SHINE 2014 Sessions

Click on links to view session descriptions below.
1. When and why does Space weather forecasting fail? (Nieves et al.)
2. Waves in the Solar Atmosphere and the Solar Wind (Hahn/ Perez)
3. The Contribution of Electron Microphysics to the Evolution of the Solar Wind (Salem/Verscharen)
4. Turbulence in the Solar Wind and Solar Corona (Shay/Howes)
5. Magnetic Reconnection in Partially Ionized Chromospheric Plasmas (Murphy/Tian)
6. Solar Energetic Particle Events in the Weak Solar Cycle 24 (Makela/Lario/Ho)
7. Progress in understanding the spatial distribution and temporal evolution of solar energetic particles (Nitta/Masson)
8. Scientific Validation of Heliophysical Models (MacNeice/Jian)
9. Observations of Solar Wind Turbulence: Current Progress and Future Measurements (Chen/Bale)
10. Magnetic reconnection and flux redistribution: multi-scale and 3D dynamics (Intrator/Murphy/Guidoni/Qiu)
11. Heating of Solar Wind Heavy Ions: Observations and Theory (Isenberg/Bourouaine)
12. Earth-affecting CMEs (Zhang/Lugaz)
13. Turbulence and Dissipation in the Solar Wind Plasma: Current Challenges and New Diagnostics (Salem/Parashar)
14. Data-driven and Data-constrained Models and Simulations of Solar Eruptions and Active Region Evolution (Sacheva/Lugaz/Downs)
15. Identifying Solar Coronal Holes: A Tale of two Carrington rotations(Arge/Hock)


1. When and why does Space weather forecasting fail?
R. Evans, T. Nieves-Ch., I. Richardson, N. Savani

Session Description

Space weather forecasting has made tremendous strides in recent years. Nevertheless, there are numerous examples of mismatches between predicted and measured impacts. We propose a session to discuss examples of these failures, and connect them to limitations in observations, modeling, forecasting methods, and our understanding of the physics involved. Invited speakers from the forecasting community, e.g. the Space Weather Prediction Center (part of the National Weather Service , and the Community Coordinated Modeling Center (located at NASA Goddard Space Flight Center will lead the discussion. We encourage contributions from the research community on all aspects of space weather predictions, including flares, energetic particle events, coronal mass ejections, high speed streams, and impacts to spacecraft and planetary environments. One goal of this session is to identify specific events that have challenged forecasters and scientists in order to plan the research directions needed to improve future forecasts. Ultimately, the aim of these discussions will be to identify areas in which forecasting might be improved and the methods that might be employed.

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2. Waves in the Solar Atmosphere and the Solar Wind
Michael Hahn and Jean Perez

Sessions Description

Recent observational studies have demonstrated the ubiquity of waves in the corona, particularly Alfven waves and have begun to reveal detailed aspects of these waves, such as their power spectrum and damping properties. Additionally, a number of recent theoretical models have been developed that use a framework in which waves heat the entire corona and where the varying temperature of coronal structures is due to differences in the wave propagation and damping in those structures. These models have successfully reproduced many aspects of observed coronal properties. Such evidence suggests that waves play a critical role in the heating of the corona and the driving of the solar wind. However, a more detailed understanding of their influence is needed. We propose a session to discuss waves in the corona. Some questions for discussion include:
1. What is currently known unambiguously about waves?
2. What are the most important properties of waves that are not understood?
3. What are the limitations of current diagnostics and how can they be addressed?
4. Are observations of waves in different structures consistent? How are observations of waves in the chromosphere and transition region, related to those in the corona and how are waves in the corona related to those found in the solar wind?
5. What is the source of coronal waves?
6. What causes the damping of waves in the corona? How can theoretical damping mechanisms be tested empirically?
7. Are wave-driven theoretical models of the corona consistent with observations of waves? Do such models make specific predictions about the properties of waves that can be tested by observation?
8. How can observational and theoretical results about waves be used to reduce the number of free parameters in coronal models?

