Working Group Descriptions:

Shortcut to working group: B C D E F G H I J

Group	Topic	Leader	Scope
B	Fast Solar Wind & Plumes [Participants]	Craig Deforest [deforest@boulder.swri.edu]	Solar sources, basic physics
	This working group will assess current knowledge of how polar plumes and coronal holes are heated, and how they relate to the solar wind. Polar plumes have been an on-again, off-again candidate source for the solar wind; because the plasma topology is simpler than for the quiet sun or active regions, this portion of the corona is a convenient laboratory for general coronal heating mechanisms; and recent improvements in resolution, vantage point, and theoretical modeling may significantly change our understanding of how plumes originate and relate to the solar wind. Specific questions for discussion include: Are plumes fundamentally caused by magnetic reconnection at the footpoint, and how does that reconnection proceed? Can we shed new light on the debate over whether plumes are significant sources of solar wind? What has been learned recently about the time scales and associated mechanisms for plume formation and maintenance? What is the relationship between jets, plumes, and helical structure in the open coronal hole? What steps are needed to generate realistic numerical models of plume formation and evolution?
C	Magnetic Field Evolution [Participants]	Marc DeRosa [derosa@lmsal.com]	Energy storage, connectivity
	This working group will assess our current knowledge on the evolution of magnetic flux in and near the surface layers of the sun, focusing on the properties associated with the emergence of flux, its subsequent evolution, and its influences on the evolution of the overlying coronal magnetic field. Questions to be discussed include: How have the new high-resolution observations from Hinode affected our views of flux emergence and evolution? In what ways do additional emergence of flux into a previously established active region affect the overlying coronal dynamics? How do currents enter and/or form in the corona? How do helicity and twist enter and/or form in the corona? How do recent numerical models of flux emergence help us to understand what is happening?
D	Global event energetics [Participants]	Brian Dennis [Brian.R.Dennis@nasa.gov]	Partition of energy
	This group is a follow-on to the similar group at the Taos ACE-RHESSI-Wind workshop held in Taos, NM, in 2003 that resulted in papers on the energetics of two flare/CME events (Emslie et al., JGR, 109, A10104, 2004; JGR, 110, A11103, 2005). We will first update these earlier results as appropriate and then apply the same techniques to determining the energetics of several more well-observed large events, particularly those that occurred during the period of high solar activity in October and November, 2003. A list of events for study will be determined well before the meeting, and group members will be expected to bring measured estimates of the energies contained in specific components of the flares, CMEs, and SEPs that comprise each event. The objective will be to publish the comprehensive results for these specific events with as wide a coverage as possible so that the average energy partition amongst the various components can be established and significant event-to-event differences identified.
E	Flares [Participants]	Gordon Holman [Gordon.D.Holman@nasa.gov]	Initiation, basic physics
	The Flares Working Group will assess our current knowledge of the initiation, evolution and basic physics of solar flares. The primary goal will be to use this knowledge to determine the combinations of coordinated multi-spacecraft, multi-wavelength observations and modeling efforts that will lead to the greatest progress in solar cycle 24. Topics of special interest include: Active region/magnetic field evolution and flare initiation. The relationship between particle acceleration and plasma heating. The evolution of heated plasma and accelerated particles in flares. The escape of energetic particles into interplanetary space. The location and role of magnetic reconnection in flares.
F	Coronal Mass Ejections [Participants]	Alphonse Sterling [alphonse.sterling@nasa.gov]	Initiation, flare association
	This group will work at establishing a definitive connection between ICMEs, CMEs, and their source regions on the Sun, for a few specific eruptive events. We will select events that have available both interplanetary data and a wide range of corresponding solar data. Interplanetary data will be from ACE and WIND, and solar data will include white light, EUV, soft X-ray, hard X-ray, and magnetic data obtained from as many instruments as possible, such as STEREO, SOHO, TRACE, RHESSI, and Hinode. For each eruption we will address topics such as: the magnetic configuration of the erupting region at the Sun; the likely eruption-initiation mechanism; whether the mass of the CME can be accounted for in totality by mass deficits in intensity-dimming regions; the relationship between the solar CME source locations and the locations of the corresponding flares; the connection between the angular extent of the CME and the magnetic and spatial characteristics of the source region; and the eruption's evolution in interplanetary space. We will circulate a list of candidate events prior to the workshop among members who sign up for the session, and participants will be asked to help collect data sets prior to the meeting. During the workshop we will perform simple analysis of the aggregate data, and summarize our findings. Event List, with notes: - 2007 May 19 - 2007 May 20 These two events came from the same region, AR 10956, and were observed at least with Hinode. - 2008 Feb 4 - 8. - 2008 Jun 2 - 6. These two events were followed from initiation at the Sun, until interaction with one of the STEREO spacecraft. The earlier dates in the time span (Feb 4, Jun 2) are the days on which the eruptions occurred, while the second dates (Feb 8, Jun 6) are the days when the interaction with STEREO occurred. - 2008 Apr 26. This event had a fast CME and EUV wave seen by SECCHI on both STEREO's A and B, and also detected in-situ by ACE and by STEREO-B. It should be possible to learn about this event's 3D shape, velocity, etc. - 2008 Apr 9. A "run-of-the-mill" CME, occurring over the west limb. It was well-observed by Hinode with excellent coverage in XRT and EIS, and also by both SECCHI instruments and by UVCS. The CME seems to interact with a coronal hole and change direction, and there is also a sideways filament eruption.
