DOCSLIB.ORG

The Current State of Ionospheric Wind Dynamo Theory Is Reviewed

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Current State of Ionospheric Wind Dynamo Theory Is Reviewed J. Geomag. Geoelectr., 31, 287-310, 1979 Ionospheric Wind Dynamo Theory: A Review A. D. RICHMOND SpaceEnvironment Laboratory, National Oceanic and Atmospheric Administration,Boulder, Colorado 80302, U. S. A. (Accepted June 10, 1978) The current state of ionospheric wind dynamo theory is reviewed. Observation- al and theoreticaladvances in recent yearshave permitted more accurate models of the dynamo mechanismto be presentedthan previously,which have lent further credenceto the validity of dynamo theory as the main explanation for quiet-day ionosphericelectric fields and currents at middle and low latitudes. The diurnal component of the wind in the upper E region and lower F region appears to be primarily responsiblefor averagequiet-day currents, although other wind compo- nents give significantcontributions. Observationally,there is a need for better spatial and temporal coverage of wind and electric field data. Theoretically, there is a need for further considerationof the mutual dynamiccoupling among winds, conductivities,electric fields, and electric currents, and for better modeling of nighttimeconditions. 1. Introduction This paper is intended to review the present state of knowledge concerning the theory of the ionospheric wind dynamo. The main emphasis is on current theoreti- cal conceptions, with historical aspects, observational evidence, and treatments of temporal and spatial variability covered more briefly. For further information on dynamo theory and ionospheric currents, previous reviews (K. MAEDA and KATO, 1966; MATSUSHITA, 1967, 1968, 1971a, 1973, 1975, 1977; H. MAEDA, 1968; PRICE, 1969a, b; WAGNER, 1971; AKASOFU and CHAPMAN, 1972; MATSUSHITA and MOZER, 1973; VOLLAND, 1974a; FATKULLIN, 1975; KANE, 1976) will be found useful. 2. Formulation of Dynamo Theory The basic features of ionospheric wind dynamo theory can be formulated as follows. Atmospheric winds at ionospheric heights, by moving the electrically con- ducting fluid through the earth's magnetic field, generate electromotive forces which result in electric current flow, buildup of polarization charges, and electrostatic fields. At middle and low geomagnetic latitudes (below 60) the dynamo mechanism is believed to be the primary source of ionospheric currents and electric fields, as well as ground-level magnetic variations, on geomagnetically quiet days. Although other mechanisms for causing quiet-day ionospheric electric currents and fields have been advanced (e. g., MATSUSHITA, 1971a, b, 1972; GLUSHAKOV and SAMOKHIN, 287 288 A. D. RICHMOND 1974, 1975; LYATSKIY and MAL'TSEV, 1975), the dominant importance of the iono- spheric dynamo mechanism now appears to have been well established. Because the theory links winds, conductivities, electric currents, and electric fields in the iono- sphere, none of whose distributions in space and time is completely known, it can be a useful tool to synthesize and extend the available information on these quantities. The central equation relating the winds, electric fields, and electric currents is a form of Ohm's Law: J=oEii+a1(El+vxB)+albX(E1+vXB) (1) where J is the current density; E11 and El are the components of the electric field parallel and perpendicular to the geomagnetic field B; v is the wind velocity; b is a unit vector in the direction of B; a is the conductivity parallel to B; a1 is the Pedersen conductivity; and a2 is the Hall conductivity. For time scales longer than a minute or so, the electric field can be assumed to be electrostatic, E=-7φ (2) where is the electrostatic potential. Throughout the ionosphere and plasmasphere, the parallel conductivity 6o is usually so large that the parallel electric field E11is almost completely shorted out. Thus it is reasonable to assume in dynamo theory that magnetic field lines are equipotentials along their entire length between conju- gate points, and that electric fields can be mapped between the ionosphere and mag- netosphere (FARLEY, 1960; SPREITER and BRIGGS, 1961; DOUGHERTY, 1963; H. MAEDA, 1964, 1966a, b, 1971, 1974; DEWITT and AKASOFU, 1964; HINES, 1964; K. MAEDA, 1964; REID, 1965; VAN SABBEN, 1966, 1969, 1970; STENING, 1968, 1973; MATSUSHITA and TARPLEY, 1970; MATSUSHITA, 197lb; GUREVICH et al., 1972, 1974; KRYLOV and SHCHERBAKOV, 1972; KRYLOV et al., 1973; SCHIELDGE et al., 1973; RICHMOND, 1973a; KRYLOV, 1973; JONES, 1974; GAGNEPAIN etal., 1976; ANANDARAO et al., 1977; MOHLMANN, 