arXiv subjects

K. Wilhelm

Publications and source records attributed to K. Wilhelm.

13 recordsLinked to original sources

arXiv2022

Gravitational matter-antimatter impact interactions

The production of antihydrogen by several research groups provides the opportunity to measure the gravitational behaviour of antimatter in the gravitational field of the Earth. The predictions in the literature range from normal attraction to repulsion. Applying our gravitational impact model, which is of a purely phenomenological nature, we conclude that there will be neither attraction nor repulsion under the assumption of a symmetric antigraviton distribution near the antihydrogen atom. However, a very small asymmetry must be expected and could effect the conclusion. The model, in addition, predicts normal gravitation between antimatter and antimatter particles at large distances, but strong repulsion at close range for matter as well as for antimatter pairs, whereas strong attraction will result for matter-antimatter encounters. We have further refined the model assumptions in light of recent CERN ALPHA-g measurements that indicate a certain attraction of antihydrogen by the gravitational field of the Earth.

physics.gen-ph↗

arXiv2018

Impact models of gravitational and electrostatic forces: Potential energies, atomic clocks, gravitational anomalies and redshift

The far-reaching gravitational force is described by a heuristic impact model with hypothetical massless entities propagating at the speed of light in vacuum and transferring momentum and energy be- tween massive bodies through interactions on a local basis. In the original publication (Wilhelm et al. 2013), a spherical symmetric emission of secondary entities had been postulated. The potential energy problems in gravitationally and electrostatically bound two-body systems have been studied in the framework of this im- pact model of gravity and of a proposed impact model of the electrostatic force (Wilhelm et al. 2014). These studies have indicated that an anti-parallel emission of a secondary entity - now called graviton - with respect to the incoming one is more appropriate. This article is based on the latter choice and presents the modifications resulting from this change. The model has been applied to multiple interactions of gravitons in large mass conglomerations in several publications. They will be summarized here taking the modified interaction process into account. In addition, the speed of photons as a function of the gravitational potential are considered in this context together with the dependence of atomic clocks and the redshift on the gravitational potential.

physics.gen-ph↗

arXiv2017

Understanding disk galaxy rotation velocities without dark matter contribution--a physical process for MOND?

An impact model of gravity designed to emulate Newton's law of gravitation is applied to the radial acceleration of disk galaxies. Based on this model (Wilhelm et al. 2013), the rotation velocity curves can be understood without the need to postulate any dark matter contribution. The increased acceleration in the plane of the disk is a consequence of multiple interactions of gravitons (called "quadrupoles" in the original paper) and the subsequent propagation in this plane and not in three-dimensional space. The concept provides a physical process that relates the fit parameter of the acceleration scale defined by McGaugh et al. (2016) to the mean free path length of gravitons in the disks of galaxies. It may also explain the modification of the gravitational interaction at low acceleration levels in MOND (Milgrom 1983, 1994, 2015, 2016). Three examples are discussed in some detail: The spiral galaxies NGC 7814, NGC 6503 and M 33.

astro-ph.GA↗

arXiv2017

Gravitational redshift and the vacuum index of refraction

A physical process of the gravitational redshift was described in an earlier paper (Wilhelm & Dwivedi 2014) that did not require any information for the emitting atom neither on the local gravitational potential U nor on the speed of light c. Although it could be shown that the correct energy shift of the emitted photon resulted from energy and momentum conservation principles and the speed of light at the emission site, it was not obvious how this speed is controlled by the gravitational potential. The aim of this paper is to describe a physical process that can accomplish this control. We determine the local speed of light c by deducing a gravitational index of refraction nG as a function of the potential U assuming a specific aether model, in which photons propagate as solitons. Even though an atom cannot locally sense the gravitational potential U (cf. Muller et al. 2010), the gravitational redshift will nevertheless be determined by U (cf. Wolf et al. 2010)- mediated by the local speed of light c.

