Solar Energetic Particles, Solar Modulation and Space Radiation: New opportunities in the AMS Era #3

23 Apr 2018, 08:00 → 26 Apr 2018, 23:45 US/Eastern

Washington DC

Solar Energetic Particles (SEP), Solar Modulation and Space Radiation Workshop #3 will be held in Washington DC, from April 23 to 26, 2018.

The workshop aims to bring together experts on these topics. The talks will present the most recent results on SEP, Solar Modulation, Space Radiation and related phenomena.

For more details about the workshop, hotels and transportations please visit:
http://www.phys.hawaii.edu/ams02/pages/workshop.php

Topics: 

• Solar Energetic Particle Theory
• Solar Energetic Particle Experiments
• Solar Observations
• Solar Flares and Coronal Mass Ejections
• Solar Modulation of Galactic Cosmic Rays
• Propagation of Cosmic Rays inside the Heliosphere
• Propagation of Particles in the Earth's Magnetosphere 
• Geomagnetic Cutoff Space Radiation Environment

Monday 23 April

08:45 → 09:45 Registration, Networking & Coffee

09:45 → 12:00 Monday Morning

Gerstenmaier_William.pdf

Guhathakurta_Madhulika.pdf

Roussev_Ilia.pdf

11:00 NSF’s Geospace Section: New Challenges and Opportunities.

This talk summarizes the new challenges and opportunities facing the NSF’s Geospace Section for 2018-2019.

Speaker: Dr Ilia Roussev (National Science Foundation - Division of Atmospheric and Geospace Sciences)

11:30 Next Generation Ionizing Radiation Characterization From Aviation Altitude To Deep Space

Human access to space is expanding in a new realm of deep space exploration, space tourism and the society’s increasing reliance on rapid and reliable aviation. Particle radiation poses significant hazards for astronauts, satellites, aviators and passengers and affects planetary bodies. Increasing galactic cosmic ray fluxes near successive solar minima highlight the increasing radiation hazard.

NASA held a Space Radiation Workshop in early November, 2017, with the stated purpose of exploring ways to enable data-rich characterization, forecasting and monitoring of space radiation environments relevant to NASA science, aviation, and deep space exploration. The discussions about galactic cosmic rays, solar particle events, and solar event prediction are all highly relevant to the sustained deep space operations and flights, as well as useful closer to home on aviation and
space tourism very much in support of the new space policy directive.

The workshop set out to combine participation from traditional NASA technology, science and engineering communities with participants from non-NASA organizations with relevant technologies not previously applied to space mission applications in the hope of spurring some cross-discipline pollination.

The main goal was to create a multi-disciplinary (within NASA the goal was multi-directorate, multi-center), approach with academia and industry to start a dialogue within the domain of radiation characterization. So, there was consideration for radiation in multiple contexts (aviation, deep space, LEO, etc.) and from multiple angles of specialization such as computational, sensor development, and avionics.

In this talk, I will summarize the findings of the NASA Ames Research Center Radiation Workshop.

Speaker: Dr Madhulika Guhathakurta (NASA Ames Research Center)

12:00 → 13:30 Lunch

13:30 → 15:00 Early Monday Afternoon

Bindi_Veronica.pdf

Cohen_Christina.pdf

Moskalenko_Igor.pdf

13:30 Latest Results from the AMS Experiment on the International Space Station.

The Alpha Magnetic Spectrometer (AMS) is a general-purpose high-energy particle physics detector. It was installed on the International Space Station (ISS) in May 2011 to conduct a unique long-duration mission of fundamental physics research in space. AMS has acquired the largest number of particles ever measured in space by a single experiment, performing the most precise measurement of galactic cosmic rays (GCR) to-date. An overview of the latest results from AMS will be presented.

Speaker: Veronica Bindi (University of Hawai'i at Manoa (US))

14:00 GALPROP Code for Galactic Cosmic Ray Propagation and Associated Photon Emissions

Last decade is marked with many breakthroughs in astrophysics of cosmic rays, and more are expected in the nearest future. Their proper interpretation is impossible without a well-developed propagation code. The GALPROP project celebrates its 22nd anniversary this year. This project is devoted to the development of a self-consistent model for cosmic-ray propagation in the Galaxy and associated diffuse emissions (radio, microwave, X-rays, gamma-rays). The project stimulated independent studies of the interstellar radiation field, distribution of the interstellar gas (H2, H I, H II), synchrotron emission and the Galactic magnetic field, and isotopic production cross sections. An important recent development is a combination of GALPROP with the HelMod code for cosmic ray propagation in the heliosphere. The combined model is able to reproduce a variety of measurements made in the local interstellar space (Voyager 1) and deep inside the heliosphere at different modulation levels, and at both polarities of the solar magnetic field. I will talk about recent updates to the GALPROP model and most important results.

Speaker: Igor Moskalenko

14:30 GLE and GLE-wannabe Events in Solar Cycle 24

Among the most extreme types of solar energetic particle (SEP) events are those that have hard enough particle spectra to penetrate the Earth’s atmosphere, interact, and cause sufficient secondary particles to be measured by ground-based instrumentation; they are commonly referred to as ‘ground level enhancement’ (GLE) events. By their very definition, GLE events cannot be identified with only space-based instrumentation or at locations far from Earth, yet as we send instrumentation to distant locations with increasing frequency, our need to understand the creation of such strong SEP events and predict them throughout the heliosphere rises.

