8,414 research outputs found
Intermittent heating in the solar corona employing a 3D MHD model
We investigate the spatial and temporal evolution of the heating of the
corona of a cool star such as our Sun in a three-dimensional
magneto-hydrodynamic (3D MHD) model. We solve the 3D MHD problem numerically in
a box representing part of the (solar) corona. The energy balance includes
Spitzer heat conduction along the magnetic field and optically thin radiative
losses. The self-consistent heating mechanism is based on the braiding of
magnetic field lines rooted in the convective photosphere. Magnetic stress
induced by photospheric motions leads to currents in the atmosphere which heat
the corona through Ohmic dissipation. While the horizontally averaged
quantities, such as heating rate, temperature or density, are relatively
constant in time, the simulated corona is highly variable and dynamic, on
average reaching temperatures and densities as found in observations. The
strongest heating per particle is found in the transition region from the
chromosphere to the corona. The heating is concentrated in current sheets
roughly aligned with the magnetic field and is transient in time and space.
This supports the idea that numerous small heating events heat the corona,
often referred to a nanoflares
Terahertz dynamic aperture imaging at stand-off distances using a Compressed Sensing protocol
In this text, results of a 0.35 terahertz (THz) dynamic aperture imaging
approach are presented. The experiments use an optical modulation approach and
a single pixel detector at a stand-off imaging distance of approx 1 meter. The
optical modulation creates dynamic apertures of 5cm diameter with approx 2000
individually controllable elements. An optical modulation approach is used here
for the first time at a large far-field distance, for the investigation of
various test targets in a field-of-view of 8 x 8 cm. The results highlight the
versatility of this modulation technique and show that this imaging paradigm is
applicable even at large far-field distances. It proves the feasibility of this
imaging approach for potential applications like stand-off security imaging or
far field THz microscopy.Comment: 9 pages, 13 figure
Model Based Sensor System for Temperature Measurement in R744 Air Conditioning Systems
The goal is the development of a novel principle for the temperature
acquisition of refrigerants in CO2 air conditioning systems. The new approach
is based on measuring the temperature inside a pressure sensor, which is also
needed in the system. On the basis of simulative investigations of different
mounting conditions functional relations between measured and medium
temperature will be derived.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/handle/2042/16838
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