Cosmic Ray Anisotropy Workshop 2013

26 Sep 2013, 07:30 → 28 Sep 2013, 21:00 US/Central

Union South, UW-Madison

The Cosmic Ray Anisotropy Workshop

The goal of the workshop is to bring together different scientific communities to discuss the origin of the anisotropy of cosmic rays and their spectral anomalies in a variety of energy ranges. We invite experts in the detection of cosmic rays on the ground, with balloons, or in space and from a variety of fields — cosmic ray physics, astrophysics, plasma physics, heliospheric physics, interstellar medium, and particle interactions in magnetic fields. Participants will explore scenarios on the origin of cosmic rays and their acceleration and transport in the interstellar medium and in the heliosphere.                           

Registration and abstract submission can be completed on Indico.  For travel and accommodations can be found on the conference website.

Thursday, sessions run from 8:45 to 18:00, with two 30-minute breaks and 1 hour for lunch;  Friday, from 9:00 to 18:00 with the same breaks and lunch; and Saturday, we'll begin at 9:00 and finish at 13:00, with one break and no afternoon session.

Thursday, 26 September

08:00 → 08:45 Registration / Information all day

08:45 → 08:59 Welcome - Marcos Santander

08:59 → 09:00 Cosmic Rays: Indirect Observations chaired by Stefan Westerhoff

09:00 → 09:40 Cosmic Ray Anisotropy: A Review - Gus Sinnis, Los Alamos National Laboratory

09:00 Cosmic Ray Anisotropy: A Review

The anisotropy of the cosmic radiation has been studied for over half a century. For much of this time the results have been contradictory and difficult to understand. In the past decade there has been an increasing number of well measured anisotropies, that exhibit interesting energy dependence. In this talk I will summarize the status of both large and small scale anisotropy measurements from a few TeV to above 10^19 eV. While some features of the observed anisotropies are firmly established others are not - for example the time dependence of the large scale anisotropy reported by Milagro and the chemical composition of the anisotropic component of the cosmic rays. I will discuss the observations that are on firm foundation and point to further measurements that must be made to confirm some of the more important but unconfirmed features of the anisotropies. Finally, I will discuss a new interpretation of the small-scale anisotropy as a local clump of dark matter.

Speaker: Dr Gus Sinnis (Los Alamos National Laboratory)

Slides CRAnisotropy.pdf

09:40 → 10:10 Cosmic-Ray Anisotropy with the HAWC Observatory - Dan Fiorino, UW-Madison

09:40 Cosmic-Ray Anisotropy with the HAWC Observatory

The High-Altitude Water Cherenkov (HAWC) Observatory is a TeV gamma-ray and cosmic-ray detector operating at an altitude of 4100 meters in Mexico. HAWC is an extensive air-shower array comprising 300 optically-isolated water Cherenkov detectors. While the observatory is only partially deployed, with 100 Cherenkov detectors in data acquisition since summer 2013, statistics are already sufficient to perform studies of cosmic-ray anisotropy. We discuss the status and performance of the detector, including the pointing accuracy and angular resolution as inferred from the observation of the moon shadow and simulations, and present first results on small-scale cosmic-ray anisotropy.

Speaker: Daniel Fiorino (UW-Madison)

Slides Fiorino_HAWC_CRanisotropy2013.09.28_CRA-Madison.ppt

10:10 → 10:40 Cosmic-ray anisotropy studies at TeV and PeV energies with AMANDA, IceCube, and IceTop - Marcos Santander, UW-Madison

10:10 Cosmic-ray anisotropy studies at TeV and PeV energies with AMANDA, IceCube, and IceTop

The study of the cosmic ray anisotropy in the TeV-PeV energy range could provide clues about the origin and propagation of cosmic rays in our galaxy. The measurement of this per-mille-anisotropy requires data sets with several billion cosmic-ray events. A sample of this size has been collected over the last six years by the IceCube neutrino telescope at the south pole, which detects cosmic ray muons at a rate of about 2 kHz. In the IceCube data, we observe a significant anisotropy in the southern sky for primary energies between 20 and 400 TeV. The anisotropy has a large-scale component of per-mille strength, accompanied by localized excess and deficit regions with smaller amplitudes and typical angular sizes between $10^{\circ}$ and $20^{\circ}$. A study of the time variability of the anisotropy is performed by combining data from IceCube and its predecessor experiment, AMANDA, which operated between 2000 and 2007. Finally, A change in the shape and an increase in the amplitude of this anisotropy is observed at PeV energies by including events of IceTop, the air shower array above IceCube.

