The intensity of energetic particles at the evolving Earth

2021 ◽  
Author(s):  
Donna Rodgers-Lee ◽  
Andrew Taylor ◽  
Aline Vidotto ◽  
Turlough Downes
Keyword(s):  
Energetic Particle ◽  
Cosmic Ray ◽  
Galactic Cosmic Rays ◽  
Energetic Particles ◽  
Particle Energy ◽  
Prebiotic Molecules ◽  
The Origin Of Life ◽  
Particle Fluxes ◽  
Life On Earth ◽  
Galactic Cosmic Ray

<p>Energetic particles can drive the formation of prebiotic molecules in exoplanetary which are important for the origin of life. On the other hand, large energetic particle fluxes are known to be detrimental to developed life by damaging DNA. Thus, in order to understand the origin, and subsequent survival, of life on Earth it is necessary to first understand the energetic particle fluxes incident on Earth at that time. There are two types of energetic particles that are important: stellar energetic particles accelerated by their host star and Galactic cosmic rays.</p> <p>I will present our recent results that model the propagation of these energetic particles through the wind of a Sun-like star during its lifetime. We find, at the time when life is thought to have begun on Earth, that Galactic cosmic ray fluxes were greatly suppressed in comparison to present-day values. However, I will show that stellar energetic particle fluxes would have been larger than present-day values. I motivate that the maximum stellar energetic particle energy increases for younger stars. This is extremely important because higher energy particles are more likely to impact the surface of a planet, in addition to its atmosphere. I will briefly discuss how we applied our model to an exoplanetary system and how this can be linked to upcoming observations.</p>

scholarly journals The Galactic cosmic ray intensity at the evolving Earth and young exoplanets

2020 ◽  
Author(s):  
Donna Rodgers-Lee ◽  
Aline Vidotto ◽  
Andrew Taylor ◽  
Paul Rimmer ◽  
Turlough Downes
Keyword(s):  
Solar Wind ◽  
Cosmic Rays ◽  
Cosmic Ray ◽  
Galactic Cosmic Rays ◽  
The Sun ◽  
Cosmic Ray Intensity ◽  
Chemical Signature ◽  
Exoplanetary Systems ◽  
Life On Earth ◽  
Galactic Cosmic Ray

<p>Cosmic rays may have contributed to the start of life on Earth. Cosmic rays also influence and contribute to atmospheric electrical circuits, cloud cover and biological mutation rates which are important for the characterisation of exoplanetary systems. The flux of Galactic cosmic rays present at the time when life is thought to have begun on the young Earth or in other young exoplanetary systems is largely determined by the properties of the stellar wind. </p> <p>The spectrum of Galactic cosmic rays that we observe at Earth is modulated, or suppressed, by the magnetised solar wind and thus differs from the local interstellar spectrum observed by Voyager 1 and 2 outside of the solar system. Upon reaching 1au, Galactic cosmic rays subsequently interact with the Earth’s magnetosphere and some of their energy is deposited in the upper atmosphere. The properties of the solar wind, such as the magnetic field strength and velocity profile, evolve with time. Generally, young solar-type stars are very magnetically active and are therefore thought to drive stronger stellar winds. </p> <p>Here I will present our recent results which simulate the propagation of Galactic cosmic rays through the heliosphere to the location of Earth as a function of the Sun's life, from 600 Myr to 6 Gyr, in the Sun’s future. I will specifically focus on the flux of Galactic cosmic rays present at the time when life is thought to have started on Earth (~1 Gyr). I will show that the intensity of Galactic cosmic rays which reached the young Earth, by interacting with the solar wind, would have been greatly reduced in comparison to the present day intensity. I will also discuss the effect that the Sun being a slow/fast rotator would have had on the flux of cosmic rays reaching Earth at early times in the solar system's life.</p> <p>Despite the importance of Galactic cosmic rays, their chemical signature in the atmospheres’ of young Earth-like exoplanets may not be observable with instruments in the near future. On the other hand, it may instead be possible to detect their chemical signature by observing young warm Jupiters. Thus, I will also discuss the HR 2562b exoplanetary system as a candidate for observing the chemical signature of Galactic cosmic rays in a young exoplanetary atmosphere with upcoming missions such as JWST.</p>

scholarly journals Charting nearby stellar systems: The intensity of Galactic cosmic rays for a sample of solar-type stars

