DOCSLIB.ORG

Near-Earth Cosmic Ray Decreases Associated with Remote Coronal Mass Ejections

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Near-Earth Cosmic Ray Decreases Associated with Remote Coronal Mass Ejections The Astrophysical Journal, 801:5 (8pp), 2015 March 1 doi:10.1088/0004-637X/801/1/5 C 2015. The American Astronomical Society. All rights reserved. NEAR-EARTH COSMIC RAY DECREASES ASSOCIATED WITH REMOTE CORONAL MASS EJECTIONS S. R. Thomas1,2,M.J.Owens2, M. Lockwood2, L. Barnard2, and C. J. Scott2 1 Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Surrey, RH5 6NT, UK 2 Department of Meteorology, University of Reading, Reading, RG6 6BB, UK; [email protected] Received 2014 October 13; accepted 2014 December 25; published 2015 February 23 ABSTRACT Galactic cosmic ray (GCR) flux is modulated by both particle drift patterns and solar wind structures on a range of timescales. Over solar cycles, GCR flux varies as a function of the total open solar magnetic flux and the latitudinal extent of the heliospheric current sheet. Over hours, drops of a few percent in near-Earth GCR flux (Forbush decreases, FDs) are well known to be associated with the near-Earth passage of solar wind structures resulting from corotating interaction regions (CIRs) and transient coronal mass ejections (CMEs). We report on four FDs seen at ground-based neutron monitors which cannot be immediately associated with significant structures in the local solar wind. Similarly, there are significant near-Earth structures which do not produce any corresponding GCR variation. Three of the FDs are during the STEREO era, enabling in situ and remote observations from three well-separated heliospheric locations. Extremely large CMEs passed the STEREO-A spacecraft, which was behind the West limb of the Sun, approximately 2–3 days before each near-Earth FD. Solar wind simulations suggest that the CMEs combined with pre-existing CIRs, enhancing the pre-existing barriers to GCR propagation. Thus these observations provide strong evidence for the modulation of GCR flux by remote solar wind structures. Key words: cosmic rays – Sun: coronal mass ejections (CMEs) – Sun: heliosphere – Sun: magnetic fields 1. INTRODUCTION commonly referred to as a “Forbush decrease” (FD). Due to the recent “weak” solar cycle (e.g., Lockwood et al. 2012), there When a galactic cosmic ray (GCR) proton enters the atmo- have been fewer fast/large CMEs than is normally expected for sphere, it interacts with atmospheric particles and produces a this phase of the solar cycle (Webb & Howard 2012), and thus cascade of secondary particles, such as neutrons. Some of these we can expect a smaller number of FDs in this period. neutrons with high enough energies are able to penetrate through A number of studies have investigated how FDs vary with to the surface can be detected by neutron monitors, located at a the properties of the driving solar wind structure (e.g., Blanco number of stations at a variety of latitudes and longitudes. Thus et al. 2013 and references therein). However, not all FDs are neutron count rates serve as an indirect proxy for the top-of-the- associated with an obvious signature of a CME or CIR seen atmosphere GCR flux, once the dependence of the atmospheric in near-Earth space. Indeed, Cane et al. (1993) found FDs that absorption of neutrons on the atmospheric pressure is consid- appear to have arisen from remote connections with shocks, ered (e.g., Raubenheimer & Stoker 1974). The standard pressure primarily driven by CMEs propagating from toward the east correction to neutron monitor counts is applied to all neutron limb of the Sun. This study provides strong evidence for such monitor stations used in this study. modulation of GCRs by remote solar wind structures. In Sec- The flux of GCRs is modulated within the heliosphere on a tion 2 we examine a particularly large example of an FD with- wide range of timescales. On decadal timescales, GCRs are out a significant structure in near-Earth space. In Section 3 we influenced by differing energetic particle drift patterns and present further events from a period with greater spatial sam- long-term variations in the heliospheric magnetic field (HMF) pling of the heliosphere from the STEREO spacecraft. Finally, in magnitude and direction (e.g., Jokipii et al. 1977; Thomas et al. Section 4 we use solar wind simulations to provide interpreta- 2014a). Over timescales of hours to days, solar wind structures tion of these observations in terms of the global structure of the associated with coronal mass ejections (CMEs; Cane 2000)or inner heliosphere. corotating interaction regions (CIRs; e.g., El Borie et al. 1998; 2. A “PHANTOM” FORBUSH DECREASE Thomas et al. 2014b) affect GCR flux at Earth. The passage of a CME past an observing spacecraft is frequently associated Figure 1 shows a large FD, observed in neutron monitor