Speaker: Marcos Santander (University of Wisconsin-Madison)

Slides anisotropy_workshop2013.pdf

10:40 → 11:00 Break

11:00 → 11:25 Measurement of cosmic ray energy spectrum with IceCube - Bakhtiyar Ruzybayev, U of Delaware

11:00 Measurement of cosmic ray energy spectrum with IceCube

We report on the measurement of the all-particle cosmic ray energy spectrum with IceCube. Results of two different techniques will be presented. The first result is a measurement of the all-particle cosmic ray energy spectrum in the energy range from 1.58 PeV to 1.26 EeV using the IceTop air shower array, which is the surface component of the IceCube Neutrino Observatory at the South Pole. The second result is a measurement of cosmic ray energy spectrum using neural network techniques and the full IceCube as a 3-dimensional cosmic ray detector. The measured energy spectrum exhibits clear deviations from a single power law above the knee around 4 PeV and below 1 EeV.

Speaker: Bakhtiyar Ruzybayev (o=udel,ou=Institutions,dc=icecube,dc=wisc,dc=edu)

Slides CRA_2013_IT73_Spectrum.pdf

11:25 → 11:50 Measurements of the cosmic rays spectrum and large scale anisotropies with the KASCADE-Grande experiment - Andrea Chiavassa, U of Torino

11:25 Measurements of the cosmic rays spectrum and large scale anisotropies with the KASCADE-Grande experiment

The KASCADE-Grande experiment measured with high precision EAS generated by cosmic rays in the 10^16-10^18 eV energy range, for each event the total number of charged particles and the number of muons were determined. Based on these two observables we estimate the primary energy of each event and we separate the events into two samples generated by light and heavy primaries respectively. The measurement of the all particle and of the light and heavy mass groups energy spectra will be presented. Our results show that: a) the all particle spectrum cannot be described by a single index power law; b) the heavy primaries mass group one show a steepening at ~8x10^16 eV; c) the light primaries mass group one show a hardening at ~10^17 eV. A search for large scale anisotropies, based on the east-west method, will also be presented. No significant anisotropies were detected. The obtained upper limits will be discussed and compared with the results of other experiments.

Speaker: Andrea Chiavassa (Universita` di Torino)

Slides Chiavassa-CRA2013.pdf

11:50 → 12:15 Large-Scale Distribution of Arrival Directions of Cosmic Rays Detected at the Pierre Auger Observatory Above ~10 PeV - Olivier Deligny, CNRS / IN2P3 - IPN Orsay

11:50 Large-Scale Distribution of Arrival Directions of Cosmic Rays Detected at the Pierre Auger Observatory Above ~10 PeV

Harmonic analyses dedicated to searches for large-scale anisotropies in both right ascension and declination distributions of cosmic rays detected above ~10 PeV at the Pierre Auger Observatory are presented. Though additional statistics is still needed to characterize unambiguously the patterns as a function of the energy due to their relatively low dipole and quadrupole amplitudes, the focus is given to the few current hints that may be indicative of the presence of a structure at large scale over a wide energy range. On the other hand, the constraints on the production of cosmic rays provided by the upper limits obtained on the dipole and quadrupole amplitudes in the EeV energy range are discussed.

Speaker: Dr Olivier Deligny (CNRS/IN2P3 - IPN Orsay)

Slides CRAW13-Deligny.pdf

12:15 → 13:39 Lunch on your own

13:39 → 13:40 Astrophysics chaired by Justin Vandenbroucke

13:40 → 14:20 The Cosmic Ray - Anisotropy Connection - Pasquale Blasi, INAF / Arceti Astrophysics Observatory

13:40 The Cosmic Ray - Anisotropy Connection

I will illustrate the type of information that we can gather on acceleration and propagation of cosmic rays from measurement of anisotropy. More specifically I will focus on two issues: 1) a discussion the the problems arising from the measured anisotropy when compared with the standard supernova remnant paradigm for the origin of cosmic rays; 2) a discussion of the implications of the Pierre Auger, ICETOP and KASCADE-Grande measurements for the transition from Galactic to extragalactic cosmic rays and how these implications confront the measured anisotropy in the EeV energy range.

