SH21A-0275
Role of field line topology and anomalous viscosity and resistivity in the mechanism leading to the formation of the slow solar wind
The observation by the Large Angle and Spectrometric Coronagraph (LASCO) instrument on the Solar and Heliospheric Observatory of blobs of plasma generated near the cusp region of the streamer belt has sparked the hope of gaining new insight into the genesis of the slow solar wind. The observations suggest that open and closed field lines reconnect near the cusp of the helmet streamer to form blobs of higher density plasmas that are ejected into the slow solar wind. Models of this process have been suggested, and simulation studies have been conducted. We take the recent simulation work of Einaudi et al.[1] as our starting point to investigate the formation of the slow solar wind and of the blobs observed by LASCO. We report two main conclusions. First, we consider the role of resistivity and viscosity in the evolution time-scale. Second, by employing more realistic two- dimensional configurations including the cusp and bent field lines with fast solar wind flow [2], we find that reconnection giving rise to plasma blobs is driven by converging flows with reconnection rates largely insensitive to changes in resistivity. [1] Einaudi et al, ApJ, 547, 1167 (2001) [2] Lapenta and Knoll, 624,1049 (2005)
SH21A-0276
ON THE GLOBAL DISTRIBUTION OF SLOW SOLAR WIND
The heliosphere is composed of three types of solar wind: solar wind from coronal holes (mostly fast wind), solar wind associated with streamers (mostly slow wind), and transient interplanetary coronal mass ejections (ICMEs). In this work, Advanced Composition Explorer (ACE) and Ulysses data from 1997 to 2006 are used to investigate the properties and relative contributions of these three sources of solar wind during solar cycle 23. Plasma composition (C6+/C5+, O7+/O6+, Fe/O, average charge state of Fe), moments of the proton distribution function (density, velocity, and temperature), and the magnetic field are analyzed. The ratio of O7+/O6+ is used as a criterion to separate ICMEs and the two types of quasi-stationary solar wind based on the results by Richardson & Cane (2004). Similarly, streamer-associated wind is distinguished from coronal hole wind based on its compositional signature O7+/O6+. Furthermore, by adding the location of the heliospheric current sheet from a PFSS model, the ACE and Ulysses data are extrapolated into a global heliospheric structure at 2.5 solar radii. In these maps, we estimate the normal distance from the origin of streamer wind and coronal hole wind to the local current sheet and find that streamer wind comes from a band with width of approximately 23° around the current sheet and coronal hole wind originates from a region 23° beyond the current sheet. This study provides important constraints on the origin of the solar wind and its relation to the global heliospheric structures. A new theoretical explanation of this distribution of the slow wind source region is also provided.
SH21A-0277
The scaling properties of inertial range turbulence and coronal ~ 1/f fluctuations as seen by ULYSSES
Solar wind fluctuations typically are suggestive both of intermittent turbulence (for example, a robust power law region of the power spectrum with ~ -5/3 exponent) and at lower frequencies, of fluctuations of coronal origin (with scaling close to ~ 1/f). The respective roles of the coronal driver, and the evolving turbulence, in generating the observed scaling signature are yet to be unambiguously determined. In order to eliminate the effect of the large scale complex magnetic topology of the corona, which can also show scaling, we examine ULYSSES magnetic field data during intervals when the spacecraft spent many months in the quiet fast solar wind above the Sun's polar coronal holes. We quantify the scaling properties of fluctuations in a statistical sense, on different time-scales τ using generalised structure functions (GSF) to test for a power law scaling ~ τζp. We recover approximate power law scaling for the ~ 1/f range using GSF and test the scaling exponents for secular trend with latitude and radial distance from the sun. At higher frequencies, were we would expect an inertial range of turbulence, the structure functions do not show power law scaling with τ; however power law scaling is recovered under Extended Self Similarity (ESS), that is, in the ratios of structure functions. Thus the inertial range scaling is of the form g(τ)ζp. We show that a single function g(τ) captures all the time periods examined, i.e. no latitudinal or radial dependency was found. This is highly suggestive that the higher frequency range is indeed generated by local phenomenology, that is, evolving turbulence, whereas at lower frequencies (the ~ 1/f range) the relevant phenomenology may be coronal, with implications for our understanding of coronal heating of the solar wind.
