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Planetary-period oscillations in Saturn’s magnetosphere

By David Jeremy Andrews

Abstract

This thesis is concerned with the study of near-planetary rotation period oscillations\ud in Saturn’s magnetic field. Similar oscillations are present in a variety of other\ud magnetospheric phenomena, most notably kilometre-wavelength radio emissions,\ud and together they have a substantial influence throughout the Saturnian plasma\ud environment. However, their origin remains poorly understood, despite more than a\ud decade of study. Surprising new discoveries have been made regarding the seasonality\ud of these oscillatory phenomena, and their intrinsic connection to the high-latitude\ud upper atmosphere and ionosphere of the planet, though a complete theory of their\ud origin remains to be developed.\ud In this thesis, three detailed studies of this phenomenon are presented, each of\ud which uses magnetic field data recently obtained by the Cassini spacecraft. The first\ud consists of an extensive survey of near-equatorial field data during southern summer,\ud from which the structure of the rotating oscillations is determined and the electrical\ud currents flowing through the equatorial plane are calculated. The second study is\ud prompted by the recent discovery of a north-south asymmetry in the period of related\ud radio emissions, and consists of a survey of high-latitude magnetic field data in which\ud evidence for a corresponding asymmetry in the magnetic field rotation period is found.\ud Finally, the third study concerns the presence of long-termdrifts between the phase of\ud the magnetic field oscillation and the Saturn kilometric radiation (SKR) modulation,\ud which, through construction of a simple theoretical model, is shown to arise as a\ud consequence of ‘rotational’ modulations in the SKR rather than the hitherto assumed\ud ‘strobe-like’ modulations. These three studies substantially further our understanding\ud of these phenomena, and in the case of the detection of a rotational modulation in the\ud SKR overturn three decades of previous thought. Consequently, the results presented\ud here elucidate characteristics of these phenomena that any theoretical understanding\ud of their origin must serve to explain, and will therefore be of central importance in\ud further development of this topic in the future.\ud Before presenting these three studies, an introduction to the topics of space plasma\ud physics and planetary magnetospheres is presented in Chapter 1. This is followed in\ud Chapter 2 with a discussion of Saturn’s magnetosphere, and the topic of near-planetary\ud period oscillations, and in Chapter 3 by descriptions of the instruments with which\ud data used in this thesis have been obtained

Publisher: University of Leicester
Year: 2011
OAI identifier: oai:lra.le.ac.uk:2381/9995

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  1. (2007c). Evidence for spiral pattern in Saturn’smagnetosphere using the new SKR longitudes.
  2. (2010b). Dawn-dusk oscillation of Saturn’s conjugate auroral ovals.
  3. (2009). A diffusive equilibrium model for the plasma density in Saturn’s magnetosphere.
  4. (2010). A dynamo model for axisymmetrizing saturn’s magnetic field.
  5. (2004). A model for the azimuthal plasma velocity in Saturn’s magnetosphere.
  6. (2005). A nightside source of Saturn kilometric radiation: Evidence for an inner magnetosphere energy driver.
  7. (2010). A plasmapause-like density boundary at high latitudes in Saturn’s magnetosphere.
  8. (1986). A prescription for period analysis of unevenly sampled time series.
  9. (2006). A regular rotation period for Saturn’s magnetic field that may track its internal rotation.
  10. (2011). A saturnian cam current system driven by asymmetric thermospheric heating.
  11. (2007). A Saturnian longitude system based on a variable kilometric radiation period.
  12. (2006). A statistical analysis of the location andwidth of Saturn’s southern auroras.
  13. (1979). A theory of the terrestrial kilometric radiation.
  14. (2009). An auroral oval at the footprint of Saturn’s kilometric radio sources, colocated with the UV aurorae.
  15. (2008). An empirical model of Saturn’s bow shock: Cassini observations of shock location and shape.
  16. (2008). An update to a Saturnian longitude system based on kilometric radio emissions.
  17. (2008). Auroral current systems in Saturn’s magnetosphere: comparison of theoretical models with Cassini and HST observations.
  18. (1998). Auroral radio emissions at the outer planets: Observations and theories.