Solar cycle 24 has had a surprising dearth of GLE events (2 versus the 16 in cycle 23). However, there have been several extreme SEP events observed by STEREO that likely would have been classified as GLE events had they been directed towards Earth. We present an overview of the two cycle 24 GLE events (concentrating on the most recent September 2017 event), along with detailed analysis of the ‘GLE-wannabe’ events observed by the STEREO spacecraft. Detailed solar wind and coronal mass ejection modeling during these events will also be discussed, which may provide some insight into the generation of these extreme events.

Speaker: Christina Cohen (Caltech)

15:00 → 15:15 Afternoon Break

15:15 → 16:15 Late Monday Afternoon

15:15 Multi-Year Measurements of Radiation Belt Electrons: Acceleration, Transport, and Loss

A principal goal of the Radiation Belt Storm Probes (RBSP) mission was to develop a much deeper understanding of the structure and dynamics of Earth’s radiation belts. Almost immediately after the late-August 2012 launch of the dual RBSP spacecraft into their highly elliptical orbits, it was discovered that a third Van Allen belt (or “storage ring”) of highly relativistic electrons can exist near the inner part of the traditionally recognized outer Van Allen zone. This feature has been the subject of much theoretical investigation and speculation since its discovery. In addition to morphological structures of the radiation zones such as the third belt, it has also been a major achievement of the RBSP program (renamed the “Van Allen Probes” mission in November 2012) to understand more thoroughly how ultra-relativistic electrons are accelerated deep inside the radiation belts due to various wave-particle interactions. Van Allen Probes studies have demonstrated that electrons up to energies over 10 megaelectron volts (MeV) can be produced over broad regions of the outer Van Allen zone on timescales of minutes to a few hours. The key to such rapid acceleration is the interaction of “seed” populations of ~10 to ~200 keV electrons (and subsequently higher energies) with electromagnetic waves in the lower band whistler-mode chorus frequency range. In this presentation, we report observations of some of the largest geomagnetic storms of the last several years. We focus on storms that produced dramatic effects on the relativistic and ultra-relativistic electrons measured by the Relativistic Electron-Proton Telescope (REPT) sensors on board the Van Allen Probes spacecraft. This work describes the radiation belt acceleration, transport, and loss characteristics of these intense geomagnetic events. We emphasize features seen repeatedly in the data (3-belt structures, “impenetrable” barrier properties, radial diffusion signatures) in the context of acceleration and loss mechanisms. We especially highlight solar wind forcing of the ultra-relativistic (E ≳ 5 MeV) electron populations.

Speaker: Prof. Daniel Baker (Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO, USA.)

15:45 Insight for Deep-Space (Mars) Mission Planning using Recent Measurements from RAD on the Mars Science Laboratory

The space radiation environment is one of the outstanding challenges of a manned deep-space mission to Mars. To improve our understanding and take us one step closer to enabling a human Mars to mission, the Radiation Assessment Detector (RAD) on the Mars Science Laboratory (MSL) has been characterizing the radiation environment, both during cruise and on the surface of Mars for the past 5+ years.

Perhaps the most significant difference between space radiation and radiation exposures from terrestrial exposures is that space radiation includes a significant component of heavy ions from Galactic Cosmic Rays (GCRs). Acute exposures from Solar Energetic Particles (SEPs) are possible during and around solar maximum, but the energies from SEPs are generally lower and more easily shielded. Thus the greater concern for long duration deep-space missions is the GCR exposure.

In this presentation, I will review the current MSL RAD observations, including observations of the recent SEP event in September 2017, and discuss current approaches to radiation risk estimation used by NASA and other space agencies.

Speaker: Don Hassler (SwRI)

16:15 → 16:45 Poster Session

17:30 → 20:00 Networking Dinner

Tuesday 24 April

09:00 → 10:30 Early Tuesday Morning

Omodei_Nicola.pdf

Petrosian_Vahe'.pdf

09:00 Fermi LAT Observation of High Energy Solar Flares

The Fermi Large Area Telescope (LAT) observations of the active Sun provide the largest sample of detected solar flares with emission greater than 30 MeV to date. These include detections of impulsive and hours-long sustained emission coincident with GOES X-ray flares of X, M and C classes as well as very fast Coronal Mass Ejections (CME). Of particular interest are the detections of three solar flares whose position behind the limb was confirmed by the STEREO-B spacecraft. Fermi LAT detections of solar flares at high energy present an unique opportunity to diagnose the mechanisms of high-energy emission and particle acceleration and transport in solar flares. We will present the results from the observation of Solar Cycle 24 by the Fermi-LAT, including correlation studies with the associated Solar Energetic Particles (SEP) and CMEs.

Speaker: Dr Nicola Omodei (Stanford University)

09:30 What We Can Learn From Fermi Observations of Solar Flares About Acceleration and Transport of Particles in the Flare and CME-shock Environments.

Solar eruptive events produce flares in the corona and coronal mass ejections (CMEs). Flares radiation producing particles (RPPs) are believed to be accelerated in the coronal reconnection, while the acceleration of solar energetic particles (SEPs) is assumed to occur in the CME driven shocks. However, there is considerable observations, in particular in impulsive-prompt events, indicating a close connection between these two processes. Recent observations of long duration gamma-rays from many flares, in particular, three behind-the-limb (BTL) flares, has provided new information on this connection.
I will review some earlier observations relevant for this connection and use a detailed modeling of the Fermi flares to shed further light on this connection. The interpretation of these data will be based on a hybrid stochastic acceleration at the flare site, and re-acceleration of flare particles injected into the CME environment. I will emphasize an important aspect that plays a central role in this scenario, which is the processes of escape of accelerated particles up and down from flare site and from downstream and upstream of the CME.

