Role Of Cosmic Rays Research Articles

CHANG-ES

Context. Galactic winds play a key role in regulating the evolution of galaxies over cosmic time. In recent years, the role of cosmic rays (CRs) in the formation of the galactic wind has increasingly gained attention. Therefore, we use radio continuum data to analyse the CR transport in edge-on galaxies. Aims. With newly reduced radio continuum data of five edge-on galaxies (NGC 891, NGC 3432, NGC 4013, NGC 4157, and NGC 4631), we plan to set new constraints on the morphology of radio halos and the physical properties of galactic winds driven by stellar feedback. By distinguishing between the central and outer regions of the galaxies, our study setup allows us to search for variations in the radio halo profile or CR transport along the galactic disk. Methods. Data from the LOFAR Two-metre Sky Survey (LoTSS) Data Release 2 at 144 MHz (HBA) and reprocessed data from the Very Large Array (VLA) at 1.5 GHz (L band) from the Continuum Halos in Nearby Galaxies – an EVLA Survey (CHANG-ES) enable us to increase the extent of the analysed radio continuum profile significantly (up to a factor of 2) compared to previous studies. We computed thermal emission maps using a mixture approach with Hα and near-infrared data, which were then subtracted to yield radio synchrotron emission maps. Then we compiled non-thermal spectral index maps and computed intensity profiles using a box integration approach. Lastly, we performed 1D CR transport modelling. Results. The non-thermal spectral index maps show evidence that the LoTSS maps are affected by thermal absorption in star-forming regions. The scale height analysis reveals that most of the galaxies are equally well fitted with a one-component instead of a two-component exponential profile. We find a bi-modality within our sample. While NGC 3432 and NGC 4013 have similar scale heights in the L band and HBA, the low-frequency scale heights of NGC 891, NGC 4157, and NGC 4631 exceed their high-frequency counterpart significantly. The 1D CR transport modelling shows agreement between the predicted magnetic field strength and the magnetic field strength estimates of equipartition measurements. Additionally, we find an increasing difference in wind velocities (with increasing height over the galactic disk) between the central and outer regions of the analysed galaxies.

The Role of Cosmic Rays in the Modulation of Lower Atmosphere Temperature

Observational evidences suggest that there is an apparent relationship between solar variability and the lower atmosphere. The assumption made in climate models that the variation in solar radiation can explain observed variations in the lower atmosphere is not entirely true. Past studies suggest that cosmic rays of both galactic and solar origin might be responsible for temperature change in the lower atmosphere. It is a fact that solar cycle is strongly correlated with the cosmic ray flux therefore it is desirable to search the physical mechanisms which mediate between solar activity and the global temperature. It is suggested that the observed variation in cloud cover might provide a possible link between varying solar activity and global temperature. Some other mechanisms might also be playing their roles in modulating the earth’s atmospheric processes. In this research article, we have attempted to explain how cosmic rays could modify the terrestrial temperature.

Role of cosmic rays in the circumgalactic medium

We explore the impact of cosmic rays (CRs) on cosmological adaptive-mesh refinement simulations of a forming 10^12 Msolar halo, focusing on the circumgalactic medium (CGM), and its resulting low-redshift structure and composition. In contrast to a run with star formation and energetic feedback but no CRs, the CR-inclusive runs feature a CGM substantially enriched with CRs and with metals to roughly 0.1 Zsolar, thanks to robust, persistent outflows from the disk. The CR-inclusive CGMs also feature more diffuse gas at lower temperatures, down to 10^4 K, than the non-CR run, with diffuse material often receiving a majority of its pressure support from the CR proton fluid. We compare to recent observations of the CGM of L ~ L* galaxies at low redshift, including UV absorption lines within background quasar spectra. The combination of metal-enriched, CR-driven winds and large swaths of CR pressure-supported, cooler diffuse gas leads to a CGM that provides a better match to data from COS-Halos (for HI, SiIV, CIII and OVI) than the non-CR run. We also compare our models to recent, preliminary observations of diffuse gamma-ray emission in local group halos. For our lower CR-diffusion runs with kappa_CR in the range 0.3 to 1 x 10^28 cm^2/s, the CR enriched CGM produces an inconsistently high level of gamma emission. But the model with a relatively high kappa_CR = 3 x 10^28 cm^2/s provided a gamma-ray luminosity consistent with the extra-galactic gamma-ray background observed by FERMI and roughly consistent with preliminary measures of the emission from M31's CGM.