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3. The Contribution of Electron Microphysics to the Evolution of the Solar Wind
Chadi Salem, Daniel Verscharen, Marc Pulupa, and Stuart Bale

Session Description

One of SHINE's key science goals is to understand how the Sun impacts the Earth and near-Earth environment. Part of this goal involves developing predictive, physics-based models of the solar wind. Not only does the solar wind directly impact Earth's magnetosphere, but the solar wind is the medium within which shocks and energetic particles propagate. A critical unsolved problem in solar-wind physics is the contribution of electrons to the generation of the solar wind. Some theories, such as the velocity-filtration model and the exospheric model, hold that non-thermal electrons escaping from the solar atmosphere are the primary mechanism that powers the solar wind. In other theories, the electron contribution to solar-wind heating and solar-wind acceleration is more modest, with the primary acceleration and heating arising from waves and turbulence. In order to develop an accurate physics-based model of the solar wind that extends from the corona to Earth, it is essential to determine more accurately the role and importance of electrons. Part of this goal can be accomplished through analysis of existing spacecraft data. However, in order to gain further insights into the role of electrons closer to the Sun, it is important to understand the basic physical mechanisms that control the electron heat flux and strahl properties in the solar wind, so that we can extrapolate inwards inside of 0.3 AU and make predictions that can be tested by future spacecraft.

Not only is this special session important for the SHINE-related science goal of developing accurate, physics-based solar-wind models, but it also relates to recent SHINE sessions on turbulence. A hotly debated topic at SHINE sessions is the nature of small-scale fluctuations in the solar wind, and in particular, whether fluctuations at frequencies exceeding roughly 1 Hz are predominantly kinetic-Alfven-wave-like or whistler-like. The latter component of small-scale fluctuations can be generated by electron-driven instabilities.

We would like to encourage discussions about the following questions:
- What are the effects of electron microphysics on the global evolution of the solar wind?
- What is the role of electron-driven instabilities for the regulation of non-thermal features of the electron distribution functions?
- How do electron-driven instabilities contribute to electro-magnetic fluctuations and what is their relation to the overall level of turbulence?

This session will stimulate the dialogue between theory, observations and numerical simulations towards a better understanding of the role of electron microphysics in the evolution of the solar wind.

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4. Turbulence in the Solar Wind and Solar Corona
Gregory G. Howes (University of Iowa), Michael Shay (University of Delaware)

Session Description

Kinetic plasma physics plays an important role in governing the flowof energy in the heliosphere from the sun, through interplanetary space, to the magnetospheres of the Earth and other planets, and tothe outer boundary of the heliosphere. This session focuses on the investigation of the physical mechanisms in the solar wind and solar corona that govern the turbulent transport of energy from large scale motions down to the small kinetic scales at which the turbulent fluctuations are damped and their energy ultimately converted to plasma heat.

The first half-day discussion focuses on theories of turbulence that incorporate the three leading candidates for the damping of turbulence: (i) wave-particle interactions, (ii) stochastic heating, and (iii) dissipation in coherent structures such as current sheets. The dominant dissipation mechanism depends intimately on the nature of the nonlinear turbulent fluctuations and determines the resulting plasma heating. Therefore, for each of these three models for turbulent dissipation, the discussion will focus on answering the following key questions:

(1) What is the physics governing the nonlinear transfer of energy from large to small scales?

(2) What is the detailed physical mechanism that leads to the damping of the turbulent fluctuations?

(3) What is the prediction for the partitioning of the dissipated turbulent energy into heat of the protons, electrons, and minor ion species?

In particular, we will focus on the properties of turbulence predicted by each of these theories and on possible observational signatures that may enable us to distinguish the different models. For example, the character of the turbulent fluctuations (such as compressibility,
frequency, etc.), their potentially anisotropic distribution of power in wavevector space, and the development of intermittency and coherent structures are important aspects of the turbulence that may distinguish one model from another.

The second half-day discussion will focus on numerical and observational evidence that supports or conflicts with the turbulent properties predicted by the three theories of turbulence. In particular, we hope to tackle several controversial issues at the forefront of solar wind turbulence research. Possible questions include:

(1) What are the key observational or numerical characteristics of solar wind turbulence that must be explained by each theory? Specific questions include:

(a) Is it possible to reconcile a wave description of the turbulence with the observed presence of intermittent coherent structures, such as current sheets? How does this relate to observations of spatially localized heating?