  19. Carbary (2009a). Discovery of a north-south asymmetry in Saturn’s radio rotation period.
  20. (2005). Cassini magnetometer observations during Saturn orbit insertion.
  21. (2010). Cassini observations of a Kelvin-Helmholtz vortex in Saturn’s outer magnetosphere.
  22. (2010). Cassini observations of narrowband radio emissions in Saturn’s magnetosphere.
  23. (2006). Cassini observations of planetary-period magnetic field oscillations in Saturn’s magnetosphere: Doppler shifts and phase motion.
  24. (2006). Cassini observations of planetary-period oscillations of Saturn’s magnetopause.
  25. (2007). Cassini observations of the variation of Saturn’s ring current parameters with system size.
  26. (2006). Cassini observes the active south pole of enceladus.
  27. (2004). Cassini Plasma Spectrometer investigation. Space Sci.
  28. (2008). Cassini plasma spectrometer thermal ion measurements in Saturn’s inner magnetosphere.
  29. (1982). Charged particle periodicity in the Saturnian magnetosphere.
  30. (2009). Cloud features and zonal wind measurements of Saturn’s atmosphere as observde byCassini/VIMS.
  31. (2010). CMI growth rates for Saturnian kilometric radiation.
  32. (2005). Composition and dynamics of plasma in Saturn’s magnetosphere.
  33. (2003). Corotation-drivenmagnetosphere-ionosphere coupling currents in Saturn’s magnetosphere and their relation to the auroras.
  34. (2006). Current-voltage and kinetic energy flux relations for relativistic field-aligned acceleration of auroral electrons.
  35. (1983). Currents in saturns magnetosphere.
  36. (2011). Direct evidence of differences inmagnetic rotation rate between Saturn’s northern and southern polar regions.
  37. (2000). Directional Statistics.
  38. Discovery of heavy negative ions in Titans’s ionosphere.
  39. Dougherty (2003a). How can Saturn impose its rotation period in a noncorotating magnetosphere?
  40. Dougherty (2003b). Reanalysis of Saturn’s magnetospheric field data in view of spin-periodic perturbations.
  41. Dougherty (2008a). Thermal electron periodicities at 20RS in Saturn’smagnetosphere.
  42. Dougherty (2009a). Characterization of auroral current systems in Saturn’s magnetosphere: High-latitude Cassini observations.
  43. (1958). Dynamics of the interplanetary gas andmagnetic fields.
  44. (2009). Enceladus: An active cryovolcanic satellite.
  45. (2007). Enceladus: The likely dominant nitrogen source in Saturn’s magnetosphere.
  46. Energetic neutral atom (ENA) and charged particle periodicities in Saturn’s magnetosphere.
  47. F.Müller-Wodarg (2009). Atmospheric structure and composition.
  48. (2009). Goniopolarimetric study of the revolution 29 perikrone using the Cassini Radio and PlasmaWave Science instrument high-frequency radio receiver.
  49. Gurnett (2008b). Saturn kilometric radiation: Average and statistical properties.
  50. (2006). Identification of a Dynamic Atmosphere at Enceladus with the CassiniMagnetometer.
  51. (1961). Interplanetarymagnetic field and the auroral zones.
  52. Khurana (2009b). Signatures of field-aligned currents in Saturn’s nightside magnetosphere.
  53. Krimigis (2008a). ENA periodicities at Saturn.
  54. Krupp (2007a). Spinperiod effects in magnetospheres with no axial tilt.
  55. Krupp (2007b). Electron periodicities in Saturn’s outher magnetosphere.
  56. Krupp (2009b). Dual periodicities in energetic electrons at Saturn.
  57. Kurth (2009b). A north-south difference in the rotation rate of auroral hiss at Saturn: Comparison to Saturn’s kilometric radio emission.
  58. (2008). Large-scale dynamics of Saturn’s magnetopause:
  59. (1976). Least-squares frequency analysis of unequally spaced data.
  60. Lecacheux (2010b). The reversal of the rotational modulation rates of the north and south components of Saturn kilometric radiation near equinox.
