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The proposed model of particles transport in the solar atmosphere during flares consists in a low density plasmoid originating deep in the atmosphere and rising under magnetic and buoyancy forces. Confined particles are selectively released during the ascent and their interaction with the solar atmosphere produces X and γ bremsstrahlung. The characteristics of high energy particles released in the interplanetary medium are found to agree with observations.
We present preliminary results on solar filaments observed from the ground and from SOHO in September 1996. Motions in the network and close to the filament “barbs” are shown at different levels of the chromosphere and the transition region.
During the June 1996 campaign using the MSDP spectrograph at Pic du Midi and SUMER/CDS (JOP 12) on board SOHO, quiescent prominences were observed. We present observations and physical quantities of the June 5 prominence. Doppler shifts, temperatures and electron densities of fine structures were deduced from Hα data.
The Solar Section of the Societé Astronomique de France has organized various programmes designed to enable amateurs to carry out high-quality and scientifically useful observations. Two particular programmed will be described.
During an unusually massive filament eruption on 7 June 2011, SDO/AIA imaged for the first time significant EUV emission around a magnetic reconnection region in the solar corona. The reconnection occurred between magnetic fields of the laterally expanding CME and a neighbouring active region. A pre-existing quasi-separatrix layer was activated in the process. This scenario is supported by data-constrained numerical simulations of the eruption. Observations show that dense cool filament plasma was re-directed and heated in situ, producing coronal-temperature emission around the reconnection region. These results provide the first direct observational evidence, supported by MHD simulations and magnetic modelling, that a large-scale re-configuration of the coronal magnetic field takes place during solar eruptions via the process of magnetic reconnection.
We have employed current-voltage (IV), capacitance-voltage (CV) and deep level transient spectroscopy (DLTS) techniques to characterise the defects induced in n-Si during RF sputter-etching in an Ar plasma. The reverse leakage current, at a bias of 1 V, of the Schottky barrier diodes fabricated on the etched samples was found to decrease with etch time reaching a minimum at 6 minutes and thereafter increased. The barrier heights followed the opposite trend. The plasma processing introduced six prominent deep levels below the conduction band of the substrate. A comparison with the defects induced during high energy (MeV) alpha-particle, proton and electron irradiation of the same material revealed that plasma-etching created the VO- and VP-centres, and V2-10. Some of the remaining sputter-etching-induced (SEI) defects have tentatively been related to those formed during either 1 keV He- or Ar-ion bombardment.
Two samples, GaN silicon-doped and GaN magnesium-doped, were hydrogen
implanted and annealed. The low temperature photoluminescence and inelastic
light scattering spectroscopy were employed to investigate structural
changes as well as the changes in optical electronic transitions.
The 3D analysis (x, y, t) of the granulation intensity field
(11-hour time sequence from Swedish Vacuum Solar Telescope
on La Palma, Canary Islands), demonstrated that the granules
in the phostosphere are organized in ``Trees of Fragmenting Granules"
(TFGs). A TFG consists of a family of repeatedly splitting granules,
issued from one granule at its beginning. A striking result is
that TFGs can live much longer (up to 8h10) than individual
granules (10 mn). When averaged in time, such long-lived TFGs
can be identified to the mesogranules. We also found a
correlation between the network and the spatial distribution
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