Effects of Forbush decreases of galactic cosmic rays on anticyclone activity at middle latitudes

The baric response of the lower atmosphere to Forbush decreases of galactic cosmic rays (GCRs) is investigated. It is shown that Forbush decreases are accompanied by a weakening of cyclonic activity and a strengthening of anticyclonic activity at the extratropical latitudes (45°–70°) of the Northern and Southern hemispheres. These results show an important role of cosmic rays in solar-terrestrial relationships.

The role of cosmic rays on magnetic field diffusion and the formation of protostellar discs

The formation of protostellar discs is severely hampered by magnetic braking, as long as magnetic fields remain frozen in the gas. The latter condition depends on the levels of ionisation that characterise the innermost regions of a collapsing cloud. The chemistry of dense cloud cores and, in particular, the ionisation fraction is largely controlled by cosmic rays. The aim of this paper is to evaluate whether the attenuation of the flux of cosmic rays expected in the regions around a forming protostar is sufficient to decouple the field from the gas, thereby influencing the formation of centrifugally supported disc. We adopted the method developed in a former study to compute the attenuation of the cosmic-ray flux as a function of the column density and the field strength in clouds threaded by poloidal and toroidal magnetic fields. We applied this formalism to models of low- and high-mass star formation extracted from numerical simulations of gravitational collapse that include rotation and turbulence. For each model we determine the size of the magnetic decoupling zone, where collapse or rotation motion becomes unaffected by the local magnetic field. In general, we find that decoupling only occurs when the attenuation of cosmic rays is taken into account with respect to a calculation in which the cosmic-ray ionisation rate is kept constant. The extent of the decoupling zone also depends on the dust grain size distribution and is larger if large grains (of radius $\sim 10^{-5}$ cm) are formed by compression and coagulation during cloud collapse. We conclude that a realistic treatment of cosmic-ray propagation and attenuation during cloud collapse may lead to a value of the resistivity of the gas in the innermost few hundred AU around a forming protostar that is higher than generally assumed.

A beginning investigation into the possible role of cosmic rays in the initiation of lightning discharges at the Pierre Auger Observatory

The means by which lightning is initiated inside storms is not yet understood and remains a primary unsolved problem in advancing our understanding of lightning. Due to the inconsistency between the estimated required and measured field strengths in thunderclouds, an increasing amount of research has focused on energetic electron/particle runaway processes as the basic initiating mechanism. An important class of these ideas and models is that the seed energetic electrons for runaway processes are provided by energetic cosmic rays. However, as yet there is little experimental or observational evidence to support or refute this idea. Consequently, we are beginning with a Lightning Mapping Array (LMA) in conjunction with the Pierre Auger Observatory in Argentina. The goal is to determine if discharges are initiated when high energy cosmic ray air showers pass through electrified storms. The planned instrumentation will combine the Pierre Auger Observatory with the LMA. The later will include stations placed to span the observatory to accurately measure the arrival times of impulsive VHF radiation events. These data will provide detailed 3 -dimensional pictures of individual lightning discharges inside storms, The approach of the proposed study is to identify air showers that pass through electrified storms and to look for temporal and spatial correlations with lightning in the storms, paying particular attention to the initial stages of the lightning. The study will be conducted for at least several years to assess fully the possible effects of cosmic rays in initiating lightning.

