|1. Disentangling Expansion Effects and Collisional Relaxation in the Solar Wind
Organizers: Benjamin L. Alterman (UMICH) , Kristopher G. Klein (UMICH), Bennett A. Maruca (U. of Delaware), Daniel Verscharen (UNH)
The particle distribution functions in the solar wind often exhibit kinetic structures such as temperature anisotropies, relative drifts, and beams indicating a departure from local thermodynamic equilibrium. The existence of these features implies that the solar wind can be in a state of weak collisionality in which binary Coulomb collisions among the particles are inefficient in reducing these non-equilibrium features. On the other hand, ordering particle observations by their collisional age shows that the solar wind also exhibits states in which collisions are able to equilibrate the plasma. These findings imply that both collisional and collisionless processes are important for the evolution of the solar wind.
In concert with local microphysical processes, the global expansion of the solar wind creates these non-equilibrium features. For a complete, physics-based description of the solar wind, it is crucial to include macrophysical expansion effects, microphysical collisionless processes, and collisions. Yet, the interplay among these phenomena is poorly understood. We tackle this outstanding fundamental problem of space science by addressing the principal science question:
How do global expansion and collisional relaxation determine the state of the solar wind?
Specifically, this session will center on the question of where these effects act as a function of the distance from the Sun as well as the scale size in both coordinate space and in the velocity space of the particle distributions. In the interest of the upcoming Solar Probe Plus and Solar Orbiter missions, we will discuss the radial evolution of the plasma with a special focus on the inner heliosphere. This session’s science question is critical for these missions' top-priority goal of determining the processes that transport and thermalize energy in the solar wind.
We solicit contributions based on observational, theoretical, and numerical studies to stimulate an interdisciplinary discussion of global and local plasma effects in the solar wind. The objectives of this session are of great importance to the broader SHINE community due to their far-reaching implications for both fundamental space research and physics-based space-weather-prediction models.
|2. Suprathermal population in interplanetary space: Current Understanding and Challenges Organizers: Maher Dayeh (SWRI), Noé Lugaz (UNH), Robert Ebert (SWRI)
Over the last two decades, in situ measurements have provided compelling evidence that a significant fraction of interplanetary (IP) shock-accelerated events, such as large solar energetic particle (SEP) events accelerated by IP shocks, corotating interaction regions, and the Earth’s bow shock draw their source material from a persistent but highly dynamic suprathermal (ST) tail between a ~few keV up to ~100s keV energy rather than from the more abundant solar wind peak. Ubiquitous suprathermal tails have also been observed across the heliosphere at few keV to tens of keV. Despite the prevalence of these ST ions in interplanetary space, the origin of this population is highly controversial, mainly because many local and remote sources can contribute and cause large variations in the population properties such as intensity, spectral indices, and ion composition. Consequently, most theoretical concepts for the origin and acceleration of ST ions fall into one of two main categories, namely (1) continuous acceleration of solar wind-like or other low-energy material in interplanetary space or (2) mixing of particles accelerated during discrete events such as solar flares and CME or CIR shocks. This session provides a forum to present and debate the latest results from in-situ spacecraft observations, the theoretical concepts of understanding the suprathermal population in IP space, and the potential implications on space weather and solar- terrestrial connections. The following questions will be addressed:
- What are the properties of ST ions in different locations of the heliosphere? 2. What observational characteristics can be used to distinguish between discrete and continuous ion acceleration processes? 3. How can our understanding of ST population in different space environments help us develop theoretical models to describe ST acceleration? 4. What are the implications of understanding the ST population on space weather forecasting?