2021 ◽  
Author(s):  
Donna Rodgers-Lee ◽  
Aline Vidotto ◽  
Amanda Mesquita
Keyword(s):  
Cosmic Rays ◽  
Cosmic Ray ◽  
Galactic Cosmic Rays ◽  
Stellar Winds ◽  
Habitable Zone ◽  
Chemical Modelling ◽  
Solar Type ◽  
Prebiotic Molecules ◽  
Exoplanetary Atmospheres ◽  
Galactic Cosmic Ray

<p>Galactic cosmic rays are important for exoplanetary atmospheres. They can contribute to the formation of hazes, prebiotic molecules and atmospheric electrical circuits. A number of so-called fingerprint ions, such as oxonium, have been identified from chemical modelling which are thought to be signatures of ionisation by energetic particles, such as Galactic cosmic rays. These fingerprint ions may be observed in exoplanetary atmospheres with upcoming JWST observations.</p> <p>I will discuss our recent results that model the propagation of Galactic cosmic rays through the stellar winds of a number of nearby solar-type stars. Our sample comprises of 5 well-observed solar-type stars that we have constructed well-constrained stellar wind models for. This allows us to calculate the transport of Galactic cosmic rays through these systems. I will present our results of the Galactic cosmic ray fluxes that reach (a) the habitable zone and (b) the location of known exoplanets. The systems show a variety of behaviour and I will discuss the most promising systems for upcoming JWST observations. </p>

scholarly journals Particle Acceleration by Supernova Shocks and Spallogenic Nucleosynthesis of Light Elements

2018 ◽  
Vol 68 (1) ◽  
pp. 377-404 ◽  
Author(s):  
Vincent Tatischeff ◽  
Stefano Gabici
Keyword(s):  
Cosmic Rays ◽  
Light Element ◽  
Cosmic Ray ◽  
Nuclear Interaction ◽  
Galactic Cosmic Rays ◽  
Light Elements ◽  
Halo Stars ◽  
The Standard Model ◽  
Low Metallicity ◽  
Galactic Cosmic Ray

In this review, we first reassess the supernova remnant paradigm for the origin of Galactic cosmic rays in the light of recent cosmic-ray data acquired by the Voyager 1 spacecraft. We then describe the theory of light-element nucleosynthesis by nuclear interaction of cosmic rays with the interstellar medium and outline the problem of explaining the measured beryllium abundances in old halo stars of low metallicity with the standard model of the Galactic cosmic-ray origin. We then discuss the various cosmic-ray models proposed in the literature to account for the measured evolution of the light elements in the Milky Way, and point out the difficulties that they all encounter. It seems to us that, among all possibilities, the superbubble model provides the most satisfactory explanation for these observations.

scholarly journals Structure of the Power Spectral Density of Galactic Cosmic Ray Variation during 1953-2016

2017 ◽  
Vol 13 (S335) ◽  
pp. 82-86
Author(s):  
Pauli Väisänen ◽  
Ilya Usoskin ◽  
Kalevi Mursula
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Cosmic Ray ◽  
Galactic Cosmic Rays ◽  
Period Range ◽  
Power Spectral ◽  
Hourly Data ◽  
Spectral Peaks ◽  
Two Peaks ◽  
Galactic Cosmic Ray