G	Microflares and Nanoflares [Participants]	Paolo Grigis [pgrigis@cfa.harvard.edu]	Basic physics, heating
	The Napa conference offers the extraordinary opportunity to meet different communities interested in the coronal heating question: the flare community, the solar wind community, and the coronal loop community. The group will focus on the energy input apparent in small flares and review all observed forms of flaring that are possibly related to the heating of the corona. This includes chromospheric and transition region events that may provide wave energy, microflares in active regions, jets in polar regions and smallest events in the quiet corona. We are particularly looking forward to new observations by Hinode, Stereo, RHESSI, SOHO and others. Observations of time variations in different wavelengths and locations may be compared. Indirect signatures of small flares will also be discussed: high-energy particles in the quiet hard X-ray spectrum, high temperature plasma in the quiet corona, the temperature distribution in active region loops etc. New theoretical studies on the energy input of flares into the corona, excitation of waves and the distribution of energy are of great interest. The main goal of this group is to learn about the latest developments in the different communities. A possible outcome of this group may be a Manifesto on time-variable aspects of coronal heating.
H	The Chromosphere [Participants]	Bart De Pontieu [bdp@lmsal.com]	Basic physics, activity
	Recent observations from Hinode, TRACE and ground-based telescopes, and numerical simulations have significantly changed our views of the chromosphere, a region in which over 90% of the non-radiative energy that goes into the outer atmosphere to drive solar activity and space weather is deposited. This working group will assess the current state of our understanding of the dynamics and energetics of the chromosphere, and the coupling between the chromosphere, transition region and corona. Questions and topics of discussions will include, but are not limited to: How have recent observations and numerical models changed our views of chromospheric heating? What role do waves play vs. currents, and other forms of non-thermal energy? How is this energy transported, modified and deposited in the chromosphere? How does the plasma beta=1 surface affect the chromosphere and particularly the propagation and properties of waves? How do waves leak from the photosphere and impact the chromosphere and beyond? How are various wave modes generated, coupled to other modes in the chromosphere, and transported into the corona and solar wind? Do we understand these issues well enough to use chromospheric waves as a diagnostic of changes in the magnetic topology (flares, CMEs...)? How have recent numerical models improved our understanding of the chromosphere? Which features/characteristics of the chromosphere are unexplained, and which physical processes are still missing from these models? How important are the effects of neutral particles in the chromosphere? What kind of observations and modeling are needed to better understand the impact of chromospheric dynamics and energetics on the transition region and corona, and vice versa (for flares)? For flares, how does the release of energy in the corona affect the chromosphere, and how is the flare energy thermalized in the chromosphere? What kind of new insights have we developed about chromospheric evaporation?
I	Active-region Loops [Participants]	Mike Marsh & Aveek Sarkar [rwwalsh@uclan.ac.uk]	Basic physics, flows, waves
	A more detailed schedule for Working Group I: Active Region Loops, courtsey of Robert Walsh, is available here [PDF]. A major advance in our understanding of the solar corona came about in the discovery that a significant proportion of the radiation emitted from this part of the solar atmosphere is concentrated along well-defined loop-like structures. These loops are the basic structural elements of active regions and are now believed to coincide with magnetic flux tubes where plasma and thermal energy can flow along (but not easily across) these features. Building upon the wealth of observations from SOHO and TRACE, already Hinode and STEREO are providing new insights and novel views of active region loops that are both strengthening and challenging our current understanding of their fundamental nature. The torrent of data from the up-coming SDO mission will stretch further our current thinking on their basic make-up, how they are heating and their activity. Given the above, this working group will address several key science themes associated with active region loops. These will include (but not necessarily restricted to): Physical properties: At current instrumental resolution, are the active region loops we observe isothermal or multi-thermal? Are they monolithic or multi-threaded? Will we ever be able to distinguish between these two paradigms? Temporal properties: Is the heat input to loops steady or impulsive? How can we use the techniques of coronal seismology in the Hinode/STEREO/SDO era? Magnetic properties: Do we now truly have a 3D picture of active region loop topology? How well do current MHD models reproduce the magnetic structure of a "global" active region? On the other hand, how well do these models reproduce the local magnetic structure within an active region? It could be envisaged that a number of the WGI sessions could overlap with other WGs. For example, this could include joint sessions between: * WG-C on magnetic connectivity in active regions through the atmosphere * WG-G on the consequences of localized, small scale heating in active region loops * WG-H on the propagation of oscillations along loops
J	Filaments and Prominences [Participants]	Tom Berger [berger@lmsal.com]	Basic physics, flows, bubbles
	Recent observations from the Hinode/SOT and ground-based instruments have confirmed that filaments are highly dynamic objects, found to be in constant motion along horizontal threads in the spines of Active Region objects, or in ubiquitous vertical downflows, upflows, and vortices seen in quiescent prominences at the limb. Hinode/SOT observations have also revealed previously unseen upflows in the form of smaller dark turbulent plumes rising into the prominence, as well as large "bubble inflation" events that can disrupt the entire structure. Larger bubble eruption events have also now been identified in MLSO H-alpha observations. This working group will assess our current understanding of prominence structure, dynamics, the role of magnetic fields in the photosphere and corona, and the origin of prominence mass in the context of the newly discovered flows and bubbles. In addition we will discuss future instrumentation and mission requirements that will enable further progress in the field. Specifically we will: Review the latest observations of filaments and prominences. Review our current state of knowledge on filament formation, structure, and dynamics. Discuss future theoretical directions needed for a more comprehensive understanding of the filament environment and filament magnetic fields and their plasma dynamics. Discuss how filament channels and filaments are essential to setting the stage for eruptive solar events Discuss future instrumentation and mission characteristics for filament research. Each working group session will be composed of two to three key talks that will be designed to give a broad overview of a topic and to stimulate discussion.