SHINE 2013 Sessions

Click on links to view session descriptions below.
1. Identifying Coronal Holes in Solar Disk Observations
2. What Exactly is a Coronal Mass Ejection?
3. Mechanisms of Heavy Ion Heating in the In Situ Solar Wind
4. What do we learn from observations and modeling of the solar corona for understanding solar energetic particle events?
5. Diagnostic of Chromospheric Flare Plasma
6. Plasma Turbulence at Fluid and Kinetic Scales
7. Campaign Event: The Extreme CME of 2012 July 23
8. Corotating Interaction Regions and the Connection Between Their Trailing Edges and Energetic Particle Acceleration Near 1 AU
9. Turbulent Dissipation Challenge: Towards a convergence of current ideas
10. Investigating the Origin of the Long-Duration High-Energy Gamma-Ray Flares
11. Abundances in the solar atmosphere and in the solar wind


Conference Links
1. Identifying Coronal Holes in Solar Disk Observations (How Best to Compare Them with Models)
Nick Arge, Rachel Hock, Carl Henney

Session Description

Solar coronal holes are defined observationally as regions of reduced emission in X-ray and EUV wavelengths, 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. It is well known, however, that coronal holes appear differently in different wavelengths and from different viewpoints (e.g. STEREO vs. SDO or limb vs. disk center). This makes it difficult to consistently identify coronal holes in solar images. Moreover, it is not entirely clear whether there is a one-to-one relationship between the observational and theoretical definitions of coronal holes. For example, do all magnetically open regions on the Sun appear dark in X-ray and EUV emission? Recently, there have been substantial efforts by several groups (e.g., Henney et al., 2005; de Toma et al., 2005; Krista et al., 2011 & Martin’s et. al. 2012) to develop more reliable, objective, and automatic methods to identify coronal holes in solar observations. Thus, it is timely to discuss these new methods for identifying coronal holes and how best to use them for constraining and validating models.

In this session, we provide a brief

  1. Overview of the complexities of identifying coronal holes in solar observations.
  2. Theoretical/modeling perspective of what coronal holes are, and how observationally derived coronal hole maps are used for model validation.

We then open the discussion to

  1. Identifying coronal holes in solar disk observations
    1. What methods are currently used?
      1. What are the strengths and limitations of these techniques?
      2. What data set(s) do each of these methods use?
    2. Is there a consensus as to what the best methods/approaches are?
      1. Are the methods substantially different?
      2. Have the different methods been compared?
      3. Are all of the available observations being used?
    3. How well do automated methods work?
      1. Do we know?
      2. Have they been compared to traditional, hand drawn ones?
    4. How can uncertainties in coronal hole detections be quantified?
      1. Important to know for making comparisons with models.
      2. What uncertainties are needed/useful for modelers? (e.g., fuzziness in the boundary of a coronal hole, confidence that a region is a coronal hole and not a filament, etc.)

  1. To what degree are the observational and modeling definitions of coronal holes the same?
    1. Do we know?
    2. Are there studies that can be performed to find out?
  1. How best to compare coronal models with observations?
    1. Are there metrics we can agree on?

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2. What Exactly is a Coronal Mass Ejection?
Noe Lugaz, Charlie Farrugia, Teresa Nieves-Chinchilla

Sessions Description

The definition of a coronal mass ejection (CME) appears self-explanatory, i.e., an ejection of mass from the corona. However, it means different things to different communities or researchers. Does CME refer only to the magnetic ejecta or should it also include the swept-up and shocked solar wind? Should we continue to distinguish between CMEs and ICMEs?

With the advancement of Sun-to-Earth numerical modeling and remote-sensing observations of the whole Sun-to-Earth space as well as the continuous in situ measurements at 1 AU, these questions can now be addressed. It is not just a matter of nomenclature, since it is important to understand the global heliospheric magnetic flux budget and potentially the nature of the slow solar wind, among other topics.
We are particularly interested in the following science questions:
- Does the origin of a CME (filament eruption, streamer blob, active region eruption, stealth CME) matter when observed in the heliosphere or in situ at 1 AU?

- Is any part of the sheath region observed in situ from coronal origin or does it fully consist of accreted solar wind material? Do CME-driven shock ever decouple from the CMEs?