Speaker: Dr Pasquale Blasi (INAF/Arcetri Astrophysical Observatory)

14:20 → 14:50 A New Analysis Method for High-Energy CR Hadron Arrival Directions - Philipp Kronberg, U of Toronto

14:20 A New Analysis Method for High-Energy CR Hadron Arrival Directions

A new approach to understanding the VHECR / UHECR sky is presented. I describe a multi-parameter analysis that is based on the observed CR arrival direction distribution. The sky plot origin can be any chosen reference source of cosmic rays. This source-centered sky (unlike [l,b] etc.) displays simulated energy-species-direction data. I discuss a preliminary UHECR-determined estimate of the intergalactic magnetic field out to ~4Mpc on the assumption that Cen A is the principal UHECR source. Other assumptions and models can be applied within this general conceptual framework. The analysis method (Yüksel, Stanev, Kistler & Kronberg ApJ 2012) can be applied to data from AUGER, HiRes, TA, and their successors. A specific example shows, within our reference assumptions, how the strength and structure of B(sub{IGM}) is approximately constrained at >~ 20 nG out to D~4Mpc, based on recent AUGER data. This is new "territory" for IGM magnetic field probes, and also the first VHECR sky-based probe of B(sub{IGM}) on nearby-Universe supra-galactic scales. It is a potentially powerful template for the understanding, and future modeling, of VHECR / UHECR propagation at greater distances. I also discuss the dependence of CR energy and species on the observed distribution of arrival directions.

Speaker: Prof. Philipp Kronberg (University of Toronto)

Slides Kronberg.pdf

14:50 → 15:20 Developments on Galactic Magnetic Field and UHECR deflections - Glennys Farrar, NYU

15:20 → 15:40 Break

15:40 → 16:05 Anisotropic diffusion of cosmic rays and the TeV-band cosmic ray anisotropy - Rahul Kumar, Ben Gurion University

15:40 Anisotropic diffusion of cosmic rays and the TeV-band cosmic ray anisotropy

We calculate the time-dependent transport of cosmic rays from point like sources in the Galaxy, assuming it can be described as diffusion. We show that the surprisingly small anisotropy in the TeV band, as recently reported by IceCube and others, can be reproduced assuming a small radial diffusion rate, without assuming a uniform distribution of the sources in the Galaxy.

Speaker: Mr rahul kumar (ben-gurion university)

Slides rahul_kumar.pdf

16:05 → 16:30 Newborn Pulsars as sources of Ultrahigh Energy Cosmic Rays - Ke Fang, U of Chicago

16:05 Newborn Pulsars as sources of Ultrahigh Energy Cosmic Rays

The workings of the most energetic astrophysical accelerators in the Universe are encoded in the origin of ultrahigh energy cosmic rays (UHECRs). Current observations by the Auger Observatory, the largest UHECR observatory, show a spectrum that agrees with an extragalactic origin, as well as an interesting transition in chemical composition from light element to heavier element as energy increases. Candidate sources range from young neutron stars to gamma-ray bursts and events in active galaxies. In this talk, we will discuss newborn pulsars as the sources of ultrahigh energy cosmic rays.  We will show that a newborn pulsar model naturally injects heavier elements and can fit the observed spectrum once propagation in the supernova remnant is taken into account. With the proper injection abundances, integrated cosmic rays from the extragalactic pulsar population can match observation in all aspects - energy spectrum, chemical composition, and anisotropy. We will also examine the fingerprints of their Galactic counterparts on cosmic ray spectrum. Lastly, we will discuss the multi-messenger smoking gun of this scenario - the detectability of high energy neutrinos from pulsars and magnetars.

Speaker: Ke Fang (University of Chicago)

Slides K_Fang.pdf

16:30 → 16:55 Galactic magnetic deflections of UHECRs including realistic random fields - Azadeh Keivani, Louisiana State University

16:30 Galactic magnetic deflections of UHECRs including realistic random fields

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Speaker: Azadeh Keivani (Louisiana State University)

Slides Keivani-CRA.pdf

16:55 → 17:20 Telescope Array: Results & Plans - Douglas Bergman, U of Utah

16:55 Telescope Array: Results & Plans

I will present recent Telescope Array measurements of the spectrum, composition and anisotropy of ultra-high energy cosmic rays. I will then present our current work and plans for the future.

Speaker: Prof. Douglas Bergman (University of Utah)

Slides TA-Results-Plans.pdf

17:20 → 17:45 Sensitivity of the orbiting JEM-EUSO mission to large-scale anisotropies - Peter Denton, Vanderbilt University

17:20 Sensitivity of the orbiting JEM-EUSO mission to large-scale anisotropies

The two main advantages of space-based observation of extreme-energy (>~10^19 eV) cosmic-rays (EECRs) over ground-based observatories are the increased field of view and the all-sky coverage with nearly uniform systematics. The former guarantees increased statistics whereas the latter enables a partitioning of the sky into spherical harmonics. We have begun an investigation, using the spherical harmonic technique, of the reach of JEM-EUSO into potential anisotropies in the extreme-energy cosmic-ray sky-map for several different source models. The technique is explained here, and first results are presented. The discovery of anisotropies would help to identify the long-sought origin of EECRs.

