• Login
    View Item 
    •   Home
    • University of Alaska Fairbanks
    • UAF Graduate School
    • Physics
    • View Item
    •   Home
    • University of Alaska Fairbanks
    • UAF Graduate School
    • Physics
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of Scholarworks@UACommunitiesPublication DateAuthorsTitlesSubjectsTypeThis CollectionPublication DateAuthorsTitlesSubjectsType

    My Account

    Login

    First Time Submitters, Register Here

    Register

    Statistics

    Display statistics

    A theory of field-aligned current generation from the plasma sheet and the poleward expansion of aurora substorms

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    Yamauchi_M_1990.pdf
    Size:
    3.613Mb
    Format:
    PDF
    Download
    Author
    Yamauchi, Masatoshi
    Chair
    Akasofu, Syun-Ichi
    Keyword
    Geophysics
    Plasma physics
    Metadata
    Show full item record
    URI
    http://hdl.handle.net/11122/9358
    Abstract
    This dissertation reports a study of the generation of field-aligned currents in the plasma sheet in terms of magnetosphere-ionosphere coupling. For the study, the plasma sheet and the ionosphere are treated as two-dimensional layers by height integration. In the magnetosphere between them, the Alfven wave transition time through this region is assumed to be zero. The ionospheric momentum is allowed to be transferred to the plasma sheet. Both linear analyses and numerical simulation are performed to study the field-aligned current generation. In the linear analysis, evolution from initial perturbations is studied. Zero order configurations are steady state without field-aligned currents. The field-aligned currents are treated as a perturbed quantity and linearly related with the other perturbed quantities. One result for the linear waves is that the magnetohydrodynamics (MHD) fast mode and Alfven mode are coupled through the ionospheric Hall current. The Hall current causes the dawn-dusk asymmetry: a westward-travelling wave is amplified on the region 1 current system, while an eastward-travelling wave is amplified elsewhere. The expansion phase of the magnetospheric substorm after the onset is numerically simulated on the near-earth plasma sheet. The inner edge of the plasma sheet is taken as the outflow boundary. As the initial condition, an enhanced earthward magnetospheric convection is assumed to cause a finite pressure increase at the inner edge of the plasma sheet. The numerical results are as follows. An MHD fast-mode wave is generated. It propagates tailward accompanied by the field-aligned currents. The wave propagation and the field-aligned currents account for the poleward expansion of the aurora and the region 1 field-aligned current during the expansion phase of the substorm. The region 1 field-aligned currents are linked with the dusk to dawn current on this wave, which is driven by the dynamo mechanism of the wave. The ionospheric Hall current causes asymmetry of the wave, and hence, of the field-aligned current distribution. This asymmetry accounts for the stronger field-aligned current in the premidnight sector.
    Description
    Dissertation (Ph.D.) University of Alaska Fairbanks, 1990
    Date
    1990
    Type
    Dissertation
    Collections
    Physics

    entitlement

     
    ABOUT US|HELP|BROWSE|ADVANCED SEARCH

    The University of Alaska is an affirmative action/equal opportunity employer, educational institution and provider and prohibits illegal discrimination against any individual.

    Learn more about UA’s notice of nondiscrimination.

    Open Repository is a service operated by 
    Atmire NV
     

    Export search results

    The export option will allow you to export the current search results of the entered query to a file. Different formats are available for download. To export the items, click on the button corresponding with the preferred download format.

    By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.

    To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export. The amount of items that can be exported at once is similarly restricted as the full export.

    After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.