1. Solar Mass Ejection Imager (SMEI) Analysis of the 20 January 2005 CME B.V. Jackson, P.P. Hick, A. Buffington, M.M. Bisi, and E.A. Jensen Center for Astrophysics and Space Sciences (UCSD) email: {bvjackson, pphick, abuffington, mmbisi, ejensen}@ucsd.edu} Abstract: Solar Mass Ejection Imager (SMEI) brightness measurements are analyzed to determine the 3D volumetric density of the 20 January 2005 CME. We use this system to measure the distribution of structure and provide a 3D mass of the ejecta associated with the large CME viewed in SMEI observations. The primary mass of the 20 January 2005 CME moves to the northwest of the Sun following the event observed earlier in LASCO coronagraph observations. There are two other very large coronal responses to the coronal energy input beginning around 6:30 UT near the time of CME onset. One of these is the large and extremely prompt Solar Energetic Particle (SEP) proton event observed at Earth beginning about 6:50 UT. Another response is an outward-propagating fast shock that arrives at Earth 34 hours following the event onset. A response that may be attributed to this shock is observed slightly more than 5 days following this at the Ulysses spacecraft situated 5.3 AU from the Sun,17º south of the ecliptic, and 27º from the Sun-Earth line to the west. SMEI observes the white- light response of this shock at Earth in the interplanetary medium around the spacecraft, and limits the shock 3D extent. UR: http://cass185.ucsd.edu/smei/smei.htmlhttp://cass185.ucsd.edu/smei/smei.html Introduction: Following the successful launch of the Solar Mass Ejection Imager (SMEI) on January 6, 2003 (Eyles et al., 2003; Jackson et al., 2004), we have been developing an image analysis technique that, as much as possible, retains the long-term brightness variation and data frame resolution of the instrument. We provide this data base partially to provide a tomographic analysis of heliospheric structures that include both CMEs and longer-term heliospheric density structures such as the extensions of coronal streamers. The Solar Mass Ejection Imager (SMEI) launched January 6, 2003 (Figure 1a) records the whole sky data on each 102-minute orbit from 840 km. SMEI, a zenith- nadir pointing spacecraft, rotates once per orbit (Figure 1b) and views three strips of sky away from Earth using CCD camera technology. The three cameras on SMEI have been used to provide sky maps that include orbit differences that have provided the elongation-time plot of Figure 3a and images from which a long-term base has been removed (Figure 2), and have been turned into time series at given sidereal locations in order to provide brightness over time that can be used in the 3D reconstruction program analysis at UCSD (Figure 3b). The 20 January 2005 coronal mass ejection (CME) was a very energetic event, and the ejected material associated with the X7.9 flare at about 6:00UT appeared high in the corona in LASCO data shortly after, indicating a very high-speed CME following the flare. Unfortunately, only one LASCO coronagraph image is available for this event, and this plus the flare onset time give only a vague indication of the total CME mass and outward speed. Following the flare, and initial CME observations, an extremely prompt (~ 20 min later) Solar Energetic Particle (SEP) event was observed at Earth. This prompt event was exceptional in that it was one of the most energetic in terms of numbers of particles arriving at Earth, and these particles had an extremely hard energy spectrum. The January 20, 2005 CME Event: To understand more about the total energy associated with this event, one needs information about the associated CME energy and the ensuing shock at Earth 35 hours following the CME initiation (see Figure 4a). This high-speed shock is observed in SMEI sky maps (see Figure 2), and in the time series measured for the event (Figure 4b). These time series show a spike in brightness associated with the shock passage, and are used to determine the approximate extent of the shock. To the East (upper Figure 4b) the average brightness of the shock is an increase of 1.0 S10 at Earth 90º from the Sun-Earth line and has an extent as given in situ of ~8 hours, and 20 e - cm 2 density increase during this 8 hours (see Figure 4a). This implies a structure that is 0.6 AU in length East of the Earth in order to support this brightness (Billings, 1966). To the West (lower Figure 4b) the average brightness of the shock