Cosmic Ray Induced Ion Production in the Atmosphere

Cosmic rays cause ionisation in all planetary atmospheres. As they collide with particles in the atmosphere, secondary charged particles are produced that lead to the formation of cluster ions. The incident cosmic ray flux and atmospheric density of the atmosphere in question determine a profile of ion production rate. From the top of the atmosphere to the planetary surface, this rate increases with atmospheric density to a point where the flux becomes attenuated such that the rate then decreases, resulting in a peak ion production rate at some height known as the Pfotzer-Regener maximum. When these ions interact with aerosols and cloud particles, a net charge results on those particles and this is known to affect their microphysical attributes and behaviour. For example, charging may enable the activation of droplets at lower saturation ratios and also enhance collision efficiency and droplet growth. This becomes important when clouds occur at a height where ionisation is sufficient to have a substantive charging effect on the cloud particles. This has very little direct effect on Earth as peak ion production occurs high above the clouds at 15-20 km; however, on Venus for example the Pfotzer-Regener maximum occurs at ~63 km, coinciding with the main sulphuric acid cloud deck. In situations such as this, the direct result of cloud charging due to cosmic ray induced ionisation may strongly influence cloud processes, their occurrence, and behaviour.This work uses laboratory experiments to explore the effects of charging on cloud droplets. Individual droplets are levitated in a vertical acoustic standing wave and then monitored using a CCD camera with a high magnification objective lens to determine the droplet lifetime and evaporation rate. Experiments were conducted using both the droplets&#8217; naturally occurring charge as well as some where the region around the drop was initially flooded with ions from an external corona source. The polarity and charge magnitude of the droplets was determined by applying a 10 kV/m electric field horizontally across the drop and observing its deflection towards one of the electrodes. Theory predicts that the more highly charged a droplet is, the more resistant to evaporation it becomes. Experimental data collected during this study agrees with this, with more highly charged droplets observed to have slower evaporation rates. However, highly charged drops were also observed to periodically become unstable during evaporation and undergo Rayleigh explosions. This occurs when the droplet evaporates until its diameter becomes such that its fissility reaches the threshold at which the instability occurs. Each instability of a highly charged drop removes mass, reducing the overall droplet lifetime regardless of the slower evaporation rate. Therefore, where enhanced ionisation occurs in the presence of clouds the end result may be to reduce droplet stability.

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Galactic cosmic ray induced ionisation on Venus and its effect on cloud droplet stability

10.5194/egusphere-egu2020-3000 ◽

2020 ◽

Author(s):

Martin Airey ◽

Giles Harrison ◽

Karen Aplin ◽

Christian Pfrang

Keyword(s):

Cosmic Rays ◽

Evaporation Rate ◽

Cloud Droplet ◽

Ccd Camera ◽

Cosmic Ray ◽

Galactic Cosmic Rays ◽

Cloud Droplets ◽

Droplet Stability ◽

Ion Production ◽

Galactic Cosmic Ray

Galactic cosmic rays are ubiquitous in solar system atmospheres. On Venus, the altitude of peak ion production due to cosmic rays (the Pfotzer-Regener maximum) occurs at ~63 km, within the optically thick region of the upper clouds. This indicates the possibility of electrical effects on droplets within Venusian clouds. Motivated by this, our VENI (Venusian Electricity, Nephology, and Ionisation) project explores effects of galactic cosmic ray (GCR) induced ionisation on cloud droplets in circumstances with relevance to Venus&#8217; atmosphere. Charge is known to lower the critical supersaturation required for cloud droplets to form; slightly larger droplets are stable at lower saturation ratios if sufficiently charged. Condensation of gas directly onto ions is also potentially possible on Venus if the atmosphere is sufficiently supersaturated. GCRs and the secondary charged particles they produce are therefore anticipated to affect cloud droplet behaviour on Venus.Experiments have been conducted using electrically isolated droplets, through levitation in a standing acoustic wave. The droplets are monitored with a high-magnification CCD camera to determine their evaporation rate and charge. The charge is measured both by the deflection in an electric field and by passing the droplet through a custom-built induction ring. A relationship between the evaporation rate and charge of the droplets is found to be consistent with theory, allowing droplet lifetime to be predicted for a given charge. Further experiments using sulphuric acid droplets in a carbon dioxide environment offer more direct relevance to the Venusian environment and cosmic ray enhancement due to solar energetic particles (SEPs) in space weather events will be simulated using a corona source.

