Table of Contents ============================================================================ 1. GemWiki: A New GEM Web Site 2. CALL FOR PAPERS: JGR Special Section "Entropy properties, constraints, and transitions related to plasma transport, turbulence, and information flow throughout the heliosphere, magnetosphere, and boundaries" ============================================================================ *************************** ** THE GEM MESSENGER ** *************************** Volume 18, Number 6 April 9, 2008 ---------------------------------------------------------------------------- 1. GemWiki: A New GEM Web Site ---------------------------------------------------------------------------- From: Peter Chi and C. T. Russell We have set up a Wiki site for GEM to replace the old GEM web pages. The GemWiki includes the updated information about the program structure and bylaws of GEM (by courtesy of Jimmy Raeder). It also retains all the essential functions provided by the old GEM site. The new GemWiki site at UCLA can be accessed at: http://aten.igpp.ucla.edu/gemwiki/ The URL of the old GEM web site will redirect you to the new GemWiki. ---------------------------------------------------------------------------- 2. CALL FOR PAPERS: JGR Special Section "Entropy properties, constraints, and transitions related to plasma transport, turbulence, and information flow throughout the heliosphere, magnetosphere, and boundaries" ---------------------------------------------------------------------------- From: Simon Wing and Jay R. Johnson Papers are being solicited for a JGR special section on entropy which may be of interests to one or more current GEM focus areas. JGR Special Section: Entropy properties, constraints, and transitions related to plasma transport, turbulence, and information flow throughout the heliosphere, magnetosphere, and boundaries Submission Opens: July 1, 2008. Submission Deadline: October 15, 2008 Entropy in its most basic form is a measure of the number of states available to a system. When the system evolves in an adiabatic manner without dissipation, the entropy is conserved. On the other hand, dissipative processes increase the entropy relaxing the system towards a more stable state. Macroscopic fluid approaches, such as MHD, usually assume an adiabatic pressure law that conserves entropy. In the MHD approach assuming an adiabatic pressure evolution, the frozen-in condition implies the conservation of the global entropy per unit flux of convecting plasma as well as the local (or specific) entropy, P/rho**gamma. Observations and simulations in space indicate that entropy is not conserved across boundaries such as the magnetopause and heliopause, during dynamical transitions such as substorms and coronal mass ejections, as well as during steady flows in the plasma sheet of the magnetosphere. Nonconservation of entropy in space plasmas can result from magnetic reconfiguration as well as nonadiabatic processes such as turbulent transport, thermal energy transport due to nonadiabatic particle drifts, energizations, mixing of two or more plasma populations etc. Examination of entropy properties may provide insight into processes leading to plasma entry across the magnetopause on the dayside and nightside; processes leading to the tail pressure crisis; and may provide constraints on which processes are most important in the dynamical transition related to substorms or coronal mass ejections. Entropy has also been used to study intermittency, turbulence, and information- dynamics in space. In particular, the observed scale dependence of fluctuations in the solar wind appears to be related to long-range memory and interactions. Generalized nonextensive forms of the entropy have been used to examine the probability density function of fluctuations to identify intermittency and multi-fractal behavior. Entropy-based information flow is also useful for assessing the loss of information and prediction horizon for geoeffective solar wind events. We invite theoretical and observational contributions that explore the use of entropy to provide physical insight into space plasma transport, intermittency, turbulence, and information flow in the heliosphere and magnetosphere. Those who are interested, please provide the Guest Editors, Jay R. Johnson and Simon Wing , with tentative titles and author lists as soon as possible in advance of journal submission. Please contact us for further information or questions. Submission details can be found at http://www.agu.org/pubs/submit_to_AGU.html Submission URL: http://jgr-spacephysics-submit.agu.org/cgi-bin/main.plex +-------------------------------------------------------------------------+ |To subscribe GEM Messengers, send an e-mail to | | with the following command in the body of your e-mail message: | | subscribe gem | |To remove yourself from the mailing list, the command is: | | unsubscribe gem | | | |To broadcast a message to the GEM community, please contact Peter Chi at | | | |Please use plain text as the format of your submission. | | | |URL of GEM Home Page: http://www-ssc.igpp.ucla.edu/gem/Welcome.html | |Workshop Information: http://gem.rice.edu/~gem | +-------------------------------------------------------------------------+