Speaker: Mr Peter Denton (Vanderbilt University)

Slides Peter.Denton.JEM-EUSO.pdf

19:00 → 21:00 Social Dinner: Steenbock's on Orchard, 330 N. Orchard Street, Madison 53706 (across Johnson Street from Union South)

Friday, 27 September

08:40 → 08:45 Interstellar Medium and Propogation chaired by Francis Halzen

08:45 → 09:25 Local interstellar magnetic field, Loop I, and interstellar clouds - Priscilla Frisch, U of Chicago

08:45 Local interstellar magnetic field, Loop I, and interstellar clouds

Before reaching the Earth, galactic cosmic rays must traverse nearby partially ionized low density interstellar clouds. The evolved superbubble known as Loop I appears to order the cloud kinematics and the magnetic field of the interstellar medium (ISM) within tens of parsecs. The direction of the nearby interstellar magnetic field (ISMF) that is found from starlight polarized in the local interstellar medium is approximately parallel to the local surface of the Loop I shell that dominates the northern hemisphere. Nearby interstellar clouds flow through the local standard of rest with a direction that is perpendicular to the ISMF direction, to within the uncertainties. The direction of the ISMF helping to shape the heliosphere is found from the center of the Ribbon of energetic neutral atoms discovered by the Interstellar Boundary Explorer (IBEX) spacecraft, and is close to the local field direction found from polarization data. Open questions remain. The structure of the distant parts of Loop I is filamentary and there is evidence for filamentary structure in the local ISM. The role of flux freezing in local gas is unknown. The polarity of the magnetic field is not clear.

Speaker: Priscilla Frisch (University of Chicago)

Slides Frisch-CRA2013-092713-public.pdf

09:25 → 09:55 Ellen Zweibel

slides Ellen_CRA_2013.pdf

09:55 → 10:25 Aperiodic magnetic field fluctuations and their effect on cosmic rays - Reinhardt Schlickeiser, Ruhr-U Bochum

09:55 Aperiodic magnetic field fluctuations and their effect on cosmic rays

Understanding cosmic $(\delta B,\delta E)$-fluctuations in magnetized (interstellar medium) and nonmagnetized (IGM: intergalactic medium) plasmas is of crucial importance for cosmic ray transport, including the role of collective and noncollective modes and wave-like, weakly-propagating and aperiodic fluctuations. The ordering $B_0\gg \delta B\gg \delta E$ in magnetized systems, necessary for explaining the observed nearly isotropic CR momentum distribution function, is the basis for a perturbation scheme leading to the modified diffusion-convection CR transport equation and expressions for the CR anisotropy. The nonmagnetized IGM medium containes aperiodic magnetic fluctuations which are spontaneously emitted by the fully-ionized thermal electron-proton IGM plasma at a level of $\vert \delta B\vert =1.5\cdot 10^{-16}n_{-7}T_4^{-3/2}$ G. These spontaneously emitted fluctuations affect the propagation of CR protons and electrons in the IGM at energies below $10^{15}$ eV.

Speaker: Prof. Reinhard Schlickeiser (Ruhr-University Bochum, Germany)

Slides crani13.pdf

10:25 → 10:45 Break

10:45 → 11:15 Cosmic ray acceleration in the presence of super diffusion - Alex Lazarian, UW-Madison

10:45 Cosmic ray acceleration in the presence of super diffusion

Alfvenic turbulence that determines the magnetic field wandering exhibit the process of superdiffusion which results in the perpendicular displacement to change as y~x^3/2, where x is the distance measured along magnetic field is the distance perpendicular to the magnetic field, provided that y is less than the injection scale of the turbulence. This process changes substantially the acceleration of cosmic rays in perpendicular shocks, which were considered as the accelerating agent of anomalous cosmic rays. I shall discuss how the process of superdiffusion changes the acceleration in parallel and perpendicular shocks and show the analogies between the shock and reconnection acceleration.