- Is there a continuous spectrum of flux rope sizes so that small transients lasting a few hours at 1 AU can be considered as the small-scale part of a single distribution? Or is there a bimodal distribution in MCs and small transients with different properties characterizing the two sets. If so, are the small transients of solar or heliospheric origin? Do some small ejections just become part of what is referred to as the slow solar wind at 1 AU? What is the relation between small transients and streamer puffs?

- Where are we to draw the boundary between CMEs and solar wind at 1 AU, both in front and behind the magnetic ejecta, with or without a shock wave?

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3. Mechanisms of Heavy Ion Heating in the In Situ Solar Wind
Phil Isenberg, Sofiane Bourouaine, Sue Lepri

Session Description:

Identifying the operative mechanism of ion heating in the corona and solar wind is a fundamental necessity for understanding our space environment. Observations indicate that this heating mechanism must preferentially heat ions perpendicular to the magnetic field, and must heat heavy ions preferentially to protons. There are a number of potentially competing ideas being explored, including resonant cyclotron wave damping, non-conservation of ion magnetic moment due to low-frequency turbulent fluctuations, and ion energization at turbulently-generated current sheets.

New observations on ion heating have recently been presented by Kasper et al. (PRL, 110, 091102, 2013), who found that the alpha particles in the nearly collisionless solar wind at 1 AU can frequently be seen in a state of small drift speed with respect to the protons coupled with perpendicular temperatures significantly greater than mass-proportional. These populations were found in both fast and slow wind. The bulk properties of these particles seem to be organized as though heated by a stochastic Fermi interaction with counter-propagating quasi-parallel cyclotron-resonant ion cyclotron waves, implying the strong presence of such waves in the solar wind. However, this interpretation raises many questions. For instance, the Fermi mechanism requires resonant waves with phase speeds close to the Alfvén speed, but typical solar wind concentrations of alpha particles tend to prevent this. Furthermore, current theories of plasma turbulence do not suggest meaningful intensities of such quasi-parallel waves.

This session invites observational and theoretical contributions which address the question of ion heating mechanisms in the in situ solar wind, where local particle and wave measurements can be applied. We expect one focus of the session to be discussion and interpretation of the Kasper observations as a distinctive example. However, we also expect the discussion to extend to broader issues of ion heating in collisionless plasmas, as well as the impact of these ideas on future missions to the inner heliosphere. We welcome participation and further contributions on all these topics, with the intention of generating valuable interactions on these issues.

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4. What do we learn from observations and modeling of the solar corona for understanding solar energetic particle events?
Nariaki Nitta (LMSAL), Sophie Masson (CUA at NASA/GSFC)

Session Description

Following the present paradigm that emphasizes two extreme origins of solar energetic particle (SEP) events, flare (non-shock) and coronal mass ejection (CME, shock), we are still long way toward fully understanding the acceleration and transport mechanisms. One reason that prevents us from reaching a consensus may be that remote-sensing solar data and the associated models have not been adequately utilized. Now with SDO we are in a completely different era. Helped by STEREO observations there should not, in principle, be ambiguities as to identifying the source region of any SEP event. We propose this session to discuss how to improve our understanding of the occurrences and properties of SEP events (including electron events) from remote-sensing observations and numerical models of flares and CMEs. We welcome contributions both from solar and heliospheric communities that either focus on or remotely discuss the following questions: How does the magnetic configuration of the eruptive active region affect the escape of particles? Are there particular eruptive processes conducive to particle escape? What is the role of global disturbances in the corona for SEPs observed at widely separate locations? How important are sympathetic flares for the SEP angular spread? Have we found solar observables that reliably predict the properties of SEP events?