physics.gen-ph↗

arXiv2017

On the potential energy in a gravitationally bound two-body system with arbitrary mass distribution

The potential energy problem in a gravitationally bound two-body system has recently been studied in the framework of a proposed impact model of gravitation \citep{WilDwi}. The result was applied to the free fall of the so-called Mintrop--Ball in Göttingen with the implicit assumption that the mass distribution of the system is extremely unbalanced. An attempt to generalize the study to arbitrary mass distributions indicated a conflict with the energy conservation law in a closed system. This necessitated us to reconsider an earlier assumption made in selecting a specific process out of two options \citep{Wiletal}. With the result obtained here we can now make an educated selection and reverse our choice. The consequences are presented and discussed in detail for several processes. Energy and momentum conservation could now be demonstrated in all cases.

physics.gen-ph↗

arXiv2016

The Aharonov-Bohm effect: A quantum or a relativistic phenomenon?

The Aharonov-Bohm effect is considered by most authors as a quantum effect, but a generally accepted explanation does not seem to be available. The phenomenon is studied here under the assumption that hypothetical electric dipole distributions configured by moving charges in the solenoid act on the electrons as test particles. The relative motions of the interacting charged particles introduce relativistic time dilations. The massless dipoles are postulated as part of an impact model that has recently been proposed to account for the far-reaching electrostatic forces between charged particles described by Coulomb's law. The model provides a quantitative explanation of the Aharonov-Bohm effect.

quant-ph↗

arXiv2015

Solar coronal plumes and the fast solar wind

The spectral profiles of the coronal Ne viii line at 77 nm have different shapes in quiet-Sun regions and coronal holes (CHs). A single Gaussian fit of the line profile provides an adequate approximation in quiet-Sun areas, whereas a strong shoulder on the long-wavelength side is a systematic feature in CHs. Although this has been noticed since 1999, no physical reason for the peculiar shape could be given. In an attempt to identify the cause of this peculiarity, we address three problems that could not be conclusively resolved in a review article by a study team of the International Space Science Institute (ISSI; Wilhelm et al. 2011) : (1) The physical processes operating at the base and inside of plumes as well as their interaction with the solar wind (SW). (2) The possible contribution of plume plasma to the fast SW streams. (3) The signature of the first-ionization potential (FIP) effect between plumes and inter-plume regions (IPRs). Before the spectroscopic peculiarities in IPRs and plumes in polar coronal holes (PCHs) can be further investigated with the instrument Solar Ultraviolet Measurements of Emitted Radiation (SUMER) aboard the Solar and Heliospheric Observatory (SOHO), it is mandatory to summarize the results of the review to place the spectroscopic observations into context. Finally, a plume model is proposed that satisfactorily explains the plasma flows up and down the plume field lines and leads to the shape of the neon line in PCHs.

astro-ph.SR↗

arXiv2014

On the potential energy in an electrostatically bound two-body system

The potential energy problem in an electrostatically bound two-body system is studied in the framework of a recently proposed impact model of the electrostatic force and in analogy to the potential energy in a gravitationally bound system. The physical processes are described that result in the variation of the potential energy as a function of the distance between the charged bodies. The energy is extracted from distributions of hypothetical interaction entities modified by the charged bodies.

physics.gen-ph↗

arXiv2013

An impact model of the electrostatic force: Coulomb's law re-visited

The electrostatic force is described in this model by the action of electric dipole distributions on charged particles. The individual hypothetical dipoles are propagating at the speed of light in vacuum transferring momentum and energy between charges through interactions on a local basis. The model is constructed in analogy to an impact model describing the gravitational forces.

physics.gen-ph↗

arXiv2011

Morphology, dynamics and plasma parameters of plumes and inter-plume regions in solar coronal holes