1977). Experimental evidence supporting this assumption has been found by PETERSON et al. (1977). Because of this fact, it is often convenient to use dipole coordinates in performing dynamo calculations (STENING, 1968; HEELIS et al., 1974; MATUURA, 1974b; MOHLMANN, 1974b). If the conductivity and wind distributions are specified, it is a straightforward matter to calculate the electric field and current. In addition to (1) and (2), the following equation is required, expressing the fact that the current is divergenceless: ∇J=0. (3) It is also necessary to specify a high-latitude boundary condition on E or J, taking into account the effects of current flow between the magnetosphere and ionosphere due to solar wind-magnetosphere interactions which do not obey (1). The appro- priate specification of this boundary condition is beyond the scope of this paper, and in fact has generally been circumvented in dynamo calculations by ignoring the current flow between the ionosphere and magnetosphere at high latitudes. Observationally, our present knowledge of ionospheric winds, conductivities, electric fields, and currents is far from complete (WAGNER, 1971), so that the speci- Ionospheric Wind Dynamo Theory: A Review 284 fication of certain of these in order to compute the others from dynamo theory is subject to considerable uncertainty. Therefore, it is useful to invoke additional theoretical constraints, such as the facts that the winds must obey hydrodynamic equations and that the electron and ion densities must obey continuity equations including production and loss. As described by MATUURA (1968), KOHL (1969), MOHLMANN (1974c), ANDERSON and ROBLE (1974), VOLLAND (1976b), and KATO (1976), these additional equations are mutually coupled with each other and with the dynamo Eqs. (1)-(3). When the characteristic electron lifetime is longer than several minutes, as in the F region and the nighttime E region, the ionospheric plasma upon which the conductivity depends is subject to significant redistribution due to winds and electric fields (e. g., COLE, 1969; EVANS, 1972, 1975; RISHBETH, 1972; FUJITAKA and TOHMATSU, 1973; MURATA, 1974a; MATUURA, 1974a; KOHL, 1976). The plasma tends to assume the same component of velocity parallel to the magnetic field as the neutral wind, and perpendicular to the magnetic field as the convection velocity uE, defined as ue=k×D.ng (4) When the electron density is comparable to or greater than 1011rn-3, as in the F region and the daytime E region, the neutral wind can be significantly influenced by the Ampere acceleration due to electric currents, given by J×b=-σ1b4(Vl-uE)-σ2b4b×(v-uE) (5) (PIDDINGTON, 1954), where p is the mass density of the air. The first term on the right-hand side of (5) is usually the more important term, and acts as a drag on the wind, tending to bring the wind motion into conformance with the electric field con- vection velocity uE (e.g., BAKER and MARTYN, 1953; DOUGHERTY, 1961; AKASOFU and DEWITT, 1965; K. MAEDA and KATO, 1966; RISHBETH, 1971a, b, c, 1972; HEELIS et al., 1974; VOLLAND, 1976a). A completely self-consistent treatment of dynamo theory should in principle take these mutual coupling effects into account. 3. Present Knowledge of Parameters Used in Dynamo Theory Before discussing the results of dynamo calculations, in the next section, it will be useful to summarize the state of our knowledge about conductivities, currents, electric fields, and winds in the ionosphere. 3.1 Conductivities The daytime distributions of the conductivities ao, a1, and a2are reasonably well known. The transverse conductivities a1 and a2 are important primarily below 200 km, where the electron and ion densities behave in a fairly regular manner (e.g., DAVIES, 1965; RAWER and SUCHY, 1967; CHING and CHIU, 1973, 1974; NARCISI, 1974; OLIVER, 1975; KOREN'KOV et al., 1975; MIRTOV and STARKOVA, 1976; TORR 290 A. D. RICHMOND Fig. 1. Electron density N0, and parallel, Pedersen, and Hall conduc- tivities oo, o1, and 62, for an overhead sun of moderate activity, with a magnetic field strength Bo of 2.93 x 10-5T. From RICHMOND (1973a). PEDERSEN CONDUCTIVITY APRIL 17-18, 1974 TIME (AST) Fig. 2. Pedersen conductivity over Arecibo for the night of 17-18 April 1974. Note change in altitude scale at 165km. From HARPER and WALKER (1977). Ionospheric Wind Dynamo Theory: A Review 291 and HARPER,1977) and are governed mainly by a simple balance between produc- tion and loss. The conductivities are calculated from given electron and ion densi- ties, neutral densities (e. g., CIRA 1972; MOE, 1973; U. S. Standard Atmosphere, 1976; HEDIN et al., 1977a, b), and experimental or theoretical effective electron- neutral and ion-neutral collision frequencies (e. g., MASON, 1970; ITIKAWA, 1971; HILL and BOWHILL, 1977), using standard formulas (e. g., BAUER, 1973). Figure 1 shows typical noontime low-latitude profiles of the conductivities. Nighttime conductivities are far less well understood, because the E-region electron densities are somewhat difficult to measure and are found to be highly variable (e. g., WAKAI, 1971; KNIGHT, 1972; ROWE, 1973, 1974a, b; RoWE and MATHEWS,
