64 research outputs found
Theoretical studies on rapid fluctuations in solar flares
Rapid fluctuations in the emission of solar bursts may have many different origins e.g., the acceleration process can have a pulsating structure, the propagation of energetic electrons and ions can be interrupted from plasma instabilities and finally the electromagnetic radiation produced by the interaction of electrostatic and electromagnetic waves may have a pulsating behavior in time. In two separate studies the conditions for rapid fluctuations in solar flare driven emission were analyzed
A self-organized criticality model for ion temperature gradient (ITG) mode driven turbulence in confined plasma
A new Self-Organized Criticality (SOC) model is introduced in the form of a
Cellular Automaton (CA) for ion temperature gradient (ITG) mode driven
turbulence in fusion plasmas. Main characteristics of the model are that it is
constructed in terms of the actual physical variable, the ion temperature, and
that the temporal evolution of the CA, which necessarily is in the form of
rules, mimics actual physical processes as they are considered to be active in
the system, i.e. a heating process and a local diffusive process that sets on
if a threshold in the normalized ion temperature gradient R/L_T is exceeded.
The model reaches the SOC state and yields ion temperature profiles of
exponential shape, which exhibit very high stiffness, in that they basically
are independent of the loading pattern applied. This implies that there is
anomalous heat transport present in the system, despite the fact that diffusion
at the local level is imposed to be of a normal kind. The distributions of the
heat fluxes in the system and of the heat out-fluxes are of power-law shape.
The basic properties of the model are in good qualitative agreement with
experimental results.Comment: In press at Physics of Plasmas, July 2010; 11 pages, 5 figure
Formation and Evolution of Coherent Structures in 3D Strongly Turbulent Magnetized Plasmas
We review the current literature on the formation of Coherent Structures
(CoSs) in strongly turbulent 3D magnetized plasmas. CoSs (Current Sheets (CS),
magnetic filaments, large amplitude magnetic disturbances, vortices, and
shocklets) appear intermittently inside a turbulent plasma and are collectively
the locus of magnetic energy transfer (dissipation) into particle kinetic
energy, leading to heating and/or acceleration of the latter. CoSs and
especially CSs are also evolving and fragmenting, becoming locally the source
of new clusters of CoSs. Strong turbulence can be generated by the nonlinear
coupling of large amplitude unstable plasma modes, by the explosive
reorganization of large scale magnetic fields, or by the fragmentation of CoSs.
A small fraction of CSs inside a strongly turbulent plasma will end up
reconnecting. Magnetic Reconnection (MR) is one of the potential forms of
energy dissipation of a turbulent plasma. Analysing the evolution of CSs and MR
in isolation from the surrounding CoSs and plasma flows may be convenient for
2D numerical studies, but it is far from a realistic modeling of 3D
astrophysical, space and laboratory environments, where strong turbulence can
be exited, as e.g. in the solar wind, the solar atmosphere, solar flares and
Coronal Mass Ejections (CMEs), large scale space and astrophysical shocks, the
magnetosheath, the magnetotail, astrophysical jets, Edge Localized Modes (ELMs)
in confined laboratory plasmas (TOKAMAKS), etc.Comment: 27 pages, 31 figures; review; accepted for publication in Physics of
Plasmas 202
Similarity "Development Model for Supporting The Accoplishment of Academic Level: Case Study of Bina Nusantara University"
The physical processes, which drive powerful solar eruptions, play an
important role in our understanding of the Sun-Earth connection. In this
Special Issue, we firstly discuss how magnetic fields emerge from the solar
interior to the solar surface, to build up active regions, which commonly host
large-scale coronal disturbances, such as coronal mass ejections (CMEs). Then,
we discuss the physical processes associated with the driving and triggering of
these eruptions, the propagation of the large-scale magnetic disturbances
through interplanetary space and the interaction of CMEs with Earth's magnetic
field. The acceleration mechanisms for the solar energetic particles related to
explosive phenomena (e.g. flares and/or CMEs) in the solar corona are also
discussed. The main aim of this Issue, therefore, is to encapsulate the present
state-of-the-art in research related to the genesis of solar eruptions and
their space-weather implications.
This article is part of the theme issue 'Solar eruptions and their space
weather impact'.Comment: 3 page
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