SH21A-0278
A Kinetic Model of the Ponderomotive Force of Alfven Waves in the Solar Wind
Kinetic models of solar wind generation are essential in order to accurately test detailed mechanisms for producing the required ion acceleration and heating in the collisionless coronal hole. Among the large-scale effects that must be included in such models is the non-resonant ponderomotive force (PMF) due to parallel- propagating low-frequency Alfven waves emitted by the Sun. However, a kinetic description of this force does not seem to exist, and the well-known fluid expressions are not applicable to this problem. We present a kinetic analysis of the PMF which leads to new terms in the kinetic guiding center equation used to describe the evolution of an ion distribution in the solar wind. We discuss the physical basis for these terms and incorporate them into our kinetic model for the preferential acceleration of heavy ions in coronal holes.
SH21A-0279
Solar Probe Lite Study
NASA Headquarters has requested a short study of the Solar Probe mission to moderately reduce the cost of the mission and to find a solution that will not necessitate the use of nuclear power. The study will be delivered at the beginning of 2008 and is being conducted with coordinated overlap and in an iterative manner with the Solar Probe Science and Technology Definition Team (STDT); the team has been standing for the past few years and will have finished its final report this fall. This paper will give a status of the study with details to be published shortly and will include the possibly modified science requirements being passed on from the STDT to the engineering team. The solar cycle phase of the mission is much the same as specified by the standing STDT report (same team, September 2005) but issues such as inclination and perihelion have been addressed. After first being recommended in 1958 and having been through numerous studies, the first mission to our favorite star could well be possible.
SH21A-0280
Modeling of the Kinetic Dissipation of Alfven Waves: First Results
We present first results of an investigation of the kinetic damping of Afven wave turbulence. The methodology is based on a fully electromagnetic, three-dimensional, particle in cell code. The calculation is initialized by an Alfven wave spectrum. Subsequently, a cascade develops, and damping by coupling to both ions and electrons is observed. We discuss results of these calculations, an present first estimates of damping rates and of the effects of energy transfer on ion and electron distributions. The results pertain to solar wind heating and acceleration.
SH21A-0281
The PHOIBOS Mission : Probing Heliospheric Origins with an Inner Boundary Observing Spacecraft
Fifty years after the Sputnik launch and the beginning of the Space Physics era the time has come for the in-situ exploration of one of the last frontiers in the solar system - the solar corona and inner heliosphere. We present the PHOIBOS (Probing Heliospheric Origins with an Inner Boundary Observing Spacecraft) concept, which has been submitted to the ESA Cosmic Vision program. PHOIBOS is a mission of exploration and discovery designed to make comprehensive measurements in the never-observed region of the heliosphere from 0.3 AU to as close as 3 solar radii from the Sun's surface. The primary scientific goal of PHOIBOS will be to determine the structure and dynamics of plasmas and magnetic fields in the outer solar atmosphere which give rise to the corona, the solar wind and the heliosphere. The two main characteristics of the PHOIBOS mission are : (i) use of retractable solar panels that avoid the use of RTGs (Radioisotope Thermoelectric Generators) and (ii) insertion in the final operational orbit (4 Rs to 3.7 AU with an inclination up to about 60 deg.) by using electric propulsion and Earth and Venus flybys. With these characteristics, the PHOIBOS concepts fit very well within the new NASA "Solar Probe Lite" study.
SH21A-0282
X-rays Observations with Hinode's XRT and the Power of the Solar Wind
The X-ray Telescope (XRT) shows stunning images of solar corona. The x-ray luminosity that comes from the sun is linearly dependant on the magnetic flux of this sun. In a recent paper by Schwadron, Mc Comas, and DeForest (2006), the relationship between x-ray luminosity, magnetic flux and the power available for solar wind acceleration was explored. Using Hinode XRT data from AR 10960, quiet sun, and full disk observations, along with complimentary magnetic field data, we examine the x-ray luminosity with respect to the magnetic field flux. These results are compared with the predicted power of the solar wind and measurements taken at the ACE spacecraft at 1AU for the different regions of the solar surface.