Open problems and perspectives offered by current and future instruments

We summarize recent observational and theoretical results and discuss the open challenges for astrochemistry and the promises offered by the current and upcoming instruments. Some of the main challenges are listed below. - Characterization of the structure of the interstellar medium - Coupling of the matter with magnetic fields, role of cosmic rays - Coupling of the dynamics with the evolution of matter (chemistry, ionization degree, depletion, desorption) - Characterization of dust grains (composition, size, emissivity, polarization) - Evolution of the carbonaceous matter, PAHs, aggregates and Diffuse Interstellar Bands (DIBs) carriers - Oxygen chemistry and the low abundance of molecular oxygen - Nitrogen chemistry and its seeds, the nitrogen hydrides - Sulfur chemistry and the contribution of S + to the charge balance of translucent matter - Neutral-neutral reactions involving simple radicals (CH, CH2, OH, etc.).

Cosmic rays in the Earth’s atmosphere

This paper presents a brief historical overview of studies of cosmic rays in the Earth’s atmosphere, which were initiated and led by S.N. Vernov for over 50 years. The main results of these studies that were obtained in recent decades are given. They include the study of the processes of generation and propagation of solar cosmic rays, the modulation of galactic cosmic rays in the heliomagnetosphere, and the role of cosmic rays in atmospheric processes.

The role of cosmic rays in the Earth’s atmospheric processes

In this paper, we have provided an overview of cosmic ray effects on terrestrial processes such as electrical properties, global electric circuit, lightning, cloud formation, cloud coverage, atmospheric temperature, space weather phenomena, climate, etc. It is suggested that cosmic rays control short term and long term variation in climate. There are many basic phenomena which need further study and require new and long term data set. Some of these have been pointed out.

Possible cosmic ray signatures in clouds?

The role of cosmic rays in cloud formation, by cloud condensation nuclei, is still not fully understood. Although it has been claimed by a number of authors that cosmic ray effects should be small—or even non-existent—it is still argued by others that cosmic ray effects do occur. The present work draws attention to the fact that cosmic rays do not constitute a continuous stream of particles but are characterized by occasional near-simultaneous showers of particles. Under certain circumstances, such showers should leave a signature in clouds—near vertical ‘cigar-shaped clouds’—and this work describes their properties. Our own observations have revealed no such structure, but it would be valuable to have a more careful search made.

Clinical cosmobiology: distribution of deaths during 180 months and cosmophysical activity. The Lithuanian study, 1990–2004 The role of cosmic rays

The aim of this study is a next step of our previous, initial, publications--to explore the links between monthly death number (total, and for the major death causes and each gender) with levels of monthly cosmophysical activity in a long-term, big cohort observation. Death number during 180 consecutive months from the National Registry of Lithuania for years 1990-2004 were studied. A total of 630,205 deaths were analyzed (333,035 males). For comparison, monthly indices of solar activity, geomagnetic activity, and cosmic ray activity and year and month (1-12) of the study were used. The cosmophysical data were obtained from space research centers in the USA, Russia, and Finland. Statistics. Pearson correlation coefficients (r) and their probabilities (P) between compared parameters were calculated. A multivariate model of prediction was designed. It was a significant correlation between total monthly death number and indices of cosmic ray activity and, inverse, of solar activity; in men stronger than in women. Monthly geomagnetic activity was significantly correlated with traffic accidents, ischemic heart disease/stroke ratio, suicide victim number. Deaths from stroke, noncardiovascular causes, suicide, traffic accidents were related with cosmic ray activity and, inverse, with solar activity. Relationship of ischemic heart disease/stroke ratio to year of observation showed additional evidence for the growing role of stroke in cardiovascular mortality. Monthly death number is linked to cosmic ray activity, and inverse, to solar activity. Central place of stroke-related deaths in cardiovascular mortality is emerging. Geomagnetic activity, in monthly account, plays a relatively minor role. We presume that forces antagonistic to cosmic ray activity, like solar activity and geomagnetic activity, can prevent some negative biologic effects of cosmic ray.

