SH21B-0400 0800h
3D Breakout: Preliminary Results
We present preliminary results of the breakout model for solar coronal mass ejections in a global-scale 3D topology. Starting with a background dipole field, we use a series of point dipole sources create a latitudinally extended ($\sim 100^o$) delta-spot active region configuration with a null point high in the corona. This is the natural 3D extension of our very successful 2.5D case. Magnetic free energy is added to the initial field configuration via two compressible vortex flows that preserve $B_r$ at the surface and concentrate the shear near the central neutral line of the AR flux system. Reconnection at the null point removes the restraining overlying flux allowing rapid, unstable expansion of the innermost sheared field. We examine the evolution of the system and discuss its implications for a fully 3D breakout eruption. We also discuss observational tests of the breakout model that can be performed with the unique viewing capabilities of STEREO. This work is supported in part by NASA and ONR.
SH21B-0401 0800h
Modeling Flux Cancellation in Active Regions
We will present a study of the flux cancellation mechanism in a model of an active region. We will explore the interaction of the local magnetic field in the active region with the global magnetic fields due to the weak surrounding magnetic flux. The goal will be to see if a localized 3D configuration erupts as a consequence of flux cancellation, in the same way that 2D axisymmetric and large-scale 3D fields erupt. Research supported by NASA and the Center for Integrated Space Weather Modeling (an NSF Science and Technology Center).
SH21B-0402 0800h
A Detection of the Same Hot Plasma in the Corona - During a CME - and Later at Ulysses
We show direct evidence for the same very hot plasma being detected remotely from SOHO in the corona and subsequently, {\it in situ}, at Ulysses in the solar wind. This is, to our knowledge, the first time that such an unambiguous identification has been made in the case of hot plasma. This detection complements studies correlating other plasma and field properties observed {\it in situ} to the properties measured at the source in the corona. This observation takes advantage of a SOHO-Sun-Ulysses quadrature, during which the Sun-Ulysses included angle is $90^\circ$ and it is possible to observe {\it in situ} with Ulysses instruments the same plasma that has previously been remotely observed with SOHO instruments in the corona on the limb of the Sun. The identification builds on an existing base of separate SOHO and interplanetary detections of hot plasma. SOHO/UVCS has found evidence for very hot coronal plasma in current sheets in the aftermath of CMEs (Ciaravella et al., 2002; Raymond et al., 2003; Ko et al., 2002) in the [Fe XVIII] $\lambda$ 974 \AA\ line, implying a temperature on the order of $6 \times 10^6$ K. This temperature is unusually high even for active regions, but is compatible with the high temperature predicted in current sheets. In the solar wind, ACE data from early 1998 to middle 2000 revealed high frozen-in Fe charge state (Fe$^{16+}$)in many cases to be present in interplanetary plasma (Lepri et al., 2004). These identifications were associated with ICMEs. Ciaravella, A., Raymond, J. C., Li, J., Reiser, P., Gardner, L. D., Ko, Y.-K., & Fineschi, S. 2002, Astrophys. J., 575, 1116 Ko, Y.-K., Raymond, J. C., Li, J., Ciaravella, A., Michels, J., Fineschi, S., & Wu, R. 2002, Astrophys. J., 578, 979 Lepri, S. T., & Zurbuchen, T. H. 2004, J. Geophys. Res., 109(A1), A01112 Raymond, J. C., Ciaravella, A., Dobrzycka, D., Strachan, L., Ko, Y.-K., & Uzzo, M. 2003, Astrophys. J., 597, 1106
SH21B-0403 0800h
Studying the Heliosphere with Long Time Series of Ulysses HISCALE Ion Composition Data
Ulysses has now been in orbit for fourteen years, over two full orbits and a full solar cycle. We take this opportunity to investigate the properties of long time series of ion composition data that have been acquired by the HI-SCALE instrument. We use daily average H and He fluxes measured by the Wart Pulse Height Analysis (PHA) system of HI-SCALE in the energy ranges of 0.35 MeV/nuc to 1.0 MeV/nuc for He/H ratios, and 0.5 to 2.0 MeV/nuc for species in the Z $>$ 2 composition range from Helium to Iron. Preliminary results show the expected dependence on solar cycle as well as on heliographic latitude of the spacecraft, and S/C distance from the Sun. We show the statistical relationship between He and H fluxes over this entire time interval (and sub time intervals), as well as between Z $>$ 2 ions and He fluxes. In addition, spectral analyses of the ln(He/H) flux ratios exhibit large spectral peaks (above 99% confidence levels at numerous frequencies. All the frequencies reported in the analyses of Thomson et al. (Nature, 1995) in the 0 to 5.8 uHz range are matched within 10 nHz at significance levels above 90% confidence. We suggest that the spectral peaks in the ion fluxes are evidence for the global oscillation (`breathing') of the heliosphere, where the driving source for the breathing is the Sun, i.e., solar oscillations. A 24 nHz fine-splitting visible on many of the lines suggests that the 1.38-year oscillation of the tachocline (Howe et al, Science, 2000) modulates the modes.