Speaker: Dr Vahe' Petrosian (Stanford University)

10:00 Simulations of Relativistic Ion Energization in Collisionless Shocks

Collisionless shocks are a ubiquitous feature in numerous different heliospheric and astrophysical plasma systems. The dynamics of particle energization in shocks span multiple length scales, from kinetic interactions at the shock front to the much larger MHD scales that are driving the shock. Simulating ion energization requires modeling all of these length scales as well as a range of disparate ion velocities from thermal to relativistic. I present results of ion acceleration at collisionless shocks from the first hybrid simulations (kinetic ions-fluid electrons) to include relativistic ion dynamics. The high energy distribution of ions as well as the rate of energization is compared with predictions of diffusive shock acceleration theory. The modifications to the shock associated with relativistic ion dynamics are addressed.

Speaker: Colby Haggerty (University of Chicago)

10:30 → 10:45 Morning Break

10:45 → 12:15 Late Tuesday Morning

Popkow_Alexis.pdf

Share_Gerald.pdf

11:15 Gamma-Ray and Neutron Monitor Observations of the 2017 September 10 Solar Eruptive Event

In early September 2017, during solar minimum, Active Region 12673 produced 26 M-class and four X-class flares. Gamma-ray emission >100 MeV was observed by the Fermi Large Area Telescope (LAT) for several hours following the X8.2 flare that began at 15:35 UT on September 10 when the active region was at or beyond the solar limb. It was associated with an ~1700 km/s coronal mass ejection (CME) and a high-energy solar energetic particle event observed in space and by neutron monitors. There appear to be three distinct phases of >100 MeV gamma-ray emission, each with energy spectra consistent with the decay of neutral and charged pions produced by protons above a few hundred MeV. The early part of the first >100 MeV phase began at about 15:56 UT, about one minute after the onset of the CME, and followed the time history of the impulsive flare phase as observed in hard X-rays and nuclear de-excitation line gamma rays that lasted until about 16:05 UT.mThe second phase of the >100 MeV gamma-ray emission began at 15:58 UT and peaked two minutes later at the highest solar flux level ever recorded by LAT. This emission was observed until about 16:08UT when the slow onset of the third >100 MeV phase, lasting about 10 hours, became dominant. This is the same time when Type II radio emission, indicating the presence of a shock, was observed. These latter two phases of >100 MeV emission were not detected in hard X-rays and nuclear deexcitation line gamma-rays observed by RHESSI and GBM. We discuss our spectral and temporal analyses of these three phases of >100 MeV gamma-ray emission and their possible origins. We also compare these observations with the Fort Smith neutron monitor measurements early in the Ground Level Event to determine whether protons producing the first two phases of gamma-ray emission (GLE) were also released into interplanetary space. This work was in part supported by Thailand Research Fundgrant RTA5980003.

Speaker: Gerald Share

11:35 Properties of Coronal Shocks During Intense SEP Events and FERMI‐LAT γ‐ray Events

We study the spatial and temporal evolution of coronal shock properties inferred from observations to see if they could be the source of the particles producing the γ‐rays and the strongest Solar Energetic Particles (SEPs) measured in situ. Greater than 100 Mev γ‐rays measured in the minutes to hours following solar flares suggest that high‐energy particles interacting in the solar atmosphere can be stored and/or accelerated for long time periods. In the γ‐ray study we concentrated on events observed during occulted solar flares. We used a 3D triangulation technique, based on remote‐sensing observations to model the expansion of the CME shocks from above the solar surface to the upper corona. Coupling the expansion model to various models of the coronal magnetic field allowed us to derive the time‐dependent distribution of shock Mach numbers and the magnetic connection of particles produced by the shock to the solar surface visible from Earth. The reconstructed shock fronts for three γ‐ray events became magnetically connected to the visible solar surface after the start of the flare and just before the onset of the >100 MeV γ‐ray emission. The shock surface at these connections also exhibited supercritical Mach numbers required for significant particle energization. The strongest γ‐ray emissions occurred when the flanks of the shocks were connected in a quasi‐perpendicular geometry to the field lines reaching the visible surface. Multipoint, in situ, measurements of SEPs were consistent with the production of these particles by the same shock processes responsible for the γ‐rays. Using the observationally‐derived shock properties as input parameters to a timedependent diffusive‐shock acceleration model we show that during the 17 May 2012 GLE event particles could have been accelerated by the shock to several hundreds of MeVs within minutes of the CME onset.

Speaker: Alexis Rouillard (IRAP-CNRS-University of Toulouse)

11:55 Solar Energetic Particles and Daily GCR Variability Measured by AMS

The Alpha Magnetic Spectrometer (AMS) experiment was installed on the ISS on May 19, 2011, during the ascending phase of solar cycle 24. It will take measurements until the end of ISS operations, into the rise of solar cycle 25. It is the largest experiment capable of directly measuring Solar energetic particles (SEPs) with energies of about a few hundred MeV and above. In its first five years of operation, AMS has measured 27 SEP events; most associated with M-and X-class flares with associated fast coronal mass ejections (v > 1000 km/s). Selected SEP events measured by AMS will be presented. Furthermore, AMS serves as an important monitor of daily particle population variability in low earth-orbit. Daily variability and Forbush decreases detected by AMS will be presented.

