Journal: The Astrophysical Journal

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A; Ar, AφAθ) in a spherical polar coordinate system centered on the sun. We reported (elsewhere) the results of a detailed study of time variations of yearly radial (Ar) and east–west (Aφ) components recorded by the global network of the neutron monitors (NMs) with a long track record for 1963–2013, for four sunspot number (SSN) cycles (20–23) and the rising phase of cycle 24. A powerful new technique is used to compute and study time variations of the transverse component (Aθ) due to off-ecliptic GCR contributions, with the same NM data; GCR radial particle density gradient (Gr) drives all three components. The north–south anisotropy (Aθ) is computed from yearly NM data (Gϕ = 0), a flat heliospheric current sheet (HCS) model and the concept of GCR isotropic hard sphere scattering in the solar wind plasma. Relationships to SSN, rigidity and solar polarity intervals are studied. For a positive (p-) polarity the solar magnetic field in the northern hemisphere points outward and GCRs drift from polar regions toward equatorial plane and out along HCS, setting up a symmetric gradient (Gθs) pointing away from HCS (there is a local GCR density minimum on HCS); for n-polarity interval Gθs points towards HCS (there is a local GCR density maximum on HCS). Also, there exists a heliospheric asymmetric density gradient (Gθa) perpendicular to the ecliptic plane, it is the main contributor to Aθ for the period of our analysis. This is the most interesting and significant insight.


Ahluwalia, H.S. "North-south excess of hemispheric sunspot numbers and cosmic ray asymmetric solar modulation." Advances in Space Research 56.11 (2015): 2645+. Academic OneFile. Web. 6 Jan. 2016.
Abstract: Timeline of solar activity is reviewed for 1945-2013 with data for yearly north-south excess (NSE) of hemispheric sunspot numbers (SSNs) for six cycles (18-23) and rising phase of cycle 24. There are more sunspots in north hemisphere for 1950-1970 (cycles 18-20) and excess in south hemisphere for 1980-2010 (cycles 21-23). To the best of our knowledge, the physical cause(es) for NSE and change of its sign are not known, highlighting the fact that we do not yet understand how the solar Dynamo works. Others have analyzed NSE data for shorter periods. We study the relationship between NSE and galactic cosmic ray (GCR) asymmetric solar modulation for the space age with high latitude neutron monitor data located in USA and Europe; space age began in October 1963 with in situ measurements of the solar wind parameters at 1AU. We infer an asymmetric GCR particle density gradient normal to the ecliptic plane exists for 1963-2013 and undergoes significant temporal variations unrelated to Schwabe or Hale cycle. Furthermore, it has no physical relationship with NSE for the period of our analysis, contrary to the result of a prior study for a shorter period.


Journal: Journal of Geophysical Research: Space Physics
Title: Cosmic Ray Heliospheric Transport Study with Neutron Monitor Data
General Information: Published 24 October 2015, Volume 120, Issue 10, Pages 8229-8246
Author(s): H. S. Ahluwalia, R. C. Ygbuhay, R. Modzelewska, L. I. Dorman, M. V. Alania
Abstract: Determining transport coefficients for galactic cosmic ray (GCR) propagation in the turbulent interplanetary magnetic field (IMF) poses a fundamental challenge in modeling cosmic ray modulation processes. GCR scattering in the solar wind involves wave-particle interaction, the waves being Alfven waves which propagate along the ambient field (B). Empirical values at 1 AU are determined for the components of the diffusion tensor for GCR propagation in the heliosphere using neutron monitor (NM) data. At high rigidities, particle density gradients and mean free paths at 1 AU in B can only be computed from the solar diurnal anisotropy (SDA) represented by a vector A (componentsAr, Aϕ, and Aθ) in a heliospherical polar coordinate system. Long-term changes in SDA components of NMs (with long track record and the median rigidity of response Rm ~ 20 GV) are used to compute yearly values of the transport coefficients for 1963–2013. We confirm the previously reported result that the product of the parallel (to B) mean free path (λ||) and radial density gradient (Gr) computed from NM data exhibits a weak Schwabe cycle (11y) but strong Hale magnetic cycle (22y) dependence. Its value is most depressed in solar activity minima for positive (p) polarity intervals (solar magnetic field in the Northern Hemisphere points outward from the Sun) when GCRs drift from the polar regions toward the helioequatorial plane and out along the heliospheric current sheet (HCS), setting up a symmetric gradient Gθs pointing away from HCS. Grdrives all SDA components and λ|| Gr contributes to the diffusive component (Ad) of the ecliptic plane anisotropy (A). GCR transport is commonly discussed in terms of an isotropic hard sphere scattering (also known as billiard-ball scattering) in the solar wind plasma. We use it with a flat HCS model and the Ahluwalia-Dorman master equations to compute the coefficients α (=λ/λ) and ωτ (a measure of turbulence in the solar wind) and transport parameters λ||,λ, Gr, Gθs, and an asymmetric gradient Gθa normal to the ecliptic plane. We study their dependence on rigidity (R), p/n intervals, sunspot numbers (SSNs), and solar wind parameters at 1 AU. λ|| exhibits a strong 22y dependence but Gr does not, explaining solar polarity dependence ofλ|| Gr. The computed Gr values are an order of magnitude greater than those reported by our colleagues making an ad hoc assumption that α is low (0.01). At high rigidities, the drift contribution at 1 AU is small and unsteady. A new methodology is outlined to compute yearly GCR north-south anisotropy (Aθ) from the data for a single detector sorted for p/n intervals. We show that Gθa is the main contributor to Aθ in the steady state, and Gθa is shown not correlated with the north-south excess SSNs.