Load more

Recommended publications
  • Planetary Wave Signatures in the Equatorial Atmosphere–Ionosphere System, and Mesosphere- E- and F-Region Coupling
    ARTICLE IN PRESS Journal of Atmospheric and Solar-Terrestrial Physics 68 (2006) 509–522 www.elsevier.com/locate/jastp Planetary wave signatures in the equatorial atmosphere–ionosphere system, and mesosphere- E- and F-region coupling M.A. Abdua,Ã, T.K. Ramkumarb, I.S. Batistaa, C.G.M. Bruma, H. Takahashia, B.W. Reinischc, J.H.A. Sobrala aNational Institute for Space Research—INPE, Sao Jose dos Campos, 12245-970 SP, Brazil bNational MST Radar Facility, Gadanki, India cUniversity of Massachusetts, Lowell, USA Available online 8 November 2005 Abstract Upward transport of wave energy and momentum due to gravity, tidal and planetary waves from below and extra- tropics controls the phenomenology of the equatorial atmosphere–ionosphere system. An important aspect of this phenomenology is the development of small- and large-scale structures including thin layers in the mesosphere and E- region, and the formation of wide spectrum plasma structures of the equatorial F-region, widely known as equatorial spread F/plasma bubble irregularities (that are known to have significant impact on space application systems based on trans-ionospheric radio waves propagation). It seems that the effects of tidal and gravity waves at mesospheric and thermospheric heights and their control of ionospheric densities, electric fields and currents are relatively better known than are the effects originating from vertical coupling due to planetary waves. Results from airglow, radar and ionospheric sounding observations demonstrate the existence of significant planetary wave influence on plasma parameters at E- and F- region heights over equatorial latitudes. We present and discuss here some results showing planetary wave oscillations in concurrent mesospheric winds and equatorial electrojet intensity variations in the Indian sector as well as in the mesospheric airglow and F-layer height variation in Brazil.
    [Show full text]
  • Equatorial Ionospheric Response to Different Estimated Disturbed
    PUBLICATIONS Journal of Geophysical Research: Space Physics RESEARCH ARTICLE Equatorial Ionospheric Response to Different Estimated 10.1002/2017JA024265 Disturbed Electric Fields as Investigated Using Sheffield Key Points: University Plasmasphere Ionosphere Model at INPE • The equatorial ionosphere response to different disturbed electric fields is M. A. Bravo1,2 , I. S. Batista1 , J. R. Souza1, and A. J. Foppiano3 analyzed using the SUPIM-INPE model • fi We want to nd the best alternative of 1Instituto Nacional de Pesquisas Espaciais, São José dos Campos, São Paulo, Brazil, 2Now at Universidad de Santiago de fi disturbed electric eld, both 3 temporally and spatially, when E × B Chile, Estación Central, Santiago, Chile, Universidad de Concepción, Concepción, Chile measurements are not available • The comparison between simulations and observations will serve to find a Abstract Good ionospheric modeling is important to understand anomalous effects, mainly during hierarchy among the different types of geomagnetic storm events. Ionospheric electric fields, thermospheric winds, and neutral composition are drifts affected at different degrees, depending on the intensity of the magnetic disturbance which, in turns, affects the electron density distribution at all latitudes. The most important disturbed parameter for the equatorial Supporting Information: ionosphere is the electric field, which is responsible for the equatorial ionization anomaly. Here various • Supporting Information S1 electric field measurements and models are analyzed: (1) measured by the Jicamarca incoherent scatter radar Correspondence to: (ISR), (2) from Jicamarca Unattended Long-Term studies of the Ionosphere and Atmosphere (JULIA) radar, 0 M. A. Bravo, (3) deduced from magnetometers, (4) calculated from the time variations of the F layer height (dh F/dt), [email protected] and (5) deduced from interplanetary electric field determinations.
