Impulse-excited hydromagnetic cavity and field-line resonances in the magnetosphere |
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| Institution: | 1. Physics and Engineering Laboratory, DSIR, Lower Hutt, New Zealand;2. Division of Information Technology, DSIR, Lower Hutt, New Zealand;1. Royal Meteorological Institute (RMI), Ringlaan 3, Brussels B-1180, Belgium;2. Observatori de l''Ebre (OE), Univ. Ramon Llull – CSIC, Horta Alta 38, 43520 Roquetes, Spain;3. Leibniz-Institute of Atmospheric Physics at the University Rostock, Schlossstr. 6, Kuehlungsborn 18225, Germany;4. Lowell Digisonde International, 175 Cabot Street, Lowell, MA 01854, USA;5. University of Massachusetts Lowell, Space Science Laboratory, Lowell, MA 01854, USA;6. National Observatory of Athens, IAASARS, Metaxa and Vas. Pavlou, Palaia Penteli 15236, Greece;7. Institute of Atmospheric Physics, Czech Academy of Sciences, Bocni II 1401, 141 31 Prague, Czech Republic;1. INFN – University of Rome “Tor Vergata”, Rome, Italy;2. Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy;3. Institute of Earthquake Forecasting, China Earthquake Administration, Beijing, China;4. Institute of Crustal Dynamics, China Earthquake Administration, Beijing, China;5. INAF-Istituto di Astrofisica e Planetologia Spaziali, Rome, Italy;6. GFZ German Research Centre for Geosciences, Potsdam, Germany;7. TIFPA and University of Trento, Trento, Italy;8. University of Rome “Tor Vergata”, Rome, Italy;9. Agenzia Spaziale Italiana, Rome, Italy;1. Departamento de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av. Prof. Zeferino Vaz s/n, CEP, 14040-903, Ribeirão Preto, SP, Brazil;2. Departamento de Química Geral e Inorgânica, Instituto de Química, Universidade Federal da Bahia, Rua Barão de Geremoabo, 147, Campus Universitário de Ondina, C.E.P. 40.170-115, Salvador, BA, Brazil;3. Departamento de Física, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes, 3900, CEP, 14040-901, Ribeirão Preto, SP, Brazil;4. Barão de Mauá University Centre, 423 Ramos de Azevedo Street, Jardim Paulista, CEP 14090-180, Ribeirão Preto, SP, Brazil;1. Department of Electrical Engineering, LACOSER laboratory, University Amar Telidji, Laghouat, 03000, Algeria;2. IRIT, ENSEEIHT, BP 7122, F-31071, Toulouse Cedex, France |
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| Abstract: | We present detailed numerical results from a model which determines the time development of hydromagnetic waves within a hemi-cylindrical magnetospheric cavity subject to a short-duration compressional stimulus at the magnetopause. The model allows a realistic radial variation of Alfvén speed, arbitrary axial asymmetry, and the inclusion of ionospheric Joule dissipation.The results show the development of a set of compressional cavity resonances, and their coupling to a corresponding set of field-line resonances at positions where the cavity eigenperiods match the uncoupled field-line eigenperiods. Transient solutions having variable period with radial distance are important in establishing the field-line resonances, and can be locally dominant in certain regions of the outer magnetosphere.The variation with axial wavenumber m of the cavity eigenperiods is obtained, and it is shown that the magnetopause impulse drives the field-line resonances most efficiently for m ∼ 3. This suggests that small azimuthal wavenumbers are important in the terrestrial magnetosphere under analogous conditions. A variety of waveform and polarisation diagrams is given to aid in observational identification of such coupled resonances. |
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