3. Understanding the Structure and Morphology of CMEs by Integrating Observations and ModelingOrganizers: Miho Janvier (IAS), Noé Lugaz (UNH), Ward Manchester (UMICH), M. Linton (NRL) & T. Nieves-Chinchilla (NASA)
The past 20 years have witnessed the development in three dimensional coronal mass ejection (CME) simulations, the routine in-situ measurements of CME physical parameters at 1 AU and in the inner heliosphere, and the development of remote heliospheric imaging. However, even with multi-viewpoint and multi-location observations, understanding the global CME morphology, geometry, and the associated magnetic field topology, as well as the evolution of these structures as they evolve through the heliosphere, is still a challenge. Improving our understanding of CME structure is critical to space weather prediction. Thus, this session focuses on means by which the reconstruction of interplanetary CMEs (ICMEs) can be improved, with a view to improving space weather prediction capabilities. In addition, simulations and observations have mainly progressed in two separate directions with little integration and cross-fertilization. However, recent studies show a way forward to perform studies integrating these different techniques and make it possible to develop tools combining these different aspects.
In this session, we will discuss the following questions:
— What can we infer about the global structure of CMEs, based on remote sensing and in situ reconstructions, and how both compare with each other and with simulations?
— What advances in current reconstruction models would best enable us to improve our understanding of and ability to reconstruct ICME magnetic fields?
— How can remote sensing heliospheric observations and statistical in-situ information be used to devise models for ICME reconstruction and to improve simulations?
|4. Magnetic Reconnection in Turbulence and Turbulent Magnetic Reconnection: Outstanding Challenges
Organizers: Jason TenBarge (U. of Iowa), Vadim Roytershteyn (Space Science Institute), Michael Shay (U. of Delaware)
Turbulence and magnetic reconnection are the two primary mechanisms responsible for transferring large-scale energy to small scales, where the energy is eventually thermalized in the weakly collisional plasmas typically found in the heliosphere. Both subjects are individually major topics of research; however, in situ heliospheric observations and numerical simulations have made it clear that the two mechanisms are often inextricably linked. Yet, few studies have focused on the interface of the two processes. This session follows a successful session last year that reviewed the current state of the field and identified key frontier questions. This year, we hope to explore these frontier and related topical questions in greater detail. Specifically, we will address the following questions:
1) Is direct access from large to small scales via reconnection realizable? Is magnetic reconnection a part of the “normal” turbulent cascade of energy or a distinct process? For example, does tearing instability of sheet-like eddies modify the turbulent cascade?
2) What is the role of magnetic reconnection in the overall dissipation of plasma turbulence?
3) How do we reliably detect sites of reconnection in a turbulent environment, both in spacecraft data and 3D numerical simulations?
4) What have we learned about the interface between reconnection and turbulence from the high cadence field and particle data provided by the Magnetospheric Multiscale mission (MMS)?
Current, forthcoming, and proposed spacecraft missions, such as MMS, Solar Probe Plus, and THOR, are targeted toward understanding particle energization and heating resulting from magnetic reconnection and the dissipation of turbulence. Therefore, it is imperative for the two communities to come together to address these questions regarding the interface between magnetic reconnection and turbulence to prepare for and maximize the scientific return from these missions.
|5. Observations, modeling and predictions of solar activity
Organizers: Irina Kitiashvili (NASA Ames & BAERI), Mausumi Dikpati (HAO, NCAR), Todd Hoeksema (Stanford University), Michael J. Thompson (HAO & NCAR), Ricky Egeland(HAO & Montana State University)
Prediction of solar magnetic activity on various temporal scales is a fundamental element of space weather, which requires a wide range of theoretical and observational expertise in solar phenomena from the deep interior to the corona. Historical observations have revealed many features of cyclic variations of the solar activity; but these data are dramatically insufficient to draw a physical picture of global magnetic field evolution. New observational data, currently available from space missions and ground-based observatories, provide us with detailed information about solar dynamics and magnetism. However, because of the relatively short duration of data series and the great variety of data types and quality, it is challenging to assimilate these data in theoretical models and make reliable forecasts. The recent unexpectedly weak solar activity cycles, as well as observations of rotational and magnetic topology transitions in solar-type stars, suggest that the Sun and its magnetic dynamo are currently in a very interesting evolutionary stage. This could relate to the difficulty in getting a model of the Sun to produce solar-like – rather than anti-solar-like – differential rotation, to reproduce the rotation profile obtained from helioseismology, and to predict solar activity cycles.
