The local Galactic magnetic field in the direction of Geminga

The Milagro hot spot A, close to the Galactic anticenter direction, has been tentatively attributed to cosmic rays from a local reservoir (at a distance ~100 pc), freely streaming along diverging and smooth magnetic field lines. This is at variance with the geometry of the ~kpc scale Galactic magnetic field, which is known to be aligned with the spiral arms. We investigate the information available on the geometry of the magnetic field on the scales (~100 pc) of relevance here. The magnetic field immediately upstream of the heliosphere has been investigated by previous authors by modeling the interaction of this field with the solar wind. At larger distances, we use the dispersion measure and the rotation measure of nearby pulsars (especially towards the third Galactic quadrant). Additional information about the local field towards the North Polar Spur is taken from previous studies of the diffuse radio emission and the polarization of starlight. The asymmetry of the heliosphere with respect to the incoming interstellar medium implies a magnetic field almost orthogonal to the local spiral arm, in the general direction of hot spot A, but more to the south. This is in good agreement with the nearby pulsar data on the one side, and the North Polar Spur data on the other. The local magnetic field on scales of ~100 parsecs around the Sun seems to be oriented so as to provide a direct connection between the Solar system and a possible site of the Geminga supernova; the residual angular difference and the shape and orientation of the Milagro hot spot can be attributed to the field trailing in the wake of the heliosphere.Comment: 5 pages, 3 figures, accepted for publication in Astronomy and Astrophysic

Observation of Anisotropy in the Arrival Direction Distribution of Cosmic Rays above TeV Energies with Icecube

Between May 2009 and May 2010, the IceCube neutrino detector recorded 32 billion of atmospheric muons generated in air showers produced by cosmic rays in the TeV energy range. With such high statistics sample it is possible to observe, for the first time in the southern hemisphere, an energy dependence in the Galactic cosmic ray anisotropy up to a few hundred TeV. This study shows that the same large-scale anisotropy observed at median energies around 20 TeV is not present at 400 TeV; the anisotropy observed at 400 TeV shows substantial differences with respect to that at lower energy. In addition to the large-scale features observed at 20 TeV in the form of strong dipole and quadrupole moments, the data include several localized regions of excess and deficit on scales between 10{\degree} to 30{\degree}. The features observed at both large and small scale are statistically significant, but their origin is currently unknown.Comment: Proceedings of Rencontres de Blois 201

Estimating terrestrial uranium and thorium by antineutrino flux measurements

Uranium and thorium within the Earth produce a major portion of terrestrial heat along with a measurable flux of electron antineutrinos. These elements are key components in geophysical and geochemical models. Their quantity and distribution drive the dynamics, define the thermal history, and are a consequence of the differentiation of the Earth. Knowledge of uranium and thorium concentrations in geological reservoirs relies largely on geochemical model calculations. This research report describes the methods and criteria to experimentally determine average concentrations of uranium and thorium in the continental crust and in the mantle using site-specific measurements of the terrestrial antineutrino flux. Optimal, model-independent determinations involve significant exposures of antineutrino detectors remote from nuclear reactors at both a mid-continental and a mid-oceanic site. This would require major, new antineutrino detection projects. The results of such projects could yield a greatly improved understanding of the deep interior of the Earth.Comment: 15 pages, 2 figure

Far Field Monitoring of Rogue Nuclear Activity with an Array of Large anti-neutrino Detectors

The result of a study on the use of an array of large anti-neutrino detectors for the purpose of monitoring rogue nuclear activity is presented. Targeted regional monitoring of a nation bordering large bodies of water with no pre-existing legal nuclear activity may be possible at a cost of about several billion dollars, assuming several as-yet-untested schemes pan out in the next two decades. These are: (1) the enabling of a water-based detector to detect reactor anti-neutrinos by doping with GdCl$_3$; (2) the deployment of a KamLAND-like detector in a deep-sea environment; and (3) the scaling of a Super-Kamiokande-like detector to a size of one or more megatons. The first may well prove feasible, and should be tested by phase-III Super-Kamiokande in the next few years. The second is more of a challenge, but may well be tested by the Hanohano collaboration in the coming decade. The third is perhaps the least certain, with no schedule for construction of any such device in the foreseeable future. In addition to the regional monitoring scheme, several global, untargeted monitoring schemes were considered. All schemes were found to fail benchmark sensitivity levels by a wide margin, and to cost at least several trillion dollars.Comment: 17 pages, 8 figures, proceedings for Neutrino Sciences 2005, submitted to Earth, Moon, and Planet

Influence of fast ice on future ice shelf melting in the Totten Glacier area, East Antarctica

