SH21A-1564
Online Analysis for STEREO's IMPACT Investigation: Lessons Learned
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
IMPACT team has developed several online web portals which provide easy access to plots and data
products. These portals integrate data from other heliospheric and solar missions as well as results from the
modeling community to help scientists analyze events and trace features from their solar origins to 1 AU. We
discuss lessons learned from this experience with implications for others who might develop similar sites for
their own missions and for data providers who wish to have their data served through such sites. We
emphasize the ongoing need in our community for well-documented and consistent online data access and
the ways data providers can meet this need. Finally, we demonstrate how integrated data browsers, such as
ours, can help to enable the kinds of cross-disciplinary research necessary for a more complete
understanding of the physical processes that connect geospace with solar events.
http://sprg.ssl.berkeley.edu/impact
SH21A-1565
Temporal and Spatial Variation of the Solar Wind Bulk Properties from STEREO SWEA/PLASTIC by Multi-Spacecraft Analysis
The two STEREO spacecraft with nearly identical instrumentation were launched near solar activity minimum and they separate by about 45 degrees per year providing a unique tool to study the temporal and spatial evolution of the solar wind. We analyzed the solar wind bulk properties measured by the SWEA electron and the PLASTIC ion plasma instruments on board. We calculate the timelag between the STEREO A and B spacecraft considering their radial and longitudinal separation and time-shift the B measurements in order to forecast the A measurements. We show that the correlation between the forecasted and the real A datasets is very good. It decreases slightly as their timelag increases, which is due to the temporal evolution of the solar wind. We also find that this correlation clearly decreases when we compare structures of smaller spatial scales. As a result, the characteristic temporal and spatial changes in the solar wind bulk properties can be quantitatively determined.
SH21A-1566
Electrostatic coupling: STEREO/WAVES observations in the solar wind and Vlasov simulations.
The TDS (Time Domain Sampler) part of the WAVES experiment on board STEREO enables the study of high resolution in-situ electric field waveforms in the solar wind. From different TDS datasets, we show evidence for three-wave coupling, involving Langmuir waves and ion acoustic waves. The three waves show the expected resonant relations for doppler-shifted frequencies and bicoherence studies show a good phase locking between the three waves. Vlasov-Ampere simulations have also been performed to study the electrostatic coupling mechanism in 1D and compared to the STEREO/WAVES observations.
SH21A-1567
Laser Post-Ionization Mass Spectrometry Analysis of Genesis Solar Wind Collectors
The samples returned to Earth by the NASA's Genesis Mission contain a record of the elemental and isotopic abundances of the Solar Wind (SW). This record is formed by the SW ions implanted in the near-surface regions of the Genesis sample collectors, so that the SW material can be distinguished from a terrestrial contamination, which occurred due to the crash landing of the spacecraft Sample Return Capsule. At Argonne National Laboratory, we are conducting analyzes of the Genesis SW collectors using a specially developed Laser Post-Ionization Secondary Neutral Mass Spectrometer (LPI SNMS), SARISA. This approach, based on ion sputtering of a SW collector surface and laser post-ionization of the neutral atoms sputtered from it, has proved to be sensitive, accurate and well suited for the quantitative analysis of the Genesis samples. We will report in this work the abundances of SW Mg and Ca measured with SARISA in two types of SW collector materials, silicon and diamond-like carbon (DLC). These LPI SNMS measurements were conducted in Resonance-Enhanced Multi-Photon Ionization (REMPI) regime using a sputter depth profiling method. In order to make our analyzes quantitative, we used specially prepared standards, made from exactly the same materials as the flown Genesis SW collectors and implanted with known fluencies of Mg and Ca ions. The REMPI analyzes of these standards allowed us to characterize the actual efficiency and detection limits of the SARISA instrument: for Mg, its useful yield peaked at about 20% and detection limits corresponded to < 50 part-per-trillion. We measured concentration vs depth profiles for Mg and Ca in SW collectors (Si and DLC, respectively) and compared them to the corresponding implant standards. One striking feature of the SW implants (compared to the standards) was that maxima of the SW element concentration vs depth profiles were broad, with apparent diffusion of the implanted atoms towards the surface and into the bulk. Since these collectors (1) were subjected to intense bombardment by more abundant SW ions (H and He), and (2) the Solar light heated them to the temperature of ~160° C during the SW collection, which lasted up to 852.83 days, this feature can be explained by radiation- enhanced thermal diffusion processes. In order to evaluate how much the terrestrial contamination can affect the accuracy of our LPI SNMS measurements, we conducted a special series of experiments with sputter depth profiling of Genesis SW collectors from their backside (i.e. opposite to the one exposed to the SW). By these measurements, we have demonstrated that (1) the implanted solar wind can be identified by backside sputter depth profiling, (2) the apparent widening of depth profiles into the bulk of SW collectors is mostly due to ion mixing effects, and (3) that widening and shifting of concentration maxima towards the collectors surface is real. We also concluded that the depth resolution of our measurements has to be improved in order to accurately profile the near-surface regions of SW collectors. At the Fall Meeting, we will present these experimental results and discuss what needs to be (and what is being) done in order improve accuracy of measurements of elemental abundances by ion sputtering based analytical methods. This work is supported by NASA under Work Orders W-19,895 and W-10,091 and by the U.S. Department of Energy (BES-Materials Sciences), under Contract No. DE-AC02-06CH11357.
