Cosmic rays, aerosol formation and cloud-condensation nuclei: sensitivities to model uncertainties

Abstract. The flux of cosmic rays to the atmosphere has been reported to correlate with cloud and aerosol properties. One proposed mechanism for these correlations is the "ion-aerosol clear-air" mechanism where the cosmic rays modulate atmospheric ion concentrations, ion-induced nucleation of aerosols and cloud condensation nuclei (CCN) concentrations. We use a global chemical transport model with online aerosol microphysics to explore the dependence of CCN concentrations on the cosmic-ray flux. Expanding upon previous work, we test the sensitivity of the cosmic-ray/CCN connection to several uncertain parameters in the model including primary emissions, Secondary Organic Aerosol (SOA) condensation and charge-enhanced condensational growth. The sensitivity of CCN to cosmic rays increases when simulations are run with decreased primary emissions, but show location-dependent behavior from increased amounts of secondary organic aerosol and charge-enhanced growth. For all test cases, the change in the concentration of particles larger than 80 nm between solar minimum (high cosmic ray flux) and solar maximum (low cosmic ray flux) simulations is less than 0.2 %. The change in the total number of particles larger than 10 nm was larger, but always less than 1 %. The simulated change in the column-integrated Ångström exponent was negligible for all test cases. Additionally, we test the predicted aerosol sensitivity to week-long Forbush decreases of cosmic rays and find that the maximum change in aerosol properties for these cases is similar to steady-state aerosol differences between the solar maximum and solar minimum. These results provide evidence that the effect of cosmic rays on CCN and clouds through the ion-aerosol clear-sky mechanism is limited by dampening from aerosol processes.

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Cosmic rays, aerosol formation and cloud-condensation nuclei: sensitivities to model uncertainties

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-2697-2011 ◽

2011 ◽

Vol 11 (1) ◽

pp. 2697-2732 ◽

Cited By ~ 1

Author(s):

E. J. Snow-Kropla ◽

J. R. Pierce ◽

D. M. Westervelt ◽

W. Trivitayanurak

Keyword(s):

Cosmic Rays ◽

Solar Minimum ◽

Solar Maximum ◽

Cloud Condensation Nuclei ◽

Cosmic Ray ◽

Organic Aerosol ◽

Test Cases ◽

Primary Emissions ◽

Cosmic Ray Flux ◽

Aerosol Properties

Abstract. The flux of cosmic rays to the atmosphere has been observed to correlate with cloud and aerosol properties. One proposed mechanism for these correlations is the "ion-aerosol clear-air" mechanism where the cosmic rays modulate atmospheric ion concentrations, ion-induced nucleation of aerosols and cloud condensation nuclei (CCN) concentrations. We use a global chemical transport model with online aerosol microphysics to explore the dependence of CCN concentrations on the cosmic-ray flux. Expanding upon previous work, we test the sensitivity of the cosmic-ray/CCN connection to several uncertain parameters in the model including primary emissions, Secondary Organic Aerosol (SOA) condensation and charge-enhanced condensational growth. The sensitivity of CCN to cosmic rays increases when simulations are run with decreased primary emissions, but show location-dependent behavior from increased amounts of secondary organic aerosol and charge-enhanced growth. For all test cases, the change in the concentration of particles larger than 80 nm between solar minimum (high cosmic ray flux) and solar maximum (low cosmic ray flux) simulations is less than 0.2%. The change in the total number of particles larger than 10 nm was larger, but always less than 1%. The simulated change in the column-integrated Ångström exponent was negligible for all test cases. Additionally, we test the predicted aerosol sensitivity to week-long Forbush decreases of cosmic rays and find that the maximum change in aerosol properties for these cases is similar to steady-state aerosol differences between the solar maximum and solar minimum. These results provide evidence that the effect of cosmic rays on CCN and clouds through the ion-aerosol clear-sky mechanism is limited by dampening from aerosol processes.

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Latitudinal and radial variation of >2 GeV/n protons and alpha-particles at solar maximum: ULYSSES COSPIN/KET and neutron monitor network observations

Annales Geophysicae ◽

10.5194/angeo-21-1295-2003 ◽

2003 ◽

Vol 21 (6) ◽

pp. 1295-1302 ◽

Cited By ~ 9

Author(s):

A. V. Belov ◽

E. A. Eroshenko ◽

B. Heber ◽

V. G. Yanke ◽

A. Raviart ◽

...