The Totten Glacier in East Antarctica is of major climatic interest because of the large fluctuations in its grounding line and potential vulnerability to climate change. Here, we use a series of high-resolution, regional NEMO-LIM-based (Nucleus for European Modelling of the Ocean coupled with the Louvain-la-Neuve sea ice model) experiments, which include an explicit treatment of ocean–ice shelf interactions, as well as a representation of grounded icebergs and fast ice, to investigate the changes in ocean–ice interactions in the Totten Glacier area between the recent past (1995–2014) and the end of the 21st century (2081–2100) under SSP4–4.5 climate change conditions. By the end of the 21st century, the wide areas of multiyear fast ice simulated in the recent past are replaced by small patches of first year fast ice along the coast, which decreases the total summer sea ice extent. The Antarctic Slope Current is accelerated by about 116 %, which decreases the heat exchange across the shelf and tends to reduce the ice shelf basal melt rate, but this effect is counterbalanced by the effect of the oceanic warming. As a consequence, despite the accelerated Antarctic Slope Current, the Totten ice shelf melt rate is increased by 91 % due to the intrusion of warmer water into its cavity. The representation of fast ice dampens the ice shelf melt rate increase throughout the 21st century, as the Totten ice shelf melt rate increase reaches 136 % when fast ice is not taken into account. The Moscow University ice shelf melt rate increase is even more impacted by the representation of fast ice, with a 36 % melt rate increase with fast ice, compared to a 75 % increase without a fast ice representation. This influence of the representation of fast ice in our simulations on the basal melting rate trend over the 21st century is explained by the large impact of the fast ice for present-day conditions (∼25 % difference in m yr−1), while the impact decreases significantly at the end of the 21st century (∼4 % difference in m yr−1). As a consequence, the reduction in the fast ice extent in the future induces a decrease in the fast ice effect on the ice shelf melt rate that partly compensates for the increase due to warming of the ocean. This highlights the importance of including a representation of fast ice to simulate realistic ice shelf melt rate increase in East Antarctica under warming conditions.</p

Anisotropy of TeV and PeV cosmic rays with IceCube and IceTop

The interaction of high energy cosmic rays with the Earth's atmosphere produces extensive air showers of secondary particles with a large muon component. By exploiting the sensitivity of neutrino telescopes to high energy muons, it is possible to use these detectors for precision cosmic ray studies. The high rate of cosmic-ray muon events provides a high-statistics data sample that can be used to look for anisotropy in the arrival directions of the parent particles at the per-mille level. This paper reports on the observation of anisotropy in the cosmic ray data collected with the IceCube neutrino telescope in the 20-400 TeV energy range at multiple angular scales. New data from the IceTop air shower array, located on the ice surface above IceCube, shows an anisotropy that is consistent with the high-energy IceCube results. The sensitivity of IceTop to all the components of the extensive air shower will allow us to explore in more detail the characteristics of the primary cosmic rays associated with the observed anisotropy.Comment: To appear in the Proceedings of the 2011 Very Large Volume Neutrino Telescopes Conferenc

Influence of fast ice on future ice shelf melting in the Totten Glacier area, East Antarctica

The Totten Glacier in East Antarctica is of major climatic interest because of the large fluctuations in its grounding line and potential vulnerability to climate change. Here, we use a series of high-resolution, regional NEMO-LIM-based (Nucleus for European Modelling of the Ocean coupled with the Louvain-la-Neuve sea ice model) experiments, which include an explicit treatment of ocean–ice shelf interactions, as well as a representation of grounded icebergs and fast ice, to investigate the changes in ocean–ice interactions in the Totten Glacier area between the recent past (1995–2014) and the end of the 21st century (2081–2100) under SSP4–4.5 climate change conditions. By the end of the 21st century, the wide areas of multiyear fast ice simulated in the recent past are replaced by small patches of first year fast ice along the coast, which decreases the total summer sea ice extent. The Antarctic Slope Current is accelerated by about 116 %, which decreases the heat exchange across the shelf and tends to reduce the ice shelf basal melt rate, but this effect is counterbalanced by the effect of the oceanic warming. As a consequence, despite the accelerated Antarctic Slope Current, the Totten ice shelf melt rate is increased by 91 % due to the intrusion of warmer water into its cavity. The representation of fast ice dampens the ice shelf melt rate increase throughout the 21st century, as the Totten ice shelf melt rate increase reaches 136 % when fast ice is not taken into account. The Moscow University ice shelf melt rate increase is even more impacted by the representation of fast ice, with a 36 % melt rate increase with fast ice, compared to a 75 % increase without a fast ice representation. This influence of the representation of fast ice in our simulations on the basal melting rate trend over the 21st century is explained by the large impact of the fast ice for present-day conditions (∼25 % difference in m yr−1), while the impact decreases significantly at the end of the 21st century (∼4 % difference in m yr−1). As a consequence, the reduction in the fast ice extent in the future induces a decrease in the fast ice effect on the ice shelf melt rate that partly compensates for the increase due to warming of the ocean. This highlights the importance of including a representation of fast ice to simulate realistic ice shelf melt rate increase in East Antarctica under warming conditions.</p

