Scientific Rationale
Convection is ubiquitous throughout the Universe. Its main physical
consequences are heat transport, mixing, interaction with mean flow and
magnetic fields and the dynamo generation of magnetic fields.
Convection occurs in the majority of stars including the sun. During the last
three decades convection has become perhaps the largest factor of uncertainty
in the physical modeling of many problems in stellar evolution, stellar
structure, pulsational stability and model stellar atmospheres, to name just a
few. Nevertheless, considerable progress has been achieved in our understanding
of solar and stellar convection through new types of observations. These
include high resolution spectra and time series of spectra of solar granules,
as well as accurate measurements of the depth of the solar convection zone by
means of helioseismology and of the properties of subsurface convection by
local helioseismology.
At the same time, numerical simulations of solar and stellar convection have
become more and more powerful because of enhanced numerical resolution and more
realistic microphysics. Nevertheless, modeling and theoretical understanding of
how convection interacts with other physical mechanisms is still very much
wanting, as is the successful application of knowledge gained on convection to
the unresolved problems of solar and stellar astrophysics.
Convection is also common in planets sufficiently large to keep an atmosphere
of their own. In such atmospheres convection is usually a local phenomenon of
limited horizontal extent. Stellar convection for comparison usually occurs as
a global instability within a shell or a sphere. Convection is also present
inside planets which have a heat source in their interior and where it can
occur as a global phenomenon very much like in stars. The interior of Jupiter
provides one such example. Planetary research on flow dynamics and thermal
properties benefits from the possibility of in situ data obtained from probes
which is not available to solar and stellar research. On the other hand, the
limitations to computational capabilities and the difficulties in the modeling
and the theoretical understanding of the interaction between convection and
other physical processes are very similar to those encountered in solar and
stellar research.
The conference will deal with theoretical and observational aspects of
convection in a wide variety of objects from our own Solar system and beyond,
in the Sun, stars and planets. The sessions will be organized around physical
processes with which convection interacts in the objects studied, whether it be
gaseous giants, a brown dwarf, the sun, or other stars.
Programme
The sequence of sessions and the basic range of topics will be as follows:
 A  Modelling of convection and radiative transfer
 B  Observational probes of convection
 C  Convection in planets and brown dwarfs
 D  Stellar evolution, nucleosynthesis, and convective mixing
 E  Oscillations, mass loss, and convection
 F  Convection and rotation
 G  MHD convection and dynamos
The following aspects will be covered by this programme:
Modeling of and numerical simulation techniques for convection
Convection has been posed as a serious and difficult problem in astrophysics
for decades. The initial, and conventional, approach to handle convection was
based on heuristic arguments. The physical understanding and applications were
both irked by uncertainties. In the past two decades, numerical simulations
have made very important contributions to the understanding of astrophysical
convection. The extent to which numerical results are applicable and reliable,
however, is not without queries. In recent years, alongside the achievements
made by numerical simulations, considerable development has also been made on
the theoretical side, in attempting to improve the mathematical treatment of
the convective turbulence. Contrasting of results from mathematical modeling,
numerical simulation, and the conventional approach have also been made. The
study of astrophysical convection has become a big field, the spectra of
approaches, techniques, and phenomena involved are wide.
Observing convection
Until recently convection and turbulence have been treated in rather adhoc
manner with adjustable free parameters within model atmosphere and interior
codes. As such, these can be selected to agree with observations without any
regard to their true physical meaning, even to the extent of being unphysical.
The new theoretical developments to be discussed at this conference enable true
physicsbased predictions to be tested against observations in order to improve
our overall understanding of the physical mechanisms. The increased
sophistication and precision of instruments is pushing our theoretical models
to their limits and beyond. Example include highresolution measurements of
absorption line profiles and line shifts as diagnostics of atmospheric
convective flows, helio (and astero) seismological probing of internal
convection zones, direct imaging of surface convection of the sun and other
stars (through interferometry), and direct observations of atmospheric
circulations within planets of the Solar System.
Convection and radiation
The most outstanding property of solar surface convection, and of other stars
with surface convection, is its strong interaction with the radiation emitted
into space. Theoretical modeling of this process has remained extremely
difficult and is one of the unresolved problems in the theory of stellar
atmospheres. Numerical simulations of solar and stellar surface convection at
the same time have made significant advances and in many cases agree so well
with the data that they now become an excellent template for models and for
understanding the physical processes of radiationconvection interaction.
Despite the enormous success in the solar case, the simulation of different
types of stellar atmospheres has not been without surprises, due to the
complications involved by nonlocal thermal equilibrium in stellar atmospheres,
or interaction with other physical mechanisms such as rotation, magnetic field,
uncertainties in opacities or the circumstellar environment, and others..
