Splinter Group - Chairs: J. Scudder (Univ. Iowa), H. Hudson (ISAS), T. Terasawa (Univ. Tokyo)

As there are so many flavors of magnetic reconnection this session is devoted to tutorials about the mechanism itself. In particular speakers have been invited to highlight general requirements of the process, the influence of dimensionality on the process, and to share what distinguishes reconnection in its various forms. In this sense this session is about reconnection implemented beyond resistivity. There will be an attempt to balance theoretical discussion together with observational evidence. An attempt has also been made to incorporate theorists and observationalists from the solar as well as magnetospheric communities.

Program

H. Petschek-chair 

- Karl. Schindler "Aspects of Collisionless Reconnection"              9:00

     Abstract: A satisfactory theory of  magnetic reconnection
     in space plasmas will require tools that are appropriate for
     collisionless plasmas. This lecture deals with a number of such
     aspects. The main part is concerned with reconnection in current
     sheets with a normal magnetic field component, a configuration 
     which is believed to be relevant for both magnetospheric and solar 
     applications. The problems addressed include linear stability and
     the role of electron dynamics  in the nonlinear phase. In addition,
     a kinematic approach to three-dimensional reconnetion processes 
     based on electromagnetic topology is described. In fields without
     nulls, the electric field component parallel to the magnetic field
     and stagnation flow patterns  play important roles. 

- Amitava Bhattacharjee  "Collisionless Magnetic Reconnection:
        Geometry and Dynamics"                                         9:45

       Abstract: Magnetic reconnection is widely believed to be play an
    important role in several space and astrophysical phenomena such as
    magnetospheric substorms, solar flares, and galactic X-ray emission.
       While there has been sustained interest in magnetic reconnection
    for the last four decades, it has been only in recent years that the
    subtle role of geometry and the effects of collisionless mechanisms
    of reconnection are beginning to be better understood.  In this talk,
    we will review some of these new developments.
	 Geometry is one of the aspects of reconnection that is often
    under-emphasized. It deals with the question: Where should reconnection 
    occur? If reconnection is to be distinguished from mere diffusion,
    geometry provides the key. This point is illustrated by considering
    the classical problem of tearing stability of the earth's magnetotail
    with a normal magnetic field. Although geometrical issues now appear
    to be relatively well understood in two dimensions, three-dimensional
    geometry presents new challenges. Reconnection in three-dimensional
    geometry with and without nulls will be illustrated by means of examples
    drawn from magnetospheric and solar physics. Some new rigorous results
    on Parker's model of current sheets ("nanoflares") which has neither
    nulls nor closed field lines, will be discussed.
	Dynamics deals with the question:  how rapidly and suddenly does 
    reconnection occur? The problem of suddenness, otherwise known as the 
    trigger problem, is somewhat subtler than the problem of fast reconnection.
    We illustrate this point by two examples: the observed sudden enhancement
    of the cross-tail current density just prior to substorm onset in the
    magnetotail, and the impulsive phase of a solar flare. Not only is the
    peak growth rate of these phenomena large, but they are triggered suddenly,
    with a rapid increase in the time-derivative of the growth rate. It is
    suggested that Hall MHD, which includes electron pressure gradients and
    Hall currents in a generalized Ohm's law can provide a plausible explanation
    not only of fast reconnection (weakly dependent on resistivity) but also
    of the impulsiveness. Recent POLAR observations of the importance of
    electron pressure gradients in a magnetopause reconnection layer provides 
    encouraging corroborating evidence of the importance of such collisionless 
    processes in space plasmas.
	Finally, we will address briefly mechanisms that can cause suppression
    of magnetic reconnection. Geometry, if it is not favorable, is one way.
    Velocity shear, which can produce Alfvn resonances containing thin current
    sheets but no reconnection, is another mechanism for suppression. Possible
    relevance of these mechanisms for the magnetosphere and the solar corona
    will be discussed.    


BREAK 10:30-10:45

- Jim Drake  "Whistler Dynamics and Simulations of Collisionless
             Reconection" (tentative title)           	              10:45
- Jack Scudder "Fingerprints of Collisionless Reconnection
             at the Site"                                             11:15
- Toshi Mukai, "Electron and Ion Dynamics in a Thin Current Sheet of
            the Earth's Magnetotail"                                  11:45 
- Masaki Fujimoto, "Significance of the Hall term effects in
 magnetotail reconnection"                                            12:15

LUNCH

- Masahiro Hoshino, "Electron Heating and Acceleration during Magnetic
                 Reconnection"                                         1:30
- Iku Shinohara, "Rapid Ion-Electron Momentum Exchange via Kelvin-
       Helmholtz Instability in the Magnetotail Current Sheet"         2:00
- Jeorge Buechner, "3 D Effects of Kinetic Reconnection"               2:30
- George Doschek, "Flare spectroscopy: Non-equilibrium processes"      3:00 
- Hugh Hudson, "Geometrical views of solar reconnection"               3:30
- Guillaume Aulanier, "3D reconnection in different magnetic 
         topologies observed in the solar corona"                      4:00
- Maasaki Yamada, "Lab Plasmas Simulations of Coronal
               Reconnection" (tentative title)                         4:30

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