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10 Report of the Panel on Solar and Heliospheric Physics
Pages 261-324

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From page 261...
... Consequently, the Panel on Solar and Heliospheric Physics (SHP) identified as the first of four SHP science goals for the upcoming decade, SHP1, to determine how the Sun generates the quasi-cyclical variable magnetic field that extends throughout the heliosphere.
From page 262...
... Furthermore, the heliosphere is inherently turbulent, and so it produces internal dynamics down to kinetic dissipation scales. All those heliospheric dynamics couple directly to Earth's magnetosphere and upper atmosphere, again by the magnetic field, producing the myriad forms of space weather that we must understand and mitigate.
From page 263...
... 10.2  SOLAR AND HELIOSPHERIC PHYSICS IMPERATIVES To achieve the four major science goals listed in Box 10.1, the SHP panel developed a strategy that consists of a set of imperatives for the federal agencies involved in solar and heliospheric research. The imperatives -- actions that are essential for future progress -- are listed briefly below according to the relevant agency (or agencies)
From page 264...
... c. Determine the role of small-scale magnetic fields in driving global-scale irradiance variability and activity in the solar atmosphere.
From page 265...
... Ensure continued support of current ground-based observations of the Sun, especially the line-ofsight and vector measurements of the solar magnetic field that are being used routinely for space weather operations (§10.5.5.1)
From page 266...
... are also noted.2 10.3.1  Determining How the Sun Generates the Quasi-cyclical Variable Magnetic Field That Extends Throughout the Heliosphere As emphasized in the 2003 decadal survey,3 an enduring major science goal is to determine how the Sun generates its quasi-cyclical variable magnetic field. The practical goal of such research is to learn enough to be able to help to predict the changing space environment and its societal impact (motivation M2)
From page 267...
... Continuing and improved helioseismic measurements of the solar interior from instruments including those on the SOHO and SDO spacecraft, launched in 1995 and 2010, respectively, and from the GONG ground-based network, have shown cycle-related changes in large-scale internal zonal and meridional flows. The varying flows may play a driving role rather than just being consequences of the solar activity cycle, and they narrow the wide range of realistic solar dynamo models.
From page 268...
... . The advances highlight the need for direct sampling of the solar wind in the deep inner heliosphere as close to the Sun as possible, with high-resolution measurements of plasma and electromagnetic fluctuations; high-spatial- and high-temporal-resolution observations of the solar atmosphere from the photosphere into the corona; accurate magnetic field measurements in the low-beta chromosphere and corona; and advanced theoretical models that can couple closely to the upcoming observations.
From page 269...
... Zhao, and A Kosovichev, Detection of emerging sunspot regions in the solar interior, Science 333:993-996, 2011.
From page 270...
... Further theoretical work and joint analysis of solar wind plasma and electromagnetic fields will allow a determination of whether nonlinear plasma physics can explain the highly nonadiabatic expansion of the solar wind.
From page 271...
... With new insights into the slow wind's origin and with the upcoming Solar Probe Plus and Solar Orbiter missions, researchers are poised to solve this problem definitively in the coming decade. FIGURE 10.6  Sunspot number (top)
From page 272...
... The solar atmosphere and wind are both created and structured through the medium of the Sun's powerful magnetic field; consequently, accurate measurements of the field in the corona and wind are FIGURE 10.7  Structure of a giant reconnection event in the solar wind as inferred from the combination of Cluster, Wind, and ACE data. SOURCE: Reprinted by permission from Macmillan Publishers Ltd.: Nature, T.D.
From page 273...
... It is operated by these agencies in cooperation with the European Space Agency and NSC (Norway)
From page 274...
... 10.3.3  Determining How Magnetic Energy Is Stored and Explosively Released Major solar flares and associated fast coronal mass ejections (CMEs) are the most powerful explosions and particle accelerators in the solar system, and they produce the most extreme space weather.
From page 275...
... Nordlund, An ab initio approach to solar coronal loops, Astrophysical Journal 618(2) :1031-1038, 2005, reproduced by permission of the AAS.
From page 276...
... can now often be identified in SOHO/STEREO coronagraph images. Indeed, STEREO/HI images CMEs from the deep corona to 1 AU, revealing their solar origins, propagation to Earth, and space weather impacts.