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Solar energetic particle interactions with the Venusian atmosphere

Annales Geophysicae ◽

10.5194/angeo-34-595-2016 ◽

2016 ◽

Vol 34 (7) ◽

pp. 595-608 ◽

Cited By ~ 10

Author(s):

Christina Plainaki ◽

Pavlos Paschalis ◽

Davide Grassi ◽

Helen Mavromichalaki ◽

Maria Andriopoulou

Keyword(s):

Space Weather ◽

Solar Energetic Particle ◽

Cosmic Ray ◽

Weather Conditions ◽

Data Interpretation ◽

Field Configuration ◽

Near Earth Space ◽

Ion Production ◽

Galactic Cosmic Ray ◽

Venusian Atmosphere

Abstract. In the context of planetary space weather, we estimate the ion production rates in the Venusian atmosphere due to the interactions of solar energetic particles (SEPs) with gas. The assumed concept for our estimations is based on two cases of SEP events, previously observed in near-Earth space: the event in October 1989 and the event in May 2012. For both cases, we assume that the directional properties of the flux and the interplanetary magnetic field configuration would have allowed the SEPs' arrival at Venus and their penetration to the planet's atmosphere. For the event in May 2012, we consider the solar particle properties (integrated flux and rigidity spectrum) obtained by the Neutron Monitor Based Anisotropic GLE Pure Power Law (NMBANGLE PPOLA) model (Plainaki et al., 2010, 2014) applied previously for the Earth case and scaled to the distance of Venus from the Sun. For the simulation of the actual cascade in the Venusian atmosphere initiated by the incoming particle fluxes, we apply the DYASTIMA code, a Monte Carlo (MC) application based on the Geant4 software (Paschalis et al., 2014). Our predictions are afterwards compared to other estimations derived from previous studies and discussed. Finally, we discuss the differences between the nominal ionization profile due to galactic cosmic-ray–atmosphere interactions and the profile during periods of intense solar activity, and we show the importance of understanding space weather conditions on Venus in the context of future mission preparation and data interpretation.

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Atmospheric changes caused by galactic cosmic rays over the period 1960–2010

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-5853-2016 ◽

2016 ◽

Vol 16 (9) ◽

pp. 5853-5866 ◽

Cited By ~ 17

Author(s):

Charles H. Jackman ◽

Daniel R. Marsh ◽

Douglas E. Kinnison ◽

Christopher J. Mertens ◽

Eric L. Fleming

Keyword(s):