SH21A-1568
Modification of the Light Noble Gases From Genesis Aluminum Collectors
The Genesis mission returned samples of solar wind (SW) collected over 2 years at the L1 point for earth- based laboratory measurements. The main goal of the mission is to obtain accurate, high precision isotopic measurements of trace elements in the SW. Since there are several processes and effects that can alter the laboratory measured value from the true SW value, it is worth trying to quantify these effects. We have been doing that by looking at the light noble gases: helium, neon, and argon, but these results will have implications for other elements as well. First, isotopic fractionation can occur if the processes which accelerate the SW away from the sun are mass- dependent. It has been uncertain how large this effect might be. In an effort to quantify this effect, Genesis collected samples of SW from different flow regimes (slow, fast, CME). Our measurements of these different regimes have tightly constrained the possible isotopic fractionation of neon and argon. Second, there are implantation effects. It is known that implantation at constant velocity results in mass fractionation with depth. Heavier isotopes have higher energy, and thus a larger range. The effect of this is that if all of the gas is not recovered during the measurement, the measured isotopic ratios will be altered from their source values. Surface erosion (such as surface damage of Genesis collectors and sputtering of lunar regolithic material) will make the measured ratios heavier than the source, while incomplete degassing of the sample will make the measured ratios lighter. And third, thermally activated diffusion can alter the initial depth profiles and cause losses of shallowly implanted species, both of which cause preferential loss of the light isotopes. We are currently working on a diffusion experiment to determine the diffusion parameters of the Genesis collector materials and to quantify the changes in the measured ratios from diffusive losses. We maintained individual pieces of two different Genesis collectors, polished aluminum and aluminum on sapphire (AloS), at six different temperatures between 160 C and 360 C for 322 days. And now we are performing step-wise heating on the samples. Helium and neon are measured together in one mass spectrometer, and Ar is cryogenically separated from them and measured in a second mass spectrometer. Preliminary results show higher variation in 3He/4He than 20Ne/22Ne and little variation in 36Ar/38Ar, as expected.
SH21A-1569
The GENESIS Mission: Solar Wind Isotopic and Elemental Compositions and Their Implications
The GENESIS mission was a novel NASA experiment to collect solar wind at the Earth's L1 point for two years and return it for analysis. The capsule crashed upon re-entry in 2004, but many of the solar-wind collectors were recovered, including separate samples of coronal hole, interstream, and CME material. Laboratory analyses of these materials have allowed higher isotopic precision than possible with current in-situ detectors. To date GENESIS results have been obtained on isotopes of O, He, Ne, Ar, Kr, and Xe on the order of 1% accuracy and precision, with poorer uncertainty on Xe isotopes and significantly better uncertainties on the lighter noble gases. Elemental abundances are available for the above elements as well as Mg, Si, and Fe. When elemental abundances are compared with other in situ solar wind measurements, agreement is generally quite good. One exception is the Ne elemental abundance, which agrees with Ulysses and Apollo SWC results, but not with ACE. Neon is of particular interest because of the uncertainty in the solar Ne abundance, which has significant implications for the standard solar model. Helium isotopic results of material from the different solar wind regimes collected by GENESIS is consistent with isotopic fractionation predictions of the Coulomb drag model, suggesting that isotopic fractionation corrections need to be applied to heavier elements as well when extrapolating solar wind to solar compositions. Noble gas isotopic compositions from GENESIS are consistent with those obtained for solar wind trapped in lunar grains, but have for the first time yielded a very precise Ar isotopic result. Most interesting for cosmochemistry is a preliminary oxygen isotopic result from GENESIS which indicates a solar enrichment of ~4% in 16O relative to the planets, consistent with a photolytic self-shielding phenomenon during solar system formation. Analyses of solar wind N and C isotopes may further elucidate this phenomenon. Preliminary results from GENESIS have been reported for N, and results are still pending for C.