with an enhancement in the magnetic field magnitude and a count rates on the 2002 November 16. The top row shows variation in the magnetic field direction away from typical the percentage change in neutron count rates relative to the Parker spiral orientations (Lepping et al. 1990). If the speed 20 day mean for McMurdo (latitude 77◦.9 south; longitude of the CME exceeds that of the surrounding solar wind by 166◦.6 east; rigidity cut-off 0.3 GV), Newark (latitude 39◦.7 north; greater than the fast magnetosonic wave speed, it will drive a longitude 75◦.7 west; rigidity cut-off 2.4 GV), Oulu (latitude shock front, compressing and heating the ambient solar wind 65◦.1 north; longitude 25◦.5 east; rigidity cut-off 0.81 GV), and ahead of it in a “sheath” region bounded by the shock and CME Alma-Ata (latitude 43◦.1 north; longitude 76◦.6 east; rigidity leading edge. As GCRs can be scattered by inhomogeneities cut-off 6.7 GV) in red, blue, green, and orange respectively. and discontinuities in the HMF (e.g., Giaclone & Jokipii 1999), The estimated rigidity cut-off values are accessed from the the GCR flux at Earth is strongly modulated by the arrival of an respective neutron monitor’s Web site, e.g., the Bartol Institute Earth-impacting CME, in particular fast CMEs. This can result website for McMurdo and Newark. However, the rigidity cut- in GCR flux reducing suddenly over a number of hours, before off can be influenced substantially by geomagnetic storms and it recovers to pre-CME levels over a number of days (Forbush planetary indices such as the Kp index must be considered 1937;Forbush1954). Such a temporal variation in GCR flux is (Smart et al. 2006). 1 The Astrophysical Journal, 801:5 (8pp), 2015 March 1 Thomas et al. Figure 1. Forbush decrease on 2002 November 17. The top panel shows neutron monitor counts from McMurdo (red), Newark (blue), Oulu (green), and Alma-Ata (orange). The second panel shows the hourly variability in the near-Earth HMF, δB . The near-Earth magnetic field strength, |B|, radial solar wind speed, |Vx|,and the proton density, np, are displayed in the next three panels. The green horizontal line give the 1σ ,2σ ,and3σ occurrences of enhancements of each variable from OMNI2 with respect to the 2001–2003 mean. During the period shown in Figure 1, each of the neutron potentially GCR-modulating structures in the solar wind, we monitors show very similar variations, despite the large spread analyzed the probability distribution functions of all solar wind of rigidity cut-offs of the stations. There is a slight spread parameters, using data from 2001 through 2003. From these in the onset timings of the FD due to the longitudes of the probability density functions, we calculate the threshold values stations essentially providing different viewing angles into the corresponding to 1σ ,2σ , and 3σ above the mean, which are heliosphere. Also, it is found from NOAA data that at the time of shown as horizontal green lines in Figures 1–3. the FD the Kp index did not increase above a value of 3 ruling out For each station, the neutron count rates reduce from ap- influence on neutron monitor counts from geomagnetic activity. proximately 2%–3% above the background to 4%–5% below The second panel shows a measure of the variability in the it. This represents one of the largest FDs within the neutron HMF (δB ) calculated from the hourly OMNI-2 data set (King monitor data series. Such a decrease in neutron count rates is & Papitashvili 2005). Here δB is the modulus of the differences expected to be due to a sizable GCR barrier in near-Earth space, between consecutive HMF vectors, i.e., δB =|Bi − B i −1|. typically resulting from a large, fast Earth-directed CME or a The third panel shows HMF magnitude (|B|), the fourth the particularly strong Earth-impacting CIR. Although a CME in radial solar wind speed (|Vx|), and the final shows the proton near-Earth space identified at this time (Richardson & Cane density (np). In order to objectively assess the presence of 2010) primarily on the basis of a reduced proton temperature, 2 The Astrophysical Journal, 801:5 (8pp), 2015 March 1 Thomas et al. Figure 2. Forbush decrease on 2012 May 30. The top panel shows neutron monitor counts from McMurdo (red), Newark (blue), Oulu (green), and Alma-Ata (orange). The second shows the hourly magnetic field variability, δB , in near-Earth space (black), at STEREO-A (red) and STEREO-B (blue). STEREO data are scaled so that the probability density functions match OMNI2 data, to allow direct comparisons of significance. The remaining three panels show (unscaled) magnetic field strength, |B|, radial solar wind speed, |Vx| and the proton density, np. The green horizontal lines give the 1σ ,2σ ,and3σ from OMNI2 with respect to the 2011–2013 mean. The schematic in the bottom-right gives the approximate locations of the measurement spacecraft.