    [Show full text]
  • Dynamo Theory 1 Dynamo Theory
    Dynamo theory 1 Dynamo theory In geophysics, dynamo theory proposes a mechanism by which a celestial body such as the Earth or a star generates a magnetic field. The theory describes the process through which a rotating, convecting, and electrically conducting fluid can maintain a magnetic field over astronomical time scales. History of theory When William Gilbert published de Magnete in 1600, he concluded that the Earth is magnetic and proposed the first theory for the origin of this magnetism: permanent magnetism such as that found in lodestone. In 1919, Joseph Larmor proposed that a dynamo might be generating the field.[1] [2] However, even after he advanced his theory, some prominent scientists advanced alternate theories. Einstein, believed that there might be an asymmetry between the charges of the electron and proton so that the Earth's magnetic field would be produced by the entire Earth. The Nobel Prize winner Patrick Blackett did a series of experiments looking for a fundamental relation between angular momentum and magnetic moment, but found none.[3] [4] Walter M. Elsasser, considered a "father" of the presently accepted dynamo theory as an explanation of the Earth's magnetism, proposed that this magnetic field resulted from electric currents induced in the fluid outer core of the Earth. He revealed the history of the Earth's magnetic field through pioneering the study of the magnetic orientation of minerals in rocks. In order to maintain the magnetic field against ohmic decay (which would occur for the dipole field in 20,000 years) the outer core must be convecting.
    [Show full text]
  • Dynamo Theory and GFD
    Dynamo theory and GFD Steve Childress 16 June 2008 1 Origins of the dynamo theory Dynamo theory studies a conducting fluid moving in a magnetic field; the motion of the body through the field acts to generate new magnetic field, and the system is called a dynamo if the magnetic field so produced is self-sustaining. 1.1 Early ideas point the way In the distant past, there was the idea that the earth was a permanent magnet. In the 1830s Gauss analyzed the structure of the Earth's magnetic field using potential theory, decomposing the field into harmonics. The strength of the dominant field was later found to change with time. In 1919 Sir Joseph Larmor drew on the induction of currents in a moving conductor, to suggest that sunspots are maintained by magnetic dynamo action. P. M. Blackett proposed that magnetic fields should be produced by the rotation of fluid bodies. The `current consensus' is that the Earth's magnetic field is the result of a regenerating dynamo action in the fluid core. The mechanism of generation of the field is closely linked dynamically with the rotation of the Earth. Similar ideas are believed to apply to the solar magnetic field, to other planetary fields, and perhaps to the magnetic field permeating the cosmos. 1.2 Properties of the Earth and its Magnetic Field The magnetic field observed at the Earth's surface changes polarity irregularly. The non- dipole components of the surface field also vary with time over many time scales greater than decades, and have a persistent drift to the west.