(b) For a turbulent dissipation range consisting of current sheets, what are the dynamics that lead to the observed magnetic energy spectrum in the solar wind?

(c) How does one obtain strong, and possibly anisotropic, ion heating from wave models of turbulence?

(2) Does reconnection play a significant role in the dissipation of turbulence at small scales (possibly on electron scales)?

(3) Can dissipation in turbulence be self-consistently modeled with linear theory? Under what conditions?

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5. Magnetic Reconnection in Partially Ionized Chromospheric Plasmas
Nick Murphy and Hui Tian

Session Description

In contrast to the fully ionized corona, the solar chromosphere has an ionization fraction that is often below 1%. New observations by the Interface Region Imaging Spectrograph (IRIS) show numerous small-scale jets and explosive events that most likely result from chromospheric reconnection events. Moreover, recent simulations show that partial ionization effects can significantly modify the dynamics of reconnection. While some simulations make observational predictions, many others do not. In this session, we will discuss the strategies we can use to connect observations and simulations of partially ionized reconnection in the chromosphere.

The discussion will start from the following questions:

-How do we connect simulations of partially ionized chromospheric reconnection to observations from IRIS, SDO/AIA, Hinode/EIS, and other instruments? What predictions from simulations would be most useful to observers?

-What are the characteristics of small-scale jets in the chromosphere? How can these characteristics be used to constrain simulations of partially ionized reconnection?

-How do the presence of neutrals and non-equilibrium ionization affect the dynamics of reconnection in weakly ionized plasmas?

-How can the structure of reconnection regions in the chromosphere be investigated using a combination of remote observations and numerical simulations? Are there ways to investigate effects such as plasmoid development and asymmetry?

-What future instrumentation would allow better diagnostics of chromospheric reconnection in order to constrain simulations?

-What insights can be gained through laboratory experiments on partially ionized reconnection?

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6. Solar Energetic Particle Events in the Weak Solar Cycle 24
Pertti Makela, David Lario, George Ho

Session Description

The exceptionally weak solar cycle 24 is now well into its maximum phase and we have a sufficiently extensive set of solar energetic particle (SEP) measurements by multiple spacecraft to consider differences between the SEP events in this cycle and previous ones. Observations so far suggest that, compared to cycle 23, the most noticeable difference is the paucity of the biggest SEP events, including ground level events, though it remains to be seen whether this difference will hold into the declining phase of the cycle. These observations suggest that SEP events are affected by the weak solar cycle. In this session, we propose to compare cycle 24 SEP events with events observed during previous solar cycles to attempt to understand why this should be. We also invite studies dealing with any aspect related to cycle 24 SEP events that can provide insight into their properties. In particular, we will discuss questions such as the following:

1) Why are we observing fewer energetic SEP events during solar cycle 24? For example, is this related to the weak cycle? Have we just, by chance, missed the largest SEP events at Earth?

2) What are the possible causes for these differences between cycles? For example: Are CME and shock properties affected by the weaker solar magnetic field? Is preconditioning by a preceding CME, that is known to be associated with high-intensity SEP events, less important in this cycle? Are there fewer large, very active, active regions that tend to give rise to major SEP events in this cycle?

3) What other differences are there between cycles in SEP properties (e.g., event frequency, composition, energy spectrum)?

4) Do observations of other SEP-related phenomena (e.g., type II and III radio bursts, flares) provide any insight?

5) Is it possible theoretically to quantify the dependence of event intensity on magnetic field strength? For example, the location in energy of spectral rollovers and/or transitions between power-law portions of the spectrum generally depend on the spatial diffusion coefficient and, therefore, magnetic field strength. Do observations reveal shifts in these energy locations between cycles?

6) What are the consequences of these new observations for space weather activities?