Load more

Recommended publications
  • Solar Modulation Effect on Galactic Cosmic Rays
    Solar Modulation Effect On Galactic Cosmic Rays Cristina Consolandi – University of Hawaii at Manoa Nov 14, 2015 Galactic Cosmic Rays Voyager in The Galaxy The Sun The Sun is a Star. It is a nearly perfect spherical ball of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. 3 The Sun & The Heliosphere The heliosphere contains the solar system GCR may penetrate the Heliosphere and propagate trough it by following the Sun's magnetic field lines. 4 The Heliosphere Boundaries The Heliosphere is the region around the Sun over which the effect of the solar wind is extended. 5 The Solar Wind The Solar Wind is the constant stream of charged particles, protons and electrons, emitted by the Sun together with its magnetic field. 6 Solar Wind & Sunspots Sunspots appear as dark spots on the Sun’s surface. Sunspots are regions of strong magnetic fields. The Sun’s surface at the spot is cooler, making it looks darker. It was found that the stronger the solar wind, the higher the sunspot number. The sunspot number gives information about 7 the Sun activity. The 11-year Solar Cycle The solar Wind depends on the Sunspot Number Quiet At maximum At minimum of Sun Spot of Sun Spot Number the Number the sun is Active sun is Quiet Active! 8 The Solar Wind & GCR The number of Galactic Cosmic Rays entering the Heliosphere depends on the Solar Wind Strength: the stronger is the Solar wind the less probable would be for less energetic Galactic Cosmic Rays to overcome the solar wind! 9 How do we measure low energy GCR on ground? With Neutron Monitors! The primary cosmic ray has enough energy to start a cascade and produce secondary particles.
    [Show full text]
  • Pos(ICRC2019)1148 1 GV
    Evolution of geomagnetic cutoffs at the South Pole and neutron monitor rates PoS(ICRC2019)1148 Laura Rose Rosen∗ Washington State University E-mail: [email protected] Surujhdeo Seunarine University of Wisconsin-River Falls E-mail: [email protected] Neutron monitors are among the most robust and reliable detectors of GeV cosmic rays and are sensitive, with high precision, to modulations in Galactic Cosmic Rays (GCR). Hence, they can be deployed for extended periods of time, decades, and are able to observe the modulation of GCR over many solar cycles. The South Pole Neutron Monitor, located at the geographic South Pole, which is both high latitude and high altitude, has an atmospheric cutoff of around 0:1 GV. In the first four decades of its operation, a secular decline in the neutron rates have been observed. The decline may have leveled off recently. Environmental effects, including snow build up around the housing platform and the emergence and relocation of structures at the South Pole have been ruled out as causes of the decline. A recent study challenged the assumption that geomagnetic effects can be ignored at the South Pole, in particular for cosmic rays approaching from select regions in azimuth and at large zenith angles. This work confirms that ignoring geomagnetic cutoff effects could be important for the South Pole Neutron Monitor rates. We extend the investigation to include particle propagation in the Polar atmosphere, and the evolution of cosmic ray cutoffs at the South Pole over several decades. A connection is made between the evolving cutoffs and the decline in neutron monitor rates.
