SPA-Solar and Heliospheric Physics General Contributions VI Posters
Presiding: N Craig, University of California, Berkeley; I Richardson, NASA Goddard Space Flight Center
SH43A-01 1330h
New Synoptic Maps of the Solar Corona from UVCS Observations
We present for the first time synoptic maps of the extended solar corona (r/Ro > 1.5) based on eight years of data from the SOHO Ultraviolet Coronagraph Spectrometer (UVCS). The data reveal the changes in the physical properties of the large scale features in the corona. Maps of O VI line intensities, line widths, and line ratios for the O VI 1032/1037 doublet and intensities and line widths for the H I Ly-alpha line reveal information about the evolution of coronal densities, temperatures, and outflow velocities over the solar cycle. In particular these data are used in support of program to understand the solar cycle variation of coronal holes and coronal streamers. This work is supported by NASA Grant NAG5-12781 to the Smithsonian Astrophysical Observatory and NASA subcontract OGSP21010200061SAO awarded to SAO through a grant to Southern Universty at Baton Rouge.
SH43A-02 1330h
The Global Magnetic Topology of the Solar Corona Preceding CME Eruptions
Understanding coronal mass ejections (CMEs) is a key step to understanding and eventually predicting Space Weather. Three CME event periods have gained great interest lately due to the wide range of observations made before, during and after each event. These include the Halloween storms from October 2003, the eruption involving AR 8210 during CR 1935, and the May 12, 1997 halo CME. These events have been selected by several groups as an example of a real event that they will try to simulate. We present preliminary results of MHD simulations of the pre-eruption global coronal magnetic topology for each event, using a synoptic map-based ZEUS-3D MHD model of the solar corona. We compare and contrast the results to gain insight into the prevailing conditions, especially the open/closed field configurations surrounding the event sites.
SH43A-03 1330h
Identifying Interplanetary Shock Parameters in Heliospheric MHD Simulation Results
One of the challenges of integrating SEP models into heliospheric space weather event simulations is the identification and characterization of the shock in the underlying MHD simulation results. We investigate the numerical method by which the jumps can be identified, the shock surface orientation characterized, and the upstream and downstream conditions defined. Our approach uses snapshots of observer-connected interplanetary magnetic field lines. First we determine whether a shock is on the connected field line, and record its position and the change in the MHD variables (field, density, velocity). We also examine several adjacent field lines and similarly determine the shock positions. The identification of the jumps takes into account the lack of spatial resolution at the shock front. The shock surface orientation is determined by a cross-product method. Then the shock normal angle is determined from the upstream and downstream vector fields and the normal. These calculations are relatively fast and can be embedded in a simulation run for use in overlaid SEP shock source descriptions or for analyzing the evolution of the connected shock parameters with time.
SH43A-04 1330h
Statistical Study of Shocks and CMEs Associated With Interplanetary Type II Bursts
We present a study of some spectral properties associated with interplanetary Type II radio emission. Type II radio bursts are signatures of violent eruptions from the Sun that result in shock waves propagating through the corona and the interplanetary medium. We investigated the relative bandwidth of all the type II bursts observed by the Radio and Plasma Wave Experiment (WAVES) on board the Wind spacecraft from 1997 up to 2003. We obtained three sets of events, based on the frequency domain of occurrence: 109 events in the low frequency domain (30 KHz to 1000 kHz detected by the RAD1 receiver), 216 events in the high frequency domain (1-14 MHz, observed by the RAD2 receiver), and 73 events that spanned both domains (RAD1 and RAD2). We present statistical results for the bandwidth-to-frequency ratio (BFR) in the three subsets as well as a comparision of our results with the Type II solar radio bursts observed by ISEE-3 radio experiment, which is similar to WAVES/RAD1. We analyzed the bandwidth and BFR evolution with the heliocentric distance as well as an analysis of drift rate magnitude of type II radio bursts and its starting frequency. We also present some properties of shocks and coronal mass ejections associated with interplanetary type II bursts. This work is partially supported by NSF/SHINE (ATM 0204588)
SH43A-05 1330h
Survey of Interplanetary Coronal Mass Ejections in the Near-Earth Solar Wind During 1996 -- 2005
We extend and update our comprehensive survey of ICMEs in the near-Earth solar wind (Cane and Richardson, JGR, 2003) to include the declining phase of solar cycle 23, and take into account compositional signatures of ICMEs which help to refine the event identifications. We discuss the variation in properties such as occurrence rate (including evidence for a ~150-day periodicity), speed, magnetic field intensity, fraction of ICMEs that are magnetic clouds, the relationship between geomagnetic storms and ICME properties, and association between LASCO halo CMEs and near-Earth ICMEs. An updated list of ICMEs will also be presented.