11:15 → 11:40 Alexander Dosch

slides Perp_diffusion.pdf

11:40 → 12:05 Recovering the observed B/C ratio in a dynamic spiral-armed cosmic ray model - David Benyamin, Hebrew University

11:40 Recovering the observed B/C ratio in a dynamic spiral-armed cosmic ray model

We develop a fully three dimensional numerical code describing the diffusion of cosmic rays in the Milky Way. It includes the nuclear spallation chain up to Oxygen, and allows the study of various cosmic ray properties, such as the CR age, grammage traversed, and the ratio between secondary and primary particles. This code enables us to explore a model in which a large fraction of the cosmic ray acceleration takes place in the vicinity of galactic spiral arms and that these spiral arms are dynamic. We show that the effect of having dynamic spiral arms is to limit the age of cosmic rays at low energies. This is because at low energies the time since the last spiral arm passage governs the Cosmic Ray (CR) age, and not diffusion. Using the model, the observed spectral dependence of the secondary to primary ratio is recovered without requiring any further assumptions such as a galactic wind, re-acceleration or various assumptions on the diffusivity. In particular, we obtain a secondary to primary ratio which increases with energy below about 1 GeV.

Speaker: Mr David Benyamin (The Hebrew University)

12:05 → 12:30 Explanation for the Anisotropies at Small and Medium Angular Scales - Gwenael Giacinti, U of Oxford

12:05 Explanation for the Anisotropies at Small and Medium Angular Scales

The diffusion approximation (DA) predicts a dipolar anisotropy, but cannot explain the anisotropies at smaller scales. However, the DA is not designed to predict phenomena arising on spatial scales smaller than the cosmic ray mean free path. We demonstrate here that energy-dependent smaller scale anisotropies naturally appear on the sky and reflect the local concrete realization of the turbulent magnetic field within the cosmic ray mean free path.

Speaker: Dr Gwenael Giacinti (University of Oxford)

Slides Giacinti_CRA2013_Madison.pdf

12:30 → 13:54 Lunch on your own

13:54 → 13:55 Cosmic Rays: Direct Observations chaired by Albrecht Karle

13:55 → 14:35 Direct Measurements of Cosmic Rays - Eun-Suk Seo, University of Maryland

13:55 Direct Measurements of Cosmic Rays

Direct measurements of cosmic rays with balloon-borne and space based instruments are used for understanding cosmic ray origin, acceleration and propagation, as well as exploring the supernova acceleration limit and searching for exotic sources such as dark matter. The energy reach of direct measurements is limited by the detector size and exposure time, but incident particles are identified element-by-element with excellent charge resolution. Recent results and their implications will be reviewed. The outlook of future experiments will also be discussed.

Speaker: Prof. Eun-Suk Seo (University of Maryland)

14:35 → 15:05 Super-TIGER and the search for Galactic Cosmic-Ray Origins - John Ennis Ward, Washington University

14:35 Super-TIGER and the search for Galactic Cosmic-Ray Origins

Super-TIGER is a large area (5.4 m^2) balloon-borne instrument designed to measure cosmic-ray nuclei in the charge interval 30 <= Z <= 42 with individual-element resolution and high statistical precision, and make exploratory measurements through Z = 56. These measurements will provide sensitive tests of the emerging model of cosmic-ray origins in OB associations and models of the mechanism for selection of nuclei for acceleration. Furthermore, Super-TIGER will measure with high statistical accuracy the energy spectra of the more abundant elements in the interval 10 <= Z <= 28 at energies 0.8 < E < 10 GeV/nucleon to test the hypothesis that nearby micro-quasars could superpose features on the energy spectra. Super-TIGER, which builds on the heritage of the smaller TIGER, was constructed by a collaboration involving WUSTL, NASA/GSFC, Caltech, JPL and U Minn. It was successfully launched from Antarctica in December 2012, collecting high-quality data for over one month. Particle charge and energy were measured with a combination of plastic scintillators, acrylic and silica-aerogel Cherenkov detectors, and a scintillating fiber hodoscope. Details of the flight, instrument performance, data analysis and preliminary results of the Super-TIGER measurement will be presented.

Speaker: Dr John Ennis Ward (Washington University in St. Louis)

15:05 → 15:35 Elemental and Isotopic Abundances and Their Implications for Cosmic Ray Origins - Georgia De Nolfo, NASA/GSFC

15:05 Elemental and Isotopic Abundances and Their Implications for Cosmic Ray Origins

