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The Role and Dynamics of Oxygen of Ionospheric Origin in Magnetopause Reconnection

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The Role and Dynamics of Oxygen of Ionospheric Origin in Magnetopause Reconnection The Role and Dynamics of Oxygen Of Ionospheric Origin in Magnetopause Reconnection Kevin J. Genestreti12 In collaboration with: L. M. Kistler1 and C. G. Mouikis1 A thesis submitted for the degree of Bachelor of Science Spring, 2012 1 Space Science Center, University of New Hampshire, Durham, NH 2 Undergraduate, Department of Physics, UNH, Durham, NH Table of Contents 1. ABSTRACT .................................................................................................................................. 2 2. INTRODUCTION .......................................................................................................................... 3 3. THEORY ..................................................................................................................................... 5 3.1. The Basic Geometry of Magnetic Reconnection ............................................................................. 5 3.2. The Magnetopause Boundary Layer .................................................................................................... 7 3.3. Ionospheric Oxygen In the Magnetosphere ...................................................................................... 9 3.4. The Finite Gyroradius Effect ................................................................................................................ 10 3.5. Magnetopause Reconnection ............................................................................................................... 11 3.6. Detail of the Reconnection Region .................................................................................................... 13 3.6.1. The LMN Boundary Normal Coordinate System ...................................................................... 16 3.6.2. Structure of the Magnetic Field ....................................................................................................... 17 3.6.3. Structure and Dynamics of Reconnection Plasma Flows ..................................................... 19 3.6. The Reconnection Rate ........................................................................................................................... 20 3.8. Summary of Theory / Restatement of Thesis ............................................................................... 21 4. EXISTING LITERATURE ON HEAVY IONS IN RECONNECTION .................................................. 23 4.2. Existing Experimental Studies ............................................................................................................ 23 4.3. Simulation / Theory ................................................................................................................................. 23 4.4. Contributions of This Study to Current Understanding ........................................................... 24 5. METHODOLOGY ...................................................................................................................... 25 5.1. Overview of the Cluster Mission ......................................................................................................... 25 5.2. Capabilities of the Cluster Spacecraft ............................................................................................... 25 5.3. The Cluster CIS / CODIF Instrument ................................................................................................ 26 5.3.1. Saturation of Cluster-CODIF in High Count Rate Environments ....................................... 27 5.3.2. Cross-Calibration Results of the High Rates Correction ....................................................... 29 5.3.3. Effects of Contamination of H+ in the O+ TOF Bins .................................................................. 31 5.4. Identifying Magnetopause Reconnection Events ........................................................................ 33 5.4.1. Identifying Cluster Crossings of the Magnetopause ................................................................ 34 5.4.2. The Walén Test for the Magnetopause as a Rotational Discontinuity ........................... 36 5.4.3. Identifying the deHoffmann-Teller (dHT) Reference Frame .............................................. 37 5.5. Finding and Quality Checking the LMN Coordinate System ................................................... 38 5.6. Methods for Determining the Rate of Reconnection ................................................................. 41 6. RESULTS AND ANALYSIS ......................................................................................................... 43 6.1. February 20, 2002 .................................................................................................................................... 43 6.1.1. Event Overview ....................................................................................................................................... 43 O+ IN MAGNETOPAUSE RECONNECTION K. J. GENESTRETI 6.1.2. Calibration of Cluster-CODIF ............................................................................................................ 46 6.1.3. Qualitative Assessment of Jet ............................................................................................................ 47 6.1.3. Results from Minimum Variance Analysis .................................................................................. 50 6.1.4. Quantitative Assessment of Jets with the Walén Test ............................................................ 54 6.1.5. Analysis of O+ Dynamics ...................................................................................................................... 56 6.1.5. Estimation of Reconnection Rate .................................................................................................... 57 6.2. January 4, 2004 .......................................................................................................................................... 58 6.2.1. Event Overview ....................................................................................................................................... 58 6.2.2. Qualitative Assessment of Jets .......................................................................................................... 61 6.2.3. Minimum Variance Analysis Results .............................................................................................. 66 6.2.4. Quantitative Assessment of Jets with the Walén Test ............................................................ 69 6.2.6. Estimation of the Reconnection Rate ............................................................................................ 71 6.2.5. Analysis of O+ Dynamics ...................................................................................................................... 71 7. CONCLUDING REMARKS AND FUTURE GOALS ........................................................................ 74 8. REFERENCES ........................................................................................................................... 76 9. ACKNOWLEDGEMENTS ............................................................................................................ 81 1 1. Abstract In this study we analyze the dynamics of ionized oxygen (O+) of ionospheric origin in magnetopause reconnection events. We seek to determine whether or not the large gyroradius of O+ inhibits its coupling to the reconnection region. In order to do so, we analyze the properties of the magnetopause boundary layer and the dynamics of the nearby ions using Cluster/CODIF and magnetometer data. To identify reconnection events we use minimum variance analysis and the Walén relation to demonstrate that the properties of the ions and fields at the magnetopause are consistent with those of a locally, rotationally discontinuous boundary. In order to better understand the role of O+ in magnetopause reconnection, we present detailed case studies where O+ is observed in reconnection jet encounters. For four separate jets in two distinct events we find O+ to be either fully or partially magnetized and streaming close to the velocity predicted by the Walén relation. We also estimate the normalized reconnection rate for two of the four reconnection encounters using the relationship BN / BL ≅ RNORM and find a nominal normalized rate of ~0.1 for each. In the concluding remarks, we discuss ways that this study may be broadened to estimate the impact of O+ on the various parameters of magnetopause reconnection. O+ IN MAGNETOPAUSE RECONNECTION K. J. GENESTRETI 2. Introduction Magnetic reconnection is the vehicle through which magnetized plasmas expel magnetic energy into particle kinetic energy. The conditions necessary to initiate magnetic reconnection are found commonly in plasmas throughout the universe; in these various regimes of plasmas reconnection is thought to a common process for driving such energy exchange. It is a mechanism that has been used to explain the generation of solar flares (Giovanelli et al., [1947]), high-energy bursts on magnetized neutron stars (Somov et al., [2003]) and many phenomena observed in the Earth’s magnetosphere/ionosphere (Dungey, [1961]). Near Earth, reconnection is known to be an important link in the chain of events which generates auroral events and geomagnetic storms (Many papers, e.g. several by Dungey, 1950’s). It is also considered to be the main mechanism which allows for mass, energy and momentum flux across the boundary between the Earth’s magnetic field and the solar wind (Paschmann
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