    [Show full text]
  • Lecture 2: Dynamo Theory
    Lecture 2: Dynamo theory Celine´ Guervilly School of Mathematics, Statistics and Physics, Newcastle University, UK Basis of electromagnetism: Maxwell’s equations Faraday’s law of induction: if a magnetic field B varies with time then an electric field E is produced. @B r × E = - @t Ampere’s` law (velocity speed of light) r × B = µ0j where j is the current density and µ0 is the vacuum magnetic permeability. Gauss’s law (electric monopoles from which electric field originates) ρ r · E = 0 with ρ the charge density and 0 the dielectric constant. No magnetic monopole (no particle from which magnetic field lines radiate) r · B = 0 Ohm’s law Relates current density j to electric field E. In a material at rest, we assume the simple form j = σE with σ the electrical conductivity. In the reference frame moving with the fluid, the electric, magnetic fields and current become E0 = E + u × B, B0 = B, j0 = j In the original reference, Ohm’s law is j = σ(E + u × B) A conducting wire is wound around the disc and joins the rim and the axis: electric current flows in the wire and across the disc. Winding is such that the induced magnetic field B reinforces the applied magnetic field B0. Dynamo: conversion of kinetic energy into magnetic energy. If the disc rotation rate exceeds a critical value, B0 can be switched off and the dynamo will continue to operate: the dynamo has become self-excited. Homopolar disc dynamo A solid electrically conducting disk rotates about an axis. Uniform magnetic field B0 aligned with the rotation axis.
    [Show full text]
  • Ye= Pfl,'3(Cos 0) [Cos M#O, Sin M,]
    Proc. Nat. A cad. Sci. USA Vol. 68, No. 6, pp. 1111-1113, June 1971 The Magnetic Field Induced by the Bodily Tide in the Core of the Earth (dynamo theory/coupling coefficient) C. L. PEKERIS Department of Applied Mathematics, The Weizmann Institute, Rehovot, Israel Corninunicated March 15, 1971 ABSTRACT The motion in the liquid core of the earth The coupling term V X H in (1) generates combination due to the bodily tide can induce a periodic magnetic field having the frequency a of the tide as well as multiple fre- frequencies, including a steady term of zero frequency. quencies, including a steady term. The coupling coefficient The periodic components of H will not be observed at for the steady term between the convectively inducing the surface of the earth because of damping of the field and induced fields is estimated to be of the order of crH2/X, where H denotes the height of the equilibrium tide, and by conduction in passing through the mantle [3]. The only X = 1/4K7rK, K denoting the electrical conductivity of the component of the magnetic field induced by the bodily core. With a = 1.4 X 10-4 sec-', H = 20 cm, and K = 3 X tide that would be observed at the surface is the one of 10-6 emu, the coupling coefficient comes out only of the order of 10-6, as against unity in the case of the dynamo zero frequency. In the homogeneous dynamo theory theory. [3 ], the steady field is visualized to be maintained through the convection by a process of bootstrapping.
    [Show full text]
  • ESA Space Weather STUDY Alcatel Consortium
    ESA Space Weather STUDY Alcatel Consortium SPACE Weather Parameters WP 2100 Version V2.2 1 Aout 2001 C. Lathuillere, J. Lilensten, M. Menvielle With the contributions of T. Amari, A. Aylward, D. Boscher, P. Cargill and S.M. Radicella 1 2 1 INTRODUCTION........................................................................................................................................ 5 2 THE MODELS............................................................................................................................................. 6 2.1 THE SUN 6 2.1.1 Reconstruction and study of the active region static structures 7 2.1.2 Evolution of the magnetic configurations 9 2.2 THE INTERPLANETARY MEDIUM 11 2.3 THE MAGNETOSPHERE 13 2.3.1 Global magnetosphere modelling 14 2.3.2 Specific models 16 2.4 THE IONOSPHERE-THERMOSPHERE SYSTEM 20 2.4.1 Empirical and semi-empirical Models 21 2.4.2 Physics-based models 23 2.4.3 Ionospheric profilers 23 2.4.4 Convection electric field and auroral precipitation models 25 2.4.5 EUV/UV models for aeronomy 26 2.5 METEOROIDS AND SPACE DEBRIS 27 2.5.1 Space debris models 27 2.5.2 Meteoroids models 29 3 THE PARAMETERS ................................................................................................................................ 31 3.1 THE SUN 35 3.2 THE INTERPLANETARY MEDIUM 35 3.3 THE MAGNETOSPHERE 35 3.3.1 The radiation belts 36 3.4 THE IONOSPHERE-THERMOSPHERE SYSTEM 36 4 THE OBSERVATIONS ...........................................................................................................................