Journal: Journal of Geophysical Research: Space Physics
Title: Measurement and Simulation of Neutron Monitor Count Rate Dependence on Surrounding Structure
General Information: Published on 6 July 2015, Volume 120, Issue 7, Pages 5253-5265
Author(s): N. Aiemsa-ad, D. Ruffolo, A. Saiz, P. –S. Mangeard, T. Nutaro, W. Nuntiyakul, N. Kamyan, T. Khumlumlert, H. Kruger, H. Moraal, J. W. Bieber, J. Clem, P. Evenson
Abstract: Neutron monitors are the premier instruments for precise measurements of time variations (e.g., of solar origin) in the galactic cosmic ray (GCR) flux in the range of 1–100 GeV. However, it has proven challenging to accurately determine the yield function (effective area) versus rigidity in order to relate a neutron monitor's count rate with those of other monitors worldwide and the underlying GCR spectrum. Monte Carlo simulations of the yield function have been developed, but there have been few opportunities to validate these observationally, especially regarding the particular environment surrounding each monitor. Here we have precisely measured the count rate of a calibration neutron monitor near the Princess Sirindhorn Neutron Monitor (PSNM) at Doi Inthanon, Thailand (18.59N, 98.49E, 2560 m altitude), which provides a basis for comparison with count rates of other neutron monitors worldwide that are similarly calibrated. We directly measured the effect of surrounding structure by operating the calibrator outside and inside the building. Using Monte Carlo simulations, we clarify differences in response of the calibrator and PSNM, as well as the calibrator outside and inside the building. The dependence of the calibrator count rate on surrounding structure can be attributed to its sensitivity to neutrons of 0.5–10 MeV and a shift of sensitivity to nucleons of higher energy when placed inside the building. Simulated calibrator to PSNM count rate ratios inside and outside agree with observations within a few percent, providing useful validation and improving confidence in our ability to model the yield function for a neutron monitor station.


Journal: Advances in Space Research
Title: Variations of Cosmogenic Radionuclide Production Rates along the Meteorite Orbits
General Information: Published 15 August 2015, Volume 56, Issue 4, Pages 766-771
Author(s): V. A. Alexeev, M. Laubenstein, P. P. Povinec, G. K. Ustinova
Abstract: Cosmogenic radionuclides produced by galactic cosmic rays (GCR) in meteorites during their motion in space are natural detectors of the GCR intensity and variations along the meteorite orbits. On the basis of measured and calculated contents of cosmogenic radionuclides in the freshly fallen Chelyabinsk and Košice chondrites some peculiarities of generation of cosmogenic radionuclides of different half-lives in the chondrites of different orbits and dates of fall onto the Earth are demonstrated. Dependence of production rates of the radionuclides on the GCR variations in the heliosphere is analyzed. Using radionuclides with different half-lives it is possible to compare the average GCR intensity over various time periods. The measurement and theoretical analysis of cosmogenic radionuclides in consecutively fallen chondrites provide a unique information on the space–time continuum of the cosmogenic radionuclide production rates and their variations over a long time scale, which could be useful in correlative analyses of processes in the heliosphere. Some applications of cosmogenic radionuclide depth distribution in chondrites for estimation of their pre-atmospheric sizes are illustrated.


Journal: American Institute of Physics: Conference Proceedings
Title: Astroparticle Physics at the Eastern Colombia Region
General Information: Conference Date 13-22 April 2015
Author(s): Hernán Asorey, Luis A. Núñez
Abstract; We present the emerging panorama of Astroparticle Physics at the Eastern Colombia region, and describe several ongoing projects, most of them related to the Latin American Giant Observatory(LAGO) Project. This research work is carried out at the Grupo de Investigaciones en Relatividad y Gravitacin of Universidad Industrial de Santander.


