Anticipating STEREO: Addressing Issues in Coronal and Heliospheric Physics II
Presiding: J Chen, Naval Research Laboratory; R A Howard, Naval Research Laboratory
SH52A-01 INVITED 10:30h
SECCHI EUVI Observations
SECCHI EUVI will observe from multiple viewpoints the EUV emission line intensities of structures in the Transition Region and inner corona (<1.5Rsun) with a cadence comparable to the speed of a fast CME. This will address a number of key scientific issues related to the initiation of CMEs including 1) Determination of the three-dimensional coronal structure of pre/post CME regions (early mission), 2) Determination of the three-dimensional properties of the CME in the low corona (early mission), and 3) Determination of the relative timing between CME related structures (cavities, dimmings, waves, brightenings) involved in CME initiation from two angles (later mission).
SH52A-02 INVITED 10:52h
Great Expectations: How STEREO Data Will Impact the Art of CME Modeling
Driven by modern space-based solar and solar-wind observations, three-dimensional (3D) models of coronal mass ejections (CMEs), both numerical magnetohydrodynamic[1-4] and semi-analytical[5-7], have produced many exciting results. From among the current avenues of model-driven CME research, we shall highlight two areas where STEREO data might be expected to have a significant impact: 1) the near-sun geometrical relationship between the CME, the embedded prominence, and the underlying magnetic structure, and 2) the morphology and dynamics of erupting flux-ropes in the interplanetary medium, especially halo CMEs. We shall discuss the expected impact of STEREO data on "state of the art", model-driven CME research. Supported by ONR and NASA [1] Roussev et al. 2003, ApJ, 588, L45 [2] Amari et al. 2003, ApJ, 595, 1231 [3] Lynch et al. 2004, ApJ, 617, 589 [4] Manchester et al. 2004, JGR, 109, doi:10.1029/2003JA010150 [5] Chen 1996, JGR, 101, 27499 [6] Gibson and Low 2000, JGR, 105, 18187 [7] Chen and Krall 2003, JGR, 108, doi:10.1029/2003JA009849
SH52A-03 11:14h
Tracking Coronal Mass Ejections with a Heliospheric Imager: Case Studies from the Solar Mass Ejection Imager
The Solar Mass Ejection Imager (SMEI) was launched on board the DoD Space Test Program's Coriolis satellite in January 2003. Two-thirds through its planned 3-year lifetime, SMEI has observed Coronal Mass Ejections (CMEs), comets and asteroids as they move through the heliosphere. More than 140 CMEs have been detected with the SMEI instrument, including well-documented "halo" events that led to geomagnetic storm conditions on Earth. These observations demonstrate the potential of a heliospheric imager for space weather specification and prediction purposes. We present several case studies of CMEs as they propagate through the SOHO LASCO and SMEI fields of view, and examine SMEI's "hit" rate for detection of geoeffective CMEs.
http://smei.nso.edu/
SH52A-04 11:29h
Are high-latitude forward-reverse shock pairs driven by over-expansion?
During its passage through the high-latitude heliosphere, Ulysses observed Interplanetary CMEs (ICMEs) bounded by shocks. These forward-reverse shock pairs have only been observed at high latitude in the fast solar. It has been suggested (e.g. Gosling et al. 1995) that these shock pairs are the result of the expansion of the coronal mass ejection in the ambient solar wind, so called "over-expansion". Here we demonstrate and alternative explanation for forward-reverse shock pairs by means of a three-dimensional (3-D) numerical ideal magnetohydrodynamics (MHD) model of a CME interacting with the solar wind. Our global steady-state coronal model possesses fast and slow speed solar wind at high and low latitude respectively reminiscent of near solar minimum conditions. Within this model system, a CME erupts from the coronal streamer belt with an initial speed in excess of 1000 km/s which naturally drives a forward shock. When the CME is greater than 40 Rs from the Sun, we find that a reverse shock forms poleward of the CME as a result of the interaction of the CME with the bimodal solar wind. In front of the CME, the slow wind is deflected to higher latitude while behind the CME, fast wind is deflected to low latitude. The deflected streams collide to form a reverse shock. The shock pair formed in this way naturally forms at high latitude in the fast wind stream. We will discuss these model results in the context of in situ solar wind data and make testable predictions based on this model.
SH52A-05 11:44h
Forward Modeling of CMEs Using LASCO Data and for the STEREO Mission
The future STEREO mission, due to launch in early 2006, will have two twin satellites that will observe the Sun and its corona from two different points of view. The main goal of the mission is to understand how the CMEs are initiated and how they evolve during time. Using the two points of view will permit a reconstruction of the electron density and morphology of coronal structures such as CMEs. Two approaches are possible to reach that goal: an inversion technique, assuming no or little a priori assumptions of the structure, and a forward modeling technique, for which a morphology and location of the studied structure is assumed. In this poster we present a forward modeling method used to determined the electron density of different CMEs from SOHO-LASCO data. We used the graduated cylindrical shell (GCS) model, an empirical simulation of a flux-rope CME. We used time sequences and assumption of self similarity to have many views of the same CME for a best fit. We used also minimization techniques to find the best fit of the different model parameters.