Keyword(s):

Magnetic Field ◽

Cosmic Rays ◽

Neutron Monitor ◽

Solar Minimum ◽

Latitudinal Gradient ◽

Solar Maximum ◽

Cosmic Ray ◽

Galactic Cosmic Rays ◽

Alpha Particles ◽

Polar Regions

Abstract. Ulysses, launched in October 1990, began its second out-of-ecliptic orbit in September 1997. In 2000/2001 the spacecraft passed from the south to the north polar regions of the Sun in the inner heliosphere. In contrast to the first rapid pole to pole passage in 1994/1995 close to solar minimum, Ulysses experiences now solar maximum conditions. The Kiel Electron Telescope (KET) measures also protons and alpha-particles in the energy range from 5 MeV/n to >2 GeV/n. To derive radial and latitudinal gradients for >2 GeV/n protons and alpha-particles, data from the Chicago instrument on board IMP-8 and the neutron monitor network have been used to determine the corresponding time profiles at Earth. We obtain a spatial distribution at solar maximum which differs greatly from the solar minimum distribution. A steady-state approximation, which was characterized by a small radial and significant latitudinal gradient at solar minimum, was interchanged with a highly variable one with a large radial and a small – consistent with zero – latitudinal gradient. A significant deviation from a spherically symmetric cosmic ray distribution following the reversal of the solar magnetic field in 2000/2001 has not been observed yet. A small deviation has only been observed at northern polar regions, showing an excess of particles instead of the expected depression. This indicates that the reconfiguration of the heliospheric magnetic field, caused by the reappearance of the northern polar coronal hole, starts dominating the modulation of galactic cosmic rays already at solar maximum.Key words. Interplanetary physics (cosmic rays; energetic particles) – Space plasma physics (charged particle motion and acceleration)

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Variation with solar cycle of the diurnal variation of cosmic rays underground

Canadian Journal of Physics ◽

10.1139/p68-351 ◽

1968 ◽

Vol 46 (10) ◽

pp. S784-S787 ◽

Cited By ~ 14

Author(s):

Victor H. Regener ◽

Derek B. Swinson

Keyword(s):

New Mexico ◽

Diurnal Variation ◽

Solar Minimum ◽

Solar Maximum ◽

Cosmic Ray ◽

Local Solar Time ◽

The North ◽

Primary Particles ◽

Cosmic Ray Flux ◽

Diurnal Maximum

The cosmic-ray diurnal variation has been observed with scintillator telescopes at a depth of 40 m.w.e. at Chacaltaya, Bolivia, since the last solar maximum, and at the same depth near Albuquerque, New Mexico, since the last solar minimum. During the solar maximum from 1958 to 1960 the amplitude of the diurnal variation was 0.3% for the Chacaltaya telescopes, but at solar minimum early in 1965 it was as low as 0.05%. Since that time, the amplitude has been steadily increasing, and it is now between 0.1% and 0.2% at both the Bolivia and the New Mexico stations.The telescopes measure the cosmic-ray flux from the north, south, east, and west directions, as well as from the vertical; and the various observed times of the diurnal maximum for these directions confirm the extraterrestrial nature of the anisotropy. The maximum occurs at approximately 15 h local solar time in the vertical telescopes. A study of the asymptotic directions of these telescopes for differing primary energies, and of the behavior of the phases of the diurnal variation at the two stations, gives indications of the energies of the primary particles responsible for the diurnal variation. The results are compared with the models of Axford and of Ahluwalia and Dessler.

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Ulysses COSPIN observations of cosmic rays and solar energetic particles from the South Pole to the North Pole of the Sun during solar maximum

Annales Geophysicae ◽

10.5194/angeo-21-1217-2003 ◽

2003 ◽

Vol 21 (6) ◽

pp. 1217-1228 ◽

Cited By ~ 56

Author(s):

R. B. McKibben ◽

J. J. Connell ◽

C. Lopate ◽

M. Zhang ◽

J. D. Anglin ◽

...