SH21B-0404 0800h
Raytracing Software for the Simulation of the Solar K-Corona
In this talk we will present RAYTRACE, a raytracing software developed at the U.S. Naval Research Laboratory. The program is an implementation of the Thomson scattering equations applied to the solar corona (Billings 1966). Synthetic coronal images in total or polarized brightness can be calculated using models of various coronal structures. We have implemented many models for quiescent and dynamic coronal stuctures such as streamers, the heliospheric current sheet (HCS), jets and CMEs. The models are generally analytic representations of the volume electron density, but a generic data cube of electron density can also be used. The core of the program has been written in C++ pimarily for computation speed. An earlier version was written in IDL, but was quite slow. Due to the processing speed of common computers, a high resolution image (512 x 512) of the HCS streamer belt for instance can be generated in less than 1 minute (Pentium 4, 2.5 GHz, 512 Mb RAM, Linux OS). A graphical user interface has been developed in IDL and allows the user to easily enter the parameters required for each model, specifying the position and orientation of the observer and structure, the size and resolution of the images, and then to visualize the output and compare the results to actual coronal images obtained by SOHO/LASCO and in the future by the STEREO/SECCHI coronagraphs (COR1 and COR2). Some of the main features of the front-end interface include mesh plot positioning of structures in space, parameter tuning for the structures and movie making. Different studies have already been done using this software, such as the inversion of the electron density of the streamer belt or the modeling of CMEs for the STEREO mission (presented in another paper at this meeting).
SH21B-0405 0800h
Stereo Solar Radio Observations in the Inner Heliosphere
The evolution of solar transient phenomena through the inner heliosphere can be remotely revealed via the radio emissions that they generate. The type II radio bursts are signatures of the propagation of CMEs, while type III radio bursts represent the propagation of energetic electrons associated with flares. Up to now, the remote radio tracking of these solar transients has been somewhat limited due to the lack of detailed knowledge of the interplanetary density structure in the inner heliosphere. The STEREO radio (SWAVES) observations will greatly improve this situation by locating the radio sources by two-spacecraft triangulation, thus eliminating the need for postulating an interplanetary density model. Conversely, since the observed frequency of the radio sources depend on the plasma density in the source region, the tracking of solar transients by the STEREO triangulation will provide important information on the plasma density in the inner heliosphere. For example, the plasma density measured in-situ by the STEREO spacecraft can be extrapolated, albeit in a model-dependent way, to the region of the radio source and directly compared with the observed radio frequency. In this way it can be determined whether these radio emissions originate in density enhanced regions. Up to now, some two-spacecraft triangulation analyses have been possible between the Wind and Ulysses spacecraft, but these observations have been limited by the less than of ideal spatial orientations between the two spacecraft. Nevertheless, we will discuss triangulation analyses that have been achieved by Wind and Ulysses for both type II and type III radio observations and illustrate how such analyses will be improved by the STEREO mission.
