A certain class of non-thermal electron distributions can exhibit more monoenergetic shape and a higher peak than the Maxwellian distribution. This type of electron distribution can be observed mainly in flaring plasmas. We have studied the influence of this kind of electron energy distribution on the excitation equilibrium of Fe VIIIFe XVI in the solar corona. The changes in synthetic spectra of the emission lines belonging to these ions due to this non-thermal distribution are shown. The possibilities of finding the shape of the energy distribution function of electrons from the Fe line ratios are also discussed. The results can be used for diagnostics of coronal plasmas where the deviations of particle energy distributions from the Maxwellian one can be significant.
Context. Oscillations of coronal loops in the Sun have been reported in both imaging and spectral observations at the onset of flares. Images reveal transverse oscillations, whereas spectra detect line-of-sight velocity or Doppler-shift oscillations. The Doppler-shift oscillations are commonly interpreted as longitudinal modes. Aims. Our aim is to investigate the relationship between loop dynamics and flows seen in TRACE 195 Å images and Doppler shifts observed by SUMER in Si iii 1113.2 Å and Fe XIX 1118.1 Å at the time of a C.8-class limb flare and an associated CME. Methods. We carefully co-aligned the sequence of TRACE 195 Å images to structures seen in the SUMER Si iii, Ca X, and Fe XIX emission lines. Additionally, Hα observations of a lifting prominence associated with the flare and the coronal mass ejection (CME) are available in three bands around 6563.3 Å. They give constraints on the timing and geometry. Results. Large-scale Doppler-shift oscillations in Fe XIX and transverse oscillations in intensity images were observed over a large region of the corona after the passage of a wide bright extreme-ultraviolet (EUV) disturbance, which suggests ionization, heating, and acceleration of hot plasma in the wake of a blast wave.
The expanding capability of low-cost Unmanned Aerial Vehicles (UAV's) and coincident developments in low-cost wave measurement buoys, necessitates research toward their possible integration. A new (mobile buoy) device that will be a product of such integration is expected to provide a utility in rapid measurements from an expended area of observation when data comes from water surface as well from the bulk of the water column. A targeted literature review was conducted to evaluate the technical feasibility of this technical solution. Amongst many challenges of designing and manufacturing this novel instrument two main technical difficulties have been identified, viz., (i) intermittent and contingent uncertainties in measurements emerging due to the interaction of a UAV airframe with the water surface within a wave environment, and (ii) the relatively poor performance of in-built MEMS accelerometer as a primary device to measure surface acceleration. A technical prototype of this instrument was developed to validate and overcome these difficulties. The prototype was tested in both laboratory and field trial, affirming feasibility of the solution. The prototype endured the sea environment functionally uninhibited, remaining watertight, stable in temperature, and stable against rotation. The prototype acceleration signals were processed and compared with control displacement data. Overall, the prototype comparative performance was reasonable, however it gradually declined with increased wave pattern complexity. This manifested as emerging instrumentation noise, causing erroneous distribution of energy at higher frequencies and moving down an upper wave frequency limit of measurements resulting in a greater demand for calibration. Figure 1. Prototype of UAV mobile buoy for surface waves measurements.
Bibliography 115Publications 121Acknowledgements 123Curriculum Vitae 125• An oscillation of the Fe XIX line and an intensity oscillation of 195 Å emission was seen during and after the filament eruption. Based on the fact that it spread far beyond the legs of the rising prominence, we suggested it was triggered by the blast wave.
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