SH21A-1570
First steps towards a solar wind 13C/12C ratio
The isotopic composition of the Sun provides information about the properties of the presolar nebula. One way to determine the solar isotopic abundances are spectroscopic observations of the solar surface. In the case of carbon previous measurements exploited that the rotation bands of the two stable carbon isotopes 13C and 12C in CO molecules are slightly different. The focus of this work is to determine the 13C/12C ratio in the solar wind for the first time by in situ measurements, because deviations of the isotopic composition in photospheric observations and solar wind measurements indicate fractionation processes in the chromosphere and the corona. Based on long term- data from the linear time-of-flight mass spectrometer SWICS (Solar Wind Ion Composition Spectrometer) mounted on ACE (Advanced Composition Explorer, at L1 since 1997) we present the first results and compare them with spectroscopic measurements.
SH21A-1571
Kinetic Behavior in the Formation Process of Magnetic Decrease Structures Within the Corotating Interaction Regions
A magnetic decrease (MD) structure exhibits the localized depression in the intensity of the interplanetary magnetic field, which is often identified in the region close to the rear edge of a corotating interaction regions (CIRs). In recent MHD simulations, we have investigated the numerical model for the MD formation process: When the Alfvenic field fluctuation embedded in the fast solar wind is carried into the CIR through the reverse shock, it disintegrates into two Alfven modes traveling in opposite directions in a plasma-rest frame. In the region sandwiched by these modes, the field intensity is reduced that results in the MD formation. This physical mechanism is simply accounted for as follows. Amplification through the reverse shock makes a local pulse-like structure in a monotonic component of the fluctuation field. It leads to the formation of a current reversal structure which violates the force balance. The resultant net force sweeps the plasma backward to form a pressure increase and simultaneous magnetic decrease due to the diamagnetic effect. The opposite edge of this structure, associated with the MD, affords another diamagnetic current, which becomes the source for a reverse Alfven mode at the trailing edge of the MD. In this way, these two Alfven modes (or associated current structures) constitute the MD boundaries. On the other hand, one prominent feature of the MD is a large temperature anisotropy T⊥/T∥ > 1 associated with the mirror instability, so that the MD mechanism should be referred to in terms of kinetic processes. In this paper, we further perform a hybrid simulation and will show the kinetic manifestation of the evolution of Alfvenic fluctuation within the CIR as cited above. The anisotropy generation and other kinetic properties are also discussed in order to elucidate the MD energetics.
SH21A-1572
A survey of periodicies in the solar wind velocity observed by Ulysses
Knowledge of the presence and evolution of periodicities in the solar wind at out--of--ecliptic latitudes can give information about the latitudinal structure of the solar wind and help distinguish between theories that predict the global characteristics of the solar wind and heliosheet. We have computed the spectrogram of the plasma velocity measured by the Ulysses spacecraft in the interval of 1991--2008 in the range of 5-- and 40--days and confirmed periodicities observed in previous limited--time--interval studies. A statistical method has been developed to determine if the observed periodicities are due to physical effects such as current sheet crossings or multiple coronal holes as opposed to being harmonics of the fundamental approximately 26--day period. Based on those criteria, we conclude that many 13--day periods are due to physical processes and not simply harmonics of the 26--day period. An example occurs in late 1999 when Ulysses was at mid- latitudes; a clear 13--day period is present without an accompanying 26--day period. The spectrogram also reveals 14--, 23--, and 30--35--day periods during solar minimum while Ulysses was at high southern latitudes. This feature appears for both solar cycles 22 and 23, although the periods are slightly shorter during the solar cycle 23 southern polar pass. We also notice complexity in the periods that appear during the solar cycle 23 maximum. All of these features are interpreted in the context of warped current sheets and other periodically appearing structures.
