UNIVERSITY OF CALIFORNIA Los Angeles The Jovian Magnetosheath: Factors Influencing the Size, Shape, and Mirror Mode Content and Distribution A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Geophysics and Space Physics by Steven Peter Joy 2010 The dissertation of Steven Peter Joy is approved. _________________________________ Richard A. Thorne _________________________________ Christopher T. Russell _________________________________ Raymond J. Walker _________________________________ Margaret G. Kivelson, Committee Chair University of California, Los Angeles 2010 ii To my wife, Ella, and our children, David and Danielle. They sacrificed much and often to allow me to complete this work. And to my father, a scientist who I respect tremendously and who has always been an inspiration to me. iii Table of Contents Chapter 1 Introduction ........................................................................................................ 1 1.1. Outline................................................................................................................. 2 1.2. The Shape and Location of the Earth’s Bow Shock and Magnetopause ............ 2 1.3. The shape and location of the Jovian bow shock and magnetopause................. 5 1.4. Properties of the Near-Jupiter and Near-Earth Solar Wind ................................ 7 1.5. The Earth’s Magnetosheath ................................................................................ 7 1.6. Mirror Mode Theory and Observations .............................................................. 8 1.7. Data Sources ..................................................................................................... 13 Bibliography ................................................................................................................. 14 Chapter 2 Probabilistic Models of the Shape and Location of the Jovian Magnetosheath Boundaries ........................................................................................................................ 18 2.1. The Ogino-Walker MHD Simulation at Jupiter................................................ 21 2.2. Solar Wind Dynamic Pressure Effects on the Shape and Location of the Bow Shock and Magnetopause ............................................................................................. 22 2.3. IMF Effects on the Shape and Location of the Bow Shock and Magnetopause25 2.4. Jovian bow shock and magnetopause shape models......................................... 29 2.5. Most probable Jovian bow shock and magnetopause surfaces......................... 32 2.6. Comparisons to Previous Boundary Models..................................................... 38 2.7. Solar Cycle Variation of the Size and Shape of the Jovian Boundaries ........... 39 2.8. Summary of Results.......................................................................................... 41 Bibliography ................................................................................................................. 45 Chapter 3 The Solar Wind in the Vicinity of Earth and Jupiter........................................ 49 3.1. Model predictions of the near-Jupiter solar wind ............................................. 51 3.2. Solar Wind Data Sets........................................................................................ 53 3.3. Statistical Analysis of the Data near Jupiter’s Orbit......................................... 61 3.3.1 Near-Jupiter Solar Wind: Quiet vs. Disturbed.......................................... 66 3.3.2 Near-Jupiter Solar Wind: Solar Cycle Variations..................................... 67 3.4. The Lognormal Distribution Function.............................................................. 68 3.5. Near-Jupiter Solar Wind: Probability Density Distributions............................ 69 3.6. Statistical Analysis of the Data near Earth ....................................................... 73 3.7. Summary........................................................................................................... 79 Bibliography ................................................................................................................. 81 Chapter 4 Mirror Mode Structures in the Jovian Magnetosheath..................................... 84 4.1. Identification and Classification of Mirror Modes ........................................... 86 4.2. Analysis............................................................................................................. 88 4.2.1 Distribution relative to the bow shock and the magnetopause ................. 89 4.2.2 Local time distribution.............................................................................. 92 4.2.3 Background field and plasma conditions.................................................. 92 4.3. Summary of Observations................................................................................. 97 4.4. Discussion......................................................................................................... 98 iv 4.5. Conclusions..................................................................................................... 103 Bibliography ............................................................................................................... 106 Chapter 5 Mirror Mode Structures and Evolution: Case study of a mirror mode train observed in data acquired by the THEMIS spacecraft.................................................... 111 5.1. THEMIS Instrumentation and Data Sets ........................................................ 112 5.2. Mirror Mode Event Description...................................................................... 113 5.3. Plasma distribution functions of the mirror mode structures.......................... 124 5.3.1. Linear Growth Phase of Mirror Mode Development.............................. 124 5.3.2. Non-linear Saturation of Mirror Mode Growth ...................................... 125 5.3.3. Mirror Structure Decay........................................................................... 129 5.4. Particle Distribution Functions Observed by THEMIS-D when Quasi-Periodic Mirror Mode Structures are Present............................................................................ 130 5.5. Particle Distribution Functions Observed by THEMIS-C when Mirror Mode Peak Structures are Observed. .................................................................................... 132 5.6. Particle Distribution Functions Observed by THEMIS-A when Mirror Mode Dip Structures are Observed. ...................................................................................... 133 5.7. Discussion....................................................................................................... 134 Bibliography ............................................................................................................... 137 Chapter 6 Summary and Future Work............................................................................ 139 6.1. Future Work.................................................................................................... 145 Bibliography ............................................................................................................... 146 Appendix A: Identification of Jovian Boundary Crossing Times ................................. 147 Bibligography ............................................................................................................. 161 v List of Figures Figure 1.1 Observed magnetopause crossings and the distribution of stand-off distances (after Fairfield et al. , 1976; Fairfield , 1971).............................................................. 3 Figure 1.2 An illustration of the differences between the motions of the untrapped and trapped particles in a mirror geometry (after Kivelson and Southwood , 1996).......... 9 Figure 1.3 Velocity distribution function during mirror mode linear growth (after Southwood and Kivelson , 1993). .............................................................................. 10 Figure 1.4 Wire-frame representation of the magnetic field perturbation surfaces in a mirror mode structure (after Constantinescu , 2002)................................................. 12 Figure 2.1 Summary of the observations of Jupiter boundary crossings to date projected into the Jovian equatorial plane (after Joy et al., 2002)............................................ 20 Figure 2.2 Response of the Ogino-Walker Jupiter MHD simulation to changes in solar wind dynamic pressure in the absence of an IMF (after Walker et al ., 2005). ......... 23 Figure 2.3 Simulation response to the addition of a small southward or northward IMF at low dynamic pressure (after Walker et al ., 2005)..................................................... 26 Figure 2.4 Simulation response to the inclusion of an IMF with a small B Y component (after Walker et al ., 2005)......................................................................................... 28 Figure 2.5 Contours of the flow diversion criterion used to identify the magnetopause in the MHD simulation (after Joy et al ., 2002)............................................................. 30 Figure 2.6 Bow shock (left) and magnetopause (right) surfaces generated by evaluating equation (2) at the 10 th , 50 th , and 90 th percentiles of the observed solar wind dynamic pressure in the three principal planes (rows, after Joy et al ., 2002).