Coronal plumes, which extend from solar coronal holes (CH) into the high corona and - possibly - into the solar wind (SW), can now continuously be studied with modern telescopes and spectrometers on spacecraft, in addition to investigations from the ground, in particular, during total eclipses. Despite the large amount of data available on these prominent features and related phenomena, many questions remained unanswered as to their generation and relative contributions to the high-speed streams emanating from CHs. An understanding of the processes of plume formation and evolution requires a better knowledge of the physical conditions at the base of CHs, in plumes and in the surrounding inter-plume regions (IPR). More specifically, information is needed on the magnetic field configuration, the electron densities and temperatures, effective ion temperatures, non-thermal motions, plume cross-sections relative to the size of a CH, the plasma bulk speeds, as well as any plume signatures in the SW. In spring 2007, the authors proposed a study on "Structure and dynamics of coronal plumes and inter-plume regions in solar coronal holes" to the International Space Science Institute (ISSI) in Bern to clarify some of these aspects by considering relevant observations and the extensive literature. This review summarizes the results and conclusions of the study. Stereoscopic observations allowed us to include three-dimensional reconstructions of plumes. Multi-instrument investigations carried out during several campaigns led to progress in some areas, such as plasma densities, temperatures, plume structure and the relation to other solar phenomena, but not all questions could be answered concerning the details of plume generation process(es) and interaction with the SW.

astro-ph.SR↗

arXiv2009

Stereoscopic Polar Plume Reconstructions from Stereo/Secchi Images

We present stereoscopic reconstructions of the location and inclination of polar plumes of two data sets based on the two simultaneously recorded images taken by the EUVI telescopes in the SECCHI instrument package onboard the \emph{STEREO (Solar TErrestrial RElations Observatory)} spacecraft. The ten plumes investigated show a superradial expansion in the coronal hole in 3D which is consistent with the 2D results. Their deviations from the local meridian planes are rather small with an average of $6.47^{\circ}$. By comparing the reconstructed plumes with a dipole field with its axis along the solar rotation axis, it is found that plumes are inclined more horizontally than the dipole field. The lower the latitude is, the larger is the deviation from the dipole field. The relationship between plumes and bright points has been investigated and they are not always associated. For the first data set, based on the 3D height of plumes and the electron density derived from SUMER/\emph{SOHO} Si {\sc viii} line pair, we found that electron densities along the plumes decrease with height above the solar surface. The temperature obtained from the density scale height is 1.6 to 1.8 times larger than the temperature obtained from Mg {\sc ix} line ratios. We attribute this discrepancy to a deviation of the electron and the ion temperatures. Finally, we have found that the outflow speeds studied in the O {\sc vi} line in the plumes corrected by the angle between the line of sight and the plume orientation are quite small with a maximum of 10 $\mathrm{km s^{-1}}$. It is unlikely that plumes are a dominant contributor to the fast solar wind.

astro-ph.SR↗

arXiv2009

Spectroscopic Diagnostics of Polar Coronal Plumes

Polar coronal plumes seen during solar eclipses can now be studied with space-borne telescopes and spectrometers. We briefly discuss such observations from space with a view to understanding their plasma characteristics. Using these observations, especially from SUMER/SOHO, but also from EUVI/STEREO, we deduce densities, temperatures, and abundance anomalies in plumes and inter-plume regions, and discuss their implications for better understanding of these structures in the Sun's atmosphere.

astro-ph.SR↗

arXiv1998

Sunspot transition region oscillations in NOAA 8156

Based on observations obtained with the Solar and Heliospheric Observatory - SOHO joint observing program for velocity fields in sunspot regions, we have detected 3 min transition region umbral oscillations in NOAA 8156. Simultaneous recordings of O V $λ$629 and N V $λ$1238, $λ$1242 with the SUMER instrument give the spatial distribution of power in the 3 min oscillations, both in intensity and line-of-sight velocity. Comparing loci with the same phase we find that the entire umbral transition region oscillates. The observed maxima in peak line intensity are nearly in phase with the maxima in velocity directed towards the observer. We discuss the suggestion that the waves are upward propagating acoustic waves.

astro-ph↗