AbstractFluxes of galactic cosmic rays (GCR) observed at 1 AU are modulated inside the heliosphere at different time scales. Here we study the properties of the power spectral density (PSD) of galactic cosmic ray variability using hourly data from 31 neutron monitors (NM) from 1953 to 2016. We pay particular attention to the reliability of the used datasets and methods. We present the overall PSD and discuss different parts of the spectrum and the related periodicities. We find significant spectral peaks at the periods of 11 years, 1.75 years, 155 days, 27 days and 24 hours and the harmonics of the latter two peaks. We calculate a power law slope of −1.79 ± 0.13 for the period range between 50 and 130 hours and a slope of −1.34 ± 0.17 for the period range between 40 days and 3.4 years (1000 − 30000 h).

scholarly journals On the possibility of galactic cosmic ray-induced radiolysis-powered life in subsurface environments in the Universe

2016 ◽  
Vol 13 (123) ◽  
pp. 20160459 ◽  
Author(s):  
Dimitra Atri
Keyword(s):  
South African ◽  
Cosmic Ray ◽  
Galactic Cosmic Rays ◽  
Solar Origin ◽  
Secondary Particles ◽  
Available Energy ◽  
Subsurface Environments ◽  
Terrestrial Life ◽  
Galactic Cosmic Ray ◽  
The Universe

Photosynthesis is a mechanism developed by terrestrial life to utilize the energy from photons of solar origin for biological use. Subsurface regions are isolated from the photosphere, and consequently are incapable of utilizing this energy. This opens up the opportunity for life to evolve alternative mechanisms for harvesting available energy. Bacterium Candidatus Desulforudis audaxviator , found 2.8 km deep in a South African mine, harvests energy from radiolysis, induced by particles emitted from radioactive U, Th and K present in surrounding rock. Another radiation source in the subsurface environments is secondary particles generated by galactic cosmic rays (GCRs). Using Monte Carlo simulations, it is shown that it is a steady source of energy comparable to that produced by radioactive substances, and the possibility of a slow metabolizing life flourishing on it cannot be ruled out. Two mechanisms are proposed through which GCR-induced secondary particles can be utilized for biological use in subsurface environments: (i) GCRs injecting energy in the environment through particle-induced radiolysis and (ii) organic synthesis from GCR secondaries interacting with the medium. Laboratory experiments to test these hypotheses are also proposed. Implications of these mechanisms on finding life in the Solar System and elsewhere in the Universe are discussed.

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

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

<p>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’ 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.</p><p>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.</p>

Energy spectra of carbon and oxygen - Predictions from HELIOS E6 for Solar Orbiter HET

2020 ◽  
Author(s):  
Johannes Marquardt ◽  
Bernd Heber ◽  
Robert Elftmann ◽  
Robert Wimmer-Schweingruber
Keyword(s):  
Energetic Particle ◽  
Solar Minimum ◽  
Cosmic Ray ◽  
High Energy ◽  
Energy Spectra ◽  
Particle Detector ◽  
Quiet Time ◽  
Transport Models ◽  
Galactic Cosmic Ray ◽  
Insight Into

<p>Anomalous cosmic rays (ACRs) are well-suited to probe the transport conditions of energetic particles in the innermost heliosphere. We revisit the HELIOS Experiment 6 (E6) data in view of the upcoming Solar Orbiter Energetic Particle Detector (EPD) suite that will perform measurements during a comparable solar minimum within the same distance.</p><p>Adapting the HELIOS energy ranges for oxygen and carbon to the ones given by the High Energy Telescope (HET) allows us to determine predictions for the upcoming measurements but also to put constraints on particle transport models that provide new insight into the boundary conditions close to the Sun.</p><p>We present here the adapted energy spectra of galactic cosmic ray (GCR) carbon and oxygen, as well as of ACR oxygen during solar quiet time periods between 1975 to 1977. Due to the higher energy threshold of HET in comparison to E6 gradients of about 20% at 15 MeV/nucleon are expected. The largest ACR gradient measured by E6 was obtained to be about 75% between 9 and 13 MeV/nucleon and 0.4 AU and 1 AU.</p>

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