SH43A-06 1330h
Another Look at the Solar-Magnetospheric Events of 28 October 2003Y
The solar-magnetospheric events of October-November 2003 have received much attention because of the unusual features of the energetic solar particle events and magnetospheric storms. Striking features included the injection of energetic electrons deep in to the Slot region (L from 2 to 3), and the removal of trapped energetic protons, injected during earlier solar particle events years prior to removal. On Day 301 there was a X17.2 flare leading to a high flux of energetic protons at Earth. Serendipitously b o th SAMPEX and Polar were well situated to see the energetic photons associated with the flare as well as the ensuing energetic (charged) solar particles. SAMPEX was very near the geomagnetic equator and under the trapped radiation. SAMPEX observed the h ar d gamma emission in its entirety before it moved to high latitude into the radiation belts. Polar also observed the hard photons while outside of the trapped radiation followed by the onset of the highly energetic solar particles. These data will be shown in detail along with other observations of this solar event. m
SH43A-07 1330h
Interplanetary Shock Source Population: Hybrid Simulations and ACE Observations
Recently, we started using large-scale hybrid (kinetic ions, electron fluid) simulations to describe and deliver the pertinent characteristics of the energetic shock ion populations to large-scale transport models, such as the CISM SEP model. Such transport models decouple the scales and processes of ion acceleration at interplanetary shocks (ISs) from those of further heliospheric transport by assuming that a defined "SEP source" can be associated with the shock. This approach is more easily put into reality in some regions of parameter space than in others. In particular, shock acceleration at weak and/or quasi-perpendicular shocks remains poorly understood. In an effort to remedy this situation, we are comparing in situ ACE observations of energetic ions at ISs with our hybrid simulations. Such comparisons also provide a validation mechanism to source and transport models. We discuss the role of seed particles and the question of which portion of a non-Maxwellian solar wind distribution contributes most efficiently to highly-energized ions.
SH43A-08 1330h
Energy Dependent Charge States and their Correlation with Abundances in Impulsive Solar Events
Ionic charge states of energetic ions in impulsive flare events are rather high and usually fully stripped for elements up to Mg. The charge states appear to correlate with high overabundances of heavy ions, which is puzzling because no selective acceleration mechanism is known for fully stripped ions. Thus it has been suggested that in these events the stripping occurs only after the acceleration. Corroborating this view, the ionic charge states in impulsive events have been found to be strongly energy dependent. At the lower energies the charge states tend to reflect the plasma environment of the flare, and at the higher energies stripping according to their actual energy appears to play the key role. We have combined the ionic charge state data from ACE SEPICA and abundance data from ACE ULEIS for all impulsive events during 1997 through 2000 to perform a correlation study between charge states and abundance ratios for heavy ions and 3He binned in several energy ranges. The results are evaluated to see whether the abundance ratios can be tied better to the plasma environment, the stripping, or whether mixing of particle populations still plays a role.