The proposed session will combine the expertise of observers, theoreticians and modelers and provide a unique platform to discuss the current status and challenges for understanding solar and stellar dynamics and activity on different temporal and spatial scales.
During the session the following questions will be discussed:
1) What are the important links between the solar dynamics and activity from the interior to the surface and corona?
2) What additional observations would test the hypothesis that Sun-like stars undergo a transition from large-scale to small-scale magnetic field topology?
3) What additional observations and models are needed to reconstruct solar evolution to explain current dynamical properties?
|6. Observational signatures of shocks in flares
Organizers: Kathy Reeves (SAO), Gang Li (UAH)
In the standard flare model, it was predicted that the reconnection outflow may lead to one or two terminations shocks (one above and one below the reconnection site). These termination shocks are fast mode shocks and are capable of accelerating both ions and electrons to high energies. Yet, observations of these shocks are rare, and claimed observations of termination shocks have been controversial. For example, Hara et al. (2011) observe a hot loop-top source in STEREO 195 A and EIS Fe XXIII observations co-located with hot outflowing plasma, and postulate that these observations are evidence for a termination shock. Chen et al. (2015) presented possible observations of a termination shock and its disruption using SDO/AIA images and high cadence radio imaging spectroscopy from the VLA. We propose a session to focus on observational signatures of flare termination shocks. In particular, we plan to examine how one can combine multiple spacecraft and ground-based observations to provide constraints and clues of the existence and properties of flare termination shocks. Relevant observations include those from but not limited to, SDO, Hinode, IRIS, RHESSI, Fermi, and the VLA. We will also discuss the state of the art in modeling these shocks, and how models can contribute to finding observable signatures of termination shocks.
The session will also discuss on consequences of having a TS in flare dynamics and its implications to the associated particle acceleration process.
Some open questions include,
1. Can we obtain signatures of shocks from various spectral lines of C, O, and Fe? What are the "smoking guns" we are looking for?
2. How does the shock orientation (e.g. limb event and disk event) affect the "searching"?
3. Has solid evidence of the termination shock been observed already (i.e. Chen et al., 2015)?
4. What observations are needed to differentiate between different models of shock acceleration and heating in flares?
5. Possible invited speakers: Bin Chen (NJIT), Fan Guo (LANL)
|7. Connecting Slow Solar Wind Theories to Current and Future Observations Organizers: Justin K. Edmondson and Liang Zhao (University of Michigan, Ann Arbor), Aleida Higginson (University of Michigan, Ann Arbor / NASA GSFC), Benjamin J. Lynch (UC Berkeley), Xudong Sun (Stanford)
The origin of the slow solar wind has long been one of the major unsolved problems in solar and
heliospheric physics. The slow solar wind, as compared to the fast solar wind known to emanate from coronal holes, has not only slower speeds but also 1) higher freeze-in temperatures, 2) a different elemental composition resembling the closed-field coronal plasma, 3) exhibits large variability in both time and space, and 4) can have a large angular width in the heliosphere (up to several tens of degrees away from the heliospheric current sheet). These observations suggest that the sources of the slow solar wind are the regions of closed magnetic field in the solar corona, such as helmet streamers and pseudostreamers. The dynamic properties of the slow solar wind are clearly due to the actions of the Sun’s powerful magnetic field, although the processes by which the slow solar wind is formed are still far from understood.