Speaker: Alexis Popkow (University of Hawaii at Manoa)

12:15 → 14:00 Lunch

14:00 → 15:20 Early Tuesday Afternoon

Hudson_Hugh.pdf

Kim_Roksoon.pdf

Nariaki_Nitta.pdf

Richardson_Ian.pdf

14:00 The Role of Extensive Air Showers in the Inner Heliosphere

Showers initiated by high-energy cosmic rays can inject secondary
particles into interplanetary space. This will happen best if the
primary particle arrives at an impact parameter such that the column
mass corresponds to a nuclear interaction length. A tangential
shower develops at this point in the atmosphere, and it will then
project early secondary particles of all sorts in the immediate
environment of the object. In the inner heliosphere we should see
this process at work on Earth, Venus, and the Sun, which all have
different cosmic-ray environments and physical properties. The Sun
also generates its own high-energy particles, which indeed produce
gamma-ray events detected by Fermi/LAT at GeV energies. The CRAND
mechanism for Earth's and other planetary magnetospheres is well
known, for example, as a related process. We consider the observability
of tangential showers via gamma-ray or hard X-ray observations,
such as those from Fermi and NuSTAR respectively, and predict the
occurrence of extreme limb brightening as a consequence of these
interactions.

Speaker: Dr Hugh Hudson (UC Berkeley)

14:20 Prediction of Solar Energetic Particle Peak Intensity using CME Speed and Direction in Solar Cycles 23 and 24

From a survey of solar energetic particle events observed by both the STEREO spacecraft and at the Earth in 2009-2012 during solar cycle 24, Richardson et al. (Solar Physics, 289,3059, 2014) obtained a formula relating the SEP peak intensity at 14-24 MeV with the speed of the associated coronal mass ejection and its direction with respect to the observing spacecraft. This suggests that the formula might in turn be used, if the CME parameters are known, to “predict” the intensity of the related SEP event. However, since only a small fraction of CMEs are actually associated with SEPs at this energy, many “false alarms” occur. These may be reduced by, for example, considering a minimum CME width or other phenomena, such as type II and type III radio emissions accompanying the CME. For a subset of cycle 24 CMEs, in around three quarters of cases where the observed proton intensity at 14-24 MeV was above 0.1 (cm$^2$ sr s MeV)$^{-1}$, the predicted intensity was within an order of magnitude of the observed intensity in $\sim75$% of cases. However, since cycle 24 SEP events were used to generate the formula, it is also possible that this contributes the good agreement between observed and predicted SEP intensities. We have therefore applied it to CMEs in solar cycle 23, using CME speeds from the CDAW catalog and directions inferred from the location of the associated flare, and find that there is a similar level of agreement. For earlier cycles, we use CME observations from the Solwind and SMM coronagraphs associated with SEP events. In addition, for SEP events in earlier cycles where the SEP intensity and flare location are known, the speed of the associated CME might be estimated using the formula, assuming that it also holds for these earlier cycles, thereby indicating the speeds of SEP-associated CMEs even if there are no coronagraph observations.

Speaker: Dr Ian Richardson (University of Maryland, College Park and NASA/GSFC)

14:40 The Solar Origin of High-Energy Solar Energetic Particle Events

One of the remaining questions of solar energetic particle (SEP) events is their links to solar regions and eruptions from them. The solar origin is more strongly found in SEPs at high energies including electrons, and during the early phase. We experience SEP events that apparently contradict our expectation on the onset time, the flux of, and rise time to, the (first) peak, and the angular spread, on the basis of the source location and the properties of the CME. For example, a SEP event from the source region in eastern heliographic longitudes may have a quick onset and sharp rise to the peak. The observed angular spreads of SEP events may be different from what we expect from the estimated CME widths. We try to find these puzzles in terms of the magnetic connection of the CME-driven shock with the observer, using simple models and advanced numerical simulations.

Speaker: Nariaki Nitta (Lockheed Martin Solar and Astrophysics Laboratory)

15:00 The Third class of Solar Energetic Particles

In this presentation, we introduce our recent research results about the solar energetic particles (SEPs), including a basic introduction. Particularly, we discuss on the classification of SEPs. The conventional two classes of SEPs are sorted as impulsive events accelerated by reconnection process in the flaring site and gradual events accelerated in the CME-driven shock. However, in the point of view of their acceleration mechanisms and related solar eruption events, we are noticed that there are some events showing hybrid or mixed characteristics beyond the impulsive and gradual paradigms after we examine the SEPs evolution in the multi-channel observation by SOHO/ERNE. Based on this fact, we carefully suggest that there should be the third class of SEPs accelerated by reconnection not in the flaring site, but the higher regions, such as CME-CME interaction regions. Finally, we introduce on future projects and unresolved issues that need to be studied in the future.

Speaker: Roksoon Kim (KASI)

15:20 → 15:35 Afternoon Break

15:35 → 17:15 Late Tuesday Afternoon

Cooper_John.pdf

Ryan_James.pdf

15:35 Solar energetic particle events observed by the PAMELA mission

Despite the significant progresses achieved in recent years, the physical mechanisms underlying the origin of Solar Energetic Particles (SEPs) are still matter of debate. The complex nature of both particle acceleration and transport poses challenges to developing a universal picture of SEP events that encompasses both the low energy ($>$ tens of keV) observations made by space-based instruments and the GeV particles detected by the worldwide network of neutron monitors in Ground Level Enhancements (GLEs). The high precision data collected by the PAMELA satellite experiment offer the unique opportunity to study the SEP fluxes between $\sim$80 MeV and a few GeV, significantly improving the characterization of the most energetic events. In particular, PAMELA can measure for the first time with good accuracy the spectral features at moderate and high energies, providing important constraints for current SEP models. Reported results are consistent with diffusive shock acceleration theory predicting spectral roll-overs attributed to particles escaping the shock region during acceleration. In addition, the PAMELA observations allow the relationship between low and high energy particles to be investigated, enabling a clearer view of SEP origin. No qualitative distinction between the spectral shapes of GLE, sub-GLE and non-GLE events is observed, suggesting that GLEs are not a separate class, but are the subset of a continuous distribution of SEP events that are more intense at high energies.

