Low-Resolution STELab IPS 3D Reconstructions of the Whole Heliosphere Interval and Comparison with in-Ecliptic Solar Wind Measurements from STEREO and Wind Instrumentation

We present initial 3D tomographic reconstructions of the inner heliosphere during the Whole Heliosphere Interval (WHI) – Carrington Rotation 2068 (CR2068) – using Solar-Terrestrial Environment Laboratory (STELab) Interplanetary Scintillation (IPS) observations. Such observations have been used for over a decade to visualise and investigate the structure of the solar wind and to study in detail its various features. These features include co-rotating structures as well as transient structures moving out from the Sun. We present global reconstructions of the structure of the inner heliosphere during this time, and compare density and radial velocity with multi-point in situ spacecraft measurements in the ecliptic; namely STEREO and Wind data, as the interplanetary medium passes over the spacecraft locations.     

On the Temporal Variability of the “Strahl” and Its Relationship with Solar Wind Characteristics: STEREO SWEA Observations

The “strahl” is a specific population of the solar wind, constituted by strongly field aligned electrons flowing away from the Sun, with energies >60 eV. Using the Solar Wind Electron Analyzer (SWEA) onboard STEREO, we investigate the short time scale fluctuations of this population. It is shown that its phase space density (PSD) at times presents fluctuations larger than 50% at scales of the order of minutes and less. The fluctuations are particularly strong for periods of a few tens of hours in high-speed streams, following the crossing of the corotating interaction region, when the strahl is also the most collimated in pitch angle. The amplitude of the fluctuations tends to decrease in conjunction with a broadening in pitch angle. Generally, the strongly fluctuating strahl is observed when the magnetic field is also highly perturbed. That SWEA is able to perform a very rapid 3D analysis at a given energy is essential since it can be demonstrated that the observed magnetic turbulence can only marginally perturb the PSD measurements.     

Electron-Temperature Maps of the Low Solar Corona: ISCORE Results from the Total Solar Eclipse of 29 March 2006 in Libya

We conducted an experiment in conjunction with the total solar eclipse of 29 March 2006 in Libya that measured the coronal intensity through two filters centered at 3850 Å and 4100 Å with bandwidths of ≈?40 Å. The purpose of these measurements was to obtain the intensity ratio through these two filters to determine the electron temperature. The instrument, Imaging Spectrograph of Coronal Electrons (ISCORE), consisted of an eight inch, f/10 Schmidt Cassegrain telescope with a thermoelectrically-cooled CCD camera at the focal plane. Results show electron temperatures of 10⁵ K close to the limb to 3×10⁶ K at 1.3R _⊙. We describe this novel technique, and we compare our results to other relevant measurements. This technique could be easily implemented on a space-based platform using a coronagraph to produce global maps of the electron temperature of the solar corona.     

Study of CME Propagation in the Inner Heliosphere: SOHO LASCO, SMEI and STEREO HI Observations of the January 2007 Events

We are investigating the geometric and kinematic characteristics of interplanetary coronal mass ejections (ICMEs) using data obtained by the LASCO coronagraphs, the Solar Mass Ejection Imager (SMEI), and the SECCHI imaging experiments on the STEREO spacecraft. The early evolution of CMEs can be tracked by the LASCO C2 and C3 and SECCHI COR1 and COR2 coronagraphs, and the HI and SMEI instruments can track their ICME counterparts through the inner heliosphere. The HI fields of view (4?–?90°) overlap with the SMEI field of view (>?20° to all sky) and, thus, both instrument sets can observe the same ICME. In this paper we present results for ICMEs observed on 24?–?29 January 2007, when the STEREO spacecraft were still near Earth so that both the SMEI and STEREO views of large ICMEs in the inner heliosphere coincided. These results include measurements of the structural and kinematic evolution of two ICMEs and comparisons with drive/drag kinematic, 3D tomographic reconstruction, the HAFv2 kinematic, and the ENLIL MHD models. We find it encouraging that the four model runs generally were in agreement on both the kinematic evolution and appearance of the events. Because it is essential to understand the effects of projection across large distances, that are not generally crucial for events observed closer to the Sun, we discuss our analysis procedure in some detail.