SH21A-0283
Direct Imaging of the Heliospheric Plasma Sheet from the SECCHI telescopes on the STEREO Mission
We report the first ever direct imaging observations of the fine scale structure of the solar wind in the inner heliosphere. The observations were obtained by the Sun-Earth Connection Coronal and Heliospheric Investigation (SECCHI) instrument suite on the Solar Terrestrial Relations Observatory (STEREO) mission. The SECCHI telescopes can trace the coronal plasma from its origins at the solar corona to the Earth's neighborhood. Besides coronal mass ejections, the images also reveal the fine scale structure of the heliospheric plasma sheet during quiet periods. Here, we will show the evolution of these structures from the inner corona to the inner heliosphere. We will also include comparisons with large-scale MHD models of the heliosphere and discuss the importance of such observations for understanding the physics of the solar wind.
SH21A-0284
Acquisition and Preparation of Data from Libya 2006 Total Solar Eclipse
Global temperature and wind speed of free electrons in the solar corona can be measured using light from the visible portion of the electromagnetic spectrum. Davila et al (SH06, Fall 2007 AGU) describe the results of a spectrometric investigation using this technique. In this report we describe a second technique based on filtergrams, which permit the entire inner corona to be imaged using ratios of individual exposures. The data gathered during the total eclipse in Libya March 29, 2006 has provided an opportunity to make such a measurement. Preparation of the data as well as calibration of the instrument played a critical role in eliminating uncertainty and obtaining useful results. In this presentation we will discuss the details of this preparation and present preliminary results.
SH21A-0285
Hydrogen Lyman Alpha Spectral Line Profiles in Coronal Holes from 1.5 - 6.5 Solar Radii
UVCS has made detailed measurements of H I Lyα spectral line profiles in a polar coronal hole at projected heliocentric heights from 3.5 to 6.5 R\odot during 1998 January 5 -- 11. Similar polar coronal hole measurements were made during 1998 June 16 -- 21. Earlier UVCS observations obtained at 1.5 to 2.5 R\odot are used for comparison. In addition, new measurements are being made for the current phase of the solar cycle. From these measurements we derive 1/e half widths of coronal velocity distributions at the observed heights. The velocity distribution includes all motions contributing to the Doppler shifts along the line of sight (LOS). We also measure absolute intensities that can be used to derive outflow speeds via a Doppler dimming analysis. At large heights in coronal holes, the outflowing coronal plasma becomes nearly collisionless and the ionization balance is believed to become frozen. H I Lyα profile measurements characterize the neutral hydrogen velocity distribution, which at lower heights can also be used to describe the proton distribution. However, in the regions above 3~R\odot, the H0 velocity distribution may not be the same as that for the protons because the characteristic time for charge transfer between H0 and protons becomes longer than the time it takes for the plasma to flow through a density scale height. Hence, the H0 velocity distribution may not be directly affected by transverse wave motion or wave damping. An indication of an adiabatic radial decrease in the neutral hydrogen temperature would indicate a decoupling of the protons and neutral hydrogen, and also indicate the absence of mechanisms that would heat the neutrals. We will compare the observations with the predictions of a theoretical model of the combined electron, proton and neutral hydrogen plasma. Such a comparison could lead to an improved knowledge of the proton heating at these large heights. This work is supported by the National Aeronautics and Space Administration (NASA) under Grant NNX07AL72G to the Smithsonian Astrophysical Observatory.