From page 277...
... Share, and D.M. Smith, Gamma-ray imaging of the 2003 October/November solar flares, Astrophysical Journal 644:L93-L96, doi:10.1086/505329, 2006.
From page 278...
... Antiochos, and C.R. DeVore, The mechanisms for the onset and explosive eruption of coronal mass ejections and eruptive flares, Astrophysical Journal 760(1)
From page 279...
... Strong magnetic fields in CME-driven disturbances can generate powerful geomagnetic storms that accelerate radiation-belt "killer" electrons and induce ground-level currents that disrupt electric-power grids. The past decade has seen substantial progress in modeling CMEs, shocks, and SEPs from solar eruptions.4 One system uses CME and real-time solar wind data to drive models that forecast effects on power grids (motivation M2)
From page 280...
... These in situ measurements, combined with all-sky heliospheric images by the Interstellar Boundary Explorer (IBEX) and Cassini mission, led to major advances in our understanding of how the solar system interacts with the interstellar medium (SHP science goal 4; decadal survey key science goal 3)
From page 281...
... , owing mainly to the reduced interplanetary magnetic field and an extended period of low solar activity. The extended solar minimum, reduced sunspot number, and record cosmic-ray intensity have led to suggestions that we may be entering an extended period of minimum activity such as was
From page 282...
... None of the earlier models predicted the ribbon or belt. SOURCE: Interstellar Boundary Explorer Mission Team.
From page 283...
... 10.4.1  Determine How the Sun Generates the Quasi-cyclical Variable Magnetic Field That Extends Throughout the Heliosphere The variable magnetic field that creates the heliosphere and produces space weather events results from processes in the solar interior and at the surface. Consequently, probing the solar interior and surface to determine the origins of the Sun's magnetic activity is a major goal for the next decade (SHP actions
From page 284...
... . At the same time, the interplanetary magnetic field strength (E.J.
From page 285...
... Improving the quality and extending the measurements above the surface with optical and radio methods are goals that will lead to better understanding and improved space weather forecasts. At present, limited measurements of the solar magnetic field are made by a few ground-based observatories and with the Hinode and SDO space missions.
From page 286...
... These unprecedented observatories promise exciting new observations of CME and flare eruptions as solar activity increases. Expected to come on line in the coming decade or shortly are ATST, which will measure coronal magnetic fields; SPP and Solar Orbiter, which explore SEP, CME, and interplanetary properties near the Sun; and IMAP, a spacecraft to be placed at L1 to observe ENAs from the heliospheric boundary region that also requires background measurements of the solar wind.
From page 287...
... During solar-active periods, low-coronal reconnection activity causes thousands of impulsive SEP events each year. While close to the Sun, SPP and Solar Orbiter will improve the statistical accuracy and temporal resolution of measured intensity and composition variations by 1-2 orders of magnitude over 1-AU data, enabling improved correlations with images of coronal jets and other reconnection sites, tests of models for acceleration and ion fractionation, and searches for quiet-time coronal emission.
From page 288...
... FASR would provide many new observations important with respect to space weather, including observations of coronal magnetic fields in active regions and their evolution before, during, and after flares and CMEs; "real-time" observations of coronal-shock locations and properties; measurements of the spectral evolution of electron energy-distribution functions; and radio flux-density spectra in communication bands. 10.4.4  Discover How the Sun Interacts with the Local Galactic Medium and Protects Earth The coming decade offers unique opportunities for additional breakthroughs in understanding how the heliosphere and local galactic medium interact.
From page 289...
... , Paper 227; V Florinski et al., The Outer Heliosphere-Solar System's Final Frontier, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics)
From page 290...
... Zank, The heliosphere's interstellar interaction: No bow shock, Science 336:1291, doi: 10.1126/science.1221054, May 2012. will complement those observations and provide context with ENA maps of the global response of the heliosheath to changing solar activity.
From page 291...
... . The bottom section of Table 10.1 illustrates how the SHP panel's program can help realize decadal survey key science goals 1-4 during the coming decade and beyond.
From page 292...
... Heliopause and ++ interstellar medium Decadal Survey Key Science Goals 1. Determine the origins of the Sun's ++ o ++ ++ ++ ++ ++ ++ ++ ++ magnetic activity and predict the variations in the space environment 2.