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7. Progress in understanding the spatial distribution and temporal evolution of solar energetic particles
Nariaki Nitta (LMSAL), Sophie Masson (CUA at NASA/GSFC)

Session Description

We have been greatly puzzled by the unexpected observations of impulsive and gradual solar energetic particles (SEPs) detected at locations widely separate in longitude (over 180 degrees). Such spread of SEPs could occur in the solar corona or in the interplanetary space. In other words, it can result from one or more processes including particle acceleration, release and propagation mechanisms. Developing an integrated understanding of SEP events observed at widely separate locations is an important step toward reliable space weather prediction in the future. In this working group, we plan to discuss observations and models grouped into the three main physical processes:

- How do the acceleration mechanisms affect the spatial distribution of the SEPs in the heliosphere?
- How can we constrain the release mechanisms, using the observed spatial and temporal characteristics of particles?
- How does the interplanetary magnetic field structure (including turbulence) affect the propagation and transport of SEPs in the heliosphere?
- Finally, do the long-duration, high-energy gamma-ray bursts, which have turned out to be not uncommon, provide any constraints on the acceleration site(s) of wide longitudinal SEP events?

The main goal of this session is to combine observations and models of the corona and heliosphere in order to provide new clues to the questions above. In particular, we would like to emphasize discussions about how observations can help us constrain and validate the models of acceleration, release and propagation of SEPs.

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8. Scientific Validation of Heliophysical Models
Peter MacNeice (NASA/GSFC), Lan Jian (University of Maryland)

Session Description

'Scientific' validation is a critical aspect of the development of heliophysical models.

Unlike 'operational' validation which tends to focus on a limited number of mission critical metrics, 'scientific' validation attempts to test how the models reproduce correct physical
behavior. It must also track the changing interests of our community's model user base as the models conquer some aspects of the system's physics and move on to address other less well understood aspects. All this must be acomplished within the limited manpower resources of the community.

To tackle this need, our early meetings (at SHINE 2011 and 2012) focussed on defining an online infrastructure to accept model input, and from that, generate a set of diagnostic graphics which would demonstrate the abilities of different models to reproduce various physical structures and evolutions. The infrastructure which is now in place (http://ccmc.gsfc.nasa.gov/challenges/SHINE/), is a semi-automated online system. It accepts input from the model developers and automatically creates model relevant graphics. By generating the exact same graphic style for each comparable model, different models can be compared directly. In principle, the scientific strengths and weaknesses of different physical approximations, algorithms and specific model implementations can be clearly presented and posted for the community to view.

The validation results will eventually inform model users, model developers, and funding
agencies which invest in model development.

After extensive testing the initial infra-structure became operational in early December 2013.
Now the fun begins!

It is time to refine the choices of model graphics to most effectively test the science qualities
of the models. We therefore propose a SHINE session inviting contributions from model developers and model users on the general topic of 'Scientific' validation of heliophysical models. A principal focus of the discussion would be to advance the design and content of this validation system. In this regard, topics to be discussed would include, new diagnostic graphics, additional test cases and refinements of the systems design. We would also invite more general contributions on alternate and complementary scientific validation approaches.

Many of our most heavily used models depend upon synoptic magnetograms for input. Until now these models have overwhelmingly relied on time-independent magnetograms. Our community models are beginning to transition to new sources of time dependent magnetograms, which will change the way that the models are used. We anticipate that this will have a major impact on how we validate these models, and so we would also invite contributions which address this question.

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9. Observations of Solar Wind Turbulence: Current Progress and Future Measurements
Christopher Chen & Stuart Bale

Session Description

Turbulence is pervasive throughout the heliosphere, yet remains one of the least well understood processes. Its effects are seen at a large range of spatial and temporal scales, from the large scale stream structure in the solar wind down to plasma ion and electron kinetic scales, and perhaps smaller. It is also thought to contribute to the macroscopic properties of the heliosphere, such as heating of the solar wind and corona.

With many different theoretical concepts, there is a need to focus on what can be measured to make progress. In this session, we will focus on observations of solar wind turbulence at MHD and kinetic scales. While excellent progress is being made, in some aspects the limits of the current data are being reached, so we will also discuss the future measurement requirements needed to advance the field. Theoretical, simulation and laboratory work that assists in interpreting current observations and determining future measurement requirements will also be discussed.