Cosmic Rays ◽

Climate Model ◽

Cosmic Ray ◽

Galactic Cosmic Rays ◽

Sulfate Aerosol ◽

Solar Cycle Variation ◽

Aerosol Loading ◽

Ion Production ◽

Column Ozone ◽

The Impact

Abstract. The Specified Dynamics version of the Whole Atmosphere Community Climate Model (SD-WACCM) and the Goddard Space Flight Center two-dimensional (GSFC 2-D) models are used to investigate the effect of galactic cosmic rays (GCRs) on the atmosphere over the 1960–2010 time period. The Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) computation of the GCR-caused ionization rates are used in these simulations. GCR-caused maximum NOx increases of 4–15 % are computed in the Southern polar troposphere with associated ozone increases of 1–2 %. NOx increases of ∼ 1–6 % are calculated for the lower stratosphere with associated ozone decreases of 0.2–1 %. The primary impact of GCRs on ozone was due to their production of NOx. The impact of GCRs varies with the atmospheric chlorine loading, sulfate aerosol loading, and solar cycle variation. Because of the interference between the NOx and ClOx ozone loss cycles (e.g., the ClO + NO2+ M  →  ClONO2+ M reaction) and the change in the importance of ClOx in the ozone budget, GCRs cause larger atmospheric impacts with less chlorine loading. GCRs also cause larger atmospheric impacts with less sulfate aerosol loading and for years closer to solar minimum. GCR-caused decreases of annual average global total ozone (AAGTO) were computed to be 0.2 % or less with GCR-caused column ozone increases between 1000 and 100 hPa of 0.08 % or less and GCR-caused column ozone decreases between 100 and 1 hPa of 0.23 % or less. Although these computed ozone impacts are small, GCRs provide a natural influence on ozone and need to be quantified over long time periods. This result serves as a lower limit because of the use of the ionization model NAIRAS/HZETRN which underestimates the ion production by neglecting electromagnetic and muon branches of the cosmic ray induced cascade. This will be corrected in future works.

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Cosmic Ray Induced Ion Production in the Atmosphere

Space Science Reviews ◽

10.1007/s11214-008-9339-y ◽

2008 ◽

Vol 137 (1-4) ◽

pp. 149-173 ◽

Cited By ~ 178

Author(s):

G. A. Bazilevskaya ◽

I. G. Usoskin ◽

E. O. Flückiger ◽

R. G. Harrison ◽

L. Desorgher ◽

...

Keyword(s):

Cosmic Ray ◽

Ion Production

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From decimeter-scale elevated ionic conductivity regions in the cloud to lightning initiation

Scientific Reports ◽

10.1038/s41598-021-97321-4 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

D. I. Iudin ◽

V. A. Rakov ◽

A. A. Syssoev ◽

A. A. Bulatov ◽

M. Hayakawa

Keyword(s):

Electric Field ◽

Spatial Scales ◽

Field Enhancement ◽

Cumulative Effect ◽

Cosmic Ray ◽

Ion Concentration ◽

Small Scale ◽

3D Network ◽

Ion Production ◽

Lightning Initiation

AbstractIn this work, we represent the lightning initiation scenario as a sequence of two transitions of discharge activity to progressively larger spatial scales: the first one is from small-scale avalanches to intermediate-scale streamers; and the second one is from streamers to the lightning seed. We postulate the existence of ion production centers in the cloud, whose occurrence is caused by electric field bursts accompanying hydrometeor collisions (or near collisions) in the turbulent thundercloud environment. When a new ion production center is created inside (fully or partially) the residual ion spot left behind by a previously established center, there is a cumulative effect in the increasing of ion concentration. As a result, the essentially non-conducting thundercloud becomes seeded by elevated ion-conductivity regions (EICRs) with spatial extent of 0.1–1 m and a lifetime of 1–10 s. The electric field on the surface of an EICR (due to its conductivity being at least 4 orders of magnitude higher than ambient) is a factor of 3 or more higher than ambient. For a maximum ambient electric field of 100 kV/m typically measured in thunderclouds, such field enhancement is sufficient for initiation of positive streamers and their propagation over distances of the order of decimeters, and this will be happening naturally, without any external agents (e.g., superenergetic cosmic ray particles) or extraordinary in-cloud conditions, such as very high potential differences or very large hydrometeors. Provided that each EICR generates at least one streamer during its lifetime, the streamers will form a 3D network, some parts of which will contain hot channel segments created via the cumulative heating and/or thermal-ionizational instability. These hot channel segments will polarize, interact with each other, and cluster, forming longer conducting structures in the cloud. When the ambient potential difference bridged by such a conducting structure exceeds 3 MV, we assume that the lightning seed, capable of self-sustained bidirectional extension, is formed.

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