SH43A-09 1330h
Orientation and Configuration of Magnetic Flux Ropes: From Sun to 1 AU
The Corona Mass Ejections (CMEs) are commonly modeled as magnetic flux ropes. We examine a simple and intuitive means of inferring orientation of flux rope axis from coronagraph images of halo CMEs, based on the hypothesis of flux rope configuration. Preliminary results in connection with Dst index will be presented. The interplanetary counterparts of CMEs, the ICMEs, detected in-situ by spacecraft ACE and Wind, etc, have been examined in much more details. In particular, we present the Grad-Shafranov (GS) reconstruction technique, which represents an objective means of obtaining the axis orientation of a flux rope. In addition, it is capable of deriving 2 1/2 dimensional cross-section of a cylindrical flux rope from single-spacecraft measurements. We will compare the axis orientation of flux-rope CMEs and their corresponding ICMEs. We attempt to establish the relationship between the CMEs and the Interplanetary Magnetic Field (IMF) conditions upon their arrival at 1 AU, thus to assess their geoeffectiveness. We propose to seek connections among observables of CMEs at sun, the corresponding ICMEs, and the geomagnetic storms. Theoretical work on three-dimensional generalized GS type equation will be discussed.
SH43A-10 1330h
On Decadal Evolution of the Transverse Solar Magnetic Fields
Reconstructed transverse components of the large-scale solar magnetic field are presented for discussion. To solve an inverse problem of calculating these components, two-decadal time series of the solar photospheric field Synoptic Charts (cortesy of J. T. Hoeksema) of the Wilcox Solar Observatory (years 1976 to 2004) were used. Singular value decomposition technique was chosen for solving the inverse problem. One of the time series shows behaviour of the "radial", or "site-of-view" magnetic field component, another one transversal "North-to-South" solar component. It was revealed, that the low-frequency behaviour of these fields does differ on the time scale chosen (two decades) so does the spatial distribution over the solar surface, while magnitudes of them are comparable with each other. It is supposed that the results would be highly useful for building Sun-Earth connection predictive schemes and for the source surface and solar dynamo models.
SH43A-11 1330h
Origin of Heliospheric Magnetic Field Polarity Inversion at High Latitudes
High latitude observations of the magnetic field by the Ulysses spacecraft have shown a significance number of cases where the radial magnetic field polarity is reversed with respect to the dominant polarity of the coronal hole from which the wind emanates. Such reversals have the nature of folded back magnetic field lines. It has been suggested that such reversals are due to reconnection of closed and open field lines in the lower corona which would launch a large amplitude Alfvén wave into the solar wind. We suggested an alternative mechanism for the generation of the polarity reversal, namely, the coupling of standard large amplitude Alfvénic turbulence in the low frequency regime propagating away from the sun with the microstream shears observed in the high speed solar wind. Here we show that pressure and density signals are similiar to those observed in the data, and discuss the correlation of the reversals with the high latitude microstream structure.
SH43A-12 1330h
Analysis of Concurrent Genesis and ACE Plasma Data
Concurrent hourly averaged Genesis Ion Monitor (GIM) and ACE SWEPAM solar wind proton densities (N), flow speeds (V) and temperatures (T) have been compared using the FTPBrowser interface, over the interval August 24, 2001 through March 31, 2004. Comparisons were made in flow speed bins (V<450 km/s, >450 km/s), in time bins (1-st and 2-nd halves of interval) and in bins defined by the transverse separation between the spacecraft (impact parameter, IP, <60, 60-120, >120 Re). Genesis flow speeds are less than ACE flow speeds by 10-20 km/s, with the greatest differences occurring for lower speeds. Genesis densities are less than ACE densities by 0-10%, with the least differences occurring for high N, low V and the first half of the Genesis life. Genesis temperatures exceed ACE temperatures by less than 5% for all conditions except that for low speed (V<450 km/s), the Genesis temperatures exceed the ACE temperatures by 10-20%. The scatter in the Genesis vs. ACE parameter values about the best fit regression lines increases gradually as the transverse separation is increased. For V, log N and log T, these increase from 5.6 to 6.8 km/s, from 0.077 to 0.081 and from 0.062 to 0.077, respectively, as IP increases from 0-60 Re to 120-150 Re. The corresponding ranges for the previously reported Wind/SWE-ACE/SWEPAM comparisons were 4.4 to 6.6 km/s, 0.059 to 0.068 and 0.105 to 0.106.