Specific questions to be addressed include:

  • what observational measures can be used to distinguish different turbulence models, e.g. weak, strong, critically balanced, imbalanced, forced vs decaying?

  • how do large datasets contribute to increased accuracy of turbulence measures, e.g. spectra, thirdGorder laws, cascade rates, anisotropy?

  • what fraction of discontinuities, current sheets and other intermittent structures are turbulence generated, and what is their role at kinetic scales?

  • to what extent are the properties of linear modes observed in the data and what is the cause of the similarities/differences?

  • what are the advantages and disadvantages of multiGspacecraft vs single spacecraft techniques?

  • what do current observational limitations, theory, simulations and laboratory work tell us about future measurement requirements?

 

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10. Magnetic reconnection and flux redistribution: multi-scale and 3D dynamics

Silvina Guidoni - NASA/GSFC, Tom Intrator - LANL, Nick Murphy - Harvard-Smithsonian Center for Astrophysics, Jiong Qiu - Montana State Univ.

Session Description

Magnetic reconnection is believed to be responsible for rapid restructuring of magnetic field in the Sun's atmosphere. It involves processes at multiple scales with accompanying dynamics in three dimensions. Global dynamics advect field lines and set the conditions for reconnection to take place on small scales. During this change in magnetic topology, energy is released into plasma heating, particle acceleration, radiation, and bulk flows, which in turn feed back on the global dynamics. Remote observations of the solar atmosphere have provided some indirect evidence of 3D reconnection geometry and the presence of complex, twisted filamentary structures in the corona. These solar signatures are believed to be related to observed in-situ magnetic structures in the solar wind and magnetosphere. However, present solar observations cannot resolve dissipation length scales to directly measure the plasma or field properties at reconnection sites. On the other hand, in-situ observations are limited to a small number of points, and therefore large-scale dynamics are difficult to determine. Numerical simulations and dedicated laboratory experiments are able to diagnose small or large scales, but not simultaneously. Most of the current numerical reconnection models are two-dimensional, although some 3D computational examples are being developed and tested. Their extension from 2D to 3D requires a better physical understanding of local and global magnetic structure and energetics of non-uniform current sheets, as well as dynamic redistribution of magnetic field energy. 3D laboratory experiments can bring light to this theoretical 3D extension process. We can make progress towards understanding the interplay between different scales in reconnection by combining observations, simulations, and experiments in the study of dynamics of flows, shear, topology and particle energization.

The following questions can help structure this discussion.

*** Framework Of Scientific Questions ****

LOCAL-GLOBAL INTERPLAY:

- How do small-scale effects feed back on global dynamics, and vice versa? For example, what triggers fast reconnection in the solar atmosphere: a global MHD instability or microscopic instabilities?

-Do kinetic effects associated with reconnection have observational consequences on large scales? Does shear flow link reconnection and dynamo?

-How are geometric shear models (e.g., slip-shear) different from topological models (e.g., null-spine-fan) of magnetic structure?

OBSERVATIONS:

- How are coronal flux ropes formed? What role does reconnection play in this process?

- Are the blobs observed in CME current sheets related to the plasmoid instability? If not, how are they created?

- Is coronal heating local from 3D magnetic reconfigurations (e.g., through field-line braiding) or is the heat advected from other locations (e.g., waves & upflows)?

- Are the structure and dynamics different for open (e.g., magnetic clouds) vs. closed (coronal loop) magnetic field lines and topologies?

PATH FORWARD:

- How can we combine current and future remote observations of reconnection in the solar atmosphere with in situ measurements in the solar wind, magnetosphere, and laboratory plasmas to gain a more complete understanding of the basic physics of reconnection? To what extent are these comparisons valid?

- How do we make progress in connecting small-scale kinetic models with large-scale MHD models? What modeling efforts would be most useful for observers to interpret observations?