SH21B-0406 0800h
Revisiting ISEE-3-Voyager Observations of Back-Side Type III Radio Bursts in View of the Stereo/Waves observations.
In this paper, we revisit old observations of interplanetary type III radio bursts made simultaneously by the radio instruments on the ISEE-3 spacecraft and on the Voyager spacecraft, in view of the new opportunities offered by the Stereo mission.. Type III radio emission is produced by beams of supra-thermal electrons believed to be accelerated during the flare process and traveling along open interplanetary field lines. Their observation can help trace the large scale structure of the interplanetary medium. Lecacheux et al. (1989) analyzed the properties of such radio bursts originating behind the Sun as viewed from the Earth and still also observed by the ISEE-3 spacecraft located at the L1 libration point. Information on the beaming of the radiation can be deduced from these observations. Lecacheux et al. also measured anomalous delays in burst arrival time at one spacecraft relative to the other. These anomalous delays could be explained by the presence of both the fundamental and harmonic radiation modes with different beaming properties. Such an hypothesis can be checked by the Stereo/Waves observations. Finally, we discuss previous radio wave propagation models in the interplanetary medium and emphasize their importance for the interpretation of the radio observations. Lecacheux, A., J.-L. Steinberg, S. Hoang, and G. A. Dulk, Characteristics of type III bursts in the solar wind from simultaneous observations on board ISEE-3 and Voyager, Astron. Astrophys. 217, 237-250, 1989.
SH21B-0407 0800h
SmartSat Experiment for the L5 Mission
We have planned the L5 mission for space weather research and operational forecasting experiment. In this mission, a spacecraft will be deployed at the L5 point of the Sun - Earth system for remote sensing of the Sun and the interplanetary space, and for in-situ measurements of the solar wind plasma and high energy particles. For this mission, NICT and JAXA develop wide field imager for tracking CME propagation from the Sun to the Earth and advanced high-energy particle sensor for monitoring of solar particle events, respectively. Before proceeding the L5 mission, we are planning orbital demonstration in GTO using a platform of small satellite, called "SmartSat". The SmartSat program is a collaborative program of government agencies (NICT and JAXA), and a private company (Mitsubishi Heavy Industry) in Japan. The wide field coronal imager (WCI) and space environment data acquisition experiment (SEDA) will be tested by this program as the space weather experiment, since both of the instruments will be principal components of the L5 mission. The SmartSat is planned to be launched by 2007, about 1 year after the launch of STEREO spacecrafts. Therefore, we are expecting the coordinated observation with STEREO mission. In this paper, we will report an overview of the space weather experiment in SmartSat program.
SH21B-0408 0800h
Calibration Results for the COR-1 Coronagraph on STEREO/SECCHI
COR-1 is the inner coronagraph of the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) instrument suite aboard the two STEREO spacecraft. COR-1 is a classic Lyot internally occulting coronagraph, observing the solar corona in broadband red light around 656 nm, from 1.35 to 4 solar radii. A linear polarizer is used to suppress scattered light, and to extract the polarized brightness signal from the solar corona. Calibration was performed in the Naval Research Laboratory vacuum tunnel facility previously used for the LASCO experiment aboard SOHO. We report on the results for scattered light, photometric calibration, resolution, and polarization. All performance requirements are met or exceeded. Based on these results, we demonstrate that COR-1 will be able to carry out its scientific mission.
SH21B-0409 0800h
Calibration Results for the STEREO/SECCHI COR2 Coronagraphs
The two SECCHI instrument suites aboard the upcoming STEREO mission include the COR2 coronagraphs which observe the middle/outer corona; namely, from 2.5 to 15 solar radii. As of the end of August 2004, both COR2 instruments have been assembled and delivered to the SECCHI project and their perfomance has been measured and analyzed. The coronagraphs have met (and in some cases, exceeded) their performance requirements. Here, we present in detail the results of the calibration (photometry, polarization, stray light levels, etc) of the COR2 coronagraphs. We compare these new coronagraphs to the LASCO ones and discuss how they will contribute to the scientific success of the STEREO mission.
