The Pennsylvania State University The Graduate School College of Engineering IMPROVEMENT IN THERMOSPHERIC NEUTRAL DENSITY ESTIMATIONS OF THE NUMERICAL TIE-GCM BY INCORPORATING HELIUM DATA FROM THE EMPIRICAL NRLMSISE-00 MODEL A Dissertation in Aerospace Engineering by Jung Soo Kim 2011 Jung Soo Kim Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy August 2011 ii The dissertation of Jung Soo Kim was reviewed and approved* by the following: David B. Spencer Associate Professor of Aerospace Engineering Dissertation Advisor Co-Chair of Committee Julio V. Urbina Assistant Professor of Electrical Engineering Co-Chair of Committee Timothy J. Kane Professor of Electrical Engineering and Meteorology Robert G. Melton Professor of Aerospace Engineering Victor Pasko Professor of Electrical Engineering George A. Lesieutre Professor of Aerospace Engineering Head of the Department of Aerospace Engineering *Signatures are on file in the Graduate School iii ABSTRACT The total atmospheric neutral densities derived from the CHAMP (CHAllenging Minisatellite Payload) and the GRACE (Gravity Recovery And Climate Experiment) accelerometer data are used to investigate the accuracy of the empirical as well as numerical thermospheric neutral density models during the solar maximum (year 2002) through the solar minimum (year 2007). The models used in this thesis include the empirical models of the Jacchia-Bowman models (JB2006 and JB2008) and the MSIS (Mass Spectrometer Incoherent Scatter)-class model, and the numerical model of the NCAR’s TIE-GCM (National Center for Atmospheric Research’s Thermosphere Ionosphere Electrodynamics General Circulation Model). The thermospheric neutral density models show good agreement to the variations of neutral densities from the accelerometer data, but still had uncertainties which should be taken into account for better prediction of satellites’ position in orbit. The TIE-GCM shows larger uncertainties in the root mean square (RMS) in percent deviations at 400 km compared to the empirical models: 47.1% for the TIE-GCM compared to 15.7%, 10.3%, and 20.3% for the JB2006, JB2008, and NRLMSISE-00 models, respectively. The errors gradually increase with the decline in the solar activity. The partial pressures of helium obtained from the Naval Research Laboratory’s MSIS Extension 2000 (NRLMSISE-00) model are incorporated into the TIE-GCM to reflect the helium effect in calculating the molecular viscosity, the thermal conductivity, and the specific heat. As a result, the secular increases of the percent deviations are eliminated and the RMS of the TIE-GCM is improved to 21.4% and 22.8% for the densities from the CHAMP and the GRACE-A accelerometer data, respectively, with the incorporation of 71% partial pressures of helium from the NRLMSISE-00 model. iv TABLE OF CONTENTS LIST OF FIGURES ............................................................................................................ vi LIST OF TABLES .............................................................................................................. xi NOMENCLATURE ........................................................................................................... xii ACKNOWLEDGEMENTS ................................................................................................ xiv Chapter 1 INTRODUCTION .............................................................................................. 1 Chapter 2 OVERVIEW ....................................................................................................... 4 Earth’s Atmospheric Structure ..................................................................................... 4 Atmospheric structure with thermal characteristics ............................................... 5 Atmospheric structure with characteristics of composition ................................... 9 Atmospheric structure with characteristics of charged particles ............................ 12 Energy sources from the space environment ................................................................ 18 Solar variations and irradiance ............................................................................. 19 Geomagnetic activity ........................................................................................... 29 Thermospheric neutral density variations ..................................................................... 34 Thermospheric neutral density models ......................................................................... 38 Empirical thermospheric neutral density models ................................................... 38 Drag Temperature Model (DTM).................................................................. 38 NASA Marshall Engineering Thermosphere (MET) model ........................... 39 Jacchia-class model ...................................................................................... 40 MSIS-class model ........................................................................................ 40 Numerical thermospheric neutral density models .................................................. 41 Coupled Thermosphere Ionosphere Model (CTIM) ....................................... 42 Global Ionosphere-Thermosphere Model (GITM) ......................................... 43 Thermosphere-Ionosphere-Electrodynamic General Circulation Model (TIE-GCM) ........................................................................................... 43 Thermosphere Ionosphere Nested Grid (TING) model .................................. 44 Chapter 3 MODEL DESCRIPTIONS .................................................................................. 46 Jacchia-class models .................................................................................................... 46 JB2006 model ...................................................................................................... 47 Data reduction .............................................................................................. 48 Model formulation ........................................................................................ 48 Computation of neutral temperature .............................................................. 49 Computation of neutral density ..................................................................... 54 JB2008 model ...................................................................................................... 60 Data reduction .............................................................................................. 60 New solar indices for temperature calculation ............................................... 61 Modeling semiannual density variations ....................................................... 62 Modeling geomagnetic storm variations........................................................ 63 v NRLMSISE-00 model ................................................................................................. 66 Data reduction ..................................................................................................... 66 Model formulation ............................................................................................... 67 Computation of neutral temperature ..................................................................... 68 Computation of neutral density ............................................................................ 70 TIE-GCM .................................................................................................................... 74 Boundary conditions ............................................................................................ 75 Modeling in the thermosphere .............................................................................. 76 Modeling in the ionosphere .................................................................................. 80 Chapter 4 DATA AND ANALYSIS OF MODEL SIMULATIONS .................................... 86 Thermospheric neutral density data and model comparison .......................................... 86 CHAMP and GRACE satellites ............................................................................ 87 Thermospheric neutral density derivation from the accelerometer data ................. 89 Comparison of neutral density models .................................................................. 90 Analysis of helium effects in the upper thermosphere .................................................. 102 Physics with mechanical and thermal properties of the air in the TIE-GCM .......... 102 Variation of helium in the upper thermosphere ..................................................... 105 Helium effects on the mechanical and thermal properties in a gas mixture ............ 112 Improvement of the TIE-GCM .................................................................................... 117 Incorporation of helium into the TIE-GCM .......................................................... 117 Simulation results ................................................................................................ 120 Chapter 5 CONCLUSIONS AND FUTURE WORK ........................................................... 126 Comparison of thermospheric neutral density models ........................................... 126 Contribution of helium to the physics in the upper thermosphere .......................... 127 Incorporation of helium data into the TIE-GCM ..................................................