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11. Heating of Solar Wind Heavy Ions: Observations and Theory
Phil Isenberg and Sophiane Bourouaine

Session Description

Solar wind ions more massive than protons are known to be heated perpendicular to the magnetic field to temperatures tending to be mass-proportional or higher with respect to the protons. In-situ spacecraft measurements in the fast wind and remote spectroscopy in coronal holes and the base of coronal streamers have demonstrated this consistent behavior for some time, but the responsible mechanisms are still not determined. Two leading hypotheses have emerged, basically described as 1) quasilinear Fermi acceleration by counter-propagating ion cyclotron waves and 2) nonlinear stochastic heating due to disruption of ion gyromotion by perpendicular turbulent structures. Of course, these are not the only plausible processes and furthermore one mechanism does not preclude the operation of the other. More recently, new clues have been found in the behavior of alpha particles at 1 AU, which may allow us to identify the dominant mechanism (e.g. Kasper et al., PRL, 110, 091102, 2013; Chandran et al., ApJ, 776, 45, 2013). Further observational work is taking place, both on these data and on other in-situ and coronal ion populations. Theoretical attempts to model and understand these new measurements are also ongoing. This session will focus on these new efforts, first reviewing the current status of the investigations, followed by brief reports and extensive discussion of the progress since last year's SHINE meeting.

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12. Earth-affecting CMEs
Jie Zhang (George Mason University), Noe Lugaz (New Hampshire University)

Session Description

The Sun generates CMEs over a wide range of latitudes and longitudes. Only a small fraction of CMEs arrive at the Earth, affecting the near-Earth space environment. Knowing which CMEs may impact the space environment is a central question for space weather, but it cannot be predicted until CME initiation, propagation and solar wind-magnetosphere coupling is understood. The aim of this session is to study (1) what kind of CMEs are Earth-affecting (and what kind are not), and (2) how to predict their arrival and geoeffectiveness. Earth-affecting CMEs may be launched from both active regions in the low/middle latitudes and filament channels in the middle/ high latitudes. Full halo CMEs originated from close to the central meridian may not necessarily arrive at the Earth. CMEs that produce intense geomagnetic storms may not be fast, nor accompanied by major flares. A significant fraction of Earth-affecting CMEs cannot be associated with any observable eruptive features in the lower corona. CMEs through their propagation are influenced by their interaction with the solar wind and may be subject to deflection caused by near-by coronal holes. They may also be affected by the interaction with preceding CMEs and/or corotation interaction regions (CIRs). This session brings together observers and modelers to discuss various issues related to Earth-affecting CMEs and how to improve CME arrival prediction.

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13. Turbulence and Dissipation in the Solar Wind Plasma: Current Challenges and New Diagnostics
Chadi Salem & Tulasi Parashar

Session Description

Turbulence in the solar wind has been an active research topic for several decades. From the theoretical point of view, it was originally of prime interest to understand how the energy is transferred from the very large MHD scales through the inertial range, down to kinetic scales where dissipation is believed to take place. New observational and theoretical works in recent years have focused study on how kinetic dissipation or dispersion terminates the solar wind inertial range, and how these processes relate to solar wind ion and electron heating. Competing processes may operate in different plasma conditions - wave-particle interactions, coherent structures, stochastic heating, etc. Given the lack of clarity or agreement about the underlying processes, no clear consensus has yet emerged.

To address these questions, we proposed last year a community driven effort called the Turbulent Dissipation Challenge (http://arxiv.org/abs/1303.0204), in which we wanted to bring the community (observationalists, theoreticians, and simulators) together and work together towards a convergence of our current ideas. We had a first, very successful, session at last year (2013) SHINE workshop to discuss the challenge, refine its scope, and agree upon the key questions that need to be addressed primarily.. It was followed by a special session at AGU, very successful as well.

The goal of this session is to follow up on the current state of the Turbo-Challenge. We propose here a forum to discuss the results of the preliminary efforts that are being undertaken in this direction. We will be sharing the initial conditions for the first set of runs by the end of January 2014 or so, and hope to have a discussion of preliminary results at this session. We will also discuss the possible directions we want to steer the challenge in. Of course, we invite and encourage participation from anyone with relevant observations, theories, models and simulations to stimulate the discussion, and advance our understanding of the turbulent dissipation problem.

