Number range CHAPTER**SHINE 2003 Workshop Highlights Progress in
Solar-Heliospheric Physics**

David Webb^1,2^ and Nat Gopalswamy^3^

SHINE (Solar Heliospheric Interplanetary Environment) is a grass-roots
organization affiliated with the National Science Foundation. It holds
annual workshops that provide a unique environment for interactions
among solar and heliospheric physicists, modelers and observers, those
with global viewpoints and those focused on specific events or
techniques.

SHINE 2003 was the fifth annual workshop and by far the most successful
in terms of the numbers of speakers, poster papers and attendees, about
150! This enhanced interest was undoubtedly due to the fine program of
exhilarating speakers and topics, but was certainly enhanced by the
lovely venue: Maui, Hawaii! However, the number of participants at these
meetings has grown steadily since the late 1990s.

As usual, the meeting was organized around 3 working groups (WGs) that
met individually and in joint sessions to discuss an array of timely
topics. The 3 groups were Solar, Interplanetary, and Solar Energetic
Particles (SEPs). However, this workshop was different in two respects.
First, SHINE hosted its first-ever Student Day, following the lead of
the older GEM and CEDAR NSF-sponsored organizations. Twenty students
attended the meeting and most of them were provided with travel support.
They discussed topics such as flares and CMEs, and related solar wind
composition signatures, magnetic clouds and energetic particles, the
latter reviewed by Richard Leske. The students also made their own
presentations. Second, we had a half-day plenary session introducing
Campaigns of coordinated observations and modeling of four specific
events. The Campaign events chosen before the meeting were: May 12,
1997, May 1, 1998, April 21, 2002, and August 24, 2002. The first two
were selected because they were Sun-Earth connection events with
excellent solar data for modeling and simulations. George Fisher
reviewed these solar data in the context of the MURI analysis project,
and Ian Richardson discussed the interplanetary aspects. The latter two
events were west limb CMEs observed by RHESSI that produced large SEP
events with very different spectral profiles. Allan Tylka and others
discussed these observations in terms of shock propagation models and
asked what can the solar observations tell us about these spectral
differences. These topics were then discussed in the SEP WG session
where no firm conclusions were reached, partly because the solar events
were so similar.

The Solar WG concentrated on observations of vector magnetic fields and
photospheric flows and what they can tell us about conditions leading to
the initiation of a CME. A plenary talk introducing this topic was given
by Bruce Lites who discussed the latest developments in observing the
solar surface. In particular, he focused on the issues of magnetic
structure and formation of prominences. Emergence and evolution of the
magnetic field from below the solar surface and leading to the formation
of prominence and then to CMEs seem to be within the grasp of present
day observations. One session introduced the general issues involved
with determining the vector magnetic field and photospheric flow
patterns, with local correlation tracking techniques being the main
focus. A second session focused on application of these measurements to
the CME problem. Two issues were recognized: 1) The importance of using
chromospheric lines to measure the vector field in regions where the
field is more likely to be force-free. Such measurements would provide
\"cleaner\" boundary conditions for extrapolations into the corona,
required to provide the magnetic topology in the erupting region. 2)
What is the relationship between plasma and magnetic field flows on the
solar surface? Local correlation tracking techniques follow photospheric
plasma emission, whereas we really need to know how the magnetic field
elements move to understand helicity injection, magnetic energization
and the dynamical evolution of the magnetic topology of flaring and
erupting regions.

The Solar WG also participated in joint sessions with the Interplanetary
WG on modeling magnetic fields, and with the SEP WG on the role of CME
initiation and energetic particles. The joint Solar-Interplanetary
session was introduced by a plenary talk by Karel Schrijver on
photospheric field evolution and coronal magnetic fields. He emphasized
that significant amounts of heliospheric open flux emanate from active
regions and, thus, the evolution of active regions can play a role in
the IMF. The joint session featured a second year face-off between the
Fisk and Wang-Sheeley models of how magnetic flux is transported over
the Sun and affects the heliosphere. Conclusions reached were that the
global magnetic field is very important, and our representation of it is
much improved, that the source of the open magnetic flux is variable and
uncertain, that tracking both open flux and individual field lines is
important, that stochastic, statistically-tuned flux emergence may
explain the activity cycle, and that the motion of flux elements is not
necessarily the same as the plasma.