The Hiroshima thermal-neutron discrepancy for 36Cl at large distances. Part II: Natural in situ production as a source

For Hiroshima, a large discrepancy between calculated and measured thermal-neutron fluences had been reported in the past, for distances to the epicenter larger than about 1,000 m. To be more specific, measured (36)Cl concentrations in environmental samples from Hiroshima were too large at these distances, and the ratio of measured to calculated values reached about 70, at a distance of 1,800 m. In an attempt to identify other sources that might also produce (36)Cl in Hiroshima samples, the role of cosmic rays and of neutrons from natural terrestrial sources was investigated. Four reaction mechanisms were taken into account: spallation reactions of the nucleonic (hadronic) component of the cosmic rays on potassium (K) and calcium (Ca) in the sample material, particle emission after nuclear capture of negative muons by K and Ca, reactions of fast-muon induced electromagnetic, and hadronic showers with K and Ca, and neutron capture reactions with (35)Cl in the sample where the neutrons originate from the above three reaction mechanisms and from uranium and thorium decay. These mechanisms are physically described and mathematically quantified. It is shown that among those parameters important for the production of (36)Cl in granite, the chemical composition of the sample, the depth in the quarry where the sample had initially been taken, and the erosion rate at the site of the quarry are most important. Based on these physical, chemical, and geological parameters, (36)Cl concentrations were calculated for different types of granite that are typical for the Hiroshima area. In samples that were of these granite types and that had not been exposed to atomic bomb(A-bomb) neutrons, the (36)Cl concentration was also determined experimentally by means of accelerator mass spectrometry, and good agreement was found with the calculated values. The (36)Cl signal due to natural in situ production was also calculated in granite samples that had been exposed to A-bomb neutrons at distances up to 1,500 m from the hypocenter. It is demonstrated that, for granite samples from Hiroshima exposed to A-bomb neutrons beyond distances of about 1,300 m from the hypocenter, the (36)Cl signal is dominated by natural in situ production.

Formation of large NAT particles and denitrification in polar stratosphere: possible role of cosmic rays and effect of solar activity

Abstract. The formation of large nitric acid trihydrate (NAT) particles has important implications for denitrification and ozone depletion. Existing theories have difficulty in explaining the formation of large NAT particles at temperatures above the ice frost point, which has been observed recently over wide Arctic regions. Our analyses reveal that high-energy comic ray particles might induce the freezing of supercooled HNO3-H2O-H2SO4 droplets when they penetrate these thermodynamically unstable droplets. The cosmic ray-induced freezing (CRIF) appears to be consistent with the observed, highly selective formation of NAT particles. We suggest a possible physical process behind the CRIF mechanism: the reorientation of polar solution molecules into the crystalline configuration in the strong electrical fields of moving secondary ions generated by passing cosmic rays. A simple formula connecting the CRIF rate to cosmic ray flux is derived with an undefined parameter constrained by observed NAT formation rates. Our simulations indicate that strong solar proton events (SPEs) may significantly enhance the formation of large NAT particles and denitrification. The CRIF mechanism offers a possible explanation for the observed high correlations between the thin nitrate-rich layers in polar ice cores and major SPEs, and the observed enhancement in the aerosol backscattering ratio at PSC layers shortly after an SPE and the significant precipitation velocity of the enhanced PSC layers. The key uncertainty in the CRIF mechanism is the probability (P) of freezing when a CR particle hits a thermodynamically, unstable STS droplet. Further studies are needed to either confirm or reject the CRIF hypothesis.

The effect of the electric field of the atmosphere on cosmic rays

A review of the present-day situation in the experimental studies of variations of cosmic rays during thunderstorms is given. It is shown that these experiments can be a useful tool for studying very interesting physical effects in the electrically disturbed atmosphere. The main emphasis is laid on the experimental verification of the runaway breakdown theory and on the role of cosmic rays in the processes of lightning initiation.