From page 293...
... To accomplish those goals, SPP is equipped with a tailored payload for the first near-Sun in situ measurements of solar wind ion and electron thermal plasma, suprathermal and energetic particles, and DC to high-frequency electromagnetic fields. Remote observations include a large-field-of-view white-light imager to provide global context and a directional radio receiver to locate and track flares and shocks.
From page 294...
... When close to the Sun, Solar Orbiter will observe emissions, solar wind, and energetic particles from a single area for much longer than is possible from 1 AU and will provide improved insight into the evolution of sunspots, active regions, coronal holes, and other solar features and phenomena. Solar Orbiter's high spatial and time-resolution observations close to the Sun and its long observations during near corotation with the Sun will probe key questions for understanding the formation of the heliosphere and the generation of space weather events: • How and where do the solar wind plasma and magnetic field originate in the corona (SHP action 2d)
From page 295...
... , Paper 246; M.H. Israel et al., The Effect of the Heliosphere on Galactic and Anomalous Cosmic Rays, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics)
From page 296...
... provide real-time solar X-ray, solar energetic-particle, magnetic-field, and X-ray imaging data Hinode JAXA-led mission that measures the full solar vector magnetic field and 1, 2, 3 coordinated optical, X-ray, and EUV images Interstellar Boundary Explorer Provides ENA all-sky images of heliospheric boundary and measures interstellar H, 4 (IBEX) He, O, and Ne neutral gas at 1 AU Ramaty High Energy Solar Explorer mission that provides spatial and time-resolved X-ray and gamma-ray 2, 3 Spectrographic Imager (RHESSI)
From page 297...
... , Paper 130; S.L.Keil et al., Generation, Evolution, and Destruction of Solar Magnetic Fields, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics) , Paper 131; T
From page 298...
... That cannot be done now except as a matter of blind-targeting good luck. 10.5  IMPERATIVES FOR THE HEALTH AND PROGRESS OF SOLAR AND HELIOSPHERIC PHYSICS This section describes the imperatives proposed by the SHP panel for three groups: NASA, NSF, and multiagency.
From page 299...
... 10.5.2.1  Solar and Heliospheric Physics Panel Participation in the Cost and Technical Evaluation Process At the SHP panel's first meeting in November 2010, it reviewed 30 white papers (for a list of titles, see Appendix I) describing future mission concepts, including potential strategic and Explorer missions for this decade and beyond.
From page 300...
... McComas et al., Interstellar Mapping Probe (IMAP) Mission Concept: Illuminating the Dark Boundaries at the Edge of Our Solar System, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics)
From page 301...
... and properties of the outer heliosheath; • PUI composition (implications for big bang cosmology and nucleosynthesis with a dedicated PUI instrument: He3/He4 and Ne22/Ne20 with better than 5 percent accuracy) ; • Seed populations of energetic particles with high time resolution (several minutes)
From page 302...
... Mazur, and J.R. Dwyer, 3He enhancements in large solar energetic particle events, Astrophysical Journal 525:L133-L136, doi:10.1086/312349, 1999.
From page 303...
... sphere, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics) , Paper 60.
From page 304...
... Lin et al., Solar Eruptive Events (SEE) 2020 Mission Concept, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics)
From page 305...
... Figure 10-22 for most flares, even in the presence of intense footpoint emission, with about 30-100 times RHESSI's dynamic range and sensitivity. FOXSI will also detect accelerated electrons in impulsive SEP events and type III radio bursts in the corona, as well as nanoflares.
From page 306...
... Some SEE measurements (such as HXR or ENA of near-Sun SEP intensities) may be good precursors of these major eruptions; near-real-time data could be downlinked for space weather warnings.
From page 307...
... 16  Vourlidas et al., Mission to the Sun-Earth L5 Lagrangian point: An Optimal Platform for Heliophysics and Space Weather A Research, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics)
From page 308...
... Instruments at L5 could also contribute to new advances in space weather forecasting. From L5, it is possible to observe and forecast Earth-directed CMEs with high precision, observe emerging and developed active regions about 4 days earlier than from Earth, forecast corotating interaction regions about 4 days before they cause geomagnetic storms, and measure photospheric magnetic fields over about 60° of additional longitude, improving models of coronal magnetic fields rotating toward Earth.