The Interplanetary WG focused on coronal and heliospheric field
modeling, areas where great strides have been made recently. A major
uncertainty of heliospheric MHD models is introduced by the inputs
assumed (i.e., inner boundary conditions). It is important to understand
the limitations of a given model and its realm of applicability, and the
impacts of magnetic topology on characteristics of the solar wind at 1
AU. Specifically, why does the potential field, source surface (PFSS)
model do so well? For example, the ambient solar wind speed,
***V**~sw~*, and IMF polarity can be predicted at 1 AU well with the use
of a coupled PFSS+current sheet model and a new empirical velocity
relationship that is a function of magnetic field expansion factor
(***f*~s~**) and the angular distance between an open field footpoint
and its nearest coronal hole boundary (***?*~b~**). We don\'t understand
why there is such a good inverse correlation between ***f*~s\ ~**and
***V**~sw~*, and modelers and theorists need to confront this issue and
explain it. Does the ***?*~b~** relation imply different heating
mechanisms for fast and slow wind, or is it a fudge factor for the PFSS
model? Quality control of the input magnetic data was considered
essential for improving the predictive success of the models. A brief
overview of the new Solar Mass Ejection Imager (SMEI) experiment now
imaging the whole sky in white light once per orbit was also presented.
SMEI will provide important new data of the inner heliosphere for the
models. Although calibration of the instrument is just beginning, the
all-sky images already show CME-like transients and should be able to
detect other heliospheric features such as corotating structures.

As followup to the discussion about the Campaign events, the SEP WG
continued with discussions of particle acceleration mechanisms near the
Sun, A plenary talk introducing this topic was given by Marty Lee. After
summarizing the observed properties of impulsive and gradual SEP events,
he pointed out that shock acceleration is directly observed, while
stochastic acceleration is necessarily inferred. After pointing out the
important elements of complexities in shock-acceleration, he outlined
the following as the outstanding issues: (i) variation of the
acceleration efficiency with distance because of the increasing
gyroradii of ions, (ii) radial dependence of the Alfven speed profile of
the corona/solar wind, (iii) shock refraction and its relation to
phenomena such as Moreton waves, and (iv) the availability of seed
particles near the Sun. The SEP WG then focused on the effects of shocks
and flares on SEP composition and, particularly, on the spectral
variability noted in the 2002 events. The joint session with the Solar
WG focused on the acceleration and transport of energetic particles and
what we can learn about the relationship between SEP events, CMEs and
flares. Joint Solar-SEP topics included understanding the location and
strength of shocks in the important range of 2-5 solar radii, the
magnetic topology in terms of connections to the flare and the role of
interchange reconnection, the pre-eruption history of events having
SEPs, especially of the campaign events, the role of blast waves as
diagnostics and whether they can accelerate particles to significant
energies. Understanding the relative timing of observables in SEP
events, especially in the Campaign events, was considered important.
Topics involving the SEP group were the need to find more examples and
develop more techniques for evaluating the injection profiles of SEPs,
to better understand the energy budget of SEPs, especially involving the
particles themselves and their associated shocks, and to model parallel
and perpendicular shocks to test observational differences between
events, such as timing.