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14. Data-driven and Data-constrained Models and Simulations of Solar Eruptions and Active Region Evolution
Co-chairs: Antonia Savcheva, NoƩ Lugaz, Cooper Downs

Session Description

Understanding the energy storage and release cycl e of active regions is a key ingredient for the prediction and characterization of eruptive events. Numerical investigations of active region evolution and solar eruptions can be generall y split in two classes: 1) data-driven static non-linear force-free (NLFFF) models and extrapolations and 2) dynamical magnetofrictional or MHD simulations. While the first category captures a snapshot of the magnetic field structure of the studied event, these models lack the ability to follow the evolution of the field in time, and do not include any data about the plasma properties and their evolution. On the other hand, dynamic magnetofrictional simulations with updateable lower boundary conditions can incorporate field evolution driven by observations, and MHD calculations can provide the complete time-dependent plasma and magnetic field picture. While many significant insights have been gained from global , or partial box MHD simulations in the past decade, a common feature is that they use an idealized initial configuration for the magnetic field and/or considerably simplify the boundary evolution. In this session we wil l discuss bridging the gap between these categories of methods with the goal of improving model realism and better l everaging observations to understand how active regions evolve and ultimately lead to an eruption, and consequently determine the properties of the CMEs.

The discussion will focus on several main questions:

  • Is an MHD simulation necessary to capture the time-dependent nature of the energy storage or is a sequence of NLFFF equilibria is sufficient? Are the free energy and hel icity the most important parameters and what do we need to be able to measure them accurately?

  • Is there a significant advantage into using NLFFF initial condition instead of a prescribed or a potential one? What are the challenges in using NLFFF initial condition?

  • Which boundary conditions are required or optimal , which developments are required for the codes and what are the challenges to implement them?

  • What are some future or ongoing devel opments in global MHD codes towards more realistic boundary and initial conditions?

  • What observations are necessary to constrain the models in order to l ead to predictive capabilities?

 

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15. Identifying Solar Coronal Holes: A Tale of two Carrington rotations
Arge & Rachel Hock

Session Description

Solar coronal holes are defined observationally as regions of reduced emission in the X-ray and EUV, enhanced brightness in Helium emission, or reduced brightness in coronagraph images. From a theoretical or modeling perspective, coronal holes are normally thought of as regions with “open” magnetic flux. Reliable methods for identify coronal holes are needed to help constrain and validate models of the Sun’s surface magnetic field, corona, and solar wind. 

In this session, we propose to build on last year’s successful discussion on the different methods and complexities for identify coronal holes in solar disk data/maps by examining the coronal holes during two periods:

  • CR 2099 (13 July 2010 to 9 August 2010)
  • CR 2106 (20 January 2011 to 16 February 2011)

These periods have multiple coronal holes both at high and low latitudes and have been studied in some detail in the literature.  A wide variety of data sources are available for both periods including SDO, STEREO A and B, and SOHO/EIT.

Each group that submits one or more coronal hole maps (see below) will be given an opportunity to briefly describe their method to the group. The majority of the session, however, will be interactive, focusing on the comparison of the different coronal hole maps.  Potential discussion topics include:

  • Synchronic vs. diachronic: what is the effect of using synoptic observations generated over an entire Carrington rotation versus using images taken at a single time?
  • Boundary evolution: How rapidly do coronal holes evolve? What is the appropriate time cadence of coronal hole maps for use by modelers?
  • How do we quantify the agreement or disagreement between methods?
  • Can the different methods be combined to create a more accurate “composite-map”?

 

We invite interested parties to submit at least one coronal hole map, preferably as close to the midpoint of the Carrington rotation as possible (27 July 2010, 12 UT for CR 2099 and 3 February 2011, 12 UT for CR 2106). If possible, submission of additional maps made at various times during the two Carrington rotations will allow further comparisons and are encouraged. If you are interested in submitting a coronal hole map(s), please contact Rachel Hock (Rachel.Hock.ctr@kirtland.af.mil) no later than 1 June 2014. All maps will be made available to those who submit maps prior to the SHINE meeting, allowing contributors a chance to do their own comparisons.

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