Parker's Theory Research Articles

Ancient Egyptian Calendars: How Many Were There?

In 1950, Richard A. Parker hypothesized that pharaonic Egypt had three separate calendars: original lunar; civil; later lunar, of which the most ancient was the original lunar. l To be fair, it should be noted that Ludwig Borchardt first discussed the idea of a second lunar calendar in great detail, and earlier scholars, such as Brugsch (in volume I of his Thesaurus inscriptionum Aegyptiacarum) had also attempted also attempted to explain various anomalies by hypothesizing multiple lunar calendars. The evidence for a Predynastic lunar calendar is explicit in double-dated inscriptions that occur throughout ancient Egyptian history.2 In particular, correlations of a lunar month-and-day date with a civil month-and-day date confirmed Parker's theory that a functioning lunar calendar co-existed with the civil calendar.

A Model of the Double Magnetic Cycle of the Sun

It has been argued that the solar magnetic cycle consists of two main periodic components: a low-frequency component (Hale's 22 yr cycle) and a high-frequency component (quasi-biennial cycle). The existence of the double magnetic cycle on the Sun is confirmed using Stanford, Mount Wilson, and Kitt Peak magnetograph data from 1976 to 1996 (solar cycles 21 and 22). In the frame of the Parker's dynamo theory, a model of the double magnetic cycle is presented. This model is based on the idea of two dynamo sources separated in space. The first source of the dynamo action is located near the bottom of the convection zone, and the second operates near the top. The model is formulated in terms of two coupled systems of nonlinear differential equations. It is demonstrated that in the case of a weak interaction between the two dynamo sources, the basic features of the double magnetic cycle, such as the existence of two components and the observed temporal variations of the high-frequency component, can be reproduced.

On the winding of the IMF spiral for slow and fast wind within the inner heliosphere

Magnetic field and plasma hourly data, recorded within the inner heliosphere from 1975 through mid 1981, have been used to test the interplanetary magnetic field configuration as predicted by the Parker theory against observed interplanetary magnetic field spiral configuration. Following this theory, magnetic field lines should always be aligned with wind flow direction when observed in a reference system corotating with the Sun. Our observations showed a general tendency for the field lines to be more tightly wound with respect to the predicted spiral configuration in agreement with similar studies performed around and beyond 1 AU by other authors. If we set the corotation radius b = 20 Rs we obtain an average overwinding of about 2.7° ± 0.3°. Our results also showed that field lines associated with fast and slow wind have different winding offsets with respect to the predicted Parker spiral. A possible explanation might be in a different value of the corotating radius b depending on the speed of the wind. A value of b = 20 Rs for slow wind would suggest a b = 12 Rs for fast wind.

Radial and azimuthal components of the heliospheric magnetic field: Ulysses observations

Two invariants associated with the Parker model of the solar wind involve the radial, B R, and azimuthal, B T, components of the heliospheric magnetic field. These invariants have been investigated using Ulysses data obtained at high latitudes in both the north and south solar hemispheres. The magnetic flux invariant, r 2B R, is essentially independent of latitude in both hemispheres. However, comparisons with in-ecliptic IMP-8 and WIND observations reveal a small decrease with time of ∼6%. Average values of the second invariant, rV RB T, which is related to the heliospheric electric field, differ systematically from the Parker theory, the difference being a function of latitude that cannot be accounted for simply by a changing solar rotation period. No asymmetry in the discrepancy is found between the two hemispheres. The difference vanishes at the solar equator as shown by a comparison with the in-ecliptic measurements. These results are consistent with the average spiral angle being more radial (underwound) at high latitude than is predicted by the Parker angle and an interval has been identified in which the observed angle is approximately zero on average. This behavior contrasts with the most probable value of the invariant or the spiral angle which does agree with theory. The difference between the average and the most probable value is caused by an asymmetry in the probability distribution. This apparent reduction in average B T may bear on the long-standing issue of a “flux deficit” in the distant heliospheric field.