Keyword(s):

Cosmic Rays ◽

Solar Maximum ◽

Cosmic Ray ◽

Energetic Particles ◽

Solar Energetic Particles ◽

Polar Regions ◽

The Sun ◽

The South ◽

The North ◽

Inner Heliosphere

Abstract. In 2000–2001 Ulysses passed from the south to the north polar regions of the Sun in the inner heliosphere, providing a snapshot of the latitudinal structure of cosmic ray modulation and solar energetic particle populations during a period near solar maximum. Observations from the COSPIN suite of energetic charged particle telescopes show that latitude variations in the cosmic ray intensity in the inner heliosphere are nearly non-existent near solar maximum, whereas small but clear latitude gradients were observed during the similar phase of Ulysses’ orbit near the 1994–95 solar minimum. At proton energies above ~10 MeV and extending up to >70 MeV, the intensities are often dominated by Solar Energetic Particles (SEPs) accelerated near the Sun in association with intense solar flares and large Coronal Mass Ejections (CMEs). At lower energies the particle intensities are almost constantly enhanced above background, most likely as a result of a mix of SEPs and particles accelerated by interplanetary shocks. Simultaneous high-latitude Ulysses and near-Earth observations show that most events that produce large flux increases near Earth also produce flux increases at Ulysses, even at the highest latitudes attained. Particle anisotropies during particle onsets at Ulysses are typically directed outwards from the Sun, suggesting either acceleration extending to high latitudes or efficient cross-field propagation somewhere inside the orbit of Ulysses. Both cosmic ray and SEP observations are consistent with highly efficient transport of energetic charged particles between the equatorial and polar regions and across the mean interplanetary magnetic fields in the inner heliosphere.Key words. Interplanetary physics (cosmic rays) – Solar physics, astrophysics and astronomy (energetic particles; flares and mass ejections)

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The Ulysses fast latitude scans: COSPIN/KET results

Annales Geophysicae ◽

10.5194/angeo-21-1275-2003 ◽

2003 ◽

Vol 21 (6) ◽

pp. 1275-1288 ◽

Cited By ~ 8

Author(s):

B. Heber ◽

G. Sarri ◽

G. Wibberenz ◽

C. Paizis ◽

P. Ferrando ◽

...

Keyword(s):

Magnetic Field ◽

Cosmic Rays ◽

Solar Magnetic Field ◽

Solar Maximum ◽

Cosmic Ray ◽

Galactic Cosmic Rays ◽

Solar Particle Events ◽

Interplanetary Magnetic Fields ◽

Solar Particle ◽

Interplanetary Physics

Abstract. Ulysses, launched in October 1990, began its second out-of-ecliptic orbit in December 1997, and its second fast latitude scan in September 2000. In contrast to the first fast latitude scan in 1994/1995, during the second fast latitude scan solar activity was close to maximum. The solar magnetic field reversed its polarity around July 2000. While the first latitude scan mainly gave a snapshot of the spatial distribution of galactic cosmic rays, the second one is dominated by temporal variations. Solar particle increases are observed at all heliographic latitudes, including events that produce >250 MeV protons and 50 MeV electrons. Using observations from the University of Chicago’s instrument on board IMP8 at Earth, we find that most solar particle events are observed at both high and low latitudes, indicating either acceleration of these particles over a broad latitude range or an efficient latitudinal transport. The latter is supported by "quiet time" variations in the MeV electron background, if interpreted as Jovian electrons. No latitudinal gradient was found for >106 MeV galactic cosmic ray protons, during the solar maximum fast latitude scan. The electron to proton ratio remains constant and has practically the same value as in the previous solar maximum. Both results indicate that drift is of minor importance. It was expected that, with the reversal of the solar magnetic field and in the declining phase of the solar cycle, this ratio should increase. This was, however, not observed, probably because the transition to the new magnetic cycle was not completely terminated within the heliosphere, as indicated by the Ulysses magnetic field and solar wind measurements. We argue that the new A<0-solar magnetic modulation epoch will establish itself once both polar coronal holes have developed.Key words. Interplanetary physics (cosmic rays; energetic particles; interplanetary magnetic fields)

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A New Determination of Muon Directional Coupling Coefficients