During the past decade, theory, modeling, and observations have had a transformational impact on our understanding of how topological complexity and non-steady dynamics at the Sun are absolutely essential for understanding the Sun-heliosphere connection. The recent S-Web model postulates that the structure and dynamics of the slow solar wind are determined by the topological properties of the open-closed boundary in the corona. New MHD simulations appear to support this hypothesis. At the same time, new analyses of remote and in-situ observations have yielded new insight into the dynamic nature of the slow solar wind. It is clear that testing the models and interpreting the observations requires being able to connect the slow solar wind in the heliosphere back to the Sun. Consequently, the upcoming Solar Orbiter and Solar Probe Plus missions are poised to make a breakthrough in our understanding of the nature of the slow solar wind. As we prepare for these missions, it is imperative to connect current theories, models, and observations to the next generation of slow solar wind measurements.
The purpose of the session is to bring together remote-sensing observers, in situ observers, theorists, and modelers to discuss the following questions:
• What do current S-Web theory and modeling efforts predict about the properties of the slow solar wind? • What are the properties of the slow solar wind as determined by current remote and in-situ observations? • What new observations of the slow solar wind will Solar Orbiter and Solar Probe Plus be able to provide?
• What work needs to be done to connect current theory, modeling, and observations to the new observations?
We would like to be considered as a SHINE Working Group to organize and sustain this session for multiple years. This session is suitable for multiple years as we are now crucially positioned between the Ulysses/ACE age and the new missions of Solar Orbiter and Solar Probe Plus, as well as beginning to transition to the next solar minimum phase. For the first one or two years (2017-2018), our session will be working with the currently available observations and models, preparing to utilize the new data from the two future missions. For the 3rd year (2019), when the observations by Solar Orbiter and Solar Probe Plus will be available, we will continue our discussion emphasizing the observations from the two new missions. This session also has appeal beyond simply the slow solar wind community, as the issue of mapping observations back to the Sun is an important challenge for both the solar and heliospheric communities at large, as well as for the geospace environment modeling and space weather prediction communities. We believe that this session on the slow solar wind is essential to preparing for Solar Orbiter and Solar Probe Plus, and would be a successful working group; however, at the very minimum, we would like this to be a single-year session.
|8. DKIST Coronal Spectroscopy: The Missing Link in Coupling the Sun and Heliosphere Organizers: Steven Cranmer (CU Boulder), Valentin Martinez Pillet (NSO), Mari Paz Miralles (SAO), Scott McIntosh (HAO)
The only way to answer long-standing questions about coronal heating, solar wind acceleration, and space weather prediction is to have detailed observations of the global Sun-heliosphere system. We now have petabytes of imaging data for the Sun itself, and more than a half-century of detailed in-situ plasma/field data (soon to be complemented by exploration of the inner heliosphere by Solar Probe Plus and Solar Orbiter). Intermediate regions that connect the solar disk to the rest of the heliosphere are also observed, but not as comprehensively as is needed to
answer the fundamental questions of our field. The combination between coronagraphic occultation and high-resolution spectroscopy has been found to be able to probe the physics of coronal and prominence plasma in regions where: (a) extended coronal heating is taking place, (b) the solar wind is beginning to accelerate, and (c) collisionless kinetic effects may be important.
Thus, in this session we will explore how the combination of coronagraphs and spectroscopy can help fill in the gaps in our understanding. A main highlight will be NSO's upcoming DKIST, which will have unprecedented collecting area and resolution, in combination with coronagraphic occultation for use with the Cryo-NIRSP near-infrared spectropolarimeter. In addition, this session provides a timely venue for discussing other new and planned instruments of this kind, such as HAO's COSMO facility and the METIS, SoloHI, and SPICE instruments on Solar Orbiter. This session will address the following questions:
(1) Do we understand the data analysis challenges in converting direct measurements into useful constraints on models/theory (e.g., contamination due to stray light and line-of-sight crowding)?
(2) What computational tools are needed to make the best use of the coming flood of new data?
(3) Do we understand the atomic physics effects well enough to be able to extend the range of Zeeman/Hanle spectropolarimetric analysis sufficiently far to improve 3D coronal magnetic field measurements?