  61. Leinweber (2008b). Warping of Saturn’s magnetospheric and magnetotail current sheets.
  62. Longitude dependences of energetic HÅ and OÅ at Saturn.
  63. (2010). Low-energy electrons in saturn’s inner magnetosphere and their role in interchange injections.
  64. (2008). Magnetic field structure of Saturn’s daysidemagnetosphere and itsmapping to the ionosphere: Results from ring current modeling.
  65. Magnetopause oscillations near the planetary period at Saturn: occurence, phase and amplitude.
  66. (2011). Magnetospheric period magnetic field oscillations at Saturn: Equatorial phase ‘jitter’ produced by superposition of southern- and northernperiod oscillations.
  67. (2010). Magnetospheric period oscillations at Saturn: Comparison of equatorial and high-latitude magnetic field periods with north and south SKR periods.
  68. Magnetospheric period oscillations of Saturn’s bow shock.
  69. (2005). Model of a variable radio period for Saturn.
  70. Modeling the size and shape of Saturn’s magnetopause with variable dynamic pressure.
  71. (2004). Modelling of global variations and ring shadowing in Saturn’s ionosphere.
  72. (2005). Morphological differences between Saturn’s ultraviolet aurorae and those of Earth and
  73. (2008). Multi-instrument analsis of electron populations in Saturn’s magnetosphere.
  74. (2010). Nature of the ring current in saturn’s dayside magnetosphere.
  75. Nichols (2009b). Phase relation of oscillations near the planetary period of Saturn’s auroral oval and the equatorialmagnetospheric magnetic field.
  76. O’Rourke (2004). A simple quantitativemodel of plasma flows and currents in Saturn’s polar ionosphere.
  77. (2008). On the cause of Saturn’s plasma periodicity.
  78. (2006). Orientation, location, and velocity of saturn’s bow shock: Initial results from the cassini spacecraft.
  79. (2005). Origin of the cataclysmic late heavy bombardment period of the terrestrial planets.
  80. (2001). Origin of the main auroral oval in Jupiter’s coupled magnetosphere-ionosphere system.
  81. (2009). Origin of the Saturn System. In Saturn from Cassini-Huygens,
  82. (2008). Oscillation of Saturn’s southern auroral oval.
  83. (2010). Particle pressure, inertial force, and ring current density profiles in the magnetosphere of Saturn, based on Cassini measurements.
  84. (2000). Periodic pertubations in Saturn’smagnetic field.
  85. Periodic tilting of Saturn’s plasma sheet.
  86. (2009). Periodicity in Saturn’s magnetosphere: Plasma cam.
  87. Phase relations between energetic neutral atom intensisites and kilometric radio emissions at Saturn.
  88. (2010). Planetary magnetic field measurements: missions and instrumentation.
  89. (2008). Planetary period oscillations in Saturn’s magnetosphere: Phase relation of equatorial magnetic field oscillations and SKR modulation.
  90. (1981). Planetary radio astronomy observations from Voyager-1 near Saturn.
  91. (1982). Planetary radio astronomy observations from Voyager-2 near Saturn.
  92. (1983). Plasma distribution and flow.
  93. (2009). Plasma in Saturn’s nightside magnetosphere and the implications for global circulation.
  94. (1981). Plasma waves near Saturn: Initial results from Voyager 1.
  95. Prangé (2008a). Modeling of Saturn kilometric radiation arcs and equatorial shadow zone.
  96. (2005). Properties of local plasma injections in Saturn’s magnetosphere.
  97. (2010). Properties of Saturn kilometric radiationmeasured within its source region.
  98. (2005). Radio and plasma wave observations at Saturn from Cassini’s approach and first orbit.
  99. (1981). Random sample consensus: a paradigm for model fitting with applications to image analysis and automated cartography.
  100. (2007). Report of the IAU/IAG Working Group on cartographic coordinates and rotational elements:
  101. (2009). Ring particle composition and size distribution.
  102. (2004). Rotation rate of saturn’s interior frommagnetic field observations.
  103. (1982). Saturn kilometric radiation: source locations.
  104. (1981). Saturn kilometric radiation: Statistical properties and beam geometry.