    [Show full text]
  • Daytime Dynamo Electrodynamics with Spiral Currents Driven by Strong Winds Revealed by Vapor Trails and Sounding Rocket Probes
    UCLA UCLA Previously Published Works Title Daytime Dynamo Electrodynamics With Spiral Currents Driven by Strong Winds Revealed by Vapor Trails and Sounding Rocket Probes. Permalink https://escholarship.org/uc/item/2386m69r Journal Geophysical research letters, 47(15) ISSN 0094-8276 Authors Pfaff, R Larsen, M Abe, T et al. Publication Date 2020-08-03 DOI 10.1029/2020gl088803 Peer reviewed eScholarship.org Powered by the California Digital Library University of California RESEARCH LETTER Daytime Dynamo Electrodynamics With Spiral Currents 10.1029/2020GL088803 Driven by Strong Winds Revealed by Vapor Trails and Key Points: • Comprehensive observations of the Sounding Rocket Probes daytime Sq dynamo electrodynamics R. Pfaff1 , M. Larsen2 , T. Abe3 , H. Habu3, J. Clemmons4 , H. Freudenreich1, D. Rowland1, have been gathered for the first time 5,6 7 8 8 9 • Observed daytime winds in the T. Bullett ,M.‐Y. Yamamoto , S. Watanabe , Y. Kakinami , T. Yokoyama , dynamo region are much larger than J. Mabie5,6 , J. Klenzing1 , R. Bishop10, R. Walterscheid10 , M. Yamamoto9 , expected yet their currents are Y. Yamazaki11 , N. Murphy12, and V. Angelopoulos13 reduced by those of DC electric fields • Winds and currents exhibit an 1NASA Goddard Space Flight Center, Greenbelt, MD, USA, 2Department of Physics and Astronomy, Clemson University, interleaved spiral pattern indicative 3 4 of tidal forcing Clemson, SC, USA, Japan Aerospace Exploration Agency, Tokyo, Japan, Department of Physics and Astronomy, University of New Hampshire, Durham, NH, USA, 5Cooperative
    [Show full text]
  • Locations of Chorus Emissions Observed by the Polar Plasma Wave Instrument K
    JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 115, A00F12, doi:10.1029/2009JA014579, 2010 Click Here for Full Article Locations of chorus emissions observed by the Polar Plasma Wave Instrument K. Sigsbee,1 J. D. Menietti,1 O. Santolík,2,3 and J. S. Pickett1 Received 18 June 2009; revised 20 November 2009; accepted 17 December 2009; published 8 June 2010. [1] We performed a statistical study of the locations of chorus emissions observed by the Polar spacecraft’s Plasma Wave Instrument (PWI) from March 1996 to September 1997, near the minimum of solar cycles 22/23. We examined how the occurrence of chorus emissions in the Polar PWI data set depends upon magnetic local time, magnetic latitude, L shell, and L*. The Polar PWI observed chorus most often over a range of magnetic local times extending from about 2100 MLT around to the dawn flank and into the dayside magnetosphere near 1500 MLT. Chorus was least likely to be observed near the dusk flank. On the dayside, near noon, the region in which Polar observed chorus extended to larger radial distances and higher latitudes than at other local times. Away from noon, the regions in which chorus occurred were more restricted in both radial and latitudinal extent. We found that for high‐latitude chorus near local noon, L* provides a more reasonable mapping to the equatorial plane than the standard L shell. Chorus was observed slightly more often when the magnitude of the solar wind magnetic field BSW was greater than 5 nT than it was for smaller interplanetary magnetic field strengths.
    [Show full text]
  • The Near-Earth Plasma Environment
    Space Sci Rev (2012) 168:23–112 DOI 10.1007/s11214-012-9872-6 The Near-Earth Plasma Environment Robert F. Pfaff Jr. Received: 1 March 2012 / Accepted: 3 March 2012 / Published online: 20 June 2012 © US Government 2012 Abstract An overview of the plasma environment near the earth is provided. We describe how the near-earth plasma is formed, including photo-ionization from solar photons and impact ionization at high latitudes from energetic particles. We review the fundamental characteristics of the earth’s plasma environment, with emphasis on the ionosphere and its interactions with the extended neutral atmosphere. Important processes that control iono- spheric physics at low, middle, and high latitudes are discussed. The general dynamics and morphology of the ionized gas at mid- and low-latitudes are described including electro- dynamic contributions from wind-driven dynamos, tides, and planetary-scale waves. The unique properties of the near-earth plasma and its associated currents at high latitudes are shown to depend on precipitating auroral charged particles and strong electric fields which map earthward from the magnetosphere. The upper atmosphere is shown to have profound effects on the transfer of energy and momentum between the high-latitude plasma and the neutral constituents. The article concludes with a discussion of how the near-earth plasma responds to magnetic storms associated with solar disturbances. Keywords Ionosphere · Upper atmosphere · Electric fields 1 Introduction In this article we discuss the near-earth plasma environment, for which the ionosphere is the natural focus. Because this ionized gas co-exists with the neutral atmospheric gas to which it is coupled, the ionized/neutral gas system is more properly considered a partially ionized gas rather than a medium consisting of two distinct, independent fluids.