SH21B-0410 0800h
The Plasma and SupraThermal Ion Composition (PLASTIC) Instrument: Final Diagnostic Development Phase for the STEREO Mission
The PLAsma and SupraThermal Ion Composition (PLASTIC) instrument project is entering the final phases of instrument development prior to integration with the Solar Terrestrial Relations Observatory (STEREO) spacecraft in early 2005. The STEREO mission will provide a unique opportunity to investigate the 3-dimensional structure of the heliosphere, with particular focus on the origin, evolution, and propagation of Coronal Mass Ejections (CMEs). The mission also seeks to determine the sites and mechanisms of energetic particle acceleration as well as develop a 3-D time-dependent understanding of the ambient solar wind properties. As one of four STEREO instrument packages coordinating remote sensing and {\it in situ} measurements, the PLASTIC instruments will diagnose properties of the solar wind and suprathermal protons, alphas, and heavy ions. PLASTIC will determine bulk solar wind plasma parameters (density, velocity, temperature, temperature anisotropy, and alpha/proton ratio) and the distribution functions of major heavy solar wind ions in the energy per charge range 0.25-100keV/e. A full characterization of the solar wind and suprathermal ions will be achieved with a system that measures ion energy per charge ($E/q$), ion velocity distribution ($\vec v$), and ion energy ($E$). Two identical PLASTIC instruments located on the separate spacecraft will provide {\it in situ} plasma measurements in order to study physical processes low in the corona and in the inner heliosphere. Elemental and charge state abundances provide tracers of the ambient coronal plasma, fractionated populations from coronal and heliospheric events, and local source populations of energetic particle acceleration. In this presentation, the PLASTIC operation principles and aims will be presented along with a review of development status and current instrument calibration results.
SH21B-0411 0800h
STEREO Science Center
STEREO (Solar TErrestrial RElations Observatory) will employ two nearly identical spacecraft in heliocentric orbits, one ahead of Earth, the other trailing behind, to provide the first-ever stereoscopic measurements to study the Sun and the nature of its coronal mass ejections. Scheduled for launch in early 2006, STEREO will complement the Living With a Star program by providing a unique new viewpoint. The STEREO Science Center at the NASA Goddard Space Flight Center will be 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, will provide near-real-time images, radio, and in-situ data.
SH21B-0412 0800h
Space Weather Aspects of the STEREO Mission
The STEREO Mission includes a Space Weather Group, whose purpose is to identify and promote the development of computer programs, modeling efforts and research studies in preparation for using the STEREO observations as a tool for Space Weather. Our activities are coordinated with the STEREO PI Teams and the STEREO Science Center (SSC) at GSFC, where the Beacon data will reside. The STEREO Beacon is the main STEREO effort focused on Space Weather; its main purpose is to provide low resolution, low cadence, near-real-time imaging and in-situ data to NOAA's Space Environment Center for forecasting. These data will also be publicly available through the SSC. In addition to the real-time Beacon data, the full science data stream will be downloaded to the SSC each day. These data will also be important for space weather, both for predicting and in improving our understanding of CMEs and related phenomena. A novel instrument on the STEREO mission pertinent for detecting CMEs in the inner heliosphere and forecasting their Earth arrival is the SECCHI Heliospheric Imagers. We will summarize preliminary plans for using the Beacon and HI data, as well as the full set of STEREO instrument data, for space weather purposes. Scientists from outside the STEREO consortia are invited to join in the group's efforts. See our website for further information.
http://wwwsolar.nrl.navy.mil/STEREO/html/swindex.html
SH21B-0413 0800h
STEREO in the Virtual Solar Observatory Context
The Virtual Solar Observatory (VSO) was designed with the goal that it handle heterogeneous data sets from multiple observatories. With its two spacecraft and multiple instruments, the STEREO mission provides an excellent example of solar physics research based on multiple data sets, and a good test of the abilities of the VSO. Here we will discuss how the VSO will meet the key challenges that STEREO presents. In particular, the wide range of data classes and the non-stationary viewpoints of the two spacecraft demand a flexible underlying data model of the VSO.