http://nssdc.gsfc.nasa.gov/ftphelper/merged.html
SH43A-13 1330h
Saturation of Rapid Density Growth in Association With a Resonantly Absorbed Alfvén Wave
We use hybrid simulations with particle protons and massless fluid electrons to investigate the evolution of a resonantly absorbed Alfvén wave. Around the resonant field line, the wave refracts or phase mixes so as to produce smaller perpendicular scales. When these scales approach 10 proton inertial lengths, we find that a rapid growth of mostly density fluctuations occurs which is driven by the "pump" Alfvén wave. This growth saturates by producing magnetosonic waves which then dissipate and give proton heating. Both parallel and perpendicular proton heating occurs. The proton heating continues until the pump Alfvén wave energy is nearly exhausted. We discuss how this process could limit density fluctuations to scales larger than the proton inertial length in solar corona holes where Alfvén waves are expected to undergo resonant absorption.
SH43A-14 1330h
Proton Perpendicular Heating in Association With a Velocity Shear Instability
We examine how a velocity shear instability excites waves at proton cyclotron harmonics and heats the protons across the magnetic field. A hybrid simulation with particle protons and massless fluid electrons is employed. From the simulation results, we have obtained the proton perpendicular heating rate as a function of β ∥(= ratio of parallel proton to magnetic field pressure). Results will be presented for the rate between β _∥ = 0.01 and β ∥ =1. The instability has been previously examined in the electrostatic limit where β ∥ ≪ 1. Our results show that heating occurs at all values of β ∥. We discuss how this instability could influence the dissipation of quasi-2D turbulence in the solar wind and also contribute to the observed perpendicular heating of solar wind protons.
SH43A-15 1330h
Characteristics of Langmuir electric field waveforms and power spectra in the Earth's electron and ion foreshocks
The characteristics of Langmuir waves observed by the Cluster WBD Plasma Wave Receiver in different regions of the Earth's foreshock are presented. Our previous work on waves in the electron foreshock has shown that the electric field amplitude probability distributions for Langmuir waves observed by Cluster can follow a combination of the log-normal statistics predicted by stochastic growth theory and power law statistics. Power law deviations from log-normal statistics are often the result of spatial averaging, but can also be found for large amplitude waves near the edge of the electron foreshock, which may show evidence of non-linearity. This raises questions about the possible effects of non-linear processes on the amplitude statistics. We examine the significance of non-linear processes in the foreshock by considering the various types of Langmuir wave power spectra observed in this region. Evidence for non-linear processes such as parametric decay, has been found in Earth's electron foreshock in the form of wave spectra with double peaks near the plasma frequency. Away from the boundary between the foreshock and solar wind, Langmuir waves have been observed to shift up and down in frequency from the local plasma frequency. Far downstream, in the ion foreshock, the behavior of waves near the plasma frequency appears to be influenced by the presence of ULF waves. For selected cases, we discuss the occurrence rates of these types of Langmuir wave spectra in different regions of the Earth's foreshock.