    [Show full text]
  • Study of Intense Geomagnetic Storms and Associated Cosmic Ray
    29th International Cosmic Ray Conference Pune (2005) 2, 151–154 Study of Intense Geomagnetic Storms and associated Cosmic Ray Intensity Variation ¡ ¡ Subhash C. Kaushik , A. K. Shrivastava and Hari Mohan Rajput (a) Department of Physics, Government Autonomous PG College, Datia, M P 475 661, India (b) School of Studies in Physics, Jiwaji University, Gwalior, M P 461 005, India Presenter: H. M. Rajput(subash [email protected]), ind-kaushik-SC-abs1-sh34-oral Shocks driven by energetic coronal mass ejections (CME's) and other interplanetary (IP) transients are mainly responsible for initiating large and intense geomagnetic storms. Observational results indicate that galactic cosmic rays (GCR) coming from deep surface interact with these abnormal solar and interplanetary conditions and suffer modulation effects. In this paper a systematic study has been performed to analyze the cosmic ray intensity variation during highly geoeffective conditions, referred by geomagnetic storms. These intense geomagnetic storms period have been categorized on the basis of ¢¤£¦¥ index. Study reveals the significant decrease in the cosmic ray intensity following the similar pattern as the ¢§£¨¥ index depicts. Analysis further indicates that magnitude of all the responses depend upon © component of interplanetary magnetic field (IMF) being well correlated with solar maximum and minimum periods. Transient decrease in cosmic ray intensity with slow recovery is observed during the storm phase duration. 1. Introduction Investigators have revealed that various activities taking place on Sun and other interplanetary proxies of coro- nal mass ejection's (CME's) lead to Cosmic ray (CR) modulations at neutron monitor energies. This helio- spheric modulation process reflects the dominant role played by solar wind parameters (bulk speed and the IMF intensity).
    [Show full text]
  • South Pole Neutron Monitor Forecasting of Solar Proton Radiation Intensity
    SPACE WEATHER, VOL. 10, S05004, doi:10.1029/2012SW000795, 2012 South Pole neutron monitor forecasting of solar proton radiation intensity S. Y. Oh,1,2 J. W. Bieber,2 J. Clem,2 P. Evenson,2 R. Pyle,2 Y. Yi,1 and Y.-K. Kim3 Received 27 March 2012; accepted 4 April 2012; published 25 May 2012. [1] We describe a practical system for forecasting peak intensity and fluence of solar energetic protons in the tens to hundreds of MeV energy range. The system could be useful for forecasting radiation hazard, because peak intensity and fluence are closely related to the medical physics quantities peak dose rate and total dose. The method uses a pair of ground-based detectors located at the South Pole to make a measurement of the solar particle energy spectrum at relativistic (GeV) energies, and it then extrapolates this spectrum downward in energy to make a prediction of the peak intensity and fluence at lower energies. A validation study based upon 12 large solar particle events compared the prediction with measurements made aboard GOES spacecraft. This study shows that useful predictions (logarithmic correlation greater than 50%) can be made down to energies of 40–80 MeV (GOES channel P5) in the case of peak intensity, with the prediction leading the observation by 166 min on average. For higher energy GOES channels, the lead times are shorter, but the correlation coefficients are larger. Citation: Oh, S. Y., J. W. Bieber, J. Clem, P. Evenson, R. Pyle, Y. Yi, and Y.-K. Kim (2012), South Pole neutron monitor forecasting of solar proton radiation intensity, Space Weather, 10, S05004, doi:10.1029/2012SW000795.
    [Show full text]
  • Forbush Decreases and Turbulence Levels at Coronal Mass Ejection Fronts
    A&A 494, 1107–1118 (2009) Astronomy DOI: 10.1051/0004-6361:200809551 & c ESO 2009 Astrophysics Forbush decreases and turbulence levels at coronal mass ejection fronts P. Subramanian1,H.M.Antia2,S.R.Dugad2,U.D.Goswami2,S.K.Gupta2, Y. Hayashi3, N. Ito3,S.Kawakami3, H. Kojima4,P.K.Mohanty2,P.K.Nayak2, T. Nonaka3,A.Oshima3, K. Sivaprasad2,H.Tanaka2, and S. C. Tonwar2 (The GRAPES-3 collaboration) 1 Indian Institute of Science Education and Research, Sai Trinity Building, Pashan, Pune 411021, India 2 Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India e-mail: [email protected] 3 Graduate School of Science, Osaka City University, Osaka 558-8585, Japan 4 Nagoya Women’s University, Nagoya 467-8610, Japan Received 11 February 2008 / Accepted 25 October 2008 ABSTRACT Aims. We seek to estimate the average level of MHD turbulence near coronal mass ejection (CME) fronts as they propagate from the SuntotheEarth. Methods. We examined the cosmic ray data from the GRAPES-3 tracking muon telescope at Ooty, together with the data from other sources for three closely observed Forbush decrease events. Each of these event is associated with frontside halo coronal mass ejections (CMEs) and near-Earth magnetic clouds. The associated Forbush decreases are therefore expected to have significant contributions from the cosmic-ray depressions inside the CMEs/ejecta. In each case, we estimate the magnitude of the Forbush decrease using a simple model for the diffusion of high-energy protons through the largely closed field lines enclosing the CME as it expands and propagates from the Sun to the Earth.