(4) Which questions are best addressed by global coronagraphs such as CoMP or COSMO, and which are optimal for small field-of-view, high-throughput instruments such as Cryo-NIRSP?
(5) To what extent can "new" off-limb emission lines be used to diagnose the properties of MHD waves/turbulence, mass flows between the chromosphere and corona, and FIP-sensitive elemental abundances?
Lastly, we also welcome discussion of other complementary measurements (i.e., total eclipses) and new theoretical/computational developments that may be tested using upcoming coronagraph assets.
|9. SEP Events, Suprathermal Seed Particles and 3He
Organizers: Christina Cohen (Caltech), George Ho (APL), Ron Murphy (NRL)
It is clear that solar energetic particles (SEPs) are not accelerated out of the bulk solar wind, but rather from a suprathermal seed population. Unfortunately, the characteristics and creation mechanism(s) of this population are not well known but are vital for understanding the variability of SEP event characteristics (including size and composition). 3He ions have been identified as possible distinguishers between flare-related and CME-related acceleration processes. The goal of this full day session is to bring discussion-minded modelers, theorists, solar observers, and in-situ observers together to grapple first with questions regarding the suprathermal population in general and then with those concerning 3He ions in particular. We plan on discussing the questions given below, but will allow the discussion to evolve naturally. We hope that one result of the session will be planned collaborations and studies that can be pursued after the workshop.
- What are the mechanisms for creating them?
- what are the fundamental differences and how do we test for them?
- how is the composition made different from solar wind?
- what is the variability of the characteristics of the suprathermal population?
- How do the suprathermal characteristics affect the SEP characteristics?
- is there one systematic behavior?
- does it depend on the acceleration mechanism of the SEPs?
- What observations can be made now to differentiate the origin and effects?
- What observations can be made in the future to differentiate the origin and effects?
- How is 3He generated?
- what are the current theories/models?
- how does it relate to flare characteristics?
- what observations can be made to identify the mechanism(s)?
- How is it released?
- is the mechanism(s) particular/preferential to 3He?
- what observations can be made to identify mechanism(s) and location?
- what can comparisons of solar and in-situ 3He reveal?
- What can 3He tell us about suprathermal seed populations?
|10. What are the Energy Partition and Dominant Energy Transport Mechanisms Associated with Magnetic Reconnection for Different Heliospheric Plasmas? Organizers: Maria Kazachenko (SSL), Benjamin Lynch (SSL), Nick Murphy (CfA), Lucas Tarr (NRL), Silvina Guidoni (NASA/GSFC – CUA
This session aims to bring the solar, in situ, and laboratory heliophysics communities together to discuss the energy partition during magnetic reconnection. Magnetic reconnection is responsible for the rapid restructuring of the magnetic field allowing free magnetic energy to be released and converted into other types of energy such as particle acceleration, radiation, bulk plasma heating, wave generation, and kinetic energy of the reconnection jet outflows. Together, all these affect the system’s global dynamics. However, for each plasma environment, it is not well understood which type of energy and transport mechanisms dominate the reconnection evolution. For example, in the case of solar flares, hard X-ray observations suggest that particles are beamed by reconnection, but at the same time, the evolution of flare ribbons is consistent with a fluid description of steep temperature gradients and thermal conduction fronts. Similar issues arise in other plasma regimes. Future models will need to combine particle and fluid physics in a single theory or simulation to determine which process is energetically dominant. We can make progress towards understanding the interplay between different energy
types by combining observations, simulations, and experiments of plasmas throughout the heliosphere by focusing on the question: What are the Energy Partition and Dominant Energy Transport Mechanisms Associated with Magnetic Reconnection for Different Heliospheric Plasmas?