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5. Diagnostic of Chromospheric Flare Plasma
Debi Prasad Choudhary, California State University Northridge, Vasyl Yurchyshyn, Big Bear Solar Observatory

Session Description

The solar flares are the chromospheric counterpart of most solar eruptions and has dominant source of radiation peaking in the optical and ultraviolet range. Coronal Mass Ejections (CMEs) accompanied by solar flares result in severe space weather conditions. Solar explosions of diverse magnitude starting from micro-flares to X-class flares heat the million degree coronal plasma. Although it is generally known that these events involve magnetic field reconnection to release the energy stored in field structures, the physical mechanisms for dissipating the energy to heat the chromosphere and corona remain elusive. The free energy buildup in the active region magnetic field requires energy transport from the photosphere to the corona in the pre-flare phase which affect the line profile of several elements originating in different heights of solar atmosphere. The magnetic and spectroscopic diagnostic of chromospheric plasma above the active regions are valuable data that can be used to constrain the theoretical models of energy build up and trigger mechanism leading to flares and CMEs. Ground based instruments like “Synoptic Optical Long-term Investigations of the Sun (SOLIS)”, BBSO Full-Disk Halpha telescope and space based instrument like “Interface Region Imaging Spectrograph (IRIS)” provide synoptic data in optical and ultra-violet wavelength ranges that can be used for chromospheric plasma diagnostic by measuring magnetic field, temperature, density and mass motion. We propose a half day session during the SHINE-2013 workshop to discuss the current state-of-the-art for useful observations and future plans to explore the chromospheric plasma properties and their connection to heliosphere.

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6. Plasma Turbulence at Fluid and Kinetic Scales
Pin Wu, Jeffrey Tessein, Minping Wan, Michael Shay

Session Description

This session aims to improve the plasma physics knowledge, the modeling endeavors, and observational interpretations of the turbulent solar wind energy cascade, energy dissipation, and related plasma heating. The emphasis will be on observations, theory and simulations that are relevant at fluid and/or kinetic scales, or that connect fluid and kinetic scales. The session will cover the proposed topic in relation to coherent structures in the solar wind such as reconnection, current sheets, shocks, discontinuities, and co-rotation interaction regions (CIRs), as well as to MHD and kinetic waves and instabilities. The aim is to attract physicists studying the solar wind from various perspectives and applying various tools; and will address critical issues such as turbulent heating. The session will bring together senior researchers for converging toward an integrated understanding of the turbulent solar wind, and to provide a “big picture” for young researchers such as graduate students and postdocs. The 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.

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7. Campaign Event: The Extreme CME of 2012 July 23
Ying Liu, Chris Russell, Noe Lugaz, Maher Dayeh

Session Description

The 2012 July 23 CME, with a speed of about 3000 km/s at the Sun, produced a giant, superfast shock and magnetic cloud with a peak solar wind speed of about 2200 km/s and a peak magnetic field of about 110 nT observed at STEREO A. Although it did not hit the Earth, the CME makes what now we call an "extreme" event given its unusual energetics. The purpose of this session is to investigate the solar source and heliospheric consequences of the 2012 July 23 CME by bringing together various observations from multiple vantage points and theoretical modeling. Key discussion topics will include:

(1) What was the coronal context that made the event so extreme?
(2) How did the CME propagate and interact with the ambient heliosphere and how did the remote-sensing observations compare with in situ measurements?
(3) How was the SEP event related to CME properties?
(4) How does the CME compare with previous extreme events (e.g., the 2003 Halloween CMEs)?

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8. Corotating Interaction Regions and the Connection Between Their Trailing Edges and Energetic Particle Acceleration Near 1 AU
Robert W. Ebert (SwRI), Joe Borovsky (SSI), and Lan Jian (GSFC and UMCP)

Session Description

Corotating interaction regions (CIRs) are a major producer of 10s of keV to several MeV particle enhancements at 1 AU, especially during periods of low solar activity. The long-standing interpretation is that these energetic particles are accelerated at CIR-driven shocks between ~3–5 AU, the particles being transported to 1 AU along the interplanetary magnetic field. This paradigm has begun to shift over the past decade as studies have shown that CIR-associated energetic particles at 1 AU can be accelerated locally in events with a reverse shock or well-formed trailing edge. However, a complete understanding of the conditions needed to accelerate these particles to keV and MeV energies at 1 AU remains elusive. This is made more difficult by the fact that there has been little organized research on the trailing edges of CIRs and high-speed streams, which are prevalent throughout the solar cycle.
We propose a two-part session on this topic. Part one will examine the properties of CIRs and high-speed streams at 1 AU with a focus on their trailing edges and the physical processes ongoing there. The second part will discuss particle acceleration at CIRs and the role of the CIR trailing edge in accelerating energetic particles near 1 AU. Some of the topics we plan to discuss include:

  1. Plasma properties on the trailing edge versus the leading edge of CIRs and high-speed streams.
  2. A comparison of pseudostreamer CIRs and helmet-streamer CIRs.
  3. Differences between trailing edges that transition to pseudosteamers and trailing edges that transition to helmet streamers.
  4. Turbulence and Alfvenic structures in the trailing-edge plasmas.
  5. The connection between trailing edge properties and the acceleration of CIR-associated energetic particles near 1 AU.
  6. Differences in energetic particle properties between CIRs that have clear evidence of local acceleration versus those that do not.
  7. The acceleration site of non-local CIR-associated energetic particles.

