arXiv subjects

Leonard A Freeman

Publications and source records attributed to Leonard A Freeman.

4 recordsLinked to original sources

arXiv2026

The group height of spicules links their acceleration and velocity

This study reveals a new feature of many solar jets: a group height, which links their acceleration and velocity. The acceleration and velocity (a,V) for jets such as spicules, often displayed as scattergraphs, show a strong correlation. This can be represented empirically by the equation, V = pa + q, where p and q are two arbitrary non-zero constants. This study reanalyses the (a,V) data for nine different groups of jets, in order to test an alternative proposal that a simpler relationship directly links (a,V) to the mean height for the group of jets, without needing the empirical constants p and q. A standard mathematical test: plotting log(a) against log(V) , tests whether V ~ a^n and if so, gives the value of n. When this is done for a wide range of jets the index n is consistently found to be close to 0.5 The nine groups of jets include spicules, macrospicules and dynamic fibrils. The result, V ~ a^0.5, or equivalently V^2 = ka , with only one constant, provides as close a match to the data as the equation V = pa + q, which requires two unknown constants. It is found that the constant k, is a known quantity: just twice the mean height, s, of the group of jets being analysed. This then gives the equation V^2 = 2as for the jets in the group. This more succinct relationship links the acceleration and maximum velocity of every jet in the group to a well-defined quantity: the mean height of the group of spicules, without needing extra constants.

physics.gen-ph↗

arXiv2019

Predicting relationships between solar jet variables

Studies of spicules and similar solar jets reveal a strong correlation between some of the kinematic variables, particularly between the initial velocity V, and the subsequent deceleration, a. It has been proposed that there is a linear relationship between these two variables and that this offers proof for a shock wave mechanism acting on the spicules, although the linear equations found are all different. It is shown here that the relationship is better described by a non-linear form: V is proportional to the square root of a. This relationship between V and a also provides a simple physical interpretation for the results. The different linear equations are found to be simply tangents to this (a,V) curve. Another method used to investigate the (a,V) connection is to determine the correlation coefficients between the kinematic variables from their scatter plots . It is also shown how these correlations also can be predicted from the mean value of the acceleration and height and their standard deviations for the sample under consideration. The implications of these results and the possibility that spicule behaviour is partly due to magnetic fields are discussed.

astro-ph.SR↗

arXiv2017

Spicules: velocity, acceleration and scatter plots

Spicules and other solar jets such as bright points and fibrils generally show a parabolic height-time relationship, which means that each spicule has a constant deceleration. However the deceleration is only constant for a particular spicule and varies widely from one spicule or jet to another. Nonetheless the careful observations of a number of researchers show that the distance - time relationship is parabolic to a high level of precision. The measurements for heights, maximum velocities, decelerations and flight times are normally presented as histograms or scatter plots, which allow some general trends to be observed. The published results show a clear correlation between the maximum velocity and the deceleration of spicules on scatter plots. This correlation has been claimed to show a linear relation between the acceleration and the maximum velocity of a jet. This linear relationship has been used to help model the mechanisms responsible for the jets. However it is proposed here that the relation between velocity and acceleration is given by the normal equations of motion for constant acceleration and consequently the relationship is non-linear. Other correlations are also examined and the implications for spicule mechanisms are considered.

astro-ph.SR↗

arXiv2013

New magnetic moment theory may explain features of solar jets and spicules

Current theory states that the magnetic moment of a charged particle is constant, or invariant in a slowly changing magnetic field. It also states that the magnetic flux through a Larmor orbit is constant. The current theory is closely examined, and found to have inconsistencies. An alternative theory is developed with new results for both the energy and magnetic moment of a charged particle. The new theory predicts particle behaviour which is opposite to convention: for example, that a plasma will decelerate as it moves through a decreasing magnetic field. Conversely it will accelerate into an increasing field. The magnetic field of the sun would then act as a restraining influence on solar plasma ejections. The new theory is developed for two forms of the magnetic field: an inverse square law and an exponential. The theoretical results are compared with recent experimental results for the velocity, deceleration, time and heights of solar jets and spicules. The effect on Coronal Mass Ejections and Coronal Bright Fronts is also examined.

astro-ph.SR↗