This session builds on last year's session "Observational Signatures and Modeling of Intermittent Reconnection in the Solar Corona” by discussing recent progress and new challenges of understanding reconnection and energy transport in various contexts. The following questions aim to structure the discussion:
a) How well does the energy partition predicted by current theory and simulations (particle and fluid) compare to observations? What are the observational signatures of various energy transport mechanisms? b) How does the energy partition change with time during a reconnection event, as energy is transported outward from the reconnection region? c) Are the dominant energy transport mechanisms similar throughout the heliosphere, or do different processes dominate in the coronal, laboratory, or magnetospheric environment?
- How can we combine current and future remote and in-situ observations, laboratory experiments, and simulations to better understand energy partitioning and transport?
- What new observations do theorists need to further develop and constrain models?
- What models need to be developed to interpret current and future observations?
|11. The Space Physics of Star-Planet Interactions
Organizers: David Alexander (Rice University), Marc DeRosa (Lockheed Martin Advanced Technology Center)
Motivation: The landscape of exoplanetary science has changed considerably with the great success of the Kepler mission, which has discovered thousands of transit candidates and hundreds of confirmed exoplanets around K-M dwarf stars and a few planets within their assumed Habitability Zones (HZs). The dramatic growth of exoplanet research in astronomy and its emphasis on discovering potentially habitable planets around other stars is an emerging rich area for collaboration between heliophysics, astrophysics and planetary science communities. Understanding the possible habitability of such planets, therefore, requires a deeper knowledge of how stars and planets interact and, in particular, what role stellar and planetary magnetic magnetic fields play in this interaction. This, in turn, requires a broad range of expertise encompassing stellar magnetism, stellar variability, exoplanet discovery and characterization, and, most importantly, space plasma physics and the concomitant planetary atmospheric response. Recent efforts by NASA (NExSS) and NSF (INSPIRE) have stressed the important contribution SHINE-related science can make to the search for habitable conditions on exoplanets. In the proposed session we aim to identify the key elements in the Sun-Earth interaction that are the most relevant to address general star-planet systems. Specific questions to be addressed include:
1. Assuming increased stellar activity is associated with larger and/or more frequent active region and starspot emergence, how does this affect the asterospheric current sheet and the open/closed field distribution? What observables might we look for?
2. What is the relationship between stellar activity and the magnetic/kinetic energy density in the stellar wind? How does this relationship scale for highly active stars?
3. What would increased flux emergence (beyond solar norms) mean for large-flare, CME and SEP production?
4. What is the impact of space weather on the rate of atmospheric escape from magnetically shielded and unshielded (exo)planets?
5. What is the impact of space weather (XUV, particle radiation and interplanetary magnetic fields) on planetary atmospheric chemistry?
|12. . Lessons from 10 years of STEREO results and applicability to future heliospheric missions Organizers: Gang Li (UAH), Noé Lugaz (UNH), Teresa Nieves-Chinchilla (NASA), Barbara Thompson (NASA)
For over a decade, the Solar TErrestrial RElations Observatory (STEREO) mission has provided observations designed to better understand CME initiation and propagation, to characterize the mechanisms of energetic particle acceleration, and to determinate the solar wind ambient structure. The two STEREO spacecraft, launched in 2006 October, were placed into orbits around the Sun, with STEREO-A ahead of Earth in its orbit and STEREO-B behind drifting away from Earth at a rate of about 22 degrees per year.
During this session, we will focus on lessons learned from 10 years of STEREO observations and measurements, as well as lessons from previous heliospheric missions, and how this can be used in a future with single spacecraft measurements/observations.
The discussion will be divided into two main parts:
1) Lessons learned during the STEREO era:
- What have we learned about the 3-dimensional nature of solar wind and inner heliospheric structures (such as CMEs or CIRs) and the extent and variability of solar energetic particles (SEPs) and radio emissions? In particular, which limitations of 2-D/single-viewpoint observations do we now recognize?
2) Facing the Future
- In terms of future scientific analysis: How have we improved our ability to investigate and understand the initiation, evolution, propagation and morphology of CMEs and the acceleration and propagation of energetic particles with only one or two (rather than three) viewpoints, and with adapted models and analysis techniques?
