SH21A-0391 0800h
Using SMEI Observations to Constrain Levels of Interplanetary Scattering for Energetic Protons
An unexpected use of SMEI observations has arisen from the analysis of protons accelerated and released from CME-driven shocks and observed at the L1 lagrange point. Such protons can be uniquely linked with observed CMEs through basic analysis of their dynamic energy spectrum. Additional information regarding the evolution of CME velocities out to 1 AU can then be used to determine how these protons were released in the shock reference frame. Here we use the excellent SMEI coverage of the May 29 2003 CME to construct a model of the most likely proton energy to be accelerated and released from this CME-driven shock as a function of its position. The resulting model could serve as a useful mean to test our ideas of particle acceleration at MHD shocks. In addition, by deriving the spatial and temporal origin of protons which are subsequently observed at L1, such a model represents a novel basis to probe the effects of interplanetary scattering.
SH21A-0392 0800h
Imaging of Interplanetary Disturbances Causing Forbush Decreases
Forbush decreases (FDs) are caused by interplanetary shocks and ejecta that shield the Earth from galactic cosmic rays. The solar origins of those ejecta can be observed as coronal mass ejections (CMEs) in coronagraphs, but their propagation through interplanetary space near or past the Earth has not been previously observable. The Solar Mass Ejection Imager (SMEI), launched into polar Earth orbit in January 2003, now allows us to search for the white light signatures of interplanetary CMEs (ICMEs) responsible for FDs. SMEI is unique in that it can monitor the progress of CMEs through the inner heliosphere out to distances beyond 1 AU, and distinguish those which hit the Earth from those that do not. We discuss SMEI observations of two ICMEs that resulted in both geomagnetic storms and FDs and of two ICMEs that may have been responsible for gradual FDs without accompanying geomagnetic disturbances. The SMEI observations provide information on the approximate spatial location and trajectories of large ICMEs that may result in FDs and hence can be useful as a space weather tool.
SH21A-0393 0800h
Comparison of Solar Mass Ejection Imager (SMEI) White Light Observations with IPS Velocity
The Solar Mass Ejection Imager (SMEI) experiment is fixed to the Coriolis spacecraft and views the sky above Earth using sunlight-rejecting baffles and CCD camera technology. SMEI was designed to provide precise photometric white light images over most of the sky on each 102-minute Earth orbit. The brightness sky maps of the inner heliosphere indicate a rich variety of electron density structures that are produced by the material that propagates through it and its interaction with ambient structures. We present some of the preliminary results of the analysis of these photometric SMEI observations derived by 3D reconstructions that allow contaminant signal removal using both interplanetary scintillation (IPS) velocities and SMEI data. We use these analyses to compare preliminary SMEI tomographic white-light results with IPS velocity for the same time intervals.
http://cass185.ucsd.edu/smei/smei.html
SH21A-0394 0800h
The Deceleration of Interplanetary Transients Between the Sun and 5 AU
During the the SMEI mission, Ulysses has been at relatively low latitudes (less than 25 degrees) and near aphelion (4.8 to 5.4 AU). This has provided us with an opportunity to trace interplanetary transient disturbances from near the Sun (with LASCO), around 1AU with SMEI and ACE and then again near 5AU with Ulysses. We have selected a number of events where the identification of the disturbance is clear in LASCO, SMEI and Ulysses and use the propagation of the disturbance through the heliosphere to draw conclusions regarding the dynamics of these disturbances. In particular we focus on the duration of the "driving flow" and on the significance of "swept-up" matter.
http://www.sr.bham.ac.uk
SH21A-0395 0800h
Interplanetary Propagation Of Coronal Mass Ejections: Results From Interplanetary Scintillation Observations Using EISCAT
Coronal mass ejections (CMEs) and their interplanetary counterparts have been familiar from white-light images of the corona and in-situ measurements in interplanetary space for more than 30 years, but there are still significant gaps in our understanding of the evolution of these events with distance from the Sun and their interaction with the background solar wind. Measurements of interplanetary scintillation (IPS) have been used to study transient events in the solar wind for many years. Characteristic signatures of the passage of interplanetary CMEs (iCMEs) across the IPS ray-path were recognised by Klinglesmith (1997) and this work was subsequently developed using data from the EISCAT facility by Canals (2002). In this study we use the set of criteria for passage of an iCME developed by Canals to determine which IPS observations show the interplanetary counterparts of CMEs observed by LASCO and present a series of case studies of iCMEs, comparing velocities of transients observed in the corona, in interplanetary space and by spacecraft at 1 AU and beyond with the speed of the background solar wind ahead of each event. These results support previous radio-burst studies of interplanetary shocks in that they show that slow events are accelerated and fast ones slowed as they move out into interplanetary space and extend them by confirming that iCME speeds converge on the speed of the background solar wind as distance from the Sun increases.