We invite all to attend and encourage those with relevant observations, models and theories to prepare material that can support the discussion.

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9. Turbulent Dissipation Challenge: Towards a convergence of current ideas
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. In the past few years, some observational breakthroughs have led to a new and vigorous focus (both observationally and theoretically) on the dissipation/dispersion range of the turbulence cascade. How are dissipation and the resulting heating taking place at kinetic scales? What are the different competing processes under different solar wind conditions? Many processes have been suggested (wave-particle interactions, role of coherent structures, stochastic heating to name a few), but there is no clear understanding of which are important under a given set of solar wind conditions and no clear consensus in the community has emerged yet.
To address the problem, we propose a community driven effort called the Turbulent Dissipation Challenge, in which we would like to bring the community (observationalists, theoreticians, and simulators) together and work together towards a convergence of our current ideas. A detailed description of the Challenge is given in http://arxiv.org/abs/1303.0204 along with a set of suggested problems to focus on. We already have commitments of participation from many groups, and we encourage the entire turbulence community to actively participate.
This SHINE session is a great forum for people to discuss this Challenge in more detail, agree upon the key questions that need to be addressed primarily, and refine and focus the Challenge in its current form. We invite people to present their current work (observations, theory, models, numerical simulations) to simulate the discussion.
We will need two dedicated working group sessions. The purpose of the sessions will be the following:
1) Session 1 will be focussed on discussing the challenge and our current ideas in the topic, and refining the key questions and physical mechanisms that the effort should be focussed on.
2) Based on the outcome of session 1, session 2 will be dedicated to discussing and defining the different steps of the challenge, starting with the type of solar wind conditions to be studied…
Based on our discussions in the above sessions, the finalized set of problems will be circulated on the turbo challenge mailng list with the goal of discussing preliminary results at the Fall AGU.

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10. Investigating the Origin of the Long-Duration High-Energy Gamma-Ray Flares
Gerry Share, James Ryan, Ronald Murphy

Session Description

High-sensitivity solar gamma-ray observations at energies >50 MeV have become possible following the launch of the Fermi Large Area Telescope (LAT) in 2008. This instrument is capable of detecting, on a near-daily basis, radiation arising from the interaction of cosmic-ray protons with the solar disk and cosmic-ray electrons with blackbody photons within a few degrees around the Sun. With this excellent sensitivity LAT has also observed at least twelve >100 MeV gamma-ray events in the minutes and hours following M and X-class flares. The first of these events was associated with SOL2011-03-07T19:43 a modest M3.7 flare with measurable emission up to at most 1 MeV during its impulsive phase. The emission of >100 MeV gamma-ray emission began shortly after the flare rising to a peak about 6 hours later and lasting for at least 12 hours. The origins of such long-duration emissions are not understood. Ryan (2000) discussed earlier observations of long-duration gamma-ray flares (LDGRFs) and suggested four possible origins: 1. delayed precipitation into the chromosphere of high-energy particles accelerated in the impulsive phase of the flare and stored in magnetic structures high in the corona; 2. particles returning to the chromosphere after being accelerated remotely in an electric field or by an expanding shock; 3. precipitation of particles from the flare stored in the corona that were further accelerated by a remote shock or electric field; and 4. particles accelerated in a reconnecting current sheet behind a Coronal Mass Ejection (CME).

Understanding the origins of these sustained-emission events will require broad knowledge of the Sun and heliosphere. We therefore propose a session to understand their origins that bring together specialists in a variety of areas of SHINE research. We will focus on two of these events, SOL2011-03-07T19:43 and SOL2012-03-07T00:02. In order to explain these puzzling observations, we need to incorporate information on the relevant characteristics of the active regions, flares, magnetic field configurations, SEPs, etc. and theories of particle acceleration and trapping.