The answer to the question of the origin of galactic cosmic rays lies not only with directional anisotropies for the highest energies where direction is preserved but also with in the signatures found in their energy spectra and composition.  Elemental and isotopic measurements carry the imprint of nucleosynthesis, acceleration time scales, and residence times within the Galaxy.  Recent isotopic measurements with the Cosmic Ray Isotope Spectrometer (CRIS) from ~80-600 MeV/nucleon aboard the Advanced Composition Explorer (ACE) satellite as well as elemental data from Mg through Sr from the Trans-Iron Galactic Element Recorder (TIGER), suggest an origin linked to OB associations.  GCR ratio measurements of 22Ne/20Ne, 58Fe/56Fe, and 31Ga/32Ge in particular, are consistent with a source material that is a mixture of the interstellar material (with solar system abundances) and outflow/ejecta from massive stars. (The following is a complicated concept and may need to be longer to get the points across. I don’t understand it.) Furthermore, the ordering of refractory and volatile elements with atomic mass is improved if the source material includes massive star outflow/ejecta, resulting in power-law trend with atomic mass with similar slopes for both but with refractory elements preferentially accelerated by a factor of ~4.  Together with recent observations of high-energy gamma-rays from SNRs and extended sources, we conclude that the likely source of GCRs is consistent with an origin in OB associations and their associated superbubbles.

Speaker: Dr Georgia de Nolfo (NASA/GSFC)

15:35 → 15:55 Break

15:55 → 16:20 What do the spectral breaks in CR spectrum tell us? - Serap Tilav, U of Delaware

15:55 What do the spectral breaks in CR spectrum tell us?

Rigidity dependent breaks and the hardening of the elemental spectra observed above 200 GeV provided the most important hint on the nature of the cosmic ray knee. Model independent analysis of the CR data (direct and indirect combined) shows at least 3 different source populations needed to describe the spectrum and composition from 200 GeV up to 200 EeV.

Speaker: Dr Serap Tilav (o=udel,ou=Institutions,dc=icecube,dc=wisc,dc=edu)

Slides 01_Tilav_SpectralBreaks-CRA.pptx

16:20 → 16:45 Cosmic ray measurements with the Fermi Large Area Telescope - Justin Vandenbroucke, UW-Madison

16:20 Cosmic ray measurements with the Fermi Large Area Telescope

TBD

Speaker: Prof. Justin Vandenbroucke (UW Madison)

Slides 02_vandenbroucke_130927_cra.ppt

16:45 → 17:10 First Results of the AMS-02 Experiment on the ISS - Jorge Casaus, CIEMAT

16:45 First Results of the AMS-02 Experiment on the ISS

AMS-02 is a general purpose cosmic ray detector operating on the International Space Station since 19 May 2011. The results based on the data collected during the first 2 years of the mission include high precision measurements of the proton, helium, electron and positron fluxes, and the boron to carbon ratio in the energy range from ~1GeV/n to ~1TeV/n. Proton and helium spectra are consistent with single power laws with no fine structures or breaks. The boron to carbon ratio shows no evidence for a structure within the studied energy range. The positron fraction is determined in the energy range from 0.5 to 350GeV and its energy spectrum shows an steadily increasing fraction from 10 to ~250GeV with no fine structure. The positron to electron and positron to proton ratios are consistent with isotropy within this energy range.

Speaker: Dr Jorge Casaus (CIEMAT - Spain)

Slides 03_AMS-Casaus.pdf

17:10 → 17:35 A hadronic explanation of the lepton anomaly - Philipp Mertsch, KIPAC, Stanford

17:10 A hadronic explanation of the lepton anomaly

The anomaly in the cosmic ray positron fraction, first observed by the PAMELA experiment and later confirmed by Fermi-LAT and AMS-02, has generated a lot of interest and theoretical efforts, mostly due to the suggested interpretation as an indirect signature of dark matter annihilation in the Galaxy. I will argue that this interpretation is now strongly disfavoured by searches for gamma-rays from the galactic halo and turn to possible astrophysical explanations. A hadronic model of production and acceleration of secondaries in mature supernova remnants provides a compelling explanation of hard secondary positrons and links to signatures in other hadronic channels, like neutrinos.

Speaker: Philipp Mertsch (KIPAC, Stanford)

Slides CRA2013_Mertsch.pdf

17:35 → 18:00 Large scale anisotropy of cosmic rays and directional neutrino signals from Galactic sources - Luis Anchordoqui, UW-Milwaukee

17:35 Large scale anisotropy of cosmic rays and directional neutrino signals from Galactic sources

Quite recently the IceCube Collaboration has reported an observation of 26 neutrino candidates above ~ 50 TeV. Including the two ~ 1 PeV neutrinos reported earlier in 2013, these 28 events constitute a 4.3\sigma excess compared to the atmospheric background. In this talk, I will explore the compatibility between the data and an unbroken power-law neutrino spectrum, for various values of spectral index \Gamma >= 2. I will show that \Gamma ~ 2.3 is consistent at the ~ 1.5\sigma level with the observed events up to 1 PeV and to the null observation of events at higher energies. I will then assume that the sources of this unbroken spectrum are Galactic, and deduce (i) an energy-transfer fraction from parent protons to pions, and (ii) a discriminating test between the two most popular models ("dip" and "ankle") for the Galactic to extragalactic cosmic-ray transition. Future IceCube data will test the unbroken power law hypothesis, and, if the neutrino sources are Galactic, discriminate between the "dip" and "ankle" models of Galactic to extragalactic transition.