Reliability and Validity Estimates of the Parker Team Player Survey

The Parker Team Player Survey (PTPS) is designed as a self-report assessment of team player style as described in Parker's theory. In an attempt to estimate the psychometric properties of this instrument, both organizational and academic subject pools were used to demonstrate reliability and validity. The PTPS demonstrated acceptable test-retest reliability for all four team styles of Communicator, Collaborator, Challenger, and Contributer. The measures of internal consistency were low for the Challenger and Collaborator styles given the small number of items and the tendency for individuals to report more than one style. No significant differences were found in the reliability coefficients calculated for the business or student samples. Validity was measured through a comparison of self and peer ratings on the PTPS gathered at a variety of organizations. Whereas the correlations were all statistically significant, the correlation for the Collaborator score was low. Additionally, a panel of trained student judges participated in a sorting task in which they sorted the survey stimulus items into one of the four team style categories. This attempt at construct validity showed good agreement for all four styles, with the Collaborator again being the weakest.

Force-free magnetic fields with singular current-density surfaces

view Abstract Citations (40) References (43) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Force-free Magnetic Fields with Singular Current-Density Surfaces Low, B. C. Abstract This paper is a study of a family of nonlinear force-free magnetic fields, in Cartesian geometry and invariant in a given direction, as simple models of the magnetic fields in the solar corona. Posed as a problem in the infinite half-space bounded below by the photosphere taken as a rigid plane, the solution is constructed with the field-aligned currents confined within a cylindrical plasma surface outside of which the magnetic field is potential. An infinity of solutions are shown to be tractable by the method of images of potential theory. Among the results presented is the demonstration of a magnetic flux surface in the plasma interior, which is ideally stable, where the electric current density becomes an integrable infinity, created quasi-statically by continuous boundary displacement of the magnetic footpoints. This result is discussed in connection with Parker's theory of coronal heating by the dissipation of electric current sheets. Simple modifications of the force-free solutions are also carried out to demonstrate (1) the formation of a magnetic cusp point in a bipolar magnetic field in equilibrium with an isotropic pressure, and (2) the possibility of a Kuperus-Raadu type prominence embedded in a horizontal, helical magnetic flux rope. Publication: The Astrophysical Journal Pub Date: June 1993 DOI: 10.1086/172710 Bibcode: 1993ApJ...409..798L Keywords: Current Density; Force-Free Magnetic Fields; Solar Corona; Solar Magnetic Field; Solar Physics; Solar Prominences; Current Sheets; Solar Atmosphere; Solar Physics; MAGNETOHYDRODYNAMICS: MHD; SUN: CORONA; SUN: PROMINENCES full text sources ADS |

A new look at an old problem: magnetotelluric modelling of 1-D structures

Some features of 1-D magnetotelluric modelling (1-D/MT) are reviewed from a practical point of view. A well-known feature of 1-D modelling is that deeply buried conductors can always be perfectly fitted with ideally thin sheets of finite conductance. Less well known is that a deeply buried resistor sandwiched by two conductive layers can best be modelled with an insulating layer of minimum thickness. These two observations call to mind Parker's theory according to which the best fit to a 1-D structure is a D+ distribution (i.e. a perfectly insulating half-space containing a finite number of ideally thin sheets, each with a finite conductance). However, a structure with n layers of alternatingly low and high resistivities cannot be fitted satisfactorily by replacing the low-resistivity layers with thin sheets and the high-resistivity ones by insulators, as this would reduce the number of adjustable parameters from an initial 2n - 1 to only n or n - 1 (the positions of thin sheets with their associated conductances). To achieve its good fit Parker's D+ distribution also requires a number of adjustable parameters close to 2n - 1. In other words, it requires about twice as many layers of alternatingly infinite or vanishing resisitivity. But such models do not, in general, bear any relationship to the structures under investigation. This underlines the case in favour of making use of all possible reliable prior information to constrain the family of permissible models. This should steer the 1-D model search away from thin-sheet models toward more realistic structures.