From page 309...
... : A New View from Sun-Earth L5, white paper submitted N to the Decadal Strategy for Solar and Space Physics (Heliophysics)
From page 310...
... 22 R.P. Lin et al., Expansion of the Heliophysics Explorer Program, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics)
From page 311...
... 23  R.P. Lin et al., Expansion of the Heliophysics Explorer Program, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics)
From page 312...
... Examples are the following: • Generation, emergence, and detection of active regions and other subsurface structures; • Dynamic coupling of the ambient solar corona to the inner heliosphere; • Magnetic reconnection in the Sun and heliosphere; • Acceleration and transport of high-energy particles from the Sun; • Origin and evolution of extreme solar storms and their impact on the geospace environment; • Structure of the large-scale heliosphere and its interaction with the interstellar medium; and • Complexity, nonlinearity, and cross-scale coupling through physical processes, such as turbulence, plasma-neutral coupling, and wave-particle interactions. Making ground-breaking advances on these major problems requires teams that combine different expertise.25 The SHP panel therefore strongly supports the creation of new heliophysics science centers composed of teams of theorists, numerical modelers, and data experts working collectively to tackle the 24  NRC, The Sun to the Earth -- and Beyond: A Decadal Research Strategy in Solar and Space Physics, 2003, pp.
From page 313...
... 26  J.A. Klimchuck, Maximizing NASA's Science Productivity, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics)
From page 314...
... 28 A.J. Tylka, Heliophysics System Science and Funding for Extended Missions, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics)
From page 315...
... Reardon et al., Approaches to Optimize Scientific Productivity of Ground-Based Solar Telescopes, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics) , Paper 224.
From page 316...
... , Paper 86; D.E. Gary et al., Particle Acceleration and Transport on the Sun: New Perspectives at Radio Wavelengths, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics)
From page 317...
... In essence, FASR images the entire solar atmosphere in three dimensions once every second from the chromosphere through the corona while retaining the capability to image a restricted frequency range with time resolution as small as 20 ms. In so doing, FASR enables fundamentally new, unique observables, including: • Quantitative measurements of coronal magnetic fields, both on the disk and above the limb, under quiet conditions and during flares; • Measurements of tracers of energy release and the spatiotemporal evolution of the electron distribution function during flares; • Imaging CMEs and the associated coronal dimming, "EIT waves,"37 and coronal shocks; and • Imaging of thermal emission from the solar atmosphere from chromospheric to coronal heights, including the quiet Sun, coronal holes, active regions, and prominences.
From page 318...
... The facility will take continuous daytime synoptic measurements of magnetic fields 38  Tomczyk et al., COSMO, The Coronal Solar Magnetism Observatory, white paper submitted to the Decadal Strategy for Solar S and Space Physics (Heliophysics)
From page 319...
... The high-time-cadence observations can help to determine when, where, and how magnetic energy is released by CMEs and by dissipative processes that result in flares. 10.5.4.5  National Science Foundation Small-Grants Program SHP Imperative: To support the community effort required to analyze, interpret, and model the vast new solar and space physics data sets of the next decade, the SHP panel assigns high priority to NSF's adopting the policy of doubling the size of its small-grants programs.
From page 320...
... , Paper 108; A Pevtsov, Current and Future State of Ground-based Solar Physics in the U.S., white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics)
From page 321...
... , Paper 69; A Chutjian et al., Laboratory Solar Physics from Molecular to HighlyCharged Ions, Meeting Future Space Observations of the Solar Plasma and Solar Wind, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics)
From page 322...
... , Paper 18; H Ji et al., Next Generation Experiments for Laboratory Investigations of Magnetic Reconnection Relevant to Heliophysics, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics)
From page 323...
... Solar-irradiance observations and reconstruction and modeling of long-term variations, such as improved solar-dynamo models, are important support for the Earth science 45  Vourlidas et al., Mission to the Sun-Earth L5 Lagrangian Point: An Optimal Platform for Heliophysics and Space Weather A Research, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics)
From page 324...
... 46  Schrijver et al., The Solar Magnetic Dynamo and Its Role in the Formation and Evolution of the Sun, in the Habitability of Its K Planets, and in Space Weather around Earth, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics)


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