SH21A-1573
On the Source of Periodic Solar Wind Number Density Structures Using the Alpha to Proton Abundance Ratio
Solar wind elemental abundance ratios provide information regarding the source region of the solar wind plasma because they are not modified by propagation. We present an analysis of the alpha to proton abundance ratio during periods in the solar wind with significant long wavelength number density fluctuations. We discuss the implications of the abundance ratio variations on possible source regions of those periodic solar wind number density structures. In a recent study using 11 years (1995-2005) of solar wind number density observations taken on the Wind spacecraft, we analyzed the radial length-scales of periodic number density structures. We performed Fourier analysis on short (approximately equal to six hours) data windows and determined the wavelength (length-scale) of the number density structures. We found that particular length-scales occurred more often than others in the solar wind number density during those eleven years. For the slow wind, the most significant length-scales are approximately 73, 120, 136 and 180 Mm. For the fast wind, the most significant length-scales are approximately 187, 270 and 400 Mm. The outstanding question is the source of these periodic density structures. Using the alpha to proton abundance ratio during periodic solar wind number density events, we address whether periodic density structures are generated in the local interplanetary medium, or if they are more probably generated somewhere near the solar surface or solar corona, frozen into the solar wind, and convected out to Earth.
SH21A-1574
Ion Cyclotron Waves in the Solar Wind at 0.3 and 1 AU
A leading candidate to answer the mystery of what heats and accelerates the solar wind is the production and subsequent absorption of ion cyclotron waves. For the first time, we observed these waves in situ at 1 AU using the high-resolution magnetometer data from the STEREO spacecraft. They appear at times when solar wind conditions allow them to propagate to 1 AU. The waves are essentially left-handed polarized, propagating almost parallel to the magnetic field, and below the local proton gyro-frequency in the solar wind frame. Waves propagate both inward and outward from the Sun but are all carried out by the super-Alfvenic solar wind. We also extend our observations to the inner heliosphere based on the Helios data. We compare the properties of these waves at about 0.3 and 1 AU, to understand their radial evolution. Our study will help determine whether the power of these waves extrapolated to the corona is sufficient to accelerate the solar wind.
SH21A-1575
Langmuir Waves Upstream of Interplanetary Shocks: Dependence on Shock and Plasma Parameters
We examine several hundred interplanetary shocks observed by the Wind spacecraft to determine which plasma environments and shock parameters are favorable for the production of upstream Langmuir waves. Langmuir wave generation is a necessary condition for producing type II radio bursts, which are a primary signature of interplanetary coronal mass ejections. We split a list of roughly 250 interplanetary shocks into two populations, based on the presence or absence of upstream Langmuir waves. Our results indicate that the dominant factor in Langmuir wave production is the shock magnetic compression from the upstream to the downstream region. Other parameters, including the de Hoffmann-Teller velocity and the shock Mach number, have no discernable effect. Given these results, and assuming that Langmuir waves are created by electron beams accelerated by a fast-Fermi process, we draw the tentative conclusion that it is the fraction of incident electrons that are reflected that controls the presence or absence of upstream Langmuir waves, rather than the maximum beam energy.
SH21A-1576
Consequences of the Eigenmode Interpretation of Solar Wind Langmuir Waves
The localization and modulation implied by interpreting solar wind Langmuir waves as eigenmodes of density perturbations are incompatible with the generally used approximation that these Langmuir waves are infinite plane waves in a homogenous plasma. Therefore, aspects of type II and type III radio burst theory require a reformulation that incorporates wave localization and modulation from the outset. The electric field structure perpendicular to the local magnetic field of solar wind Langmuir waves and the conversion of electrostatic waves to electromagnetic radiation specifically are addressed. Data from the STEREO/WAVES instrument is used to show that observed Langmuir wave transverse electric field structure is consistent with an eigenmode interpretation. The connection between observed electrostatic structures at harmonics of the local plasma frequency and antenna radiation of localized wave packets is also explored.