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11. Abundances in the solar atmosphere and in the solar wind
Daniel Wolf Savin and Enrico Landi

Session Description

Element abundances are one of the main properties of the solar atmospheric plasmas. They determine the radiative losses in the solar inner atmosphere, they bear the signatures of the still unknown plasma transport, heating and fractionation processes from the photosphere to the corona the solar wind, and the solar energetic particles (SEPs); and they shape the spectrum of any structure in the solar atmosphere. Comparison between in-situ determinations of the element abundances in the solar wind and spectroscopic measurements in the solar corona holds the key to identifying the sources of the solar wind. This session will highlight outstanding questions in our understanding of the abundances and their role in the physics of the solar atmosphere,
starting from the solar surface and going out into the solar wind and SEPs. The talks have been selected to cover both theoretical models and observational constraints, both from remote sensing spectroscopic observations and in-situ measurements.

As in the past, we expect that each Session would consist of four 50 minutes Segments. We would split that time up into a 25 minute presentation followed by 25 minutes of open discussion and contributed presentations. Here now are the four Segments of the proposed Session:

First segment: Spectroscopy

One of the key goals of solar spectroscopy is to determine the abundances of the elements in the Sun, and a surprising result is that the abundances in the solar atmosphere can differ significantly from those in the photosphere. Pioneering work performed on ultraviolet data from the Skylab spectrometers taken in the 1970s revealed a wide variety of results for different solar features. Analyses of data from spectrometers on board the SOHO and Hinode spacecraft have continued to unveil the pattern of abundance variations in the solar atmosphere and allowed links to the solar wind to be studied. Results from these solar missions will be summarized, and the key analysis techniques highlighted. A particular focus will be on the role atomic data plays in abundance determinations.

Second segment: Theory

I will describe models to explain the FIP effect based on the action of the ponderomotive force associated with Alfven and fast mode waves propagating in the chromosphere. This force is due to the combine effects of wave pressure gradients and wave reflection/refraction, and for these MHD waves acts only on ions, thus giving rise to fractionation between chromospheric ions and neutrals. I will go on to describe how constraints on the wave propagation and origin arising from careful comparison of predicted and observed coronal abundances yield novel insights into the heating mechanisms of the solar corona, and possibly also the origin of the slow speed solar wind. In particular, the depletion of helium depends sensitively on the wave frequency with respect to the resonance frequency of the loop, with the best match to observations for waves on resonance. This strongly suggests a coronal origin for the waves, and heating models related to nanoflares. I will further suggest that nanoflares put most of their energy into waves, which then ultimately damp nonlocally throughout the corona, which will have implications for observational searches for localized hotspots as evidence of nanoflares.

Third segment: Solar Wind, Heavy Ions, FIP Effect, SEPs

A review will be given on our current understanding of the heavy ion elemental abundances in the solar wind. Their variation, usually through the FIP effect as well as through the absolute abundance relative to hydrogen, serves as a valuable constraint on the theory and model of solar wind formation at the Sun. A review will also be given on the abundance variation in SEPs, which is a different game involving the acceleration and transport effects that are different for different ions. That said, the abundance variations in SEPs would also depend on their seed particles, which in turn should share a common origin that produces the solar wind.

Fourth segment: Element abundances along the solar cycle

Solar wind plasma and compositional properties reflect the physical properties of the corona and its evolution over time. Studies comparing the previous solar minimum with the most recent, unusual solar minimum indicate that significant environmental changes are occurring globally on the Sun. We conduct a systematic and comprehensive analysis of the compositional changes of the solar wind during cycle 23 from 2000 to 2010 while the Sun moved from solar maximum to solar minimum. We find a systematic change of C, O, Si and Fe ionic charge states towards lower ionization distributions. We also discuss long-term changes in elemental abundances and show that there is a ~50% decrease of heavy ion abundances (He, C, O, Si, and Fe) relative to H as the Sun went from solar maximum to solar minimum. During this time, the relative abundances in the slow wind remain organized by their First Ionization Potential (FIP). We discuss these results and their implications for models of the evolution of the solar atmosphere, and for the identification of the fast and slow wind themselves.

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