Speaker: Dr Alessandro Bruno (NASA/GSFC)

16:05 Long Duration Gamma-Ray Flares & Solar Energetic Particles — Is there a Connection?

Fermi/LAT observations of Long Duration Gamma-Ray Flares (LDGRFs,) first identified with Compton Gamma-Ray Observatory (CGRO) and the Solar Maximum Mission (SMM), have transformed our picture of these unusually energetic phenomena at the Sun from a once rare occurrence to detections of dozens over the last solar cycle. The extreme energies and long temporal durations of many of these events poses challenges in terms of finding a consistent theory of prolonged acceleration. The highest energy emission has generally been attributed to pion production from the interaction of high-energy protons with the ambient matter, suggesting that particle acceleration occurs over large volumes extending high in the corona, either from stochastic acceleration within large coronal loops or from back precipitation from CME-driven shocks. It is possible to test these models by making direct comparisons between the accelerated ion population at the flare derived from the observations of Fermi/LAT with PAMELA measurements of solar energetic particles (thought to be accelerated by CME-driven shocks). Fortuitously, SEP observations from PAMELA extend beyond the energy range necessary to overcome the pion production threshold for interacting ions at the Sun. For over a dozen SEP events, we compare the two populations (SEPs in space and the interacting population at the Sun) and discuss the implications in terms of particle acceleration and transport models.

Speaker: G.A. de Nolfo (NASA/GSFC, Greenbelt, MD, USA)

16:35 What Do the SEP events and the Associated High-Energy Flares of 2012 March 7 Can Tell Us About Long Duration Gamma-Ray Flares?

Two X-class flares occurred on 2012 March 7, an X5.3 and an X1.1. The earlier X5 flare gathered much attention, initiating a powerful and fast CME from the eastern hemisphere. The “forgotten” X1 flare featured a much smaller CME from the same active region one hour later. However, extended high-energy gamma emission was present for almost the entire day of 2012 March 7. We have resolved the gamma emission into two separate, but overlapping extended occurrences, being from the two sequential X-class flares. Somewhat surprisingly, we find that the later X1 event was twice as prolific in gamma emission, mostly due to its duration, despite being much weaker in soft x rays. Additionally, several independent researchers have attributed all the SEPs on that day and the next five to the first CME. We conclude that the entirety of the gamma emission emanated from particle precipitation from the footpoints of two separate quasi-static large-scale (of order 1 solar radius) coronal loops and not from either of the associated CMEs accelerating the high-energy particles. Using constraints from ancillary data, we discuss the difficulties having SEPs produce the gamma rays at the Sun and we estimate the bounds in parameter space of the static loop sizes and embedded turbulence necessary to accelerate protons and ions to high energies producing the observed gamma emission.

Speaker: James Ryan (UNH)

16:55 Interplanetary Energetic Particle Measurements from NASA’s Heliophysics System Observatory

NASA’s fleet of geospace and interplanetary spacecraft have collectively provided long-term monitoring of solar, heliospheric, and galactic energetic particles from the inner solar system to the outer heliosphere and now with Voyager 1 in local interstellar space. The new proton and helium flux data from AMS-02 will extend Heliophysics System Observatory (HSO) data coverage in the NASA archive of the Space Physics Data Facility to the highest energies ever archived from spacecraft. Most of the measurements can be accessed through the NASA Space Physics Data Facility (SPDF) at spdf.gsfc.nasa.gov with enhanced browser access for many data sets through the associated Virtual Energetic Particle Observatory (VEPO) at vepo.gsfc.nasa.gov. These data can for example be used in conjunction with radiation transport codes, e.g. GEANT, to specify radiation dose rates for irradiation of spacecraft and surfaces of planetary bodies. Example flux spectra and dose profiles are discussed for the inner solar system at the Moon and Mars, for Pluto in the outer solar system, and for extreme Kuiper Belt Objects in the outermost heliosphere and the local interstellar medium.

Speaker: Dr John Cooper (NASA Goddard Space Flight Center)

Wednesday 25 April

09:00 → 10:30 Early Wednesday Morning

Consolandi_Cristina.pdf

Munini_Riccardo.pdf

Usoskin_Ilya.pdf

09:00 A Solar Cycle of Cosmic ray Data Measured by the PAMELA Experiment

It was the 15th of June of 2006 when the PAMELA satellite-borne experiment was launched from the Baikonur cosmodrome in Kazakstan. Then, for nearly ten years, PAMELA had been making high-precision measurements of the charged component of the cosmic radiation opening a new era of precision studies in cosmic rays and challenging our basic vision of the mechanisms of production, acceleration and propagation of cosmic rays in the galaxy and in the heliosphere. The study of the time dependence of the various components of the cosmic radiation from the unusual 23rd solar minimum through the maximum of solar cycle 24 clearly shows solar modulation effects as well as charge sign dependence. These results are fundamental in order to fully understand the propagation mechanisms of the cosmic radiation inside the Heliosphere. In this talk, PAMELA main results about the long term variation of cosmic-ray and of transient phenomena such Forbush decreases will be presented.