  105. (2007). Saturn magnetospheric dynamics: Elucidation of a camshaft model.
  106. (2009). Saturn: Composition and Chemistry.
  107. (2006). Saturn’s auroral morphology and activity during quiet magnetospheric conditions.
  108. (2007). Saturn’s gravitational field, internal rotation, and interior structure.
  109. (1998). Saturn’s hydrogen aurora: Wide field and planetary camera 2 imaging from the Hubble Space Telescope.
  110. (2010). Saturn’s internal planetary magnetic field.
  111. (1980). Saturn’s luminosity andmagnetism.
  112. (1980). Saturn’s magnetic field andmagnetosphere.
  113. (2009). Saturn’s magnetospheric configuration.
  114. (2011). Saturn’s ring current: Local time dependence and temporal variability.
  115. (2011). Saturn’s very axisymmetric magnetic field: No detectable secular variation or tilt.
  116. (1985). Solar wind flow about the outer planets: Gas dynamic modeling of the jupiter and saturn bow shocks.
  117. (1983). Source localization of Saturn kilometric radio emission.
  118. (1995). Source location of Saturn’s kilometric radiation: The Kelvin-Helmholtz instability hypothesis.
  119. (2009). Sources of rotational signals in Saturn’s magnetosphere.
  120. (2007). Spontaneous axisymmetry breaking of the external magnetic field at Saturn.
  121. (1982). Studies in astronomical time series analysis. II - Statistical aspects of spectral analysis of unevenly spaced data.
  122. (2009). Surface waves on Saturn’s dawn flank mangnetopause driven by the Kelvin-Helmholtz instability. Planet. Space Sci.
  123. (2008). Talboys
  124. (2004). The Cassini magnetic field investigation. Space Sci.
  125. (2004). The Cassini radio and plasma wave investigation. Space Sci.
  126. (2001). The Cassini/Huygens Venus and Earth flybys: An overview of operations and results.
  127. (2009). The electron density of saturn’s magnetosphere.
  128. (2006). The gravity field of the saturnian system from satellite observations and spacecraft tracking data.
  129. (1933). The magnetic field of sunspots.
  130. (2008). The magnetic memory of titan’s ionized atmosphere.
  131. (1995). The magnetopause, magnetotail and magnetic reconnection. In Introduction to space physics,
  132. (2004). The magnetostatic cleanliness program for the Cassini Spacecraft. Space Sci.
  133. (1995). The physics of space plasmas. In Introduction to space physics,
  134. (1991). The plasma environment of the Earth.
  135. (2005). The Saturnian plasma sheet as revealed by energetic particlemeasurements.
  136. (2009). The source of Saturn’s periodic radio emission.
  137. (2007). The variable rotation period of the inner region of Saturn’s plasma disk.
  138. (1984). The Z3 Model of Saturn’s Magnetic Field and the Pioneer 11 Vector Helium Magnetometer Observations.
  139. (1983). The Z3 zonal harmonic model of Saturn’s magnetic field: Analyses and implications.
  140. (2009). Thickness of Saturn’s ring current determined from north-south Cassini passes through the current layer.
  141. (2009). Upper atmosphere and ionosphere of Saturn.
  142. (2011). Variability of southern and northern SKR periodicities.
  143. (2005). Variable morphology of Saturn’s southern ultraviolet aurora.
  144. (2000). Variations of Saturn’s radio rotation period measured at kilometer wavelengths.
  145. (1980). Voyager detection of nonthermal radio emission from Saturn.
  146. (1981). Voyager measurement of the rotation period of Saturn’s magnetic field.
  147. (2008). Water vapour jets inside the plume of gas leaving enceladus.
  148. Wright (2009a). Polarization and phase of planetary period oscillations on high latitude field lines in Saturn’s magnetosphere.
  149. (2010). Z mode waves as the source of Saturn narrowband radio emissions.
  150. Zarka (2010a). Variation of Saturn’s UV aurora with SKR phase.
  151. (1982). Zonal harmonic model of Saturn’s magnetic field from Voyager 1 and 2 observations.

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