Convection in planets and brown dwarfs
The interior of gaseous giants is expected to transport its heat outwards
through deep convection zones. The same region is also considered to give rise
to planetary dynamos. The close similarity of these physical scenarios to
stellar counterparts makes a review of the state of our knowledge and the
possibility of exchange with the solar and stellar physics communities
particularly interesting. Deep convection zones are expected to appear already
during formation stages of gaseous giants, brown dwarfs, and low mass stars.
Its effects are observable through the depletion of Lithium in the latter,
while brown dwarfs show abundances close to those of the interstellar medium.
Convection and nuclear reactions
The coupling of convection and nuclear reactions is recognized as an important
process in stellar structure. It obviously requires consideration in the
dynamical phases (supernovae nucleosynthesis), but also during the fast phases
of the postAsymptotic Giant Branch (AGB), such as Sakurai's object, when
'reactive' convection can occur. It is also crucial for the expected
nucleosynthesis when convection reaches the hydrogen burning shell in the high
luminosity phases of massive AGB evolution, and for determining the properties
of excursions through the blue loops (and thus the Cepheid phase) during helium
burning in the cores of intermediate mass stars.
Convective mixing
Convective mixing at the borders of convective cores (either as 'overshooting'
or, in the convective helium burning cores, possibly as 'semiconvection') has
been recognized since the seventies as one of the key processes to understand
the basics of stellar evolution, e.g. the lifetimes and width of the main
sequence band, but the physics of such overshooting is poorly understood and
consequently is crudely parametrized when included in the construction of
stellar models. Progress in this area is perhaps one of the most needed in
stellar astrophysics, as convective mixing also influences later and final
stages of stellar evolution. Metallic fingers (thermohaline convection) have
been suggested to explain chemical peculiarities observed in stars (as the
final consequences of binary interaction or recently absorbed closeby
planets).
The question of doublediffusive convection has come up as an explanation for
the unexpected properties of the progenitor of SN 1987A and the existing
stellar evolution calculations are still very much wanting in that respect
(these have to be considered together with the binary scenario proposed for
that supernova as well). No combined treatment of rotation and doublediffusion
has ever been implemented in stellar evolution calculations of massive stars.
Progenitor models of corecollapse supernovae hence still suffer a considerable
amount of uncertainty caused by a very incomplete modeling of convective
mixing.
Convection, oscillations and mass loss
Turbulent convection can stochastically excite stellar oscillations and the
properties of the oscillations depend on the time dependent interaction of the
oscillations with the convection. The measured properties of the oscillations
provide diagnostics of both the global structure of a star (depth of convective
zone, radius of convective core, overshooting), models of turbulence and, in
the solar case, diagnostics of the properties of the subsurface convective
layers. The behaviour of oscillating stars (Cepheids, delta Scutis, Miras) and
the red edge of the zone of instability strip in the HR diagram  depend on
the detailed properties of the interaction of the pulsation with convection. In
late type giants this may also drive mass loss and envelope ejection.
Understanding of all these topics is currently being advanced by theoretical
modelling, numerical simulation and observation, but there is a long way to go
before we can be confident that we understand and can model
convectionpulsation interaction.
Convection, rotation, and disks
In astrophysical settings, rotation is not less ubiquitous than convection, and
the coupling of the two provides the drives for many energetic astrophysical
phenomena. The most basic among them, differential rotation, is still a hot
subject being intensely pursued. The relative importance of local and global
processes is a question under heated debate. At any rate, in the solar/stellar
community, since differential rotation is known to vanish below the solar
convection zone (through helioseismology), it is generally accepted that
differential rotation is a consequence of the interaction of rotation and
convection. In the planetary community, on the other hand, the claim that such
interaction is responsible for the wind bands of the outer planets is not as
popular.
Rotation convection and turbulence are important in astrophysical disks too, be
they accretion disks around compact objects or protoplanetary disks around
young stars. Our understanding of them has been enhanced by complex 3D
hydrodynamical simulations.
MHD Convection and dynamos
The magnetic fields in stars and planets (and in many other astrophysical
objects) are believed to be generated by dynamo action of convection.
Understanding the interaction of convection and magnetic fields is therefore of
major importance for astrophysics. Under what conditions is a small seed field
amplified? How can turbulent convection produce a mean field on a scale much
larger than the scale of the turbulence? Can a strong magnetic field inhibit
convection? Can we model the solar dynamo? Can a dynamo operate in stellar
convective cores? Is rotation a necessary ingredient for a dynamo to operate,
and how do rotation and magnetic fields effect the transport of energy in
convective regions? These are very difficult problems but progress has been
made in 3D simulations of MHD convection and of rotating magnetic envelopes
and cores, and in mean field models of the solar and stellar dynamos