SH21A-0286
Alfven Profile in the Lower Corona: Implications for Shock Formation
Recent events (e.g. Tylka et al. 2005) indicate that CME-driven shocks can form at 1-3 solar radii and are responsible for the GeV/nucleon energies observed in some ground level solar energetic particle events. The formation of shocks depends crucially on the background solar wind environment, in particular on the profile of the background Alfvén speed in the corona. Significant strides have been made in the effort to develop realistic models of CME events; however, there is no consensus as to the profile of the Alfvén speed in the lower corona. Here we provide an overview of ten state-of-the-art models, which includes various methods to model magnetic field and density, as well as different strategies for accelerating the solar wind. We present the Alfvén speed profile for each model in the lower corona. We find that the "valley" and "hump" structures anticipated by Mann et al. (2003) are sometimes present, but in some models the Alfvén profiles drop off quickly. We discuss the implications of these profiles, such as whether it will allow a shock to form, dissipate, and form again (i.e. multiple shocks). Our study indicates that it is crucial to establish the Alfvén speed as a function of height before determining if shocks can form in the lower corona.
SH21A-0287
The evolution of the solar wind proton temperature anisotropy from 0.3 to 2.5 AU
We report an analysis of the proton temperature anisotropy evolution from 0.3 to 2.5 AU based on the Helios and Ulysses observations. With increasing distance, the fast wind data show a path in the parameter space (β\parallel p,T\perp p/T\parallel p), and the first part of the trajectory is well described by an anticorrelation between the temperature anisotropy T\perp p/T\parallel p and the proton parallel beta, while after 1 AU the evolution with distance in the parameter space changes and the data result in agreement with the constraints derived by a fire hose instability. The slow wind data show a more irregular behavior, and in general it is not possible to recover a single evolution path. However, on small temporal scale we find that different slow streams populate different regions of the parameter space, and this suggests that when considering single streams also the slow wind follows some possible evolution path.
SH21A-0288
Observing the Influence of Alfven Waves on the Energetics of the Quiet Solar Corona and Solar Wind
We will present and discuss recent observations of Alfvén waves in the solar chromosphere, from the Solar Optical Telescope (SOT) on Hinode, and in the corona, from HAO's ground-based Coronal Multi-channel Polarimeter (CoMP). These observations unambiguously demonstrate, for the first time, that the magnetic chromosphere and corona are riddled with 3- and 5-minute (3-5mHz) Alfvénic oscillations predominantly propagating outward into the heliosphere. The combined analysis of these observations, augmented by spectroscopic data from SOHO/SUMER, provide a compelling look at the influence and importance of ubiquitously driven Alfvén waves in heating the quiet solar corona and driving the solar wind. Indeed, we believe that these direct observations of a low-frequency wave input must provoke a re-evaluation of solar wind acceleration by high frequency (kHz) ion-cyclotron modes.
SH21A-0289
Alfven Waves in the Solar Corona
We present observations of the coronal intensity, line-of-sight velocity, and linear polarization obtained in the FeXIII 1074.7 nm coronal emission line with the Coronal Multi-channel Polarimeter (CoMP) instrument. Analysis of these observations reveal ubiquitous upward propagating waves with phase speeds of 1-4 Mm/s and trajectories consistent with the direction of the magnetic field inferred from the linear polarization measurements. We can definitively identify these as Alfvén waves. An estimate of the energy carried by the waves that we spatially resolve indicates that they are unable to heat the solar corona, however, unresolved waves may carry sufficient energy.
SH21A-0290
Slow Solar Wind Formation Beyond the Cusp of an Helmet Streamer
The region beyond the cusp of an helmet streamer is characterized by the presence of a current sheet embedded in a plasma flow. In previous 3D and 2D simulations the velocity has been found, at a fixed radius, to grow from a slow value at the current sheet towards higher values towards the polar regions. The steady-state which was reached showed the bimodal characteristic of the solar wind, but the slow component did not show its characteristic variability. The velocity profile of the slow component is in fact not steady in time, and plasma density enhancements have been observed by the Large-Angle Spectrometric Coronagraph (LASCO) instrument on board the Solar and Heliospheric Observatory (SOHO). We present numerical simulations, performed with the SAIC MHD spherical code (MAS), of the region beyond the cusp of an helmet streamer from 1 R\odot up to 20 R\odot. With a sufficiently high resolution magnetic reconnection of the heliospheric current sheet is observed, which leads to the formation of density-enhanced magnetic islands that are accelerated radially outward. The reconnection process also gives rise to an acceleration profile that is not steady in time.
