SH11A-01 INVITED
Time Distance Coronal Seismology With the CoMP Instrument
Recent velocity imaging observations obtained with the Coronal Multi-channel Polarimeter (CoMP) instrument reveal the existence of ubiquitous propagating Alfvén waves in the solar corona. These data present an exciting opportunity for probing the structure and magnetic topology of the coronal plasma through coronal seismology. We present the results of a time-distance analysis of the wave observations which allows the determination of the phase speed of the waves and the relative quantity of outward and inward wave flux. This analysis also provides a k-omega diagnostic diagram of coronal waves. We discuss current and future prospects for coronal seismology with these data.
SH11A-02
STEREO Observations of Energetic Neutral Atoms during the 5 December 2006 Solar Event
We report the discovery of energetic neutral atoms (ENAs) emitted during the X9 solar event of 5 December 2006. Beginning ~1 hour following the onset of this flare, located at ~E70, the Low Energy Telescopes (LETs) on both STEREO A and B spacecraft observed a sudden increase in the count rate of 1.6 to 15 MeV protons, with a typical velocity-dispersive profile. At this time both STEREO spacecraft were located near Earth and were oriented such that both LETs viewed the Sun directly, and, in combination, covered 360° in heliographic longitude. Particle arrival directions are measured to 7° in longitude. It was found that more than 60% of the 1.6 – 15 MeV protons observed within 3 hours of the flare onset (before the bulk of the solar energetic particles began arriving at Earth) arrived from a longitude within 10° of the Sun. When the arrival time of each of ~100 individual proton events is corrected back to the Sun using the measured kinetic energy, the resulting emission profile is very similar to the GOES soft x-ray profile, and continues for ~1 hour or more. At higher energies, the 13 to 100 MeV proton count rates in the STEREO High Energy Telescopes (HETs), which do not view the Sun directly, showed only a small increase. While the time profile observed by the LETs is consistent with the possibility of neutron-decay protons, both the arrival directions and energy spectrum argue strongly that the majority of the proton events were due to energetic neutral hydrogen atoms that arrived from the solar direction and were stripped in passing through the windows of the LET telescopes. To our knowledge, this is the first reported observation of ENA emission from a solar flare/coronal mass ejection. This talk will present the observations and discuss possible origins for the production of ENAs in a large solar event.
SH11A-03
Modeling the Corona-Heliosphere Interface in Anticipation of the Murchison Wide-field Array
The Murchison Widefield Array (MWA) is an 8,000-antenna, 80-300 MHz, imaging radio array under
construction in Western Australia that features a large field of view, high sensitivity, and accurate polarization
and intensity calibration. An MWA prototype has been deployed in the field and construction of the full array
will begin in mid-2009 after the performance of the prototype is evaluated. Understanding the connection
between the upper corona and the inner heliosphere with novel low-frequency radio observations is a
primary objective of the MWA Solar, Heliospheric, and Ionospheric (SHI) science consortium. This
presentation covers progress by the SHI consortium's theory and modeling effort. We show simulations of
how Faraday rotation, interplanetary scintillation, and radio burst measurements can track and constrain the
transport of magnetic fields, density, and energetic electrons into the heliosphere.
http://www.haystack.mit.edu/mwa/index.html
SH11A-04 INVITED
The Role of Heavy Ions as Coronal Diagnostics: Recent Results from Total Solar Eclipse Observations
Recent advancements in coronal imaging capabilities and image processing techniques, have led to new diagnostic capabilities for the exploration of the solar atmosphere during total solar eclipses. In particular, the suite of Fe spectral lines in the visible and near infrared, namely Fe XIV 5303, Fe X 6374 A, Fe XI 7892 A, and Fe XIII 10747 A, together with continuum white light emission, continue to unveil the intricate topology of the magnetic field, density structures and temperature distribution in the solar corona. These spectral lines are also yielding new insights into the role of heavy ions as diagnostics of the coronal plasma. This presentation will focus on the surprising results from the eclipse observations of 2006 and 2008. With observations in H alpha, neutral helium He I 5876 A and the Fe lines representing four different ionization states of iron, it is shown how the distribution of neutrals and heavy ions in select magnetic structures in the corona, provides new insights into the physics of the coronal plasma, with implications for models of coronal heating processes. These observations also shed light on the source regions and properties of neutrals and minor ions measured in interplanetary space.
SH11A-05
Measuring Electron Temperature and Flow Speed using Thomson Scattered Emission from the Corona Observed with the Solar-C Coronagraph
A method for measuring the density, temperature, and velocity of coronal electrons was proposed by Reginald and Davila (2000) based on an extension the Thomson scattering theory of Cram (1976) to include flows. In this method the electron density is measured in the usual way (e.g. in LASCO or MkIV coronagraph images) by observing the total coronal intensity. The electron temperature and flow speed are obtained by obtaining ratios of spectral intensity measured in 50 A passbands or by fitting a portion of the spectrum to coronal models. Observations during the total solar eclipse of 2000 near Lusaka, Zambia demonstrated the feasibility of the method (Reginald et. al., 2003) using the first generation Multi-Aperture Coronal Spectrometer (MACS-1) instrument, and with the second-generation MACS in Libya in 2006 reasonable temperature and flow speeds were obtained. In this paper we continue this work by reporting on the results of new observations taken from the ground at the Solar-C coronagraph. Although eclipse measurements provide the best observation (nearly free of scattered light but with limited duration), the Solar-C coronagraph observations allowed several days of nearly continuous observation from which the repeatability and accuracy of the measurement could be determined. To deal with the increased atmospheric scatter, observations at Solar-C were done in polarized brightness (pB). Results will be reported in this talk.
SH11A-06
Predicting CME activity, do the Heliospheric Imagers hold any clues?
Inspection of images from the STEREO Heliospheric Imagers shows a remarkable amount of structure in the solar wind and streamer belt, even at times of little or no solar activity. A subset of these images were scrutinised for changes in this solar wind structure ahead of coronal mass ejections in an attempt to verify if these changes were associated with ensuing mass ejections and whether these changes could be used to identify the processes by which these mass ejections were triggered.
SH11A-07 INVITED
Comparison of MHD Simulations of CME Evolution and Structure with Coronagraph Observations
Coronal mass ejections (CMEs) expel significant amounts of plasma into interplanetary space producing large-scale variations in density that are manifest in coronagraph images. A limitation of these images is that they present two-dimensional projections of three-dimensional structures that are challenging to interpret. The circumstances are even more complex when CMEs are observed at large elongation and the location of preferential scattering is significantly curved. To address the interpretation of such coronagraph images, we examine the Thomson-scattered white-light appearance of 3D MHD simulations of CMEs to identify and reproduce features observed by LASCO and SECCHI coronagraphs. We find close quantitative comparison with LASCO observations and produce shapes at large elongations as seen by SECCHI. We find evidence of shock propagation, magnetic clouds, CME pancaking, and complex time evolution as CMEs propagate at large elongation past the Thomson sphere. A key point is to determine how the 3-D structure of CMEs is affected by propagation through a structured solar wind.