Solar cycle variation of the interplanetary magnetic field spiral

view Abstract Citations (112) References (34) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Solar Cycle Variation of the Interplanetary Magnetic Field Spiral Smith, Charles W. ; Bieber, John W. Abstract Interplanetary measurements spanning the time interval from 1965 through 1987 and a distance range from 0.7 to 15.9 AU are employed to test the Parker (1958) theory for the large-scale structure of the interplanetary magnetic field. Examination of data recorded by earth-orbiting spacecraft reveals that the interplanetary magnetic field spiral depends upon the phase of the solar cycle, such that the annual mean winding angle in the years surrounding solar maximum is about 10 deg larger than in the years surrounding solar minimum. The observed variation of the solar wind speed with the solar cycle is shown to account for much of the recorded variation in the winding angle. It is suggested that nonzero azimuthal field components arising from differential solar rotation may be convected into the corona to provide a steady source of azimuthal magnetic fields at the source point of the solar wind. A straightforward extension of the Parker theory shows how such seed fields would account for the observed discrepancy in the interplanetary spiral winding. Publication: The Astrophysical Journal Pub Date: March 1991 DOI: 10.1086/169830 Bibcode: 1991ApJ...370..435S Keywords: Interplanetary Magnetic Fields; Solar Activity; Solar Cycles; Solar Rotation; Solar Wind Velocity; Coronas; Plasmas (Physics); Solar Physics; INTERPLANETARY MEDIUM; MAGNETIC FIELDS; SUN: ACTIVITY full text sources ADS |

The Elementary Nervous System Revisited

Parker's theory of the origin of the nervous system is discussed along with later interpretations. Attention today has shifted from the cellular to the molecular level, and it has become clear that many of the molecules and mechanisms thought of as typically neuronal have homologs or counterparts in non-nervous cells and unicellular organisms. This applies to signalling chemicals, receptors, second messenger systems and ion channels, and also to the production of electrical events. Parker's view of sponges as a group lacking nerves but possessing independent effectors is still acceptable, but some sponges (and also higher animals) employ non-nervous signalling pathways to coordinate their effectors. Thus, nerves are not always necessary for coordinated behavior. Cnidarians like hydra have seemingly simple, two-dimensional nervous systems with little or no centralization, but even such systems can be surprisingly complex, and the more advanced cnidarians show neurophysiological specializations as sophisticated as those of many higher invertebrates. Examples of ingenious cnidarian solutions to behavioral problems are given. No existing animals have ‘elementary’ nervous systems if that term implies the existence of crude or inefficient functional adaptations

Simulation of geomagnetic polarity reversals by a model of interacting dipole sources

We describe a simple model, derived from Parker's dynamo theory. The field source consists of N interacting point dipoles, characterized by a finite lifetime. A Monte Carlo process gives the temporal evolution of the system. When the number of dipoles is of the order of the elementary cells present in Parker's theory, for a wide range of coupling parameters between the dipoles the thermodynamic fluctuations may generate excursions and polarity reversals, whose morphology and temporal distribution may be compared with those observed for the geomagnetic field.

A brief history of magnetospheric physics before the spaceflight era

This review traces early research on the Earth's magnetic environment, covering the period when only ground‐based observations were possible. Observations of magnetic storms (1724) and of perturbations associated with the aurora (1741) suggested that those phenomena originated outside the Earth; correlation of the solar cycle (1851) with magnetic activity (1852) pointed to the Sun's involvement. The discovery of solar flares (1859) and growing evidence for their association with large storms led Birkeland (1900) to propose solar electron streams as the cause. Though laboratory experiments provided some support, the idea ran into theoretical difficulties and was replaced by Chapman and Ferraro's notion of solar plasma clouds (1930). Magnetic storms were first attributed (1911) to a “ring current” of high‐energy particles circling the Earth, but later work (1957) recognized that low‐energy particles undergoing guiding center drifts could have the same effect. To produce the ring current and aurora, plasma cloud particles required some way of penetrating the “Chapman‐Ferraro cavity”: Alfvén (1939) invoked an electric field, but his ideas met resistance. The picture grew more complicated with observations of comets (1943, 1951) which suggested a fast “solar wind” emanating from the Sun's corona at all times. This flow was explained by Parker's theory (1958), and the permanent cavity which it produced around the Earth was later named the “magnetosphere” (1959). As early as 1905, Birkeland had proposed that the large magnetic perturbations of the polar aurora reflected a “polar” type of magnetic storm whose electric currents descended into the upper atmosphere; that idea, however, was resisted for more than 50 years. By the time of the International Geophysical Year (1957–1958), when the first artificial satellites were launched, most of the important features of the magnetosphere had been glimpsed, but detailed understanding had to wait for in situ observations.

