(1976). Nuclear Tracks in Solids (Principles and Applications) Nuclear Technology: Vol. 30, No. 1, pp. 91-92.

Nuclear Tracks in Solids (Principles and Applications)

Mid-term quasi-periodicities in solar coronal mass ejections (CMEs) during the most recent solar maximum cycle 23 are reported here for the first time using the four-year data (February 5, 1999 to February 10, 2003) of the Large Angle Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO). In parallel, mid-term quasi-periodicities in solar X-ray flares (class >M5.0) from the Geosynchronous Operational Environment Satellites (GOES) and in daily averages of Ap index for geomagnetic disturbances from the World Data Center (WDC) at the International Association for Geomagnetism and Aeronomy (IAGA) are also examined for the same four-year time span. Several conceptual aspects of possible equatorially trapped Rossby-type waves at and beneath the solar photosphere are discussed.

Periodicities in Solar Coronal Mass Ejections

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 microphysical cloud parameters to FDs. The test is subsequently applied to one ground-based and three satellite-based data sets. Responses (>95%) to FDs are found in the following parameters of the analyzed data sets. AERONET: Angstrom exponent (cloud condensation nuclei changes), SSM/I: liquid water content, International Satellite Cloud Climate Project (ISCCP): total, high, and middle, IR-detected clouds over the oceans, Moderate Resolution Imaging Spectroradiometer (MODIS): cloud effective emissivity, cloud optical thickness, liquid water, cloud fraction, liquid water path, and liquid cloud effective radius. Moreover, the responses in MODIS are found to correlate positively with the strength of the FDs, and the signs and magnitudes of the responses agree with model-based expectations. The effect is mainly seen in liquid clouds. An impact through changes in UV-driven photo chemistry is shown to be negligible and an impact via UV absorption in the stratosphere is found to have no effect on clouds. The total solar irradiance has a relative decrease in connection with FDs of the order of 10−3, which is too small to have a thermodynamic impact on timescales of a few days. The results demonstrate that there is a real influence of FDs on clouds probably through ions.

/pdf/the-response-of-clouds-and-aerosols-to-cosmic-ray-decreases-4idzv6bpbo.pdf

The response of clouds and aerosols to cosmic ray decreases

The composite (superposed epoch) analysis technique has been frequently employed to examine a hypothesized link between solar activity and the Earth’s atmosphere, often through an investigation of Forbush decrease (Fd) events (sudden high-magnitude decreases in the flux cosmic rays impinging on the upper-atmosphere lasting up to several days). This technique is useful for isolating low-amplitude signals within data where background variability would otherwise obscure detection. The application of composite analyses to investigate the possible impacts of Fd events involves a statistical examination of time-dependent atmospheric responses to Fds often from aerosol and/or cloud datasets. Despite the publication of numerous results within this field, clear conclusions have yet to be drawn and much ambiguity and disagreement still remain. In this paper, we argue that the conflicting findings of composite studies within this field relate to methodological differences in the manner in which the composites have been constructed and analyzed. Working from an example, we show how a composite may be objectively constructed to maximize signal detection, robustly identify statistical significance, and quantify the lower-limit uncertainty related to hypothesis testing. Additionally, we also demonstrate how a seemingly significant false positive may be obtained from non-significant data by minor alterations to methodological approaches.

/pdf/composite-analysis-with-monte-carlo-methods-an-example-with-ujdhmce5xs.pdf

Composite analysis with Monte Carlo methods: an example with cosmic rays and clouds

This paper reports on the modification of a small plasma focus device (UNU/ICTP PFF) to operate at low pressure for enhanced ion beam generation. For the present operation, the electrode geometry of the plasma focus device is modified to redirect the plasma motion at the end of the axial rundown phase so that normal plasma focus action will not occur. The redirection of the plasma leads to a rapid increase in the plasma resistivity and hence a high localized electric field will be established and as a result, high energy ion beam will be generated. With air as the working gas, pressure as low as 10-3 mbar has been tested. At such a low pressure, breakdown of the discharge must be initiated with the use of a set of twelve plasma injection cable guns. The modified plasma focus has been shown to be able to produce high energy ion beams of nitrogen, argon and hydrogen consistently.

http://iopscience.iop.org/article/10.1143/JJAP.41.3943/pdf

Generation Of High Energy Ion Beams from a Plasma Focus Modified for Low Pressure Operation

Monte Carlo simulations of the response of a plastic scintillator and an HPGe spectrometer in coincidence.

A novel method for atmospheric correction of cosmic-ray data based on principal component analysis

Abstract It is well known that one of the factors that influence the indoor radon variability is the floor level of the buildings. Considering the fact that the main source of indoor radon is radon in soil gas, it is expected that the radon concentration decreases at higher floors. Thus at higher floors the dominant source of radon is originating from building materials, and in some cases there may be deviations from the generally established regularity. In such sense, we chose one freestanding single-family house with loft and other 16-floor high-rise residential building for this study. The indoor radon measurements were performed by two methods: passive and active. We used passive devices based on track-etched detectors: Radtrak2 Radonova. For the short-term indoor radon measurements, we used two active devices: SN1029 and SN1030 (manufactured by Sun Nuclear Corporation). The first device was fixed in the living room at the ground level and the second was moved through the floors of the residential building. Every measuring cycle at the specified floor lasted seven days with the sampling time of 2 h. The results show two different indoor radon behaviours regarding radon variability due to floor level. In the single-family house with loft we registered intense difference between radon concentration in the ground level and loft, while in the high-rise residential building the radon level was almost the same at all floors, and hence we may conclude that radon originated mainly from building materials.

/pdf/radon-variability-due-to-floor-level-in-two-typical-4uj3zsnawy.pdf

Radon variability due to floor level in two typical residential buildings in Serbia

In Low Background Laboratory at Institute of Physics Belgrade, plastic scintillators are used to continuously monitor flux of the muon component of secondary cosmic rays. Measurements are performed on the surface as well as underground (25 m.w.e depth). Temperature effect on muon component of secondary cosmic rays is well known and several methods to correct for it are already developed and widely used. Here, we apply integral method to calculate correction coefficients and use GFS (Global Forecast System) model to obtain atmospheric temperature profiles. Atmospheric corrections reduce variance of muon flux and lead to improved sensitivity to transient cosmic ray variations. Influence of corrections on correlation with neutron monitor data is discussed.

Effect of pressure and temperature corrections on muon flux variability at ground level and underground

The possibility of utilizing a shallow underground laboratory for the study of energy dependent solar modulation process is investigated. The laboratory is equipped with muon detectors at ground level and underground (25mwe), and with an underground asymmetric muon telescope to have a single site detection system sensitive to different median energies of primary cosmic-ray particles. The detector response functions to galactic cosmic rays are determined from Monte Carlo simulation of muon generation and propagation through the atmosphere and soil, based on CORSIKA and GEANT4 simulation packages. The present setup is suitable for studies of energy dependence of Forbush decreases and other transient or quasi-periodic cosmic-ray variations.

Aleksandar Dragić

Papers

Monte Carlo simulations of the response of a plastic scintillator and an HPGe spectrometer in coincidence.

A novel method for atmospheric correction of cosmic-ray data based on principal component analysis

Radon variability due to floor level in two typical residential buildings in Serbia

Effect of pressure and temperature corrections on muon flux variability at ground level and underground

An underground laboratory as a facility for studies of cosmic-ray solar modulation