15 research outputs found
The Theory of Heating of the Solar Corona and Launching of the Solar Wind by Alfv\'en Waves
State-of-the-art MHD calculations reveal acceptable agreement with
observational data for the height profile of the temperature in the
transition region of solar corona. Simultaneously, the velocity of the solar
wind has also been calculated. The developed method gives the
possibility at given frequency dependent spectral density of Alfv\'en waves
(AW) coming from chromosphere to calculate both height
profiles and . In agreement with the concepts of the self-induced
opacity of plasma with respect of AW, the narrow width of the
transition region is determined by the fast temperature increase of the
viscosity . After more than 70 years of development of Solar
physics, the Alfv\'en hypothesis of heating of the solar corona by AW has
remained without alternatives; none of other mechanisms can explain
the value of . The performed MHD analysis explains the height
dependence of the non-thermal broadening of the chromospheric spectral lines
and predicts angular dependence of this broadening with respect of position in
solar disc. One can expect significant impact of MHD analysis in the
interpretation of the long expected data from Parker Solar Probe.Comment: University of Sofia PhD Thesis corrected and updated after defense,
PhD advisor Prof. DSc Todor Mishonov, 122 pages total (6 added in this
version), main text 74 pages (3 added in this version), bibliography 9 pages,
appendices (source code) 29 pages, 31 figures (2 added in this version
Callen-Welton fluctuation dissipation theorem and Nyquist theorem as a consequence of detailed balance principle applied to an oscillator
We re-derive the Nyquist theorem and Callen-Welton fluctuation-dissipation
theorem (FDT) as a consequence of detailed balance principle applied to a
harmonic oscillator. The usage of electrical notions in the beginning makes the
consideration understandable for every physicists. Perhaps it is the simplest
derivation of these well-known theorems in statistical physics. The classical
limit is understandable as a consequence of Waterston-Herapath equipartition
theorem.Comment: 6 pages, 1 figur
Robust formula for -point Pad\'e approximant calculation based on Wynn identity
The performed numerical analysis reveals that Wynn's identity for the compass
(here C stands for center, the other
letters correspond to the four directions of the compass) gives the long sought
criterion, the minimal , for the choice of the optimal Pad\'e
approximant. The work of this method is illustrated by calculation of
multipoint Pad\'e approximation by a new formula for calculation of this best
rational approximation. The work of the criterion for the calculation of
optimal Pad\'e approximant is illustrated by the frequently seen in the
theoretical physics problems of calculation of series summation and multipoint
Pad\'e approximation used as a predictor for solution of differential equations
motivated by the magneto-hydrodynamic problem of heating of solar corona by
Alv\'en waves. In such a way, an efficient and valuable control mechanism for
-point Pad\'e approximant calculation is proposed. We believe that the
suggested method and criterion can be useful for many applied problems in
numerous areas not only in physics but in any scientific application where
differential equations are solved. The solution of the Cauchy-Jacobi problem is
illustrated by a Fortran program. The algorithm is generalized for the case of
the first derivatives at nodal points.Comment: 12 pages, 6 figures, 2 appendix sections; Title and abstract
precised, section Introduction restated, figure captions shortened and a new
appendix section added, where the Cauchy-Jacobi problem is solved for the
case of the first derivatives at nodal point
Comment on "Adiabatic Expansion of Electron Gas in a Magnetic Nozzle" by Kazunori Takahashi, Christine Charles, Rod Roswell, and Akira Ando, Phys. Rev. Lett. Vol. 120, 045001 (2018)
Heat capacities at fixed volume and pressure as a function of the degree of
ionization are graphically depicted as functions of reciprocal temperature and
ionization degree. The polytropic index is calculated as a function of the same
variables; as it is not constant a partially ionized plasma can be only
approximately polytropic fluid. In parallel, it is launched the idea that
Alfv\'en waves can be used to heat the plasma in a propulsion jet with magnetic
nozzle.Comment: 2 pages, 3 figure
Determination of magnon mass of neodymium magnet by temperature dependence of spontaneous magnetization
The effective mass of a magnon in a neodymium magnet is evaluated using Bloch
temperature dependence of spontaneous magnetization. We used the Hall effect
magnetometer and thermo-couple thermometer for measuring of the temperature of
the water in which the encapsulated commercial magnet is immersed. The