Spectral and Spatial Characteristics of Solar Flare Hard X-Ray Emission: A Non-Uniformly Ionised Thick Target Approach

Hard X-ray emission in flares is a signature of high energy electron populations in the solar plasma. The major role these populations have in many solar flare models means that the spectral, spatial and temporal characteristics of hard X-rays will be associated with many of the diverse plasma processes ocuring during a flare. These include where and how energy release occurs, which mechanism may accelerate the particles, some methods of energy transport through the flare and eventually the radiative and atmospheric response to the distribution of the flare energy budget. The work of this thesis has been concerned with the effects introducing the non-uniform ionisation profile of the flare atmosphere has on the thick target HXR spectra and consequent interpretation of the spectra. This has involved both the theoretical modelling and observational analysis of X-ray flare emission. The data for this research was primarily obtained from the instruments on board the YOHKOH satellite. These instruments include a hard X-ray spectrometer (HXS), a grazing incidence soft X-ray telescope (SXT) and a Fourier-synthesis hard X-ray telescope (HXT). Also available is high resolution hard X-ray spectra taken by the HIREX balloon experiment. Chapter 1 gives an overview of hard X-ray observations from solar flares and describes how these observations are interpreted in the context of the varying hard X-ray production models and the implications therefore on acceleration mechanisms. This chapter also includes a brief descripition of other flare emissions, mechanisms for energy release and how these mechanisms are incorporated into the physical model of flares. Chapter 2 introduces the formulation used in this analysis for including a non-uniform ionisation profile into the the thick target model of HXR production. Using this formalism, comparisons are made of HXR yields and inferred electron spectra for the fully ionised atmosphere with a more realistic step-function atmosphere. In doing so the differing spectral characteristics of these models are desrcribed, the ultimate effect on energy and number flux budgets for these differing spectra determined and the resultant non-uniqueness of the HXR bremsstrahlung inversion for a non-uniform atmosphere discussed. Prom this point the analysis of HXR spectra moves in two directions. Firstly in Chapter 3 high resolution data from the HIREX balloon experiment is inverted using regularisation techniques. In previous analyses of this dataset, which are described in detail during this chapter, the features in the photon spectra and inferred electron spectra were thought to be suggestive of a particular mechanism of acceleration (d.c. field acceleration). In our analysis, we investigate if these features in the inferred electron spectra can instead be reproduced by choosing an appropriate atmospheric struture, and therefore cannot be considered signatures of any particular acceleration mechanism. In chapter 4 a second approach is taken to utilise HXR spectra as a diagnostic of the flare atmosphere. By assuming that the observed spectral features are caused entirely by the effects on non-uniform ionisation, (i.e. the electron population is featureless, so any break is caused by the propagation effect) and incorporating the response function of the spectrometer we attempt to relate HXR spectra to particular coronal column density. In chapter 5 this approach is used for HXR spectral observations taken by the hard X-ray spectrometer onboard YOHKOH. Based on these spectral observations estimates of the amount of material between the acceleration site and the top of the chromosphere are made. These values can be compared to estimates of the column density for the SXR loops using SXT and also those given by time of flight analysis of the hard X-ray bursts to determine if the estimates are physically realistic. Finally, in chapter 6, results of the previous chapters are drawn together, providing a summary of the work achieved in this thesis. At the same time improvements to the analysis are discussed as are the possibilites for this analysis with the expected festival of data available soon from HESSI

Prospect of the Zee model

The Zee model is one of promising models of neutrino mass generation mechanism. However, the original Zee model is not on the framework of the ground unification scenario, and moreover, it is recently pointed out that the predicted value of $\sin^2 2\theta_{solar}$ must be satisfied the relation $\sin^2 2\theta_{solar} > 0.99$. We discuss whether possible GUT versions of the Zee model can be free from the severe constraint $\sin^2 2\theta_{solar} >0.99$ or not. We will conclude that the following two models are promising: an R-parity violating SUSY GUT model and an SO(10) model with a 126-plet scalar.Comment: 3 pages, no figure, Latex, presented at KEKTC5(Nov. 2001), to be publised in the proceeding