- In terms of future mission concepts: What are the essential characteristics (orbit, instrument, etc.) that future heliospheric missions must have in light of past heliospheric missions (STEREO, Ulysses, ACE, Helios)?
|13. Dissipation in the Solar Wind: Kinetic Processes
Organizers: S. Peter Gary (LANL), Kristopher G. Klein (UMICH), Tulasi Parashar, Chadi Salem (SSL), and Daniel Verscharen (UNH)
As the solar wind flows outward, observations show ions are preferentially heated in directions perpendicular to the background magnetic field and suprathermal electrons are scattered toward isotropy. Theory and simulations model these phenomena based on the interrelated physics concepts of waves, turbulence, reconnection, current sheets, and coherent structures. The primary science question of this session is: “Where do observations and simulations of dissipation processes in the solar wind agree and disagree?” Specific questions that address aspects of this primary issue are:
1) What observations of electron and ion heating are suitable for comparison against models?
2) What are the conditions necessary for linear Vlasov theory to describe dissipation?
3) What is the resolution of the apparent contradiction between the claims of kinetic Alfven waves and magnetosonic-whistler waves for kinetic range turbulence?
4) Which computational models (gyrokinetic, Vlasov, hybrid PIC, full PIC) are necessary and/or best suited to represent the dissipation physics?
5) What are the results and predictions of the Turbulent Dissipation Challenge? In particular, how can recent turbulence simulations provide answers for the science goals of the TurboChallenge? How can TurboChallenge predictions be leveraged in preparation for the observations of Solar Probe Plus and Solar Orbiter?
(expansion of related session in 2016)
14. Energetic particles in the late phase of flares: solar tracers?
Organizers: Hilary Cane (U. of Tasmania), James Ryan (UNH), Stephen White (AFRL)
Solar eruptive events usually begin with an impulsive intensity rise and decay (or a sequence of pulses) in hard Xrays and microwaves. This is called the impulsive flare phase. For some events, mostly large ones, a second energy release follows which is characterized by a more gradual rise to possibly very high intensity values with ensuing slow decay. This is the late, gradual phase. In contrast to the impulsive phase emission, the late phase radiation may become hard and harder with time. Events with this behaviour are highly correlated with large solar energetic particle (SEP) events. Furthermore prolonged γ-ray emission >100 MeV has been detected long after flare impulsive phases indicating that high energy particle acceleration at the Sun occurs over an extended period. This session will consider observations and models that relate to questions of where and how late phase energetic particles are generated and whether and which particles accelerated in the flare environment escape to the interplanetary medium (IPM).
Some of the questions to be addressed are:
1) From a theoretical and observational viewpoint how are the impulsive phase and gradual phase related?
2) What are the important differences between the sizes of the related structures, the field strengths and other parameters as a solar event progresses?
3) What do acceleration models predict for how the particle characteristics vary with these changes in the coronal environment?
4) Can one mechanism account for impulsive phase and late phase particle acceleration?
|15. Post-Impulsive Phase Energetic Particles: in flares and in space?
Organizers: Hilary Cane (U. of Tasmania), James Ryan (UNH), Stephen White (AFRL)
Solar events with late phase radiation becoming hard and harder with time are highly correlated with large solar energetic particle (SEP) events. Similarly late phase type III emissions are correlated with SEP events. Perhaps the noted correlations do not indicate a physical link but rather are different manifestations of the eruption of an energetic coronal mass ejection (CME). It is well established that CME-driven shocks accelerate particles and are responsible for the bulk of the particles detected in the interplanetary medium (IPM). Perhaps gradual phase solar particles are also shock accelerated and have travelled back from CME shocks to the Sun. However these correlations could indicate that particles accelerated in the late phase of flares escape to the IPM.
Some of the questions to be addressed are:
1) Are there valid arguments that rule out the possibility that late phase flare particles are detected in space?