http://www.virtualsolar.org/
SH21B-0414 0800h
Doing Science with the VSO: Signatures of CME Initiation
The Virtual Solar Observatory (VSO) was designed to simplify and unify access to solar physics data. It provides a single interface to a broad range of data types and sources which previously would have required considerable effort to collect one by one. By combining access to online data sources with published scientific catalogs, the VSO can facilitate new science. This study seeks to investigate whether signatures of coronal mass ejection (CME) initiation can be used to constrain CME initiation models. We selected events from the SOHO/LASCO CME catalog, generated a time window between the calculated CME ``start time" and the first observation of the CME in LASCO C2, and examined EIT ``CME Watch" and H-alpha observations identified by a VSO query as falling in the specified time windows. We prioritized the EUV data by selecting those events for which GOES data indicated a flare, and identified flare sites and dimming regions in the EUV data, with the aim of more precisely determining CME initiation locations and times. In addition, we used H-alpha data to investigate CME's associated with by filament eruptions. The results allow us to calculate minimum acceleration rates, and determine correlations between coronal structures, ejection events, and acceleration rates. We use these correlations in turn to identify viable CME initiation mechanisms.
http://virtualsolar.org/docs/AGU200412/davey.html
SH21B-0415 0800h
Solving Science Use Cases that relate to the Sun and Heliosphere with EGSO
The European Grid of Solar Observations (EGSO) is a grid testbed funded by the European Commission's Fifth Framework Programme under its Information Society Technologies (IST) thematic priority. The project started in 2002 and is designed to provide enhanced access to solar and related data around the world. The EGSO grid is composed of two main components, Roles to set up the grid and, catalogs and registries to allow roles to answer users queries. Catalogs are made of lists of observations, events and features (a new service provided by EGSO). Registries are built from these catalogs and organized in order to enhance search capabilities. EGSO is working closely with other virtual observatory (VO) projects in the solar physics and related domains. This includes the US Virtual Solar Observatory (VSO) and the Collaborative Sun-Earth Connector (CoSEC). More recently we have been working with the Virtual Space Plasma Observatory (VSPO) and have contact with the Virtual Heliospheric Observatory (VHO). Through discussions with future missions, and within the new IAU Working Group on ``International Data Access'' (Solar and Heliospheric), the VOs are studying ways of ensuring interoperability from the ``sun to dirt''. This type of integrated access will be particularly important to missions such as STEREO and Living Witha Star. In this paper we will report the current status of EGSO, demonstrate how the catalogs and registries model serves within the user interface, and show how the user can retrieve solar and heliospheric data to match a scientific query. EGSO Release 4 is now being Beta-tested by users and anyone interested should view the Web page detailing all the EGSO capabilities under http://www.egso.org/demo
http://www.egso.org
SH21B-0416 0800h
User Access to the European Grid of Solar Observations
The European Grid of Solar Observations (EGSO) is a grid testbed funded by the European Commission's Fifth Framework Programme under its Information Society Technologies (IST) thematic priority. The project started in 2002 and is designed to provide enhanced access to solar and related data around the world. One front-end of EGSO is a Graphical User Interface (GUI) that allows the user to access all the services offered by the grid from a common and integrated interface. Other front-ends are an IDL API and various dedicated web interfaces to access all the different catalogs built in the frame of this project like the Solar Event Catalog (SEC) the Solar feature Catalog (SFC) the Unified Observing Catalog (UOC). The GUI, as well as the API, provides also users with external processing services like those offered by the Collaborative Sun-Earth Connector (CoSEC), another virtual observatory-like project. In this paper we will present the EGSO front-ends with a special focus on the GUI. We will also demonstrate interactions between catalogs and the query system underlying the user interfaces in order to help the user when specifying complex scientific queries and eventually retrieving the corresponding solar data. More information about EGSO can be found under http://www.egso.org/
SH21B-0417 0800h
Possible Virtual Space Physics Observatory (VSPO) Contributions to the STEREO Mission
The STEREO mission provides an ideal case for the unification of space and solar physics datasets, since it involves aspects of both in itself, and, for full realization of its potential, its observations will need to be directly related to observations both of the Sun and of the Earth's environment. This talk will give an update on the VSPO efforts and will note how these relate to the STEREO goals. VSPO now has over 250 solar and space physics data products registered, with direct pointers to data sites, and in many cases the ability to deliver data from, e.g., the CDAWeb SOAP interface. It thus provides access to a large number of the datasets needed for global studies of the Sun-Earth system. The STEREO datasets will fit naturally into this context, perhaps linked via VSO and VHO. We are also working on tools for visual front ends and higher-order query services, and these will be discussed.