SH21A-1577
Modelling Langmuir Wave Interaction with Plasma Inhomogeneities in the Flaring Solar Corona
We present simulations of the time and spatial evolution of electron beam driven Langmuir wave turbulence interacting with plasma inhomogeneities. This code can be used to investigate a variety of particle acceleration and propagation scenarios in the flaring corona and interplanetary space. Here we present one simple model: simulations of a beam of accelerated electrons propagating from an acceleration region at the top of a coronal loop down to the chromosphere. RHESSI imaging spectroscopy shows a flatter X-ray spectrum at the footpoints compared to coronal sources, so we investigate whether plasma waves and inhomogeneities can change the electron distribution in such a way.
SH21A-1578
Variations of Strahl Properties With Fast and Slow Solar Wind
The interplanetary solar wind electron velocity distribution function generally shows three different populations. Two of the components, the core and halo, have been the most intensively analyzed and modeled populations using different theoretical models. The third component, the strahl, is usually seen at higher energies, is confined in pitch-angle, is highly field-aligned and skew. This population has been more difficult to identify and to model in the solar wind. In this work we make use of the high angular, energy and time resolution and three-dimensional data of the Cluster/PEACE electron spectrometer to identify and analyze this component in the ambient solar wind during high and slow speed solar wind. The moment density and fluid velocity have been computed by a semi-numerical integration method. The variations of solar wind density and drift velocity with the general bulk solar wind speed could provide some insight into the source, origin, and evolution of the strahl.
SH21A-1579
Cluster/PEACE Electrons Velocity Distribution Function: Modeling the Strahl in the Solar Wind
We present a study of kinetic properties of the strahl electron velocity distribution functions (VDF's) in the solar wind. These are used to investigate the pitch-angle scattering and stability of the population to interactions with electromagnetic (whistler) fluctuations. The study is based on high time resolution data from the Cluster/PEACE electron spectrometer. Our study focuses on the mechanisms that control and regulate the pitch-angle and stability of strahl electrons in the solar wind; mechanisms that are not yet well understood. Various parameters are investigated such as the electron heat-flux and temperature anisotropy. The goal is to check whether the strahl electrons are constrained by some instability (e.g., the whistler instability), or are maintained by other types of processes. The electron heat-flux and temperature anisotropy are determined by fitting the VDF's to a spectral spherical harmonic model from which the moments are derived directly from the model coefficients.
SH21A-1580
Comparison of the Width and Intensity of the Suprathermal Electron Strahl in General Solar Wind and ICME Solar Wind.
In this study we examine the width and intensity of the solar wind suprathermal electron strahl. We report on the variability of these features across various types of solar wind flow using 70 eV-1370 eV electron data from ACE/SWEPAM. In preliminary work we have characterized general solar wind using the first 108 days of 2000 and determined strahl widths and intensities by fitting a function that consists of a Gaussian plus a constant term to the measured pitch angle distributions. Approximately 78% of the distributions are well- described by this function. We then used data from ICME intervals with clear counterstreaming suprathermal electrons and similarly determined the strahl width and intensity. Results show that the strahl is typically comprised of two populations: one of narrow width, HWHM~10°, and the other broader, HWHM~25°. Narrow suprathermal electron strahls are fractionally more likely to occur in ICME solar wind. Approximately 30% of general solar wind strahls have widths less than 20°, compared with approximately 55% of ICME strahls. Further, in ICME counterstreaming solar wind at a given time, the narrower strahl nearly always has a width less than 20° whereas the broader strahl is nearly always wider than 20°, indicating that counterstreaming suprathermal electron strahls typically have different widths.
SH21A-1581
Radial Evolution of Non-thermal Electrons in the Low-latitude Solar Wind: Helios, Cluster and Ulysses Observations
We have performed a statistical study of a substantial amount of solar wind electron velocity distribution functions (eVDFs). In our data set we combine measurements acquired on-board three spacecraft (HELIOS, CLUSTER II and ULYSSES) in the low ecliptic latitudes covering the heliocentric distance from 0.3 up to 4 AU. In this study we focus on the non-thermal properties of the measured eVDFs in both the slow and the fast solar wind regimes. All three eVDF components typically observed in the solar wind, i.e. the core, the halo and the strahl, are modeled analytically. We mainly study the fractional densities of the three electron components and also the non-Maxwellian character of the high energy eVDF tails as a function of the radial distance from the Sun. Furthermore, we provide some preliminary results concerning the higher eVDF moments, i.e. the temperature of the eVDF components and their contribution to the overall electron heat flux. In addition, we summarize all mean electron properties in the radial evolution of the model eVDF.