SH21A-0396 0800h
Comet Tail Disconnections Observed by SMEI
The Solar Mass Ejection Imager (SMEI) was launched into orbit in January 2003 with the primary mission of detecting and tracking coronal mass ejections (CMEs). The three-camera SMEI system produces a nearly complete image of the sky every 100 minutes. Providing nearly continuous monitoring of the sky, SMEI is in a unique position to make serendipitous observations of transient astronomical phenomena. From mid-April to late May 2004 SMEI observed three bright comets, Bradfield (C/2004 F4), LINEAR (C/2002 T7), and NEAT (C/2001 Q4), traversing the inner solar system. During this period both NEAT and LINEAR experienced spectacular tail disconnections. Since SMEI was designed to be sensitive to the very low level of emission from CMEs, it was able to observe and track the very faint comet remnants over much longer time and spatial scales not possible from the ground. We present these comet observations, compare them with the projected interplanetary solar magnetic fields, and discuss the possible disconnection causes including current sheet crossings and disruption from a CME front.
SH21A-0397 0800h
Compensating for the Effects of hot Pixels in the Sunward Camera of SMEI
The sunward camera of SMEI (Camera 3) is operating at a much higher temperature than its designed range. As a consequence of this there are many hot or flipper pixels in that camera which if not excluded or corrected would make the data from that camera unusable. To detect the hot pixels weekly calibrations are performed. The first line of defence against the hot pixels is the use of regular anneals which remove some of the defects causing the pixel flipping. However even with this annealing, an increasing fraction of the CCD pixels are hot. By mid-2004, the fraction of hot pixels was close to 25%, which means that when the pixels are binned about half the bins are affected. Because the flipping pixels are inherently unpredictable, it is be st to eliminate these, but those which are stably hot can be used if a temperature-dependant dark charge is used for each pixel.
http://www.sr.bham.ac.uk
SH21A-0398 0800h
Zodiacal Light Analysis and Removal From the Solar Mass Ejection Imager (SMEI) Data
The Solar Mass Ejection Imager (SMEI) experiment provides white-light photometric maps covering most of the sky each orbit of the Coriolis spacecraft. The SMEI differential photometry specification is 0.1% for each 1 square degree sky bin, and was designed to provide precise photometric white light images over most of the sky on each 102-minute Earth orbit in order to map heliospheric structures. One of the brightest contaminant signals observed in SMEI is zodiacal light brightness that must be modeled and subtracted from the data in order to provide heliospheric sky maps free from large background changes. We have devised a technique to remove zodiacal dust brightness from the SMEI maps, and in order to do so accurately measure the asymmetry of the equatorial dust to the ecliptic plane as well as the Gegenschein brightness throughout the year. We present preliminary analyses of these observations for specific intervals during the one and a half year lifetime of SMEI.
SH21A-0399 0800h
Characterization of 90 degree depletions in solar wind suprathermal electrons as a function of radial distance and latitude using Ulysses/SWOOPS observations
Suprathermal electron distributions observed in the solar wind by ACE/SWEPAM often show depletions centered on and symmetric about 90 degree pitch angle. It has been suggested that these distributions arise from a combination of focusing and mirroring associated with magnetic connection to magnetic field enhancements beyond the spacecraft. Observations from Ulysses/SWOOPS show that the occurrence of depletions is a function of both latitude and radial distance. During Ulysses' first orbit, near solar minimum, depletions were observed up to the highest latitudes covered by Ulysses, including latitudes where the solar wind flow was quite uniform and corotating interaction region (CIR) shocks were not observed. This suggests that high latitude magnetic field lines may connect to CIR shocks at lower latitudes. Alternatively, it is possible that fluctuations in field magnitude could produce the observed depletions, since the magnetic field enhancements required to produce the observed depletions are relatively weak (approximately a factor of 1.1-1.5). We characterize the occurrence and properties of depletions observed by Ulysses as a function of latitude, radial distance, and solar cycle, and consider possible mechanisms for the formation of these electron distributions.