    [Show full text]
  • By EDWARD HAROLD BLISH B.S., Syracuse University (1963)
    AN ANALYSIS OF IQSY METEOR WIND AND GEOMAGNETIC FIELD DATA by EDWARD HAROLD BLISH B.S., Syracuse University (1963) SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE OF MASTER OF SCIENCE at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY September 29, 1969 Teo I ) Signature of Author ( Department of Meteorology, 29 September 1969 Certified by 4 Thesis Supervisor 1i 4 Accepted by Departmental Committee on Graduate Students ftWN AN ANALYSIS OF IQSY METEOR WIND AND GEOMAGNETIC FIELD DATA by Edward Harold Blish Submitted to the Department of Meteorology on 29 September 1969 in partial fulfillment of the requirement for the degree of Master of Science ABSTRACT Meteor wind observations at Sheffield, U.K. for forty weekly twenty-four hour periods during the IQSY were harmoni- cally analyzed for their prevailing, solar tidal, and short- period components. Corresponding magnetic field measurements at Hartland, U.K. were similarly analyzed for their harmonic components. The results were compared to other published values and to those of tidal and dynamo theory. Significant linear correlations between the amplitudes and phase angles of the meteor wind and magnetic field harmonic components demonstrate the existence of systematic relationships between the magnetic field and ionospheric wind variations as predicted by the dynamo theory. Significant correlations re- producable by a simple dynamo mechanism were also found between the magnetic activity indices, the magnetic field, and the pre- vailing ionospheric wind components. Ionospheric current densities and electric fields were esti- mated using the overhead Sq approximation, a simplified conduc- tivity model, and the horizontal current-layer dynamo theory equations. The ionospheric dynamo electric field alone was found to be too small to account for the observed quiet-day magnetic field variations inferring that an additional ionos- pheric electric field of possible magnetospheric origin is probably the primary driving force for the ionospheric currents.
    [Show full text]
  • Dynamo Theory Then and Now
    PERGAMON International Journal of Engineering Science 36 (1998) 1325±1338 Dynamo theory then and now Gary A. Glatzmaier a, Paul H. Roberts b aLos Alamos National Laboratory, Los Alamos, NM 87545, U.S.A. bUniversity of California, Los Angeles, CA 90095, U.S.A. Abstract A brief history of dynamo theory is presented, from its earliest beginnings, through the development of successful kinematic models (those in which only the electrodynamic equations are solved), up to the present time when fully magnetohydrodynamic simulations have successfully reproduced the main features of the Earth's magnetic ®eld. A particular focus of this paper is the role of the solid inner core of the Earth on the dynamics of its ¯uid core. Some new results are presented concerning the age and topography of the inner core. # 1998 Elsevier Science Ltd. All rights reserved. 1. The kinematic geodynamo Although it has been known for many centuries that the Earth is magnetic [1±3], the reason for this, and for many puzzling features of the Earth's magnetic ®eld, have been convincingly explained only during the present century. The key was the discovery in 1906 that the Earth possesses a ¯uid core [4]. To be sure, the curious time scales of the ®eld, long compared with those of the atmosphere and oceans, but short compared with geological processes, had suggested to people like Halley [5] and Hansteen [6] that ¯uid motions within the Earth must somehow be involved, but nothing was certain until 1906. The density of the ¯uid core, deduced from seismological observations, ranges from 9904 kg m3 at the top to 12166 kg m3 at the bottom [7].
    [Show full text]