SH41A-01
The STEREO Science Center
The STEREO Science Center (SSC), at the NASA Goddard Space Flight Center, is the "one-stop shopping" location for STEREO data, observation plans, analysis software, and links to other mission resources. Along with the other data products, a special "Space Weather Beacon" telemetry stream, relayed through an array of antenna partners coordinated by NOAA, provides near-real-time images, and will soon also provide near-real- time radio and in-situ data. Through interaction with the Solar Software library, the SSC also acts as a focal point for software coordination. The SSC is closely integrated with the Virtual Solar Observatory, making data easily accessible to users. Details on access to the SSC will be given and examples of the various types of data available at the SSC will be shown.
SH41A-02
The Unique Inversion Solution of The Elliptical Cone Model: Using STEREO Observations of Halo CMEs
In the low beta coronal plasma, the free magnetic energy, that is the only energy being able to generate coronal
mass ejections (CMEs), is stored in field line-aligned electric currents, the magnetic configuration of CMEs must
be a magnetic flux rope with its two ends anchored at the solar surface.
The circular cone model has been suggested to be used to
approximate the envelope of CME plasma. However, the inversion
solution obtained by Zhao (2004) and Cremade and Bothmer (2004) is not unique because the number of
parameters obtained from observed 2-D halos is less than the unknown parameters
of the 3-D elliptic cone. This work presents an new algorithm that combines with STEREO observations of halo
CMEs and can be used to invert the unique solution of the unknown parameters of the 3-D elliptic cone.
http:sun.stanford.edu/~xuepu/PUBLICATION/sprint.pdf
SH41A-03
Early In-Situ Results from STEREO/WAVES
STEREO was launched toward the Earth's foreshock, which allowed some early results on two objectives of the in-situ part of the STEREO/WAVES experiment. The first subject is the harmonic content of Langmuir waves. This might play a role in the generation of the radio harmonic. Many previous measurements have been limited by possible nonlinearities in the measuring system. STEREO/WAVES uses 16-bit linear A/D converters, which are accurately linear. It is found that the harmonic content is quite variable, with sometimes no harmonics, sometimes the second harmonic (2 fp) and sometimes several harmonics. The harmonic content has little or no dependence on the amplitude of the primary. A second subject is the relation of Langmuir waves to density fluctuations. As is well known, typical Langmuir waves are generated so close to the ambient plasma frequency, and the fluctuations of plasma density are sufficiently strong, that the Langmuir waves should undergo frequent perturbations of their propagation, including reflection when their frequency becomes less than the local plasma frequency. Further, the density fluctuations imply that a bump-on-tail instability for a given wave number can only be resonant over a limited spatial region. Some preliminary observations of such effects will be presented.
SH41A-04
Recurrent CIR-accelerated particle events observed by Stereo/SEPT
The Solar Electron and Proton Telescope (SEPT), part of the IMPACT investigation onboard the twin STEREO spacecraft, is designed to measure energetic electrons from 30 to 400 keV and protons from 60 to 7000 keV. During January and February 2007, the solar activity was very low, and only three small solar energetic electron events were observed by SEPT on January 23-24. Under these extremely quiet conditions, the enhancements of energetic proton fluxes are characterized by series of low energy (<1 MeV) bursts originating in the Earth magnetosphere or the bow shock (upstream events) and by recurrent, several days long enhancements associated with corotating interaction regions (CIRs). During this period, two different high speed solar wind streams originating in coronal holes were present, and both of them produced recurrent series of energetic proton events. The first sequence of events was observed by SEPT in correlation with solar wind stream interfaces on January 1-2, January 29 and February 26. The second series was correlated with stream interfaces observed on January 15 and February 12. Multi-spacecraft observations of time-intensity histories and energy spectra during the events are presented and discussed.
SH41A-05
STEREO In-situ Data Analysis
STEREO's IMPACT (In-situ Measurements of Particles and CME Transients) investigation provides the first opportunity for long duration, detailed observations of 1 AU magnetic field structures, plasma and suprathermal electrons, and energetic particles at points bracketing Earth's heliospheric location. The PLASTIC instrument takes plasma ion composition measurements completing STEREO's comprehensive in-situ perspective. Stereoscopic/3D information from the STEREO SECCHI imagers and SWAVES radio experiment make it possible to use both multipoint and quadrature studies to connect interplanetary Coronal Mass Ejections (ICME) and solar wind structures to CMEs and coronal holes observed at the Sun. The uniqueness of the STEREO mission requires novel data analysis tools and techniques to take advantage of the mission's full scientific potential. An interactive browser with the ability to create publication-quality plots has been developed which integrates STEREO's in-situ data with data from a variety of other missions including WIND and ACE. Static summary plots and a key-parameter type data set with a related online browser provide alternative data access. Finally, an application program interface (API) is provided allowing users to create custom software that ties directly into STEREO's data set. The API allows for more advanced forms of data mining than currently available through most web-based data services. A variety of data access techniques and the development of cross- spacecraft data analysis tools allow the larger scientific community to combine STEREO's unique in-situ data with those of other missions, particularly the L1 missions, and, therefore, to maximize STEREO's scientific potential in gaining a greater understanding of the heliosphere.
