Energy Of Non-thermal Electrons Research Articles

The common cutoff energy of non-thermal electrons with power law distribution

The linear correlation between the logarithm of the total density and the energy index with a negative coefficient is proven as the necessary condition for the cross of the power law distribution lines or the common cutoff energy of the non-thermal electrons responsible for synchrotron and bremsstrahlung radiations. The statistical results calculated from atypical solar microwave burst shows a positive correlation coefficient, which is just opposite to the necessary condition. Therefore, the common cutoff energy does not exist in this event.

ECE diagnostic using multi-channel radiometer in Heliotron-E

Electron cyclotron emission (ECE) is measured with a multi-channel radiometer system in Heliotron-E. The system detects the second harmonic emission from 67 to 115 GHz at the magnetic field B = 1.9 T, covering the plasma confinement region up to the last closed flux surface. The radial and temporal evolution of the electron temperature has been obtained for electron cyclotron heated (ECH) and neutral beam injected (NBI) plasmas. Nonthermal electrons are observed at the plasma breakdown, and the nonthermal electron energy is estimated from the frequency downshift. We also discuss the effect of the magnetic shear on the second harmonic electron cyclotron wave propagating through the plasma with a strong magnetic shear such as heliotron/torsatron configurations.

Observation of nonthermal energy distributions during the impulsive phase of solar flares

The Fe XXV resonance line and dielectronic satellite intensities have been measured as functions of time for several flares recorded by the Naval Research Laboratory crystal spectrometer (SOLFLEX) flown on the US Air Force P78-I spacecraft. The intensity ratios of the Fe XXV resonance line, the Fe XXIV n = 2 satellite line j, and the Fe XXIV n = 3 satellite line d13 indicate that nonthermal electron energy distributions occur during the impulsive phase of the flares. For the electron energies at which the j and d13 satellites are formed (4.7 and 5.8 keV, respectively), the electron energy distributions during the impulsive phase are observed to have a bump or to be nearly flat. For all of the flares that were studied, hard X-ray bursts occurred near the time of the nonthermal distributions observed in the SOLFLEX data.

Propagation and confinement of energetic electrons in solar flares

The propagation, cofinement and total energy of energetic (>25 keV) electrons in solar flares are examined through a brief review of the following hard X-ray measurements: (1) spatially resolved observations obtained by imaging instruments; (2) stereoscopic observations of partially occulted sources providing radial (vertical) spatial resolution; and (3) directivity of the emission measured through stereoscopic observations and the center-to-limb variation of the occurrence frequency of hard X-ray flares. The characteristics of the energetic electrons are found to be quite distinct in impulsive and gradual hard X-ray flares. In impulsive flares the non-thermal electron spectrum seems to extend down to ∼2 keV indicating that the total energy of non-thermal electrons is much larger than that assumed in the past.

Electron impact polarization of resonance lines from Lithium-like ions

The Oppenheimer-Penney theory, as developed by Percival and Seaton (1958), is applied to calculate the polarization of resonance lines from Li-like ions. Two laws for the pitch-angle distribution of electrons around the magnetic field are accounted. The degrees of polarization are averaged over the energy of non-thermal electrons generated during the initial phase of solar flares. It is found that for the full space pitch-angle distribution, as adopted by Chandra and Joshi (1984), the degrees of polarization are nearly independent of the atomic number of ion. Whereas for the forward-come distribution used by Haug (1981), they depend on the choice of the free parameterE0. The polarization of the resonance lines from Li-like ions is two times larger than that of the Lα radiations from H-like ions. Hence, under favourable conditions, it may be detected during solar flares.

Effects of the internally produced nonthermal electrons on the temperature diagnostics of a hollow gas shell Z pinch

Experimental evidence is presented indicating that a nonthermal electron energy distribution occurs in a collapsing gas shell Z pinch at the time of pinch. It is estimated that these results can be explained if less than 10% of the current is associated with an energetic (∼4 keV) electron beam. Interpreting the spectroscopic diagnostics consistently with the nonthermal electron energy distribution indicates that the temperature of the plasma ‘‘hot spots’’ could be as low as ∼400 eV instead of the 1 keV obtained by assuming a thermal distribution.

Electron impact polarization of L?-radiations from hydrogen-like ions

The Oppenheimer-Penny theory, as developed by Percival and Seaton (1958), is applied to calculate the polarization of Lα radiations from hydrogen-like ions when the impact electrons are distributed such that their probability is more in the regions close to the magnetic field. The degrees of polarization are averaged over the energy of non-thermal electrons generated during the initial phase of solar flares. It is found that the degrees of polarization do not depend on the atomic number of the ion.

0.35-3.5 MICRON PHOTOMETRY OF POLARIZED QSOS.

ABSTRACT Visual and infrared photometry of strongly polarized QSOs (BL Lacertae objects) is reported. Spectral flux distributions of these objects are discussed in combination with results from earlier studies. With the exception of the well-resolved galaxies Mkn 421 and Mkn 501 only one object (1218 + 304) has a change in spectral index easily explained by the presence of an underlying galaxy. Six other sources appear to have either a break in their spectra near about 1 micron or a smoother general steepening of their spectra at shorter wavelengths. A spectral break at this wavelength may be attributed to a low flux of nonthermal radiation superimposed on a stellar energy distribution or by nonthermal electron energy losses.

Dielectronic satellite spectra for highly charged helium-like ions - IV. Iron satellite lines as a measure of non-thermal electron energy distributions

Dielectronic satellite spectra for highly charged helium-like ions - IV. Iron satellite lines as a measure of non-thermal electron energy distributions

Measurements of non-thermal electron energy distributions in high temperature laser produced plasmas

Measurement of the electron energy distribution in high temperature laser produced plasmas is discussed. The problem arises in thermonuclear fusion research with lasers, where strong enhancement of the high energy tail of the distribution may occur. It is shown that a method based on X-ray bremsstrahlung intensity, recorded as a function of metallic absorber thickness, is applicable in the energy range 1 to 40 keV. Two stages of deconvolution to obtain first the X-ray spectrum and second the electron energy distribution are considered. Simple semi-analytic methods of sufficient accuracy for experimental work are outlined and their regime of validity discussed.

The decay characteristics of models of solar hard X-ray bursts

Models of solar hard X-ray bursts are considered in which non-thermal electrons are impulsively injected into a coronal magnetic trap. Recognising that the ends of the trap are likely to be rooted in the photosphere and that the density of the ambient atmosphere may thus be highly non-uniform along the field lines, it is shown that the X-ray spectra will initially soften with time, due to collisions, when this non-uniformity is strong enough. This removes a well-known discrepancy in models with uniform density. It is shown also that non-uniformity steepens the electron spectrum required to produce a given observed X-ray spectrum. In consequence the total non-thermal electron energy involved in a given burst is greater than that previously inferred from impulsive injection models.