    [Show full text]
  • Cosmic Ray Research Unit Department of Physics Potchefstroom University for C H E Potchefstroom 2520
    hJDULATION OF COSMIC RAYS WITH PARTICULAR REFERENCE TO THE HERMANUS NEUTRON MONITOR P H STOKER DIRECTOR: COSMIC RAY RESEARCH UNIT DEPARTMENT OF PHYSICS POTCHEFSTROOM UNIVERSITY FOR C H E POTCHEFSTROOM 2520 I PREVIEW The first recordings of cosmic rays made by a n< utron monitor at the Magnecic Observatory at Hermanus, were published for July 1957, when the International Geophysical Year 1957/8 started. The operation of this 12- IGY neutron monitor was discontinued in 1964, when it was replaced by a 3NM64 as designed for the International Quiet Sun Year 1964/5. The statis= tical accuracy of the recordings was improved when in July, 1972, a 9NM64 neutron monitor was put into operation in addition to the 3NM64. The hourly data of the neutron monitor at Hermanus are published from July 1957 onwards and distributed internationally. Many papers published in international journals on the modulation of cosnic rays, have made use of the data of «-he Hermanus neutron monitor. Often requests are received from abroad for data of a shorter interval than the hourly values. The global importance of the recording of cosmic rays at Hermanus is the situation of the station at mid-latitude with a cutoff rigidity of 4,7 GV. Since most of the cosmic ray neutron monitors are situated at much lower cutoff rigidities, l>eing much closer to the geomagnetic role, the cosmic ray data of Hermanus is in high demand by investigators overseas. Our association with the Magnetic Observatory at Hermanus is not only related to the operation of the neutron monitor, but also due to our interest in the geomagnetic field as recorded in this region of the Cape Town Magnetic Anomaly known for its large secular variation.
    [Show full text]
  • Analysis of the Cosmic Ray Effects on Sentinel-1 SAR Satellite Data
    aerospace Article Analysis of the Cosmic Ray Effects on Sentinel-1 SAR Satellite Data Hakan Köksal 1, Nusret Demir 1,2,* and Ali Kilcik 1,2 1 Remote Sensing and GIS Graduate Program, Institute of Science and Technology, Akdeniz University, Antalya 07058, Turkey; [email protected] (H.K.); [email protected] (A.K.) 2 Department of Space Science and Technologies, Faculty of Science, Akdeniz University, Antalya 07058, Turkey * Correspondence: [email protected]; Tel.: +90-242-3103826 Abstract: Ionizing radiation sources such as Solar Energetic Particles and Galactic Cosmic Radiation may cause unexpected errors in imaging and communication systems of satellites in the Space environment, as reported in the previous literature. In this study, the temporal variation of the speckle values on Sentinel 1 satellite images were compared with the cosmic ray intensity/count data, to analyze the effects which may occur in the electromagnetic wave signals or electronic system. Sentinel 1 Synthetic Aperture Radar (SAR) images nearby to the cosmic ray stations and acquired between January 2015 and December 2019 were processed. The median values of the differences between speckle filtered and original image were calculated on Google Earth Engine Platform per month. The monthly median “noise” values were compared with the cosmic ray intensity/count data acquired from the stations. Eight selected stations’ data show that there are significant correlations between cosmic ray intensities and the speckle amounts. The Pearson correlation values vary between 0.62 and 0.78 for the relevant stations. Keywords: EO satellite; space weather; cosmic ray; radar; SAR; Sentinel 1; remote sensing Citation: Köksal, H.; Demir, N.; Kilcik, A.