The role of cosmic rays in the atmospheric processes

The energy flux of galactic cosmic rays falling on the earth's atmosphere is small in comparison with solar electromagnetic irradiation (by 108 times). But at altitudes of h ∼ 3 to 35 km in the atmosphere, cosmic rays are the only ionization source (from the ground level up to h ∼ 3 km, natural radioactivity is an additional source of ionization). Solar activity modulates cosmic ray flux. The cosmic rays produce atmospheric ions that define the electrical properties of the atmosphere. The electric charges play a very important role in the processes of cloud and thundercloud formation in the operation of the global electric circuit. The changes in electric properties of the atmosphere influence weather and climate. Thus, we have the following chain of the solar terrestrial relationship: solar activity—cosmic ray modulation—changes in the global electric properties of the atmosphere—changes in weather and climate. The following questions are discussed in this paper: light ion production in the atmosphere, role of electric charges in the formation of clouds and thunderclouds, experimental evidences of the relationships between cosmic ray flux and atmospheric current and lightning.

Nonthermal Origin of the EUV and Soft X-Rays from the Coma Cluster:Cosmic Rays in Equipartition with the Thermal Medium

The role of cosmic rays (CRs) in the formation and evolution of clusters of galaxies has been much debated. It may well be related to other fundamental questions, such as the mechanism that heats and virializes the intracluster medium (ICM) and the frequency at which the ICM is shocked. There is now compelling evidence, both from the cluster soft excess (CSE) and the hard-tail emissions at energies above 10 keV, that many clusters are luminous sources of inverse Compton (IC) emission. This is the first direct measurement of cluster CRs: the technique is free from our uncertainties in the ICM magnetic field and is not limited to the small subset of clusters that exhibit radio halos. The CSE-emitting electrons fall within a crucial decade of energy where they have the least spectral evolution and where most of the CR pressure resides. However, their survival times do not date them back to the relic CR population. By using the CSE data of the Coma Cluster, we demonstrate that the CRs are energetically as important as the thermal ICM: the two components are in pressure equiparition. Thus, contrary to previous expectations, CRs are a dominant component of the ICM, and their origin and effects should be explored. The best-fit CR spectral index is in agreement with the Galactic value.

On The Stratospheric Measurements of Cosmic Rays

The results of measurements of cosmic-ray intensity in the Earth's atmosphere from 1957 up to now are presented. Balloon launchings performed several times a week at northern and southern polar latitudes as well as at midlatitudes yield a homogeneous data series for the study of the spatial distribution and temporal changes in the cosmic-ray intensity. The 11- and 22-year solar modulation, north-south asymmetry, energy hysteresis and a long-term trend in the cosmic-ray intensity are discussed. The fluxes and energy spectra of protons with energy > 100 MeV for about 100 solar energetic particle events in 1958-1992 are given. The role of cosmic rays in terrestrial atmospheric processes is briefly discussed.

Cosmic Rays and Chemical Evolution

The role of cosmic rays in the processes of chemical evolution on Earth and on other bodies of the Solar System has been examined.

Cosmic ray modulation

The work expounds on the evolution of the studies of cosmic ray modulation effects and the development of the concepts concerning the processes which occur in interplanetary space and give rise to the 11-year and 22-year cosmic ray variations, to the annual and 22-year variations, to the Forbush effects and to the effects of increases before geomagnetic storms, to the solar anisotropy and scintillations of galactic cosmic ray flux. The role of cosmic rays in restricting and forming the heliosphere and in forming the terminal shock wave is discussed. The theory of cosmic ray propagation in the heliosphere is proposed to generalize for the two-component (solar wind + magnetic clouds) model. The stream kinetic instability is shown to be able of playing an important role in the cosmic ray modulation in the outer heliosphere.

Cosmic ray powered Fountains and Winds

The dynamics of galactic halos is discussed with special emphasis on the role of Cosmic Rays. Whereas Cosmic Rays should at best play a minor role for galactic fountain flows they appear essential in driving a wind from galaxies like ours. Active galaxies with a very hot interstellar medium (T ≥ 107K) have winds due to the thermal gas alone.