SH21A-0291
Numerical studies on neutral solar wind generated at high and low solar latitudes
In this work, we examine the properties of the neutral solar wind (NSW) emanating from the solar corona above few solar radii, at low and high solar latitudes. It is important to study NSW because it allows us to investigate the acceleration region of the solar wind. In fact, neutrals retain information on the three-dimensional distribution of hydrogen at the level where they are generated as the proton velocity distribution is frozen within the generated neutrals and transferred up to our observation point. NSW is flowing together with the ionized solar wind, but it has basically different characteristics in its phase space distribution function. In fact, contrary to the ionized component, NSW is unmodified along the way from the originating source. In this particular study, we will consider as our vantage point the Solar Orbiter position.
SH21A-0292
Evolution of suprathermal electron distributions with heliocentric distance
Although suprathermal electrons (> 70eV at 1 AU) form less than 1% of the total solar wind electron flux, they carry heat flux away from the Sun and provide an effective tracer of heliospheric magnetic field topology. As electrons travel antisunward, they are subject to two competing processes: Adiabatic focusing owing to the decreasing heliospheric magnetic field strength, creating a more field-aligned distribution, and pitch angle scattering by some unspecified mechanism, creating a more isotropic distribution. Close to the Sun, adiabatic focusing must dominate, as a field-aligned distribution ("strahl") is observed at 1 AU. However, scattering must become increasingly important further from the Sun, as the strahl is observed to broaden with heliocentric distance. We present a model for the evolution of suprathermal electron distributions with heliocentric distance which demonstrates the importance of the Parker spiral magnetic field: In a given amount of time, electrons of a given energy and pitch angle move the same distance along the heliospheric magnetic field, but at larger heliocentric distance the radial displacement will be smaller due to the increasing angle between the magnetic field and the radial direction. Thus scattering will begin to dominate focusing with increasing distance from the Sun without any change in the pitch-angle scattering rate. Furthermore, the rate of strahl broadening will decrease with increasing electron energy, as observed, without requiring an explicit energy-dependence in the pitch-angle scattering mechanism. We determine the scattering rate required to match observations.
SH21A-0293
Strahl properties in the solar wind: Observations
We have performed a statistical study of a substantial amount of electron data acquired in the solar wind to describe the properties of the strahl electron population. We use a large data set of electron measurements from three different spacecraft (HELIOS I, CLUSTER II and ULYSSES) collected in the low ecliptic latitudes covering the radial distance from the Sun from 0.3 up to 4 AU. Beside the thermal core, the electron velocity distribution functions in the solar wind typically exhibit two non-thermal features: supra thermal tails known as the halo population and the strahl. This last component is highly aligned in the direction parallel to the interplanetary magnetic field and is largely moving away from the Sun. Even thought it comprises less than a few percents of the total number density, it is important to study some important solar wind plasma properties. Thanks its attributes, the strahl is responsible for the main part of the electron heat flux and it can also provide a possible source of electron kinetic plasma instabilities. We fit the observed distribution functions with analytical models. The resulting characteristics are compared with other electron properties in order to study their possible correlations. In addition we examine the radial evolution of these characteristics during the expansion of the solar wind.
SH21A-0294
Comparing Coronal Heating Models by Using Their Implied EUV and Soft X-ray Emissions
The plasma heating mechanism that maintains the coronal temperature remains poorly understood after decades of research. There have been numerous theoretical models, but none of them has been confirmed by observations. Each model has a different parametric dependence on physical quantities, such as the local magnetic field, plasma density, etc. Due to these differences, they imply different thermal structures in the solar atmosphere, leading to different characteristics in electromagnetic emissions. In this study, we examine these heating models by comparing their predicted extreme ultraviolet (EUV) and soft X-ray emissions with available observations. We use an active region as a testing ground, partly because of its brightness, and partly because its complex magnetic field can reveal the unique features of each model. From the heat source, we compute the thermal structure in the neighborhood of the active region in 3D for each model. A synthetic emission image is then computed and compared with observations.