http://vspo.gsfc.nasa.gov/
SH21B-0418 0800h
DataShop - A New Tool for Multi-Data Source Analysis
Simultaneous analysis of numerous, diverse data sources--solar, heliospheric, magnetospheric, ITM, and ground-based--is essential to the use of STEREO data to fill in a complete picture of Sun-Earth interactions. We present progress in the development of DataShop, a tool to enable and simplify analysis of multiple data sources. DataShop will be able to read and plot energetic particle data, magnetic field data, plasma data, and electric field data, as well as spacecraft ephemeris data. Similar to the way popular image analysis tools can open and manipulate any of the common image formats, DataShop will be able to read data in any of the common formats used within the heliospheric community: HDF4, HDF5, CDF, netCDF, FITS, and ASCII. Finally DataShop will be designed in such a way that it can be hooked into the emerging Virtual Observatories being created for the heliospheric community (such as the VHO and the VSPO). Since most first generation VO's provide primarily a file finding service, DataShop will enable users to browse and analyze the multiplicity of files returned to them from a VO query.
SH21B-0419 0800h
The Effect of the Differential Rotation of Photospheric Magnetic Features on Synoptic Frames of the Photospheric Magnetic Field
To model the time-dependent heliosphere we need the instantaneous global distribution of the photospheric magnetic field. As a proxy for the instantaneous global distribution of the photospheric magnetic field at a particular time of interest, the synoptic frame of the photospheric magnetic field is constructed by inserting into the associated monthly Carrington map of the photospheric magnetic field a remapped magnetogram observed as close as possible to the time of interest. In such a synoptic frame, the observation time of magnetic features in pixels outside the inserted magnetogram may differ from the time of the magnetogram by as much as 14 days. During the interval the magnetic features move significantly due to differential rotation, though it may be acceptable to neglect the effects of meridian flow and random walk diffusion. We improve the synoptic frame by accounting for the differential rotation of the magnetic features in the synoptic background frame and consider how changes in the boundary around the inserted magnetogram due to the differential rotation lead to significant effects on the predicted chromospheric and coronal structures.
http://sun.stanford.edu/~zhao/fall2004.html
SH21B-0420 0800h
Solar Coronal Magnetic Fields From Cassini Faraday Rotation
For 10 days surrounding solar conjunction beginning June 16, 2002, the Deep Space Network's experimental antenna in Goldstone took Faraday rotation measurements of Cassini's radio signal. Faraday rotation is the integrated product of the electron density of the corona and the component of the magnetic field parallel to the line of sight. The line of sight of Cassini passed within 1 solar radii of the surface of the sun. Equipped with X- and Ka-band (8 and 32 GHz) capabilities, the signal of Cassini measured the Faraday rotation of the corona through the region of closest approach, 2 coronal mass ejections, and 1 magnetic transient event. Here we present the calculated coronal magnetic fields from the 2002 Faraday rotation experiment.