experiment can be repeated in every school and methodological remarks for
experimental data processing are given with great detail and attention. The
purpose of the paper is to illustrate the simple relation between the quantum
spectrum of magnons and the easily measured magnetic field of a permanent
magnet.Comment: Second version manuscript - comparison with previous papers, 7 pages,
4 figures, 21 Ref
Predicted electric field induced surface magnetization of vortex phase of superconductors
We predict a new effect in condensed matter surface magnetization of the
vortex phase of a superconductor induced by electric field. The magnetized
superconductor should be one of the plates of a plane capacitor on which a
voltage has to be applied. Applying alternating voltage to the capacitor,
electrostatic induction leads to oscillations of the magnetic moment which has
to be measured by electromotive force inducted in a detector coil. The derived
explicit formula for the magnetization contains the effective mass of Cooper
pairs and a systematic investigation of the predicted magnetization will lead
to a creation of an effective Cooper pair mass spectroscopy. For cleaved
superconductors this effective mass is a property of the bulk material.Comment: 4 pages, 1 enhanced figure, changes in abstract, final journal
version, to see discussions with referees delete %-sign before first
\end{document
Determination of Boltzmann constant by equipartition theorem for capacitors
A new experimental set-up for Boltzmann constant measurement is described.
Statistically averaged square of voltage \left is measured for
different capacitances . Boltzmann constant is determined by the
equipartition theorem C\left=k_{_\mathrm{B}}T. For fixed
capacitance, voltages could be measured for different temperatures. The set-up
consists of low-noise high frequency operational amplifiers ADA4898-2. An
instrumental amplifier is followed by an inverting amplifier, square of the
voltage is created by an analog multiplier AD633 and finally the averaged
signal is measured by a multimeter.Comment: 14 pages, 8 figures, 3 tables, 2 appendice
An undergraduate laboratory experiment on measuring the velocity of light with a catastrophic machine
An experimental setup for electrostatic measurement of ,
separated magneto-static measurement of and determination of the
velocity of light according to Maxwell theory
with percent accuracy is described. No forces are measured with the
experimental setup therefore there is no need of a scale and the experiment
price less than \pounds20 is mainly due to the batteries used. Multiplied
137~times, this experimental setup was given at the fourth open international
Experimental Physics Olympiad (EPO4) and a dozen high school students did very
well. This article, however, focuses on the catastrophe theory, which is the
basis of the methodology.Comment: 13 pages, 4 figures, 1 table. Referee recommendations are taken into
accoun
Simple do-it-yourself experimental set-up for electron charge measurement
A simple experiment for the electron charge measurement is described.
The experimental set-up contains standard electronic equipment only and can be
built in every high-school lab all around the world with pocket money budget
for several days. It is concluded that it is time such a practice to be
included in the regular high-school education. The achieved 13\% accuracy is
comparable to the best student university labs. The measurement is based on
Schottky noise generated by a photodiode. Using the criterion dollar per
accuracy for the electron charge measurement, this definitely is the
world's best educational experiment. An industrial replica can be easily sold
across the globe.Comment: 10 pages, 9 figures, 3 tables, last version corresponds to the
published version in Eur. J. Phys, Eq. (15-17) have been corrected and minor
typographical improvements have been mad
Problem of the 8th Experimental Physics Olympiad, Skopje, 8 May 2021 Determination of Planck constant by LED
This is the problem of the 8 International Experimental Physics
Olympiad (EPO). The task of the EPO8 is to determine Plank constant
using the given set-up with LED. If you have an idea how to do
it, do it and send us the result; skip the reading of the detailed step by step
instructions with increasing difficulties. We expect the participants to follow
the suggested items -- they are instructive for physics education in
general.Only the reading of historical remarks given in the first section can
be omitted during the Olympiad without loss of generality. Participants should
try solving as much tasks as they can without paying attention to the age
categories: give your best.Comment: 27 pages (10 main text), 11 figures, 3 tables, 18 references, 1
appendix of scanned solution (16 pages); latex source files in Bulgarian and
Macedonian languages included as auxiliary files. arXiv admin note: text
overlap with arXiv:1912.0736