SH21A-0295
Solar Wind Short Distance Propagation Model With Moving Boundaries
Parameters of the Interplanetary Magnetic Field (IMF) and solar wind are important factors that affect Earth's magnetosphere. Measurements of the IMF taken at the first Lagrange point (L1) by the ACE space satellite, about 230 Earth Radii away, are typically used for estimation of IMF near the Earth. In many geophysical applications, it is assumed that we can use a simple kinematic approach to map the parameters measured at the satellite to the Earth by shifting them in time by a "time delay". This time delay is calculated using solar wind velocity and the distance from the satellite to the Earth. However, this approach can lead to incorrect IMF estimation near the Earth. The kinematic approach does not take into account that IMF can be tilted with respect to the solar wind propagation direction and therefore the parameters have different time delays. Particles also interact during their way from ACE satellite to magnetosphere, which can introduce additional errors. Our model takes into account both factors. A simplified 1D solar wind propagation model was derived for this case using mass and momentum conservation laws and Maxwell's equations. The model is simple and fast enough to use even in real-time applications, yet it takes into account real conservation laws of solar wind motion. The previous model of IMF and the solar wind near Earth magnetosphere we developed was improved recently by making domain boundaries move with the satellite and by taking into account both ACE satellite and Earth's speed. The new model also takes into account the IMF's inclination with respect to the solar wind propagation vector. We validated our new models on different measurements obtained from the ACE and WIND satellites. Comparisons of these measurements and calculations shows an improvement of IMF calculations compared to the simple kinematic delay method and our previous model.
SH21A-0296
Comparison of Heliospheric In-Situ Data with the Quasi-Steady Solar Wind Models
The standard theory for the solar-heliospheric magnetic field is the so-called quasi-steady model in which the field is determined by the observed magnetic flux at the photosphere and the balance between magnetic and plasma forces in the corona. In this model, the solar magnetic flux that opens to the heliosphere can increase or decrease as the photospheric flux evolves. One of the most sophisticated implementations of the quasi-steady theory is the SAIC model, which solves the fully time-dependent 3D MHD equations for the corona and wind until a steady state is achieved. In order to test the quasi-steady theory, we compare the 3-D MHD model with observations of the heliospheric flux using multi-point measurements from the VHM instrument on the Ulysses spacecraft from 1991 through 2005 and from magnetic field measurements from various spacecraft at L1 compiled into the OMNI data set from 1976 through 2005. We also compare the observations to the predictions of the potential-field source-surface model, an older and simpler implementation of the quasi-steady theory. During solar maximum, ICMEs significantly disturb the heliospheric magnetic field, making our comparisons difficult. We find that the MHD model compares well with the general trends of the observed heliospheric fluxes. Variations on short timescales, presumably due to local effects, are missed by the model, but the long-term evolution is well matched. The model disagrees with observations most when Ulysses is in slow wind or ICME- related flows. The model underestimates the flux at solar maximum; however, this is to be expected, given the large number of ICMEs in the heliosphere at this time. We discuss the possible sources of discrepancy between the observations and the quasi-steady models.
SH21A-0297
Cluster/PEACE Electron Velocity Distribution Function Modeling in the Solar Wind
We present a study of the kinetic properties of the electron velocity distribution functions in the solar wind to model the electron heat-flux and temperature anisotropy, to investigate the stability of electron to the excitation of whistler waves. The study is based on high time resolution data from the Cluster/PEACE electron spectrometer. Our study focused in the mechanisms that control and regulates whistler electron instabilities in the solar wind. These mechanisms are not well understood. We investigate the electron heat-flux and temperature anisotropy as a function of two important parameters, namely the electron parallel plasma βe\Vert and the electron collisional age Ae defined as the number of collisions suffered by an electron during the expansion of the solar wind. The goal is to check whether the electrons are constrained and regulated by some instability (e.g., the whistler instability), or are driven by collisions. The electron heat-flux and temperature anisotropy are determined by moments of the velocity distribution functions (VDF) and/or model fitting of the electron VDF using a superposition of a bi-Maxwellian core distribution, bi-Kappa halo and strahl distributions.