SH21B-0421 0800h
Comparison of Tomographic and Forward Modeling 3D Reconstructions of a Coronal Streamer
We compare 3D reconstructions of a coronal streamer using two different techniques. Thernisien employs images from the LASCO coronagraph on board SOHO and determines the optimal parameter values of a general slab model (with folds) for electron density yielding a synthetic white light image that best matches the starting LASCO data (Thernisien et al. 2004, B.A.A.S., 36, 797). This forward modeling approach forces the solution to be of a pre-determined functional form. We compare this reconstruction with a true tomographic reconstruction using input images from multiple viewpoints, with no predetermined constraint on the geometry of the electron density distribution found. As an initial test of the tomographic reconstruction, we start with input synthetic coronagraph data rendered from the Thernisien model electron density reconstruction, and first compare the tomographic reconstruction to this known starting distribution. We next use true LASCO data from different days (rotational tomography) for a tomographic reconstruction, and compare the reconstructed electron density distribution and its rendered synthetic coronagraph data with the Thernisien electron densities and rendered coronagraph data. In general, with real data the tomographic reconstruction produces synthetic coronagraph images rendered from its electron density determination that are more similar to the input LASCO data, while the Thernisien electron density determination is more tightly structured, from its prior constraints, than the tomographic reconstruction from a very limited number of viewpoints. The two techniques are complementary, and both will provide useful reconstruction tools for use in the upcoming STEREO mission, due for launch in early 2006. JWC and JSN are supported on this work by NASA under W10135, and by the Office of Naval Research.
SH21B-0422 0800h
3D Sun Loop Tracer: A Tool for Stereoscopy of Coronal Loops for NASA's STEREO Mission
Stereoscopy and triangulation can be used to determine the three-dimensional geometry of coronal loops seen in simultaneous images from the two STEREO spacecraft. Here we demonstrate a new tool 3D Sun Loop Tracer (SLT) that uses stereoscopy to determine the 3D structure of a loop that can be identified in both images. SLT proceeds in several stages. First, the user "seeds" the tool by selecting the same loop in two simultaneous images. The user identifies any point on the same loop in the first image and any point on the same loop in the second image. The selected points can be anywhere on the loop. Next, separately for each image, the loop segment is traced automatically using an algorithm which follows edges. Last, the two traces are fed to a triangulation program that matches the two segments to find corresponding "tiepoints" and performs the inversion to obtain the (x,y,z) coordinates of points on the loop. The tool has been developed and tested using a physics-based synthetic 3D coronal (K. Schrijver, private communication). We show that the method produces accurate results for loop reconstruction over a wide range of stereo angles.
SH21B-0423 0800h
A Model For EUV Flux Throughout The 3-Dimensional Heliosphere
After July 2001, when Ulysses moved from 30 to 80 degrees in solar latitude, the Ulysses GAS instrument measured an apparent increase in the neutral He density. This is more naturally interpreted as a latitudinal dependence (decrease) of the loss rate due to solar photoionization rather than a true increase of the neutral He density. We have developed a three-dimensional model for solar EUV fluxes observed at any heliospheric position, using daily SOHO EIT observations, over successive Carrington rotations, projected to any heliospheric position. The combined effects of solar rotational and latitude-dependent flux variability are explicitly treated in this model. The flux model has been directly compared with other direct irradiance observations in the ecliptic plane with the SOHO/SEM irradiance time series for validation. We then use this flux to compute the photoionization rate of the in-flowing neutral He, and compare the modeled change with time along the spacecraft trajectory with the direct measurements from the out -of -ecliptic Ulysses GAS observations. The 3-D model developed will be directly applicable to STEREO EUV images from the SECCHI instrument suite. As the two spacecraft separate, the amount of the solar surface observed will increase through the mission, providing more accurate solar inputs.