Speaker: Prof. Luis Anchordoqui (University of Wisconsin Milwaukee)

Slides 05_cra2013-Anchordoqui.pdf

Saturday, 28 September

08:40 → 08:45 Heliosphere chaired by Alex Lazarian

08:45 → 09:25 Three-dimensional Structure of the Time-dependent Heliosphere Interacting with the Local Interstellar Medium - Nick Pogorelov, U of Alabama-Huntsville

08:45 Three-dimensional Structure of the Time-dependent Heliosphere Interacting with the Local Interstellar Medium

In this brief overview, we describe observational and modeling aspects of the solar wind (SW) interaction with the local interstellar medium (LISM) paying particular attention to three-dimensional and time-dependent effects. We demonstrate that time-dependent phenomena may substantially affect the global streamline and magnetic field topology in the inner heliosheath (IHS) - a plasma layer between the heliospheric termination shock and the heliopause. It is shown that Voyager spacecraft observations cannot be easily interpreted without invoking solar cycle, magnetic reconnection, and MHD instability effects. In particular, the solar wind flow backward toward the Sun can be explained by the evolution of magnetic barriers developing in the IHS over the solar cycle. In view of the recent announcement of the Voyager1 penetration into the LISM, we discuss some issues related to numerical modeling of the heliopause instability. The behavior of the heliospheric current sheet in the inner heliosheath is discussed, which is sometimes accompanied by transition to a turbulent flow regime. We also show the results of our numerical modeling of the SW-LISM interaction using observational boundary conditions.

Speaker: Prof. Nikolai Pogorelov (University of Alabama in Huntsville)

09:25 → 09:55 Numerical Modeling of the Heliotail - Sergey Borovikov, U of Alabama - Huntsville, given by Nick Pogorelov

09:25 Numerical Modeling of the Heliotail

The heliotail structure is of interest for the analysis of the Lyman–alpha absorption in the direction of the nearby stars, the energetic neutrals (ENA) production, and possibly cosmi ray acceleration. Recent Interstellar Boundary Explorer (IBEX) observations revealed rather complex topology of the heliotail (McComas et al. 2013). We performed 3D, MHD-kinetic modeling of the solar wind interaction with the local interstellar medium to analyze the heliotail region to distances up to 5000 AU downstream. We examined the role of the interstellar magnetic field in shaping the heliopause. The heliospheric current sheet behavior and the heliopause instability are analyzed. We determined that the heliopause is noticeably squeezed. We also show that there is no well-defined boundary between the solar wind and the local interstellar medium in at distances greater than 1500 AU.

Speaker: Prof. Nikolai Pogorelov (University of Alabama in Huntsville)

09:55 → 10:25 Some remarks on heliospheric observations - Klaus Scherer, Ruhr U. - Bochum

09:55 Some remarks on heliospheric observations

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Speaker: Dr Klaus Scherer (Institut für Theoretische Physik Lehrstuhl IV: Weltraum- und Astrophysik Ruhr-Universität Bochum D-44780 Bochum Germany)

10:25 → 10:45 Break

10:45 → 11:15 Modeling the Lyman-alpha backscatter observed by Voyager 1 and 2 in the outer heliosphere and the structure of the heliospheric bow shock - Gary Zank, U of Alabama-Huntsville

10:45 Modeling the Lyman-alpha backscatter observed by Voyager 1 and 2 in the outer heliosphere and the structure of the heliospheric bow shock