SH43A-16 1330h
The Green Bank Solar Radio Burst Spectrometer
The Solar Radio Burst Spectrometer (SRBS) is a project designed to 1) provide high quality radio dynamic spectra to the wider solar, heliospheric, and space weather communities; 2) serve as a development platform for ultra-wideband feeds and receivers. Dynamic spectroscopy is a powerful tool for observing radio bursts in the Sun's corona. These bursts are associated with solar flares and/or coronal mass ejections and result from coronal shocks (type II radio bursts), electron beams (type III radio bursts), and other forms of energy release in the corona. The community has been hampered by a lack of readily available dynamic spectra in the 12-24 hr UT time range, a shortcoming that has now been remedied. The instrument is located at the Green Bank Site of the National Radio Astronomy Observatory in the National Radio Quiet Zone, where the effects of radio frequency interference are much reduced compared with unprotected sites. The spectrometer is composed of two swept-frequency systems that together support observations from 18 MHz to 2 GHz with a time resolution of approximately 1 sec. The low frequency system, operating from 18-70 MHz, is a standalone dipole antenna. The high frequency system is fed by an antenna mounted at the vertex of a 13.7 m telescope and operates from 70-300 MHz; a broadband feed at the prime focus of the telescope provides frequency coverage from 300-2500 MHz. The data are available daily through a web-based interface. Both raw and background-subtracted data are available in a variety of formats. Users are encouraged to view and download selected data for research or forecasting purposes.
http://www.nrao.edu/astrores/gbsrbs
SH43A-17 1330h
The Atmospheric Imaging Assembly (AIA) investigation for the NASA SDO mission
The Atmospheric Imaging Assembly (AIA) is one of three science investigations selected for the NASA Solar Dynamics Observatory, the first mission in NASA's Living With a Star program that is designed to study the Sun's influence on the Earth and the nearby environment. AIA consists of four normal incidence telescopes with multilayer coated optics. It records solar EUV emission with high spatial resolution (0.6 arcsec pixels) at six wavelengths from iron ions in the solar atmosphere at temperatures between 6.3 × 105 K and 15 × 106 K: Fe IX (171Å); Fe XII,XXIV (193Å); Fe XIV (211 Å); Fe XVI (335Å); Fe XVIII (94Å); and Fe XX,XXIII (131Å). Other wavelength channels enable observations of the chromosphere (He II, 304Å; C IV) and the photosphere. Each telescope contains a 16-Mpixel CCD/camera system and has a 41 arcmin field of view. AIA will return 8 full solar-disk images every 10 s, producing 2.2 Tbytes/day of data. The AIA investigation is led by PI Alan Title (LMSAL) with major participation by the Harvard Smithsonian Astrophysical Observatory, Montana State University, and Stanford University. The SDO mission is scheduled for launch in 2008 and will have a nominal five year mission lifetime, but will carry resources for at least ten years of mission operations.
SH43A-18 1330h
Solar Wind Compositional Variability and the Need for an Ultra-High Temporal Resolution Mass Spectrometer: Introduction to the Helical Ion Path Spectrometer (HIPS)
Solar wind composition measurements serve as an indicator of the sub-coronal and coronal processes responsible for the formation of these heliospheric features. While current state-of-the-art instrumentation have identified temporal variations in solar wind/CME composition on the order of 10's of minutes, these detections have occurred during relatively quiescent periods when temporal variations of the collective solar wind (including magnetic field variations) occur over periods in excess of the current minimum instrumental duty cycle of 5-minutes. Consequently, the compositional markers of the microphysics responsible for the formation of highly variable solar wind flows and for CME/prominence formation remain overlooked. The development of a novel ultra-high temporal resolution ion mass spectrometer utilizing a helical ion path time-of-flight (TOF) system within a compact, low-mass, low-power instrument has been undertaken in order to address the need for temporally enhanced solar wind composition measurements. The Helical Ion Path Spectrometer (HIPS) is designed specifically to measure solar wind heavy ion plasma from 3He+2 ≤ M/q ≤ Fe+6 and 0.6-20.0 keV/q with an order of magnitude greater geometric factor than current solar wind ion mass spectrometers, and produce 1-10 ms mass spectra with a mass resolution of M/ΔM ~ 200 or greater, all within a duty cycle of ≤ 90-s. The temporal resolution of HIPS is sufficient to probe solar wind and CME spatial/temporal dimensions down to an ion gyroradius in solar wind flow boundaries at 1 AU. We present evidence supporting the need for greater temporal resolution solar wind composition measurement through an overview of solar wind mass spectroscopy results to date, and an introduction to the HIPS mass spectrometer instrument concept.