Journal: Advances in Space Research
Title: Local Anisotrophy of Muon Flux – The Basis of the Method of Muon Diagnostics of Extra-Terrestrial Space
General Information: Published 15 December 2015, Volume 56, Issue 12, Pages 2713-2718
Author(s): I.I. Astapov, N.S. Barbashina, A.N. Dmitrieva, R.P. Kokoulin, A.A. Petrukhin, V.V. Shutenko, E.I. Yakovleva, I.I. Yashin
Abstract: A new method for the analysis of spatial and angular characteristics of the cosmic ray muon flux registered in the hodoscopic mode using a single setup – the muon hodoscope – is presented. Various parameters of the muon flux anisotropy and methods of calculation of these parameters are discussed. It is shown that the horizontal projection of the muon flux relative anisotropy vector which characterizes lateral (horizontal) displacement of the muon flux angular distribution is the sensitive parameter to a variety of nonstationary processes in the heliosphere. The experimental data on the variation of the muon flux anisotropy during the passage of various irregularities in the solar wind and interplanetary magnetic field in the Earth’s vicinity are presented.


Journal: Advances in Space Research
Title: Powerful Non-Geoeffective Interplanetary Disturbance of July 2012 Observed by Muon Hodoscope URAGAN
General Information: Published 15 December 2015, Volume 56, Issue 12, Pages 2833-2838
Author(s): Astapov, N. S. Barbashina, A. A. Petrukhin, V. V. Shutenko, I. S. Veselovsky
Abstract: The most powerful coronal mass ejection of the 24th solar cycle took place on the opposite side of the Sun on July 23, 2012 and had no geomagnetic consequences. Nevertheless, as a result of passing of the ejection through the heliosphere, variations of galactic cosmic rays flux were observed on the Earth. These variations were registered by the muon hodoscope URAGAN (MEPhI, Moscow). Muon flux angular distributions on the Earth’s surface are reported and analyzed.


Journal: Microelectronics Reliability
Title: ASTEP (2005-2015): Ten Years of Soft Error and Atmospheric Radiation Characterization on the Plateau de Bure
General Information: Available online 11 July 2015, Volume 55, Issue 9-10, Pages 1506-1511
Author(s): J. L. Autran, D. Munteanu, S. Moindjie, T. Saad Saoud, S. Sauze, G. Gasiot, P. Roche
Abstract: This paper surveys ten years of experimentation conducted on the Altitude SEE (Single Event Effects) Test European Platform (ASTEP), a permanent mountain laboratory opened in 2005 on the Plateau de Bure (Dévoluy, France) at the altitude of 2552 m and primarily dedicated to the characterization of soft errors in electronic circuits subjected to terrestrial cosmic rays. The paper retraces the foundations of the project and gives an extensive overview of the different past, current and future experiments conducted on ASTEP in the fields of SER (soft error rate) real-time testing and natural radiation monitoring and metrology.


Journal: Water Resources Research
Title: An Empirical Vegetation Correction for Soil Water Content Quantification using Cosmic Ray Probes
General Information: Published 8 April 2015, Volume 51, Issue 4, Pages 2030-2046
Author(s): R. Baatz, H. R. Bogena, H.-J. Hendricks Franssen, J. A. Huisman, C. Montzka, H. Vereecken
Abstract: Cosmic ray probes are an emerging technology to continuously monitor soil water content at a scale significant to land surface processes. However, the application of this method is hampered by its susceptibility to the presence of aboveground biomass. Here we present a simple empirical framework to account for moderation of fast neutrons by aboveground biomass in the calibration. The method extends the N0-calibration function and was developed using an extensive data set from a network of 10 cosmic ray probes located in the Rur catchment, Germany. The results suggest a 0.9% reduction in fast neutron intensity per 1 kg of dry aboveground biomass per m2 or per 2 kg of biomass water equivalent per m2. We successfully tested the novel vegetation correction using temporary cosmic ray probe measurements along a strong gradient in biomass due to deforestation, and using the COSMIC, and the hmf method as independent soil water content retrieval algorithms. The extended N0-calibration function was able to explain 95% of the overall variability in fast neutron intensity.