Publications of the Astronomical Society of Australia ◽

10.1017/s132335800001119x ◽

1968 ◽

Vol 1 (4) ◽

pp. 154-157

Author(s):

D. J. Cooke ◽

A. G. Fenton

Keyword(s):

Cosmic Rays ◽

Solar System ◽

Cosmic Ray ◽

Accurate Information ◽

Coupling Coefficients ◽

The Earth ◽

Directional Coupling ◽

Cosmic Ray Flux ◽

Primary Cosmic Rays

Primary cosmic rays passing through the solar system carry with them valuable information about solar and astrophysical phenomena in the form of intensity and spectral variations. In order that this information be efficiently extracted from observations of the directional cosmic-ray flux at the surface of the Earth, it is essential to have accurate information available to enable the relating of the observed secondary cosmic-ray directions of motion and intensity to those outside the range of the disturbing terrestrial influences.

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Solar Wind Effects on the Transport of 3–10 MeV Cosmic‐Ray Electrons from Solar Minimum to Solar Maximum

The Astrophysical Journal ◽

10.1086/376869 ◽

2003 ◽

Vol 594 (1) ◽

pp. 552-560 ◽

Cited By ~ 18

Author(s):

S. E. S. Ferreira ◽

M. S. Potgieter ◽

D. M. Moeketsi ◽

B. Heber ◽

H. Fichtner

Keyword(s):

Solar Wind ◽

Solar Minimum ◽

Solar Maximum ◽

Cosmic Ray ◽

Wind Effects

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TeV Cosmic Ray Anisotropy and the Heliospheric Magnetic Field

ASTRA Proceedings ◽

10.5194/ap-1-65-2014 ◽

2014 ◽

Vol 1 ◽

pp. 65-71 ◽

Cited By ~ 1

Author(s):

P. Desiati ◽

A. Lazarian

Keyword(s):

Magnetic Field ◽

Cosmic Rays ◽

Particle Distribution ◽

Sudden Change ◽

Cosmic Ray ◽

Arrival Direction ◽

Energy Dependency ◽

The Galaxy ◽

Different Characteristics ◽

Cosmic Ray Flux

Abstract. Cosmic rays are observed to possess a small non uniform distribution in arrival direction. Such anisotropy appears to have a roughly consistent topology between tens of GeV and hundreds of TeV, with a smooth energy dependency on phase and amplitude. Above a few hundreds of TeV a sudden change in the topology of the anisotropy is observed. The distribution of cosmic ray sources in the Milky Way is expected to inject anisotropy on the cosmic ray flux. The nearest and most recent sources, in particular, are expected to contribute more significantly than others. Moreover the interstellar medium is expected to have different characteristics throughout the Galaxy, with different turbulent properties and injection scales. Propagation effects in the interstellar magnetic field can shape the cosmic ray particle distribution as well. In particular, in the 1–10 TeV energy range, they have a gyroradius comparable to the size of the Heliosphere, assuming a typical interstellar magnetic field strength of 3 μG. Therefore they are expected to be strongly affected by the Heliosphere in a manner ordered by the direction of the local interstellar magnetic field and of the heliotail. In this paper we discuss on the possibility that TeV cosmic rays arrival distribution might be significantly redistributed as they propagate through the Heliosphere.

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Cosmic Rays in the Galactic Centre

Australian Journal of Physics ◽

10.1071/ph800115 ◽

1980 ◽

Vol 33 (1) ◽

pp. 115

Author(s):

Masato Yoshimori

Keyword(s):

Energy Density ◽

Cosmic Rays ◽

Solar System ◽

Molecular Clouds ◽

Cosmic Ray ◽

High Energy ◽

Galactic Centre ◽

Centre Region ◽

Cosmic Ray Flux

The cosmic ray flux in the galactic centre region is predicted from the observed data for high energy y rays, y-ray lines and massive molecular clouds. The predicted cosmic ray fluxes above 1 GeVand below 100 MeV are two and four orders of magnitude respectively larger than the value in the neighbourhood of the solar system. The corresponding energy density of cosmic rays is estimated to be 100 eV cm- 3 ? Such a concentrated stream of cosmic rays could accelerate the dense and massive molecular clouds by transfer of their momentum.

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