Despite this difference, the oxidation process follows a similar mechanism to the one presented by Bork et al. for the SO 2 + O − 3 → SO − 3 + O 2 reaction, consisting of the oxygen transfer from O 3 to SO 2 . ...
... (1) aerosols are smaller than ∼ 25 nm, (2) the total number of aerosol particles is small, and (3) the condensing gas concentration (e.g. H 2 SO 4 ) is low 16,34 . The first condition is important for aerosol survival and the last two conditions are typically fulfilled over the remote oceans 8 . ...
... Experiments were additionally complemented by quantum chemical modelling of MSA clusters. Particle nucleation rates were obtained using the method described in Tomicic et al. (2018). By measuring the concentration of particles with diameters exceeding a cut-off diameter of 1.7 nm (N 1.7 ), the nucleation rate J 1.7 is defined as: ...
... Today, PIC simulations are used in a variety of fields, such as, but not limited to astrophysical phenomena, atmospheric electricity, cloud physics or space weather (e.g., Lapenta 2012; Köhn et al. 2017Köhn et al. , 2018Köhn et al. , 2020. ...
... If a mutation is from a cosmic ray, where, when, and whether it arrives are sensitive to random radioactive decays. Random cosmic ray strikes could even seed clouds [3], thus possibly serving as 'butterflies' in the chaotic weather. The formation of life may also have arisen from random, low-probability events that were not prescribed in the initial conditions. ...
... It is produced in He-shell burning of massive stars in late phases after core C-burning and ejected afterwards in CCSNe. Recent findings show that it can witness the last CCSNe near the solar system about 2 to 3 million years ago (Knie et al 2004;Firestone 2014;Wallner et al 2015Wallner et al , 2016Fimiani et al 2016;Ludwig et al 2016;Sørensen et al 2017). ...
... The main difference between high and low clouds is that the high clouds are colder. An explanation may lie in the fact that, the physical state of the cloud droplets may play a significant role in the cosmic-ray-cloud interaction (Bondo et al., 2010). It has been pointed out before that the physics of ice and liquid clouds may differ (Harrison, 2008). ...
... Some researchers studied the possible connection of the geomagnetic field with cloud formation, precipitation, temperature, and climate [42][43][44]. Their achievements showed that the cosmic rays generate electrically charged particles when they hit the atmosphere. These particles absorb the water molecules from the air and cause them to clump together until they condense into clouds. ...
... Additionally, ion-ion reaction have shown to play an essential role for the formation of CCNs on Earth in the higher atmospheric regions. 23 A basic understanding of cloud formation will help to address some of these challenges, 24 but not all. ...