Journal: Journal of Atmospheric and Solar-Terrestrial Physics
Title: A Comparison of Stratospheric Photochemical Response to Different Reconstructions of Solar Ultraviolet Radiative Variability
General Information: Accepted 10 June 2015, Available online 15 June 2015, Volume 132, Pages 22-32
Author(s): Cassandra Bolduc, Michel S. Bourqui, Paul Charbonneau
Abstract: We present calculations of stratospheric chemical abundances variations between different levels of solar activity using a simple photochemistry model in transient chemistry mode. Different models for the reconstruction of the solar spectrum, as well as observations from the SOLar STellar Irradiance Comparison Experiment (SOLSTICE) and Spectral Irradiance Monitor (SIM) on the SOlar Radiation and Climate Experiment (SORCE) satellite, are used as inputs to the calculations. We put the emphasis on the MOnte CArlo Spectral Solar Irradiance Model (MOCASSIM) reconstructions, which cover the spectral interval from 150 to 400 nm and extend from 1610 to present. We compare our results with those obtained with the Naval Research Laboratory Solar Spectral Irradiance (NRLSSI) model as well as with the Magnesium-Neutron Monitor (MGNM) model over a period of time spanning the ascending phase of Cycle 22. We also perform the calculations using SORCE composite spectra for the descending phase of Cycle 23 and with the reconstructed MOCASSIM, NRLSSI and MGNM spectra for the same period for comparison. Finally, we compare the chemical abundances obtained for the Maunder Minimum with those obtained for the Cycle 23 minimum (in March 2009) and find that stratospheric ozone concentration was slightly higher during the recent minimum, consequent to the small positive variability between the MOCASSIM spectra for both epochs, especially below 260 nm. We find that the response in stratospheric ozone is not only dependent on the variability amplitude in the solar spectrum (especially in the 200–240 nm band), but also significantly on the base level of the minimum solar spectrum.


Journal: Advances in Space Research
Title: Spectral Index of Solar Cosmic-Ray Flux from the Analysis of Ground-Level Enhancements
General Information: Accepted 24 August 2015, Available online 29 August 2015
Author(s): R. A. Caballero-Lopez, H. Moraal
Abstract: In this work we analyze the ground-level enhancement of the cosmic-ray intensity due to solar energetic particles as observed on 29 September 1989, by using two pairs of standard and lead-free neutron monitors. This enables one to separate spectral and anisotropy effects. This has been done previously by several authors for other events, but in this paper we make use of the large size and long duration of this event, as well as the fact that it is perhaps the best-observed one in the whole data base since 1942. It is shown that the method is more sensitive than the standard method that uses neutron monitors at different locations. The analysis provides a prototype for what can potentially be achieved by a new generation of mini neutron monitors.


Journal: Space Physics
Title: The Origin of “Space Weather”
General Information: Published 27 February 2015, Volume 13, Issue 2, Pages 99-103
Author(s): William B. Cade III, Christina Chan-Park
Abstract: Although “space weather” is a fairly recent term, there is a rich history of similar terms being used beginning in the middle to late 1800s. “Solar meteorology,” “magnetic weather,” and “cosmic meteorology” all appeared during that time frame. The actual first appearance of space weather can be attributed to the publication Science News Letter in 1957 (with the first modern usage in 1959) and was possibly coined by the editor at the time, Watson Davis.


Journal: Space Weather
Title: SEPEM: A Tool for Statistical Modeling the Solar Energetic Particle Environment
General Information: Published 30 July 2015, Volume 13, Issue 7, Pages 406-426
Author(s): Norma Crosby, Daniel Heynderickx, Piers Jiggens, Angels Aran, Blai Sanahuja, Pete Truscott, Fan Lei, Carla Jacobs, Stefaan Poedts, Stephen Gabriel, Ingmar Sandberg, Alexi Glover, Alain Hilgers
Abstract: Solar energetic particle (SEP) events are a serious radiation hazard for spacecraft as well as a severe health risk to humans traveling in space. Indeed, accurate modeling of the SEP environment constitutes a priority requirement for astrophysics and solar system missions and for human exploration in space. The European Space Agency's Solar Energetic Particle Environment Modelling (SEPEM) application server is a World Wide Web interface to a complete set of cross-calibrated data ranging from 1973 to 2013 as well as new SEP engineering models and tools. Both statistical and physical modeling techniques have been included, in order to cover the environment not only at 1 AU but also in the inner heliosphere ranging from 0.2 AU to 1.6 AU using a newly developed physics-based shock-and-particle model to simulate particle flux profiles of gradual SEP events. With SEPEM, SEP peak flux and integrated fluence statistics can be studied, as well as durations of high SEP flux periods. Furthermore, effects tools are also included to allow calculation of single event upset rate and radiation doses for a variety of engineering scenarios.

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