SH21A-1582
STEREO multi-spacecraft investigation of solar wind electron halo depletions at 90° pitch angle
Past studies have found that electron halo depletion at 90° pitch angle are observed in the solar wind about 10% of time. In the present study, we use STEREO multi-spacecraft data to statistically investigate (1) how this occurrence rate depends on the criteria used to define the depletions, (2) whether there is a relation between the local magnetic field strength and the magnitude of the halo depletion, (3) whether the magnitude of the magnetic field and halo depletion correlate between the two STEREO spacecraft, i.e., using appropriate lag time corrections, does a substantial halo depletion at one spacecraft correspond to a larger magnetic field at the other spacecraft if no depletion is observed there?, and (4) how these correlations evolve with inter-spacecraft separation. The results all tend to agree with the previous interpretation, based on single spacecraft event studies, that those 90° pitch angle electron halo depletions are the result of focusing and mirroring along magnetic field lines when magnetic field enhancements are present along the field line ahead and behind the observation point.
SH21A-1583
Simulation Study of Electron Heating and Nonlinear Wave-Wave Interactions in the Collisionless Ion-Acoustic Shocks
Mixing of hot electrons and cold electrons along the magnetic field line are commonly observed in the electron foreshock region and in the boundary layers of the Earth!|s magnetosphere. In this study, we use the ion-acoustic shock as an example to study the anomalous heating of electrons by means of electrostatic Vlasov simulations. Our simulation results indicated that a quasi-steady cross-shock potential jump is established within a few electron oscillation periods at the beginning of the shock simulation. The cross shock potential can accelerate the upstream electrons across the shock ramp and decelerate the leaked electrons coming from the downstream side. The mixing of the upstream and downstream electrons can result in electron-electron two-stream instability to generate electron-acoustic waves (EAWs) with phase speed close to the average speed of the low-density electron species. The transmitted electron beam from the upstream side can lead to short-wavelength EAWs on the downstream side. The EAWs can heat up the transmitted electron beam and result in the saturation of the EAWs. The bump-on-tail distribution on the upstream side due to the presence of leakage electrons can lead to the formation of EAWs with longer wavelength. The EAWs on the upstream side can smooth out the bump-on-tail structure and lead to the saturation of the EAWs. The leakage electrons can also lead to ion-electron two-stream instability and generate ion-acoustic waves (IAWs). In general, the growth rate of the IAWs is much lower than the EAWs, but the growth of IAWs can be greatly enhanced when the phase speed of the unstable IAWs is about the same as the phase speed of the local EAWs. The amplification of the IAWs can result in large-amplitude longer-wavelength waves. The phase-space mixing of the electrons by the large-amplitude longer- wavelength IAWs can produce new bump-on-tail structures on the electrons!| distribution function and lead to formation of the secondary EAWs. The IAWs and the secondary EAWs together can heat-up the electrons in a very efficient way. Our simulation results indicate that the strong field-aligned electron heating and temperature anisotropic can be completed within a few tens of ion oscillation periods. Electromagnetic waves that can be generated by the strong temperature anisotropic will be discussed.
SH21A-1584
Simulations of Effects of Coronal and Beam Parameters on Coronal Type III Bursts
A recently developed simulation model is used to investigate the effects of varying the coronal and electron heating conditions on the dynamic spectra of coronal type III bursts observed at Earth. The flux of 2fp emission is significantly higher than that of fp emission, which is unlikely to be observable except under very favorable propagation conditions. Moreover, the 2fp emission is unlikely to continue into the solar wind, although some bursts are very strong and will extend into the upper corona with lower frequencies than simulated, consistent qualitatively with observations. The flux and brightness temperature of 2fp emission are affected significantly by variations in the parameters, while the frequency drift rate and half-power duration are affected only weakly. Further, the simulations confirm the standard interpretation of the drift rate of 2fp emission in terms of the plasma density profile and an average beam speed that agrees quantitatively with the simulated beam dynamics, for wide ranges of coronal and heating conditions. For weak heating events or events with high coronal electron temperature, the remote radiation shows characteristics that agree quantitatively with microbursts. When the heating is even weaker and/or the electron temperature is even higher, the heating events are radio-quiet, consistent qualitatively with hard X-ray observations. For similar heating originating in similar frequency ranges different density models yield quantitatively similar results except for the drift rate. Variations of the levels of a given density profile, corresponding to background corona or coronal streamers, can also cause significant changes in spectral characteristics.