1) Observations made by ultraviolet (UV) detectors on board Pioneer 10 , Voyager 1 , and Voyager 2 can be used to analyze the distribution of neutral hydrogen throughout the heliosphere, including the interaction regions of the solar wind and local interstellar medium. We use state-of-the art three-dimensional (3D) magnetohydrodynamic (MHD) – kinetic neutral H models to simulate Lyman-alpha backscatter as would be seen by the three spacecraft, exploiting a new 3D Monte Carlo radiative transfer code under solar minimum conditions (Fayock et al., 2013) . Both observations and simulations of the UV backscatter intensity are normalized for each spacecraft flight path at 15 AU, and we compare simulations with Voyager 1 and 2 and Pioneer 10 Lyman-alpha data results, finding a very close match with the Voyager data. Our results predict a large increase in the Lyman-alpha intensity as the hydrogen wall is approached. 2) Recent IBEX observations indicate that the local interstellar medium (LISM) flow speed is less than previously thought (23.2 km/s rather than 26 km/s), indicating that the LISM flow may be either marginally super-fast magnetosonic or sub-fast magnetosonic. This raises two questions: (A) Can a LISM model that is barely super-fast or sub-fast magnetosonic account for Ly-alpha observations that rely critically on the additional absorption provided by the hydrogen wall (H-wall)? and (B) If the LISM flow is weakly super-fast magnetosonic, does the transition assume the form of a traditional shock or does neutral hydrogen (H) mediate shock dissipation and hence structure through charge exchange? Both questions are addressed using three-dimensional self-consistently coupled magnetohydrodynamic plasma – kinetic neutral H models with different LISM magnetic field strengths (2, 3, and 4mG) as well as plasma and neutral H number densities. The 2 and 3mG models are fast magnetosonic far upwind of the heliopause whereas the 4μ G model is fully subsonic. The 2mG model admits a broad (~50–75 AU) bow-shock-like structure. The 3mG model has a smooth super-fast–sub-fast magnetosonic transition that resembles a very broad, ~200 AU thick, bow wave. A theoretical analysis shows that the transition from a super-fast to a sub-fast magnetosonic downstream state is due to the charge exchange of fast neutral H and hot neutral H created in the supersonic solar wind and hot inner heliosheath, respectively. For both the 2mG and the 3mG models, the super-fast magnetosonic LISM flow passes through a critical point. Because the Mach number is only barely super-fast magnetosonic in the 3mG case, the hot and fast neutral H can completely mediate the transition and impose a charge exchange length scale on the structure, making the solar-wind–LISM interaction effectively bow-shock-free. The charge exchange of fast and hot heliospheric neutral H therefore provides a primary dissipation mechanism at the weak heliospheric bow shock. Both super-fast magnetosonic models produce a sizeable H-wall. We find that (1) a sub-fast magnetosonic LISM flow cannot model the observed Ly-alpha absorption profiles along four sightlines corresponding to upwind, sidewind, and downwind; and (2) both the super-fast magnetosonic models can account for the Ly-alpha observations, with possibly the bow-shock-free 3μ G model being slightly favored.

Speaker: Dr Gary Zank (University of Alabama in Huntsville)

Slides Heliospheric_structure.pdf

11:15 → 11:40 Understanding the anisotropy of TeV cosmic rays - Ming Zhang, FL Institute of Technology

11:15 Understanding the anisotropy of TeV cosmic rays

Recent IBEX observation of a ribbon structure in energetic neutral atom emissions indicates that the level of turbulence in the interstellar magnetic field is quite low. The quasilinear theory of particle transport predicts a very large parallel diffusion and a very small perpendicular diffusion. Applying this extremely anisotropic diffusion to cosmic ray transport from a past nearby point source, we find that there will most likely be a large particle intensity gradient perpendicular to the magnetic field direction. The gradient can change with particle energy rapidly because it is sensitive to the magnitude of perpendicular diffusion coefficient. While cosmic ray anisotropy from particle diffusion still points towards the point source, drift anisotropy or b cross gradient anisotropy, which is enhanced from the perpendicular diffusion anisotropy by the ratio of particle gyroradius to perpendicular mean free path, is always perpendicular to the magnetic field. In the paper, we will demonstrate how the combination the Compton-Getting effect, diffusion and drift can result in various behaviors of large-scale cosmic ray anisotropy. In the mean time, the large-scale anisotropy can be break into medium-scale anisotropy when the particles are slightly deflected by the heliospheric magnetic field.

Speaker: Prof. Ming Zhang (Florida Institute of Technology)

11:40 → 12:05 - Nathan Schwadron, U of New Hampshire

12:05 → 12:30 Heliospheric Boundary and the TeV Cosmic Ray Anisotropy - Paolo Desiati, UW-Madison

12:05 Heliospheric Boundary and the TeV Cosmic Ray Cosmic Ray Anisotropy

The observation of a small but significant anisotropy in the cosmic ray distribution on Earth as a function of energy has initiated a series of discussions on the effects of particle propagation across the local interstellar magnetized medium. The sudden topological change of the anisotropy above 100 TeV particle energy, seems to hint to a heliospheric scenario. A discussion on the effects of the heliosphere on cosmic ray transport with energy in excess of about 10 TeV is presented. Such effect may be responsible of the topological transition of the anisotropy and of some small scale features.

Speaker: Dr Paolo Desiati (University of Wisconsin - Madison)