Speaker: Riccardo Munini (INFN - Universita Studi Trieste)

09:30 Comparison between PAMELA proton spectra and neutron monitor count rates

Recently published spectra of comic ray protons measured by PAMELA instrument for the period 2006-2014 make it possible to perform a direct comparison with the neutron monitor (NM) count rates. Here we used the measured proton spectra as an input and computed, using two recent NM yield function models (Mishev et al., 2013 and Mangeard et al., 2016), the expected NM count rate. These computed count rates were systematically compared with the actual NM records. Since spectra of helium and heavier species are not presently available, we standardly considered them as a 0.3 nucleonic fraction of protons in the local interstellar spectrum (LIS). The comparison shows a good agreement between modelled and recorded NM count rates but also reveals a problem to be resolved, as the model predicts too strong dependence of the NM count rate on the level of solar modulation. This may indicate slightly underestimated contribution of high-energy cosmic rays in the NM yield function.

Speaker: Ilya Usoskin (University of Oulu)

10:00 Precision Measurement of the Monthly Cosmic Ray Fluxes with the Alpha Magnetic Spectrometer

The precision measurements of the monthly cosmic ray fluxes for the period
from May 2011 to May 2017 with the Alpha Magnetic Spectrometer on the
International Space Station are presented. This period covers the ascending
phase of solar cycle 24 together with the reversal of the Sun's magnetic
field polarity through the minimum. The detailed variations with time of
the fluxes are shown up to rigidities of 60 GV.
Impact of the solar polarity reversal is discussed in details.

Speaker: Cristina Consolandi (University of Hawai'i at Manoa (US))

10:30 → 10:45 Morning Break

10:45 → 12:05 Late Wednesday Morning

Corti_Claudio.pdf

Light_Christopher.pdf

Palermo_Matteo.pdf

Tomassetti_Nicola.pdf

10:45 Solar modulation modeling in light of new data from AMS

The Alpha Magnetic Spectrometer (AMS) has performed new measurements on the temporal evolution of the proton, helium, electron, and positron fluxes in cosmic rays. These data are revealing fine details on the cosmic-ray flux evolution in connection with changing solar activity, that can bring new insights to our understanding of the so-called solar modulation effect. In this conference, I will discuss some important physical mechanisms of cosmic-ray transport in the heliosphere that can be investigated with the large collection of time-resolved and multi-channel data provided by AMS.

Speaker: Nicola Tomassetti (Perugia University & INFN- Perugia)

11:05 Numerical modeling of cosmic ray proton and helium observed by AMS-02 during the solar maximum of Solar Cycle 24

Galactic cosmic rays (GCRs) are affected by solar modulation while they propagate throughout the heliosphere. The study of the time variation of the GCR spectrum observed at Earth can shed light on the underlying physical processes, specifically diffusion and particle drifts. The AMS-02 experiment on board the International Space Station measured with very high accuracy the time variation of the cosmic ray proton and helium flux between May 2011 and May 2017 in the rigidity range from 1 to 60 GV. In this work, a comprehensive 3D steady-state numerical model is used to solve the Parker's transport equation and to reproduce the monthly fluxes observed by AMS-02. Preliminary results on the time dependence of the diffusion coefficient for proton and helium will be presented.

Speaker: Dr Claudio Corti (University of Hawai'i at Manoa (US))

11:25 Properties of the Forbush decreases measured by AMS on the ISS

During the first 5 years of operations on board of the International Space Station, from May 2011 to May 2016, AMS has detected sudden reductions of the cosmic ray intensity —the so-called Forbush decrease events. The method used to identify the reductions of the proton flux is described. The detailed time evolution of selected events is presented in different rigidity bins.

Speaker: Matteo Palermo (University of Hawai'i at Manoa (US))

11:45 Study of Forbush Decreases Using Neutron Monitors and AMS.

This preliminary study looks at the modulation of cosmic rays (Forbush decrease) caused by Coronoal Mass ejections. Forbush decreases from 2001 through 2016 are considered using data from neutron monitors. The study considers correlation of modulation magnitude (and recovery) with in situ solar wind measurements and qualitative description of the recovery period through fitting functions to NM counts/s for selected events. The study then considers events from AMS, including fitting the recovery period for different rigidities and investigating the rigidity spectrum of cosmic ray modulation.

Speaker: Christopher Light (University of Hawaii at Manoa)

12:05 → 13:50 Lunch

Thursday 26 April

09:00 → 10:30 Early Thursday Morning

Guo_Jingnan-Hassler_Don.pdf

09:00 Challenges of space weather and space radiation predictions for human explorations in deep space

Space agencies such as ESA, NASA, the Chinese space agency and even private companies are launching new human deep space exploration programs to the Moon and Mars. Radiation is one of the most important long-term risks to such missions. In preparation, this requires a very timely and thorough study to better understand the space weather conditions and their effects as a baseline for the development of mitigation strategies against radiation risks.

Radiation damage in space comes mainly form two sources, Galactic Cosmic Rays (GCRs) and Solar Energetic Particles (SEPs). The GCR is omnipresent, ubiquitous, and increases the chance of long term health consequences. Its flux is modulated by and anti-correlated with the solar activities and this modulation is also energy-dependent. Such an effect has been measured by the radiation assessment detector (RAD) on the surface of Mars and modeled via the HZETRN particle transport code (Guo et al 2017 JGR).