2) What evidence exists to support the conventional wisdom that the products of gradual phase acceleration and IP particles are independent of one another?
3) Is it possible, and to what extent, that shock accelerated particles travel back to the Sun?
|16. The time histories and topologies of heliospheric structures measured in situ
Organizers: Bernard Jackson (UCSD) & David Webb (Boston College)
We ask the science question: “What are the time histories and topologies of heliospheric structures in the inner heliosphere plasma parameters of density, velocity, and magnetic fields, and how do these extend outward from the Sun to extant in-situ measurements?” If heliospheric structures are remotely observed well-enough, for SHINE the answer to this can be used to forecast the arrival of solar wind structures at Earth and the inner planets. In-situ measurements can determine some aspects of the time histories and topologies observed, but just how well these measurements can be extended beyond the passing column is often in doubt. Examples of this include shock structures, and magnetic field loops also measured in situ.
Here we explore two topics:
1) How well are remotely-sensed heliospheric structures depicted, and how can their time histories and topologies be confirmed?
2) How well are in-situ measurements observed and extrapolated to remote-observations, and what do they tell us about plasma time histories and structure topologies?
We welcome inputs on these topics from those who provide or plan to provide structure extrapolations from solar surface measurements, triangulation and tomographic techniques using coronal and heliospheric observations, and MHD heliospheric modeling. In this session, it is of tantamount importance that presenters explore how each input is verified.
|17. Evolution and Influence of Plasma Turbulence in the Heliosphere
Organizers: Matthaeus (U. of Delaware), Parashar (Caltech), Chasapis (U. of Delaware)
This session aims to follow up on several SHINE sessions in recent years, including one with the same title last year, that have focused on turbulence as a mechanism to heat the solar wind and corona. It has become increasingly clear that nonlinear effects and cascade, key elements of turbulence, have significant effects not only on heating, but also on other fundamental processes. Prominent among these are reconnection, transport and energization of suprathermal particles, amplification of magnetic fields, self-organization of magnetic structures, and turbulent mixing effect on field lines and heat transport. All of these processes may be impacted by kinetic physics, while also being influenced by large scale structure. The latter may appear in the guise of Reynolds number or system size effects, or even inverse cascade in some circumstances. This session invites presentation and discussion of this broader scope of turbulence influences, in addition to recent results relating effects of large Reynolds number on heating and dissipation. Applications of interest include chromosphere, corona and solar wind, magnetosheath and potentially the outer heliosphere. Physics of interest to current space craft (e.g., MMS, Cluster, ACE, Wind, Voyager,STEREO) as well as upcoming missions (Solar Orbiter, Solar Probe) and planned missions (THOR) will be of interest. The goals are to improve the plasma physics knowledge, the modeling endeavors, and observational interpretations of the heliospheric turbulence, with an eye towards broadening the discussion that has become widespread in recent years. The emphasis will include observations, theory and simulations that are relevant to connecting fluid and kinetic scales. We emphasize the following issues:
Major questions are:
• Does turbulence influence large scale dynamics? Do we understand how turbulence evolves in the heliosphere?
• How does the large magnetofluid scale cascade interact with small scale kinetic processes? What are the effects of system size? Are couplings local or nonlocal – in scale? – in space? Additional refined questions include:
• What controls partitioning of energy between thermal particles, energetic particles, flows and electromagnetic fields? What controls energy partitioning between electrons, protons, and minor ions?
• How do flux tubes, current sheets and vortices evolve? What do we know about current sheet structure? What are the observational signatures of secondary island formation? Is there evidence for “hot spots” of dissipation, or can uniform plasma theories work?
• What is the significance of observed intermittency? How does this relate to classical hydrodynamic intermittency?
This approach supports SHINE’s spirit of a research discussion oriented workshop that focuses on unsettled, provocative, and controversial issues, while also contributing to SHINE’s educational goal for young researchers.