30-Day Science Plan Angelos Vourlidas, Russ Howard SECCHI Consortium Meeting IAS 8 March 2007

STEREO Science Objectives STEREO is the first mission dedicated to understanding the physics of CMEs While CMEs have been well observed, fundamental questions still remain and are addressed by the STEREO mission level-1 science requirements: 1.Understand the causes and mechanisms of CME initiation 2.Characterize the propagation of CMEs through the Heliosphere 3.Discover the mechanisms and sites of energetic particle acceleration in the low corona and the interplanetary medium 4.Improve determination of the structure of the ambient solar wind All previous observations of CMEs have been restricted to the sun-earth line. Thus our view of CMEs has been projected onto a plane. STEREO will remove this deficiency by adding a second spacecraft with a significant separation, enabling the 3D nature of CMEs to be revealed STEREO will also provide concept verification for the LWS program by providing a real-time space weather input

30 Day Questions It has been traditional to define a set of the major questions that needed to be addressed in the first days of a mission. Since STEREO has a varying separation angle, our questions don’t fit nicely into a single calendar time period. Therefore the “30 day” designation should only be thought of as the major questions that we want to address during the mission

30 Day Science Questions (1) Morphology –What is the 3D pre-CME configuration? -What is the 3D nature of AR loops? QS Loops? Inter-AR loops? Transequatorial Loops? -What is the 3D nature of plumes? -What is the 3D nature of coronal holes? -What is the 3D nature of coronal streamers? -How do these quiescent structures evolve? –What is the 3D Structure of CMEs -In the low corona? -In the middle corona? -In the IPM?

30 Day Science Questions (2) CME Initiation –How does the pre-CME configuration evolve to initiate a CME? -What is the relative timing of the phenomena associated with the liftoff of CMEs? -What is the role of flares, prominence/filament eruptions? -What is the role of coronal cavities in the initiation/propagation? –What is the mechanism(s) for the CME initiation and liftoff? -What is the initial acceleration profile? What are the forces involved? -Is there evidence for reconnection and what is its role? –How is the pre-CME energy partitioned and how does it repartition? –Where does the mass originate?

30 Day Science Questions (3) Propagation/Interaction with the Heliosphere –What is the “real” CME speed? -What is the “real” 3D acceleration/deceleration profile? –Where and why do the fast CMEs decelerate to the solar wind speeds? –Where does the shock form and what is its 3D nature? –Where do the various radio (metric, dm, etc) Type II emissions originate? –How does the CME interact with streamers in 3D? –How does the 3D structure of the CME evolve as it propagates? –Where and how are SEP particles accelerated? –What is the 3D structure of magnetic clouds? –What is the 3D structure of complex events? Merged events? –What are the key characteristics for geoeffective CMEs?