The Interplanetary and SEP WGs had joint sessions with invited talks and
discussion focusing on two main topics: 1) Suprathermal particles and
the magnetic connectivity of CME structures, and 2) Solar wind and
energetic particle composition. The first session began with a
discussion of heat flux dropouts in the solar wind. Such electrons may
disappear or weaken in regions of high density, and the dropouts are a
result of coulomb collisions in a sufficiently high density region most
likely near the Sun. Coulomb scattering affects low energy electrons the
most. A recent concept called \"interchange reconnection\" is helping us
sort out in the heliosphere which field lines have reconnected near the
Sun. A folded-back field line can result and a local area of high beta
plasma can develop that can cause a dropout because of scattering in the
high beta plasma. The intensity of the heat flux electrons is related to
the time since the last interchange reconnection. Finally, the use of
solar flare electrons as a tracer of the connectivity within
interplanetary magnetic clouds was discussed. In several events the
flare-onset electrons within a cloud demonstrate the magnetic connection
of one leg back to a solar active region, and the field line lengths
were consistent with flux tubes. These observations also suggested that
one leg was connected to the Sun, while the other was connected to the
heliosphere. In fact one never sees a case of both cloud legs connected
to the Sun, even though filaments begin with both legs in an active
region.

Particle composition and energy states were discussed in the other
session. ICMEs tend to be \"hot\"; e.g., they contain solar wind periods
with high Fe charge states. Comparison of Ulysses and ACE data indicates
that low latitude CMEs tend to have high Fe charge states, while high
latitude CMEs do not. We don\'t know whether this is associated with the
sources of the CMEs, active regions at low latitudes and polar crown
filaments at higher latitudes, or something else. There is compositional
evidence for energy-dependent acceleration of suprathermal ions; what
are the source populations of these particles? Suggestions are remnant
particles in the interplanetary medium from previous flare suprathermals
or SEP events. Solar wind material cannot be a dominant source for this
population. During this solar cycle, the C/O ratio is lower in SEPs than
the solar wind, the frequency of 3He-rich shocks has peaked and
declined, yet the Fe/O ratio has remained high. How can we understand
these differences? In magnetic clouds, the Fe/O ratio is high, and the
Fe charge states are higher than in large IP shock events. Why is this?
It was clear to this group, that the Campaign events would be useful for
studying the process of flare and shock acceleration close to the Sun.

At the end of each SHINE workshop some specific challenges are named
with the intent of encouraging studies before next year\'s workshop.
This year we had many of these and some of the most important are as
follows. We need to know what aspects of the photospheric and coronal
evolution are necessary and/or sufficient for an eruption to occur. The
Solar WG Challenge is to provide simulated magnetograms and flow fields
as input to the various techniques used to recover velocity and field
information. Projects between Solar and Interplanetary include work on a
global solar magnetic field model that assimilates observations, the
need to track individual field lines in time from the photosphere
through the corona to the heliosphere, how to verify the origin of open
field lines, and the need to understand the degree to which flux
emergence truly is stochastic. The Solar and SEP Challenge is to
exchange ideas on CME/flare initiation and SEPs within each community
and to develop topics to investigate during the next year. Between the
Interplanetary and SEP groups a prime goal is to study the processes of
flare and shock acceleration close to the Sun, especially using the
Campaign events. Work on the Campaign events themselves among all the
groups will be a prime focus.

This summer SHINE 2004 will be held at Big Sky, MT from June 27- July 2.
Information about the meeting is available on the SHINE website at:
[[http://www.shinegroup.org/.]{.underline}]()

**Acknowledgments**

This article is based in part on reports from the working group leaders
D. Alexander, N. Arge, T. Hoeksema, C. Cohen, T. Holzer and M. Popecki.
The complete reports can be found under Meetings at the SHINE website.
SHINE 2003 was supported by the U.S. National Science Foundation under
Grants ATM 0227732 to the Catholic University of America and NASA\'s
Living With a Star (LWS). Any opinions, findings, and conclusions or
recommendations expressed in this material are those of the authors and
do not necessarily reflect the views of the National Science Foundation.

^1^ Institute for Scientific Research, Boston College, Chestnut Hill,
Mass., USA

^2^ Also at Air Force Research Lab, Space Vehicles Directorate, Space
Weather Center of Excellence, Hanscom AFB, Mass., USA

^3^ Laboratory for Extraterrestrial Physics, NASA Goddard Space Flight
Center, Greenbelt, Maryland, USA