    [Show full text]
  • A New Neutron Detector Operating at the Antarctic Laboratory for Cosmic Rays
    PROCEEDINGS OF THE 31st ICRC, ŁOD´ Z´ 2009 1 A New Neutron Detector Operating at the Antarctic Laboratory for Cosmic Rays Fabrizio Signoretti∗ and Marisa Storini∗ ∗IFSI-Roma/INAF, Via del Fosso del Cavaliere 100, 00133 Roma, Italy Abstract. The Italo-Chilean collaboration for cos- mic rays has been managing two observational sites: LARC (Antarctic Laboratory for Cosmic Rays, King George island) and OLC (Los Cerrillos Observatory, Santiago of Chile). Inside this collaboration a 3NM- 64 detector with helium counters has been realized by the Italian counterpart. During the Antarctic summer campaign of 2006-2007 the new detector has been added to the laboratory. The period June- December 2007 has been used to evaluate its perfor- mance there. Main results are discussed. Keywords: cosmic rays, nucleonic component, he- lium detector I. INTRODUCTION The Antarctic Laboratory for Cosmic Rays (LARC) is located on King George island (South Shetlands - Fildes Bay - Ardley Cove: 62.20◦S - 301.04◦E; 40 m a.s.l.). At present time the Laboratory is managed by the joint collaboration between the University of Chile (UChile/FCFM) and the Institute of Interplanetary Space Physics of the National Institute for Astrophysics (IFSI-Roma/INAF). The project is also supported by the Fig. 1. The international mini-network of neutron monitors supported by IFSI-Roma. National Antarctic Institute of Chile (INACh) and the National Program for Antarctic Research (PNRA) of Italy. Italian 3NM-64 detector with helium counters (3NM- A 6NM-64 neutron monitor has been running at LARC 64 3He) has been added to the Laboratory during the since 1991 (see, for instance, [1]).
    [Show full text]
  • Neutron Monitor Observations of the 2009 Solar Minimum
    PROCEEDINGS OF THE 31st ICRC, ŁOD´ Z´ 2009 1 Neutron Monitor Observations of the 2009 Solar Minimum H. Moraal, P.H. Stoker, and H. Kruger¨ Unit for Space Physics, North-West University, Potchefstroom 2520, South Africa Abstract. The solar minimum period in 2008 and NMD at 0.8 GV it is twice as large at ≈30%. The 2009 is characterized by a prolonged cosmic-ray now well-established alternating peak-plateau nature maximum intensity. In the so-called qA<0 magnetic of subsequent cosmic-ray maxima shows on all the cycle, one rather expects a sharply peaked profile, as stations: in May 1965 and in March 1987 the intensities occurred during the solar minimum periods 22 and reached well-defined peak values, while during the 44 years ago. The observations of the Sanae, Her- periods 1974-1977 and 1996-1997 there were much manus, Potchefstroom, and Tsumeb neutron moni- flatter, less sharply defined cosmic-ray maxima. This tors are used to investigate this behaviour in terms behaviour is understood in terms of drift of cosmic of propagation conditions due to solar activity, the rays in the heliospheric magnetic field, as described for heliospheric magnetic field, and the profile of the instance by [4]: in 11-year periods such as from ∼ 1960 wavy current sheet in the field. We conclude that, to 1970, ∼ 1980 to 1990, and ∼ 2000 to present, the although solar activity parameters are quite different solar and heliospheric magnetic fields in the northern from previous solar minima, the control of these hemisphere generally point towards the sun, and away parameters over the cosmic-ray modulation is still in the southern hemisphere.