JOINT INTERPRETATION OF GRAVITY AND MAGNETIC DATA OVER AXIAL SYMMETRIC BODIES WITH APPLICATION TO THE DARNLEY BAY ANOMALY, NWT CANADA*

ABSTRACTA method is presented for determining bounds of the properties of axial symmetric bodies from a finite number of gravity and magnetic observations based on Parker's theory of ideal bodies. Bounds on the density contrast and the intensity of magnetization are calculated as a function of depth to the top of the anomalous source, restricting the range of smallest possible solutions to fit the data.The model studied is approximated by an array of vertical annuli cylinders, each of uniform density and magnetization. Linear programming algorithms based on the ideal body theory were used to calculate the distribution of these parameters within the body.Simultaneous inversion of gravity and magnetic data is performed assuming a constant ratio between the density contrast and the intensity of magnetization and that a common body is responsible for both observed fields. The parameter k(|J|/δp) provides information about the rock type of the structure.Interpretation of gravity and aeromagnetic data from Darnley Bay, NWT, Canada, indicated the presence of a shallow ultrabasic intrusion.

Large scale temporal and radial gradients in the IMF: Helios 1, 2, ISEE‐3, and Pioneer 10, 11

Recent investigations using measurements at 1 AU have discovered three types of long term variation in the interplanetary magnetic field: solar minimum decreases, solar maximum enhancements, and small decreases around solar reversal. In this study we have examined the 1972‐1982 Helios 1,2, ISEE‐3, and Pioneer 10,11 observations between 0.3 and 12 AU to further investigate these changes. It was found that all three IMF solar cycle effects are also present in the Helios and Pioneer measurements, confirming that these variations occur throughout the low latitude heliosphere. In addition, the comparison of measurements by identical magnetometers on ISEE‐3, Pioneer 10, and Pioneer 11 has revealed a more rapid decrease in IMF intensity than predicted by classical Parker theory. Causes and ramifications of both the long term variations and steeper than expected radial gradients in the interplanetary magnetic field are discussed.

The behaviour of the cosmic-ray equatorial anisotropy inside fast solar-wind streams ejected by coronal holes

The cosmic-ray equatorial anisotropy inside broad high-speed solar-wind streams ejected by coronal holes,i.e. in quasi-stationary condition, is analysed over the years 1973–1974. From the beginning to the end of the stream the amplitudes of the first and second harmonics of the anisotropy are found to decrease remarkably by factors 2.5 and 2.0, respectively, while the phases do not show systematic variations. The development of the stream structure in the interplanetary space together with the Parker theory on the diurnal anisotropy in stationary condition give a plausible explaination for the large variation observed in the first harmonic of the anisotropy. The behaviour of the second harmonic is tentatively interpreted in the light of current theories.

The behaviour of the cosmic-ray equatorial anisotropy inside fast solar-wind streams ejected by coronal holes

The cosmic-ray equatorial anisotropy inside broad high-speed solar-wind streams ejected by coronal holes,i.e. in quasi-stationary condition, is analysed over the years 1973–1974. From the beginning to the end of the stream the amplitudes of the first and second harmonics of the anisotropy are found to decrease remarkably by factors 2.5 and 2.0, respectively, while the phases do not show systematic variations. The development of the stream structure in the interplanetary space together with the Parker theory on the diurnal anisotropy in stationary condition give a plausible explaination for the large variation observed in the first harmonic of the anisotropy. The behaviour of the second harmonic is tentatively interpreted in the light of current theories.