SH21A-1585
Coronal heating and turbulence from kinetic drift wave-Alfven waves launched by oscillating pre-coronal region current loops and instabilities
Using theory and simulations, we investigate the coronal heating rates that may be expected from electron Landau damping of kinetic Alfven waves. The Alfven waves are launched by oscillating current loops in the pre-coronal region and by convective instabilities from inverted electron density-temperature gradients. Ray trajectories are calculated from coronal equilibrium profiles data from Hinode and are used to estimate the power emitted in the waves. Estimates of the solar corona heating power from the 3D pseudo spectral simulations of the waves are used to study the anisotropy of the wave turbulence. Work partially supported by the DoE and the NSF ATM grant ATM-0638480
SH21A-1586
An Open Source MHD Code for the Study of Magnetic Structures in the Solar Wind
We have developed a 2.5D MHD code designed to study how the solar wind influences the evolution of transient events in the solar corona and inner heliosphere. The code includes the effects of thermal conduction, coronal heating and radiative cooling. Thermal conduction is assumed to be magnetic field- aligned in the inner corona and smoothly transitions to a collisionless formulation in the outer corona. In addition, we have developed a stable method to handle field-aligned conduction around magnetic null points. The inner boundary is placed in the transition region, and the mass flux across the boundary is determined from 1-D field aligned characteristics. We have developed a minimal velocity change condition which is used to stabilize the mass fluxes at the inner boundary. The 2.5D nature of this code makes it ideal for parameter studies not yet possible with 3D codes. We designed this code to be used by non-modeling experts and have made it publicly available as a tool for the community. To this end we have developed a graphical user interface which aids in the selection of options appropriate for the desired simulation and a graphical interface which can process and visualize the data produced by the simulation. As an example, we show a simulation of a dipole field stretched into a helmet streamer by the solar wind. Plasmoids periodically erupt from the streamer, and we perform a parameter study how the frequency and location of these eruptions changed in response to different levels of coronal heating. As a further example, we show the solar wind stretching a compact multi-polar flux system. This flux system will be used study breakout coronal mass ejections in the presence of the solar wind.
SH21A-1587
Three-dimensional MHD simulation of the solar wind with rotation of the Sun
It is well known from Parker model that the solar wind becomes supersonic beyond a critical radius. The 2-D structure was given by several simulation studies. In the present study, it is extended to the 3-D model when a spherically symmetric 1-D solution by Parker is used as an initial state. By using this model, we can investigate physically complex phenomena more detail. We use a dipole magnetic field as the initial conditions of the solar wind. The 3D structure of the solar wind has been simulated by using a global MHD model to demonstrate the Parker spiral configuration. At that time, magnetic field lines enter the Earthfs revolution orbit with an angle of 45 degrees. In addition, we use a split dipole magnetic field in place of the dipole magnetic field as the initial conditions to study configuration and thickness of the current sheet of heliosphere.
SH21A-1588
MHD-PIC interlocked simulation model in space plasma
We have developed a new type of simulation technique by directly interlocking a traditional Ion-Particle Hybrid simulation model (Hybrid) and an Energetic-Particle Hybrid simulation (EP-HYB) model. In the traditional Hybrid model, all ions are kinetically treated as particles. In the EP-HYB model, non-thermal energetic ions are kinetically treated, and the thermal component is calculated as a fluid. The interlocked model is applied to a two-dimensional collisionless shock problem. The domain for the Hybrid model is embedded in a part of the system, and the bounded data are exchanged to each other to keep the consistency between both models. It can handle the full ion kinetics to investigate the injection problem at the shock transition region, as well as the wave-particle interactions in even far upstream region. We have carried out the long-term simulation of the shock acceleration process using this interlocked model, and successfully reproduced the power-law distribution function, which is consistent with the diffusive acceleration theory. Since the calculation cost of the EP-HYB model is much smaller than that of the Hybrid model, we can considerably reduce the computational demand.