    [Show full text]
  • Development of Advanced Radiation Monitors for Pulsed Neutron Fields
    DEVELOPMENT OF ADVANCED RADIATION MONITORS FOR PULSED NEUTRON FIELDS Thesis submitted in accordance with the requirements of the University of Liverpool for the degree of Doctor in Philosophy by Giacomo Paolo Manessi June 2015 1 Abstract The need of radiation detectors capable of efficiently measuring in pulsed neutron fields is attracting widespread interest since the 60s. The efforts of the scientific community substantially increased in the last decade due to the increasing number of applications in which this radiation field is encountered. This is a major issue especially at particle accelerator facilities, where pulsed neutron fields are present because of beam losses at targets, collimators and beam dumps, and where the correct assessment of the intensity of the neutron fields is fundamental for radiation protection monitoring. LUPIN is a neutron detector that combines an innovative acquisition electronics based on logarithmic amplification of the collected current signal and a special technique used to derive the total number of detected neutron interactions, which has been specifically conceived to work in pulsed neutron fields. Due to its special working principle, it is capable of overcoming the typical saturation issues encountered in state-of-the-art detectors, which suffer from dead time losses and often heavily underestimate the true neutron interaction rate when employed for routine radiation protection measurements. This thesis presents a comprehensive study into the design, optimisation and operation of two versions of LUPIN, based on different active gases. In addition, two other devices, a beam loss monitor and a neutron spectrometer, which have been built using LUPIN’s acquisition electronics, are also discussed in detail.
    [Show full text]
  • Solar Cycle Variation and Application to the Space Radiation Environment
    NASA/TP- 1999-209369 Solar Cycle Variation and Application to the Space Radiation Environment John W. Wilson, Myung-Hee Y. Kim, Judy L. Shinn, Hsiang Tai Langley Research Center, Hampton, Virginia Francis A. Cucinotta, Gautam D. Badhwar Johnson Space Center, Houston, Texas Francis F. Badavi Christopher Newport University, Newport News, Virginia William Atwell Boeing North American, Houston, Texas September 1999 The NASA STI Program Office... in Profile Since its founding, NASA has been dedicated CONFERENCE PUBLICATION. to the advancement of aeronautics and space Collected papers from scientific and science. The NASA Scientific and Technical technical conferences, symposia, Information (STI) Program Office plays a key seminars, or other meetings sponsored or part in helping NASA maintain this co-sponsored by NASA. important role. SPECIAL PUBLICATION. Scientific, The NASA STI Program Office is operated by technical, or historical information from Langley Research Center, the lead center for NASA programs, projects, and missions, NASA's scientific and technical information. often concerned with subjects having The NASA STI Program Office provides substantial public interest. access to the NASA STI Database, the largest collection of aeronautical and space science STI in the world. The Program Office TECHNICAL TRANSLATION. English- is also NASA's institutional mechanism for language translations of foreign scientific disseminating the results of its research and and technical material pertinent to NASA's mission. development activities. These results are published by NASA in the NASA STI Report Series, which includes the following report Specialized services that complement the types: STI Program Office's diverse offerings include creating custom thesauri, building customized TECHNICAL PUBLICATION.
    [Show full text]
  • South Pole Neutron Monitor Lives Again 1 Introduction 2 Hardware
    32ND INTERNATIONAL COSMIC RAY CONFERENCE, BEIJING 2011 South Pole Neutron Monitor Lives Again 1 1 1 2 PAUL EVENSON , JOHN BIEBER , JOHN CLEM , ROGER PYLE 1University of Delaware Department of Physics and Astronomy 2Pyle Consulting Group [email protected] DOI: 10.7529/ICRC2011/V11/0622 Abstract: The neutron monitor at Amundsen-Scott station at South Pole was reactivated in February 2010 after a four-year, three month gap, and has since been equipped with an enhanced array of “bare” neutron detectors. We dis- cuss capabilities of the new installation and present results of our efforts to normalize the new data to the old. In light of these new results, the long-term decline in the South Pole neutron rate is more puzzling than ever. Keywords: Solar Energetic Particles; Modulation 1 Introduction Even though the sun is much closer, and many indepen- dent acceleration episodes have been observed, there is still much that is not understood about both acceleration The neutron monitor at Amundsen-Scott station at South and transport of the energetic particles. Although it now Pole was reactivated in February 2010 after a four-year, works closely with IceTop CosRay is funded separately three month gap, and has since been equipped with an by NSF as event A-118-S. enhanced array of “bare” neutron detectors.. The new configuration will greatly enhance the ability of IceTop, the surface component of the IceCube neutrino observa- tory at the South Pole, to determine spectra and element composition of solar energetic particles in the energy range 1-10 GeV. This was accomplished by recycling many components of the former South Pole neutron monitor to construct an enhanced suite of neutron detec- tors whose response functions (primarily due to hadrons) have a different dependence on energy and element com- position from those of IceTop (primarily due to photons and leptons).
    [Show full text]