On the other hand, intense SEP events can result in very high dose rates that may exceed the threshold for acute radiation syndrome (ARS) or sickness or poisoning or toxicity after a whole body exposure to high doses of radiation at the Gy [J/kg] level. Such events, despite of being rather infrequent, could result in severe damage to humans and equipment and lead to failure of the entire mission and therefore should be detected as immediately as possible.

Under different shielding environment, the intensity and composition of the GCRs/SEPs may vary due to the interactions of primary particles (of different energies and charges) with the surrounding material (such as the spacecraft and the planetary atmosphere) and the generation of secondaries. Habitable shelters on the Moon and Mars with regolith shielding could provide sufficient protection against such radiation hazards. However the situation of a transit spacecraft in deep space or an astronaut carrying out extra-vehicle or planetary surface activities may be much more severe, especially during the onset of a solar particle event (SPE). This is because SPEs generally have a sudden and sporadic nature and can be very intense, dynamic and vary drastically in time and location. Therefore radiation and particle enhancements measured near Earth (such as the onset time and intensity) may be completely different from of that detected elsewhere in the heliosphere such as on the surface Mars (Guo et al 2018 AJ).

Radiation exposure from Solar Particle Events is the result of three major procedures: (1) the acceleration process at the Sun which are often related to the flare eruptions and associated shocks, (2) the properties of the accelerated particles injected into the open magnetic fields which are connected to the missions (that can be very differently connected compared to Earth), and (3) the atomic and nuclear interactions of particles with the local shielding environment (such as the spacecraft or the Martian atmosphere). Taking into consideration of these 3 factors, we will show our recent study (Guo et al 2018 GRL) of the September 2017 event which is seen on the surface of both Earth and Mars as well as at STEREO-A (a spacecraft surrounding the Sun at 1 AU). These three locations have a heliospheric longitudinal separation of more than 240 degrees apart and they all saw the SPE with different time profiles, particle spectra and radiation intensities. We highlight the utmost importance of utilizing multi-spacecraft in-situ and remote sensing observations of the Sun and the heliosphere to better understand such dynamic events and their dynamic effects across the heliosphere in particular at locations where human explorations may take place.

Speaker: Dr Jingnan Guo (IEAP, University of Kiel, Kiel, Germany)

09:30 TBD

Speaker: Eddie Semones (NASA JSC)

10:00 Introduction to GCR Models Commonly used by the Radiation Community

Galactic cosmic ray (GCR) models have been developed by NASA, ROSCOSMOS and the European Space Agency (ESA) to provide fluxes for Hydrogen and heavy ions up to Iron over a broad energy range, while remaining computationally fast so that they may be used in an operational setting. The methodology behind the NASA Badhwar-O'Neill model (O’Neill, Golge, and Slaba 2015), the ESA DLR model (Matthia et al. 2013), and the ROSCOSMOS ISO model (Nymmik et al. 1992, 1994, and 1996) and their new SINP model (Kuznetsov, Popova, and Panasyuk 2017) will be described. These models are widely used by the radiation community to estimate the GCR particle environment at 1 AU, accounting for changes in flux due to solar modulation.

Speaker: Dr Kathryn Whitman (NASA Johnson Space Center, Houston, Texas, USA)

10:30 → 10:45 Morning Break

10:45 → 12:15 Late Thursday Morning

Mertens_Christopher.pdf

Norbury_John.pdf

Schwadron_Nathan.pdf

10:45 RECENT GCR MODELS COMPARED TO AMS DATA

Recent Alpha Magnetic Spectrometer measurements of the high energy hydrogen and helium spectra have been previously compared with NASA and ESA (European Space Agency) galactic cosmic ray (GCR) codes. The Skobeltsyn Institute of Nuclear Physics (SINP) has recently developed a new GCR code, which is used by the Russian space agency (ROSCOSMOS). This new code is compared to the AMS data and shown along-side the previous NASA and ESA comparisons.

Speaker: John Norbury (NASA)

11:15 Update on the Worsening Particle Radiation Environment Observed by CRaTER and Implications for Future Human Deep-Space Exploration

Over the last decade, the solar wind has exhibited low densities and magnetic field strengths, representing anomalous states that have never been observed during the space age. As discussed by Schwadron et al. (2014), the cycle 23--24 solar activity led to the longest solar minimum in more than 80 years and continued into the ``mini'' solar maximum of cycle 24. During this weak activity, we observed galactic cosmic ray fluxes that exceeded the levels observed throughout the space age, and we observed small solar energetic particle events. Here, we provide an update to the Schwadron et al (2014) observations from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on the Lunar Reconnaissance Orbiter (LRO). The Schwadron et al. (2014a) study examined the evolution of the interplanetary magnetic field, and utilized a previously published study by Goelzer et al. (2013) projecting out the interplanetary magnetic field strength based on the evolution of sunspots as a proxy for the rate that the Sun releases coronal mass ejections (CMEs). This led to a projection of dose rates from galactic cosmic rays on the lunar surface, which suggested a ~20% increase of dose rates from one solar minimum to the next, and indicated that the radiation environment in space may be a worsening factor important for consideration in future planning of human space exploration. We compare the predictions of Schwadron et al. (2014) with the actual dose rates observed by CRaTER in the last 4 years. The observed dose rates exceed the predictions by ~10%, showing that the radiation environment is worsening more rapidly than previously estimated. Much of this increase is attributable to relatively low-energy ions, which can be effectively shielded. Despite the continued paucity of solar activity, one of the hardest solar events in almost a decade occurred in Sept 2017 after more than a year of all-clear periods. These particle radiation conditions present important issues that must be carefully studied and accounted for in the planning and design of future missions (to the Moon, Mars, asteroids and beyond).