SH21B-0424 0800h
Modelling of the Quiet Sun Emission in the Metric Radio Range
The thermal emission from the Quiet Sun can be mapped in the metric radio range when the solar activity is low, and plasma emissions due to non-maxwellian distributions of electrons are weak or non-existent. This occurs mainly in the vicinity of the solar cycle minimum. Metric radio observations have been used in the past to infer the mean coronal temperature, and to map and study large scale coronal structures. Earlier simulations using symmetrical electron density distributions and uniform temperatures were succesful to depict some of the properties of the Quiet Sun emission but are not suitable in detailed comparisons with observations, and furthermore, they predict limb brightening in the high frequency range of the metric domain (150-450 MHz), which has not been observed so far. In this paper, we present simulations of the Quiet Sun emission based on Potential Field Source Surface extrapolations, which are used to build a global density and temperature model of the corona at a given date. Scaling laws involving the loop footpoint field strength and loop length govern the density and temperature distribution in this model. Synthetic radio images are then computed using raytracing techniques, taking into account the refraction of radio waves in the corona, and are compared with actual observations provided by the Nancay Radioheliograph.
SH21B-0425 0800h
ULYSSES-WIND Simultaneaous Radio Observations of Interplanetary Solar Activity : Energetic Electrons and Transient Shocks
In the interplanetary medium (IPM), the radio receivers on the Ulysses and Wind spacecraft have recorded many solar radio emissions which drift from high to low frequencies. Most of them are type III fast drifting bursts. These are produced by subrelativistic electrons which are ejected from active regions and then travel outward along open magnetic field lines to lower densities in the IPM. Less frequently other emissions, called type II bursts, are observed to appear as slowly drifting frequency bands with intensities often very weak of the order of the local plasma thermal background. These drifting features are due to radio emissions generated by solar wind electrons accelerated by transient shocks moving outward from the Sun to the IPM. We use radio data from Ulysses and Wind, observed simultaneously, to track type III and type II bursts , and to deduce information on the burst characteristics (radiation mode,directivity), the source region and the propagation. We present these observations in perspective of the dual radio observations of the future Stereo mission
SH21B-0426 0800h
Time-of-flight dispersed electrons at strong interplanetary shocks
Strong interplanetary shocks accelerate solar wind electrons to produce a foreshock region and, often, type II radio bursts. On upstream field lines, these electrons can be dispersed due to time-of-flight effects. We use data from instruments on the Wind spacecraft to study this effect at several strong IP shocks. At each shock, a velocity-dispersed electron beam is detected in the upstream region. We use the dispersion to calculate field line length to the shock source. The measurement of field line length indicates the existence and scale of structure on the shock front.
SH21B-0427 0800h
SEP Event Modeling for STEREO
The interpretation of Solar Energetic Particle or SEP events detected by STEREO will require a "global" picture that is consistent with the underlying solar wind context. One approach to such a model is under development by the CISM (Center for Integrated Space Weather Modeling) group. This model uses a guiding-center technique to follow ions in the >10 MeV energy range in the magnetic fields produced by CISM heliospheric MHD simulations. The model accommodates a variety of source descriptions, including flare-related sources at the Sun and those from traveling interplanetary shocks described by the MHD models as a consequence of coronal transients propagating to 1 AU. The shock source descriptions will eventually be based on parameterizations derived from local ion-kinetic hybrid simulations of shocks covering the parameter space (Mach number, plasma beta, shock normal angles) of interest. The advantage of this approach is its relative generality in that it can accommodate any complicated coronal and solar wind field and source descriptions the MHD models (and observations) may require.
SH21B-0428 0800h
Lessons from Sequences of SEP Heavy Ion Events Associated with Active Region Passages Across the Disk
The origin and heliospheric transport of SEP heavy ions are important areas for study due to both the hazards to humans and technologies these ions represent, as well as the information they contain about the processes of particle acceleration by the Sun. It has been suggested that compositional differences which depend on solar event longitude are associated with the particular geometry of the observer's connection to the CME-related shock. To learn more about this hypothesis, we analyze a number of significant heavy ion SEP events that occur in sequences of three as a CME-productive active region makes its way across the disk from east to center to west limb. For this purpose we use the SIS data from ACE, including ions above 5 MeV/n and masses up to and including Fe. We report on trends in the relative fluxes of heavy species that suggest altitude of connection rather than longitude of connection effects.