Three-Dimensional Configuration and Evolution of Coronal Mass Ejections Von der Fakultät für Physik und Geowissenschaften der Technischen Universität Carolo-Wilhelmina zu Braunschweig zur Erlangung des Grades einer Doktorin der Naturwissenschaften (Dr.rer.nat.) genehmigte D i s s e r t a t i o n von María Hebe Cremades Fernández aus Mendoza / Argentinien Bibliografische Information Der Deutschen Bibliothek Die Deutsche Bibliothek verzeichnet diese Publikation in der Deutschen Nationalbibliografie; detaillierte bibliografische Daten sind im Internet über http://dnb.ddb.de abrufbar. 1. Referentin oder Referent: Prof. Dr. Karl-Heinz Glaßmeier 2. Referentin oder Referent: Prof. Dr. Rainer Schwenn eingereicht am: 24.02.2005 mündliche Prüfung (Disputation) am: 10.05.2005 Copyright © Copernicus GmbH 2005 ISBN 3-936586-40-3 Copernicus GmbH, Katlenburg-Lindau Druck: Schaltungdienst Lange, Berlin Printed in Germany Vorveröffentlichungen der Dissertation Teilergebnisse aus dieser Arbeit wurden mit Genehmigung der Gemeinsamen Naturwissenschaftlichen Fakultät, vertreten durch die Mentorin oder den Mentor/die Betreuerin oder den Betreuer der Arbeit, in folgenden Beiträgen vorab veröffentlicht: Publikationen Cremades, H. and Bothmer, V., On the Three-Dimensional Configuration of Coronal Mass Ejections, A&A, 422, 307-322, 2004. Tripathi, D., Bothmer, V., and Cremades, H., The Basic Characteristics of EUV Post-Eruptive Arcades and their Role as Tracers of Coronal Mass Ejection Source Regions, A&A, 422, 337-349, 2004. Cremades, H. and Bothmer, V., Geometrical Properties of Coronal Mass Ejections, in Proc. IAU Symp. 226 on Coronal and Stellar Mass Ejections, eds. Dere, K. P., Wang, J., and Yan, Y., 48-54, 2005. Gopalswamy, N. et al., The pre-CME Sun, Report of Working Group E, in Space Science Series of ISSI, in press. Cremades, H., Bothmer, V., and Tripathi, D., Properties of Structured Coronal Mass Ejections in Solar Cycle 23, Adv. Space Res., in press. Tagungsbeiträge Cremades, H., V. Bothmer, and D. Tripathi: 3D Magnetic Field Configuration & Evolution of CMEs (Oral). Seminar at the Astrophysics and Space Sciences Section, JPL, Pasadena, CA, USA, 12 March 2003. Cremades, H., V. Bothmer, D. Tripathi, and K. -H. Glassmeier: 3D Magnetic Field Configuration & Evolution of CMEs (Oral). EGS-AGU-EUG Joint Assembly, Nice, France, 7-11 April 2003. Cremades, H., V. Bothmer, and K. -H. Glassmeier: 3D Magnetic Field Configuration & Evolution of CMEs (Oral). Seminar of the Institut für Geophysik und Meteorologie, TU Braunschweig, 28 October 2003. Cremades, H., V. Bothmer, and D. Tripathi: On the Three-Dimensional Configuration of Coronal Mass Ejections (Poster). 1st EGU General Assembly, Nice, France, 25-30 April 2004. Cremades, H., V. Bothmer, and D. Tripathi: Properties of Structured Coronal Mass Ejections in Solar Cycle 23 (Oral). 35th COSPAR Scientific Assembly, Paris, France, 18-25 July 2004. Cremades, H., V. Bothmer, and D. Tripathi: Geometric Properties of Coronal Mass Ejections (Oral). IAU Symposium 226 on Stellar and Coronal Mass Ejections, Beijing, China, 13-17 September 2004. Who loves the Sun, Who cares that it makes plants grow, Who cares that it is shining? Who cares what it does, since you broke my heart? The Velvet Underground To my family Abstract Coronal mass ejections (CMEs) are a direct consequence of the dynamic nature of the Sun. They represent fundamental powerful processes in which energy is transferred from the Sun into interplanetary space, including geospace. Their origin, three-dimensional structure, and internal magnetic field configuration are to date not well understood. The unprecedented data provided by the Solar and Heliospheric Observatory (SOHO) allow for the first time the resolution of fine structures within CMEs, which can help to deduce their three-dimensional configuration. From a detailed investigation of the full set of SOHO/LASCO (Large Angle Spectroscopic Coronagraph) observations from 1996 to the end of 2002, a set of “structured CMEs” has been identified, i.e. events which exhibit white-light fine structures, likely indicative of their internal magnetic field configuration and possible 3D structure. Their source regions in the low corona and photosphere have been inferred by means of complementary analyses of data from the EUV Imaging Telescope (EIT) and Michelson Doppler Imager (MDI) onboard SOHO, and ground-based Hα measurements. From the characteristic pattern of the CMEs’ source regions in both solar hemispheres, a generic scheme of three-dimensional configurations is deduced. According to the scheme, the projected white-light topology of a CME depends primarily on the heliographic position and orientation of the source region’s underlying neutral line that separates opposite magnetic polarities. The cylindrical geometry found in the structured CMEs implies that they are organized along an axial direction. Furthermore, the typical dimensions of structured events exhibiting extreme projections (viewed along their axis or perpendicular to it) were investigated. These events originated from limb and near-limb regions. The measured dimensions indicate that these CMEs would be better approximated by elliptic cones, rather than by the classical cone of circular cross section. The dimensions of halo CMEs originating near Sun center are expected to agree with those obtained for the structured events. In order to understand the CME topology better, an elliptical cone model was developed as an improvement to an existing circular cone model, in an effort to fit and reproduce a set of halo CMEs from LASCO. Contents Introduction 1 Chapter 1 Sun’s essentials – The solar atmosphere 5 1.1 Introduction .................................................................................................................................5 1.2 The spotted photosphere..............................................................................................................6 1.3 The jagged chromosphere..........................................................................................................10 1.4 The grand corona.......................................................................................................................13 1.5 The solar wind and its impact on Earth .....................................................................................22 Chapter 2 Instrumentation and Data 25 2.1 Introduction ...............................................................................................................................25 2.2 The SOHO Mission ...................................................................................................................25 2.2.1 LASCO Coronagraphs......................................................................................................27 2.2.2 EIT....................................................................................................................................29 2.2.3 MDI ..................................................................................................................................30 2.3 Ground-based instruments.........................................................................................................31 2.3.1 Meudon Spectroheliograph...............................................................................................31 2.3.2 Big Bear 20-cm Refractor.................................................................................................32 2.3.3 NSO/KP Spectromagnetograph ........................................................................................32 2.4 Data formats and processing......................................................................................................32 2.4.1 Structured CMEs ..............................................................................................................32 2.4.2 Source regions of the Structured CMEs............................................................................34 2.4.3 Halo CMEs .......................................................................................................................35 Chapter 3 Analysis of structured CMEs 37 3.1 Introduction ...............................................................................................................................37 3.2 Selection of events.....................................................................................................................37 3.3 Basic properties .........................................................................................................................40 3.3.1 Rate of occurrence............................................................................................................41 3.3.2 Angular widths and position angles..................................................................................41 3.3.3 Speeds...............................................................................................................................44 3.4 Source regions ...........................................................................................................................46 3.4.1 Identification.....................................................................................................................46 3.4.2 Solar location....................................................................................................................48 3.4.3 Tilt and length...................................................................................................................50