SH21A-1589
A new multi-fluid code for solar coronal plasma simulations
Multi-fluid dynamics of plasma is more complex than MHD because the ion and electron motions need not be identical. The multi-fluid model takes into account electron inertia, charge separation and the full electromagnetic field equations and allows for separate electron and ion motion. Temperature anisotropy effects are taken into account by self consistently evolving the anisotropic pressure tensor. We adopt central semi-discrete finite volume scheme to evolute dynamics of each plasma species. This algorithm allows to incorporate source terms (e.g. Lorentz force) without operator splitting method. Extended stencil discretization have been used for the Maxwell equations. This method results in isotropic al representation of electromagnetic waves and keeps divergence of magnetic field constant. Presented multi-fluid-Maxwell code is applied to study of driven magnetic reconnection. Magnetic reconnection driven by plasma flow is observed in various plasma systems such as solar flares, earth's magnetosphere and laboratory plasma. We have studied the the process collisionless reconnection resulting from charge separation effects. The comparison of the results of full multi-fluid reconnection with Hall-MHD simulation have shown that velocity difference of ions and electrons from the multi-fluid simulation is large than that from Hall-MHD. This is because in Hall MHD electrons move with ions along the direction of local magnetic, but for perpendicular direction electron can move separately and generate the so called Hall current. So multi-fluid simulation demonstrates more precise physics than Hall MHD.
SH21A-1590
3D Numerical Simulations Of Magnetized Winds Of Solar-Like Stars
By means of self-consistent three-dimensional (3D) magnetohydrodynamics (MHD) numerical simulations, we analyze magnetized solar-like stellar winds and their dependence on the plasma-β parameter (the ratio between thermal and magnetic energy densities). This is the first study to perform such analysis solving the fully ideal 3D MHD equations. We analyze winds with polar magnetic field intensities ranging from 1 to 20~G. We show that the wind structure presents characteristics that are similar to the solar coronal wind. The steady-state magnetic field topology for all cases is similar, presenting a configuration of helmet streamer-type, with zones of closed field lines and open field lines coexisting. Higher magnetic field intensities lead to faster and hotter winds. For the maximum magnetic intensity simulated of 20~G, the wind velocity reaches values of ~ 1000 km~s-1 at r ~ 20~r0 and a maximum temperature of ~ 6 × 106~K at r~ 6~r0. The increase of the field intensity generates a larger "dead zone" in the wind, i. e., the closed loops that inhibit matter to escape from latitudes lower than ~ 45° extend farther away from the star. The Lorentz force leads naturally to a latitude-dependent wind. We show that by increasing the density, the system recover back to slower and cooler winds. The key parameter in determining the wind velocity profile is the β-parameter. Therefore, there is a group of magnetized flows that would present the same terminal velocity despite of its thermal and magnetic energy densities, as long as the plasma-β parameter is the same. This degeneracy, however, can be removed if we compare other physical parameters of the wind, such as the mass-loss rate.
SH21A-1591
NASA's Heliophysics Theory Program Accomplishments in its Last Cycle
NASA's Heliophysics Theory Program (HTP) is now into a new triennial cycle of funded research, with new research awards beginning in 2008. The theory program was established by the (former) Solar Terrestrial Division in 1980 to redress a weakness of support in the theory area. It has been a successful, evolving scientific program with long-term funding of relatively large "critical mass groups" pursuing theory and modeling on a scale larger than that available within the limits of traditional NASA Supporting Research and Technology (SR&T) awards. The results of the last 3 year funding cycle, just ended, contributed to ever more cutting edge theoretical understanding of all parts of the Sun-Earth Connection chain. Advances ranged from the core of the Sun out into the corona, through the solar wind into the Earth's magnetosphere and down to the ionosphere and lower atmosphere, also contributing to understanding the environments of other solar system bodies. The HTP contributions were not isolated findings but continued to contribute to the planning and implementation of NASA spacecraft missions and to the development of the predictive computer models that have become the workhorses for analyzing satellite and ground-based measurements.