SH41A-06
Simulated CMEs and Predictions for STEREO
We compare results of our global MHD simulations of CMEs propagating from Sun-to-Earth to observations made with STEREO. We model a number of events of varying degree of complexity, and model the observations that are made by the SECCHI coronagraph suite and in situ observations by IMPACT and PLASTIC. We make synthetic Thomson-scattered white light images from the simulations as they would appear to the COR1, COR2, and wide-angle coronagraphs HI1 and HI2. We identify shock structures in the coronagraph images and follow their evolution to Earth orbit. At large elongation, we find complex time evolution of the white- light images as a result of three-dimensional structures encountering large variations in scattering efficiency as they pass through the Thomson sphere. We then compare the modeled ICME plasma structures with observations from PLASTIC. We also model solar energetic particles and compare them with IMPACT observations.
SH41A-07
Multipoint Studies of Interplanetary Shocks over Variable Baselines
The successful launch and commissioning of the in situ instruments on the STEREO A and B spacecraft together with the existing instruments on Wind and ACE near Earth's L1 libration point allow us to investigate the structure of interplanetary shocks at four different locations nearly simultaneously. The most variable parameter in the solar wind is the direction of the magnetic field. These four observing sites are sufficiently separated that the magnetic field is generally quite different at the four spacecraft. The observations allow us to elucidate how the theta BN angle controls the nature of upstream waves in front of the low Mach number interplanetary shock.
SH41A-08
Study of CME Related Phenomena Using STEREO/EUVI Data
The main goal of the STEREO mission is to address the three-dimensional structure of the Sun's corona, with emphasis in the origin and development of coronal mass ejections (CMEs). SECCHI/EUVI, the extreme ultraviolet imager onboard STEREO, provides full Sun coverage with improved cadence and spatial resolution with respect to SOHO/EIT. This allows an improved study of CME signatures in EUV. The present work provides an insight analysis of CME related phenomena in the EUV, such as filaments and post-eruptive arcades. By combining simultaneous images from both spacecraft, information on the 3D configuration of the solar structures can be obtained. The identification of the same feature in both images and the calculation of the displacement between them (parallax) are used to obtain the height of the structures seen in EUV images.
SH41A-09
STEREO and ACE Observations of Energetic Particles from Corotating Interaction Regions
In the present declining phase of the solar cycle, corotating interaction regions (CIRs) have once again become more prevalent. Since the launch of the two STEREO spacecraft in October 2006, at least 5 significant particle enhancements due to CIRs have been observed at 1 AU. The Low Energy Telescope (LET) on each STEREO spacecraft has been operating since mid-November 2006. This instrument is capable of measuring elemental composition and spectra for particles from H to Ni (and beyond) from ~2 to ~50 MeV/nucleon, depending on species, and in addition provides anisotropy information for 6 different species or element groups. Another STEREO instrument, the Suprathermal Ion Telescope (SIT), measures ion composition from ~0.05 to 5 MeV/nucleon. Using data from these STEREO instruments, supplemented with measurements from ULEIS and SIS on ACE, we obtain preliminary results on the spectra, composition, and anisotropy of these CIR events. This work was supported by NASA under grants NAS5-03131 and NAG5-12929.
SH41A-10
Bulk Properties of Solar Wind Protons: Inter-comparison of Observations From STEREO, SOHO, ACE, and WIND
The twin STEREO observatories were launched in October 2006. The PLASTIC experiment onboard both spacecraft analyzes ions with energies between 0.25 and 80 keV/charge, including solar wind protons. Information on bulk properties such as density, speed, and temperature are obtained. In early 2007 STEREO A was separated from SOHO, ACE, WIND, and STEREO B by hundreds of earth radii within the ecliptic plane, and by tens of earth radii out of the ecliptic plane. We report on comparisons of bulk parameters between these spacecraft, and what they show us about small-scale temporal and spatial variations in the solar wind.
SH41A-11
The Impact of Geometry on CME Observations Made by SEECHI
Optical observations of Coronal Mass Ejections (CME's) during the past several decades have generally been confined to events observed near the sun. Although events originating from most regions of the sun can be observed, the assumption has often made that the CME is propagating in the plane-of-the-sky. This assumption is generally adequate to give lower limits of CME mass and speed. However, continuous observations of CME's are now being made from very near the solar surface to large distances from the sun by the SECCHI instrument on STEREO. When CME's are observed at great distances from the sun, plane-of-the-sky assumptions are not adequate for analysis of these events. In this presentation we will discuss some recent observations made by the SEECHI instruments and the impact of geometry on our interpretation of these events.
SH41A-12
3D Simulations of Solar Observations in Radio, Millimeter and Submillimeter Wavelengths.
In this work we present 3D simulations of solar radio emission at different frequencies (1.4, 3.9, 17, 34, 43, 110GHz and 12GHz), in the centimeter - submilimeter wavelength range. We build a 3D, spherically symetric, solar model and solve the clasical equation of radiative transfer using quiet Sun temperature and electron density models. We compare our results with observations from Nobeyama Radio Heliograph and SMT submillimeter telescope at CASILEO. The 3.9 and 43 GHz images will be useful to calibrate the observations of new millimeter telescope (RT5) which is being constructed at "Sierra Negra" Volcano, in the state of Puebla, Mexico, at an altitude of 4,600 m. This project is a collaboration between Universidad Nacional Autonoma de Mexico (UNAM) and Instituto Nacional de Astrofisica Optica y Electronica (INAOE).