Intraspecific shell exchange in the hermit crab Clibanarius virescens (Krauss)

Intraspecific shell exchange in the hermit crab Clibanarius virescens (Krauss) was studied by field and laboratory experiments. Shell exchange frequencies were determined in potentially competitive (only one individual of a pair would benefit from an exchange) and potentially mutualistic (both members benefit) situations. The frequency of competitive exchanges in laboratory experiments, which paired individuals occupying very poor quality shells and individuals occupying the shells in which they were collected, was very low (2%). Higher exchange frequencies were observed between individuals in poor quality shells and individuals in shells of their preferred size. Shell exchange frequencies were highest in mutualistic situations and situations in which all individuals occupied poor quality shells. Crabs which had been evicted from their shells by the experimenter prior to selecting new shells were evicted from the new shells in subsequent shell fight experiments significantly more often than crabs which had not been evicted. Field experiments resulted in exchange frequencies similar to those observed in the laboratory. The relevance of the present experiments to Maynard Smith and Parker's theory of asymmetric contests is discussed.

Temperature and impurity dependence of the vibrational collision number for O2−H2, O2−He, and O2−CO2 systems between 300°–675°K

The oxygen vibrational collision number for three binary systems (O2−H2, O2−He, and O2−CO2) has been measured between 300°–675°K at low impurity concentration using an acoustic resonant technique. For the pure oxygen case extrapolated from the O2−He system, for instance, the experimental vibrational collision numbers follow closely the curve derived from the Parker's theory [J. G. Parker, J. Chem. Phys. 34, 1763 (1961)] and high temperature (> 1700°K) shock tube data [R. G. Millikan and D. R. White, J. Chem. Phys. 39, 3209 (1963)]. However, our experimental data disagree strongly with the shock tube data trend below 1700°K. The experimental vibrational collision numbers for the binary systems have been found in good agreement with Parker's theoretical prediction. A new data analysis technique has been developed to sort out the ever-elusive background loss in the resonant chamber resulting in a more reliable number for the molecular absorption at low impurity concentrations. [Work supported by NASA under Contract Number NAS7-100.]

The large‐scale structure of the interplanetary magnetic field between 1 and 0.3 AU during the primary mission of Helios 1

The macroscale and mesoscale structure of the interplanetary magnetic field during the primary mission of Helios 1 is discussed. The radial field component behaves essentially in agreement with Parker's theory. The transverse component shows a larger variability than the radial component; its radial variation is in good agreement with Parker's theory for high speeds, but some deviation is found for low speeds. The radial variation of the field variance is also studied. Its dependence upon the heliocentric distance r is expressed by the law r−3, which is necessary but not sufficient for Alfvén waves. The available data do not allow a unique interpretation of the r−3 dependence. No big differences are observed between low (≤500 km/s) and high (≥600 km/s) solar wind velocity regimes.

The emission-line spectrum of a sunspot in the far-ultraviolet

The emission-line spectrum between 1200 and 1817 A from a sunspot in McMath region 12510 near the solar center is discussed. The spectrum was obtained by the normal-incidence spectrograph on Skylab. The principal results are: (1) the widths of emission lines originating in the chromosphere and lower transition region over the sunspot are much narrower than those previously reported for a polar coronal hole observed above the limb and a quiet chromospheric network observed near the solar center, indicating that the mass motions in the sunspot are less than in these other regions; (2) the sunspot spectrum, aside from the narrow widths of emission lines, is similar to spectra from the chromospheric network boundary. The intensities of lines in the sunspot are much enhanced relative to the network interior. From the full-width at half-maximum of the 1207-A Si III line, an optical depth at line center of 3.6 is deduced. Comparison with Parker's (1974) theory of sunspots shows that, if the enhancement of emission lines is due to enhanced transport of hydromagnetic waves generated in the sunspot convective zone, the mode of the waves is predominately Alfvenic.

On the radial variation of the interplanetary magnetic field: Pioneer 6

Analysis of simultaneous plasma and magnetic field observations by Pioneer 6 suggests, at heliocentric distances of 0.8 to 1.0 AU, significant deviations from Parker's theory: in particular, a radial variation as r−2 is estimated for the azimuthal magnetic field component.