strong text

Speaker: Prof. Nathan Schwadron (University of New Hampshire)

11:45 Active Dosimeter-Based Estimate of Astronaut Acute Radiation Risk for Real-Time Solar Energetic Particle Events

Radiation exposure from solar energetic particle (SEP) events becomes a much greater concern as human exploration extends beyond low Earth orbit (LEO) and the protective environment of Earth's magnetic field. Free space SEP events have an increased impact on mission planning and operations, as countermeasures may be necessary to avoid exceeding astronaut permissible exposure limits (PELs) and acute radiation syndrome (ARS). Operational analysis tools are needed to assess acute radiation risk during SEP events in order to determine courses of action during the mission. A methodology has been developed to meet this need, which utilizes onboard vehicle dosimeter measurements to estimate organ dose quantities at astronaut crew locations in real-time. The estimated organ doses provide the necessary inputs to acute biological response models that predict radiation induced performance decrement and other acute radiation effects. The real-time SEP organ dose estimate methodology has been combined with an acute biological response model, providing an active dosimeter-based acute radiation risk model for operational mission planning, and determining radiation exposure mitigation measures for deep-space exploration missions. This new tool has been developed specifically for NASA's Orion Multi-Purpose Crew Vehicle (MPCV) storm-shelter environment. The methodology for estimating SEP organ doses is evaluated and assessed in this presentation, and a simulation of the acute radiation responses in the MPCV storm-shelter are shown for the historical October 1989 SEP event. The operational acute radiation risk model will be utilized on NASA's EM-1 and EM-2 missions.

Speaker: Christopher Mertens (NASA Langley Research Center)

12:15 → 14:00 Lunch

14:00 → 14:40 Thursday Afternoon

Ratliff_Martin.pdf

14:00 Characterizing Solar Energetic Particles, from the Perspective of Engineering and Exploration

Abstract:
Successful ventures into space for scientific or human exploration depend in part on our anticipation of the hazards that are encountered. Although it is inherent in exploration that much is unknown, any efforts to extrapolate to, and bound, the parameters of that unknown can improve our chance of success. Each time we send spacecraft out into space, the radiation environment for that mission needs to be characterized. Situational awareness is useful, particularly for diagnosing problems and informing future missions, but knowing what is happening at the moment is of little use if the spacecraft design did not anticipate that environment. Accomplishing this requires that the spacecraft have a radiation design specification, or "spec", to quantify the hazards the designers have to address in their spacecraft design. The presentation will provide an example of a radiation design spec and discuss areas in which new scientific insight is needed.

This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Government sponsorship acknowledged.

Speaker: Dr Martin Ratliff (Jet Propulsion Laboratory, California Institute of Technology)

14:20 PENETRATING PARTICLE ANALYZER (PAN)

PAN is a scientific instrument suitable for deep space and interplanetary missions. It can precisely measure and monitor the flux, composition, and direction of highly penetrating particles (> ~100 MeV/nucleon) in deep space, over at least one full solar cycle (~11 years). A possible mission opportunity is the Deep Space Gateway (DSG). The science program of PAN is multi- and cross-disciplinary, covering cosmic ray physics, solar physics, space weather and space travel. PAN will fill an observation gap of galactic cosmic rays in the GeV region, which is crucial for improving our still limited understanding of the origin of cosmic rays, and of their propagation through the Galaxy and the Solar system. It will provide precise information of the spectrum, composition and timing of energetic particle originated from the Sun, which is essential for studying the physical process of solar activities, in particular the rare but violent solar events that produce intensive flux of penetrating particles. The precise measurement and monitoring of the energetic particles is also a unique contribution to space weather studies, in particular to the development of a predictive solar activity model in a multi-wavelength and multi-messenger approach, using observations both space and ground based. As indicated by the terminology, penetrating particles cannot be shielded effectively. PAN will map the flux and composition of these particles precisely and continuously, providing valuable input for the assessment of the related health risk, and for the development of an adequate mitigation strategy. PAN has the potential to become a standard on-board instrument for deep space human travel.

PAN is based on the proven detection principle of a magnetic spectrometer, but with novel layout and detection concept. It will adopt advanced particle detection technologies and industrial processes optimally for deep space application. The device will require limited mass (~20 kg) and power (~20 W) budget. Dipole magnet sectors built from high field permanent magnet Halbach arrays, instrumented in a modular fashion with high resolution silicon strip detectors, allow to reach an energy resolution better than 10% for nuclei from H to Fe at 1 GeV/n. The charge of the particle, from 1 (proton) to 26 (Iron), can be determined by scintillating detectors and silicon strip detectors, with readout ASICs of large dynamic range. Low power pixel detectors will maintain the detection capabilities for even the strongest solar events. A fast scintillator with silicon photomultiplier (SiPM) readout will provide timing information to determine the entering direction of the particle, and some isotope identification capability of light nuclei. Low noise, low power and high density ASIC will be developed to satisfy the stringent requirement of the position resolution and the power consumption of the tracker.

Speaker: Xin Wu (Universite de Geneve (CH))

SEP_AMSERA03.pdf

SEP_AMSERA03.pptx

14:40 → 16:00 Discussion Panel