SH21A-0298
Measurements of Coronal Proton Velocity Distributions
The Ultraviolet Coronagraph Spectrometer (UVCS) on the Solar and Heliospheric Observatory is being used to measure precise coronal H I Ly-alpha spectral line profiles out to several Doppler half widths. Such observations can be used to reveal the proton velocity distribution along the line-of-sight. Departures from a Maxwellian distribution are believed to be needed for the acceleration of solar energetic particles (SEPs) by coronal mass ejection (CME) shocks. Our initial attempt to measure suprathermal proton velocity distributions has been described by Kohl et al. (2006). We have made considerable additional progress on such measurements since then. Improvements include the following: a much more accurate instrument spectral line profile, an increase in the wavelength range used for the observations, an increase in the statistical accuracy of the observations by increasing the observation time, and inclusion of a background measurement as part of every set of observations. We have also investigated the sensitivity to the detector high voltage, investigated the effects of diffraction in the instrument, determined the stray light effects and the Thompson scattering effects, which both turn out to be small except for scattering of Si III 120.6 nm. That scattered light is out of the primary wavelength range of interest. We believe that we have now demonstrated that UVCS has the sensitivity to distinguish between a Gaussian coronal velocity distribution and a kappa = 4 or smaller distribution. It is generally believed that the required seed particle population needed to produce SEPs of interest with a CME shock would have a velocity distribution with 0.001 to 0.01 of the particles with speeds that exceed 1000 km/s. Assuming a kappa distribution that is symmetric in the tangential plane and Maxwellian in the radial direction, this would correspond to a distribution with kappa = 3.5 or smaller. This paper will report the results of examining a fairly large body of new observations obtained with the new procedure and report the departures from a Maxwellian distribution. It will also report the CME predecessor history of each observation. This work is supported by the National Aeronautics and Space Administration (NASA) under Grant NNX07AL72G to the Smithsonian Astrophysical Observatory. Kohl J. L., Cranmer, S. R., Fineschi, S., Gardner, L. D., Phillips, D. H., Raymond, J. C., and Uzzo, M., Proc. SOHO 17 - 10 Years of SOHO and Beyond (ESA SP-617, July 2006).
SH21A-0299
Neutral Effects on Alfvén Wave Propagation and the Effect on Coronal Heating
Alfvén waves are ubiquitous in space plasmas, influencing the dynamics of, for example, solar flares and magnetospheric reconnection. In particular, Alfvén waves are considered as one candidate for the heating of the solar transition region and corona. Importantly, because both the chromosphere and transition regions are dominated by neutral gas, Alfvén wave interaction with neutral particles may be important in this heating process. To better understand the effect of neutrals on Alfvén waves we have undertaken a program to study these waves in the laboratory. We present results from both the HelCat and the ALESPI devices. The HelCat (Helicon-Cathode) device is 4 m long, with a 0.5 m diameter using both helicon and cathode plasma sources; ALESPI (Auburn Linear Experiment for Space Plasma Studies) is a 2 m helicon device. The high density steady-state, current-free plasma allows detailed study of both shear and compressional waves with a varying neutral fraction. We launch shear waves with an asymmetric exciter. Depending on this neutral fraction, the measured dispersion curve changes dramatically. We observe propagation above the ion cyclotron frequency ω ci, the nominal cutoff for shear waves. However, theoretical models show that the propagating wave is dominated by shear waves with both m=0 and higher order mode components due to the asymmetry of the launching scheme, which accounts for the observed propagation above ω ci.