is an increase of 1.2 S10 at Earth 90º from the Sun-Earth line and has an extent in situ of ~8 hours. This implies a structure that is 0.7 AU in length to the West of Earth in order to provide this brightness. These observations are summarized in Figure 5 depicting the 3D extent of this feature assuming it passes Earth at an average speed of 900 kms -1. REFERENCES: Billings, D.E.: 1966, A Guide to the Solar Corona, p. 150, Academic, New York Eyles, C.J., G.M. Simnett, M.P. Cooke, B.V. Jackson, A. Buffington, P.P. Hick, N.R. Waltham, J.M. King, P.A. Anderson, and P.E. Holladay (2003), The Solar Mass Ejection Imager (SMEI), Solar Phys., 217, 319. Jackson, B.V., A. Buffington, P.P. Hick, R.C. Altrock, S. Figueroa, P. Holladay, J.C. Johnston, S.W. Kahler, J. Mozer, S. Price, R.R. Radick, R. Sagalyn, D. Sinclair, G.M. Simnett, C.J. Eyles, M.P. Cooke, S. J. Tappin, T. Kuchar, D. Mizumo, D.F. Webb, P. Anderson, S.L. Keil, R. Gold, and N.R. Waltham (2004), The Solar Mass Ejection Imager (SMEI) mission, Solar Phys., 225, 177. Mizuno, D., A. Buffington, M.P. Cooke, C.J. Eyles, P.P. Hick, P.E. Holladay, B.V. Jackson, J.C. Johnston, T. Kuchar, J.B. Mozer, S. Price, R.R. Radick, G.M. Simnett, D. Sinclair, J. Tappin, and D.F. Webb (2005), Very High-Altitude Aurora Observations With the Solar Mass Ejection Imager, J. Geophys. Res., 110, A7, A07230, doi:10.1029/2004JA010689. (a) (b) Figure 1. (a) The Coriolis spacecraft with the Solar Mass Ejection Imager (SMEI) instrument and the Windsat antenna prior to launch from Vandenberg AFB. The three camera baffles (circled) are seen on the lower portion of the spacecraft. (b) SMEI in its terminator polar orbit at 840 km with an orbital inclination of 98 . SMEI looks away from the Earth at 30  above the local horizontal to avoid sunlight reflected from the Earth and from the Windsat antenna. The fields of view of the three cameras (each shown as shaded extensions from the satellite) together cover nearly 180  of sky, and as the instrument orbits Earth, map out nearly the whole sky around it. Figure 5. A 20 January 2005 CME diagram that depicts the structure passing Earth at 1 AU as seen from above the ecliptic plane. The CME structure outflow as reconstructed in 3D is shown to the west of the Sun, and the shock at 1 AU is depicted at ~22 UT January 22, 2005. Figure 2. Hammer-Aitoff Sky maps that show orbit-to- orbit images (time from upper left to lower right as given) derived from the three cameras on SMEI. The time period of the 20 January 2005 shock passage of Earth is observed in SMEI as a bright band of sky near 90º first to the upper right of the sky map on 18:32 UT, and second to the lower left of the sky map on 20:14 UT. Other portions of the sky maps presented at these times have no useable data or are overwhelmed by light associated with high-altitude aurora (see Misuno et al., 2005). The brightness scale is in ADU (1 S10 ~ 0.5 ADU) and have been adjusted to vary with elongation (ε-angular distance from the Sun in degrees) by a factor ε -2.3 / 90 -2.3 so that the bright inner regions do not dominate to overwhelm the signal, and so that outward-propagating signals can be better-observed. (a) (b) Figure 4. January 20 CME observed near Earth in situ. a) In situ plasma density and velocity observed in ACE. The shock associated with the CME arrives at about 17 UT. b) Sample average time series to the southeast and northwest of the Sun at about 90º elongation during the interval. Dashed red lines indicate that data is missing from one orbit to the next and interpolated from points at the ends of the sequence. (a) (b) Figure 3. January 20 CME observed in the heliosphere. a) An elongation-time CME plot determined from SMEI difference images (Webb, private communication, 2006). b) Sample of reconstructed 3D SMEI density for the CME at the time indicated. The CME is truncated at a 1.0 AU height to allow only the additional CME mass for the January 20 CME to be calculated. If the bulk of the CME 3 x 10 17 g of material reached 1 AU in about one day this indicates an average speed for this mass of approximately 1600 km s -1, or a total energy upper limit for the CME of ~2 x 10 33 ergs. This is not an accurate estimate since the speed for this event is uncertain and only determined from the propagation of an outward- moving feature observed in the SMEI difference images. The speed of this event could actually be nearly halved for the center of the CME mass, implying a total energy of ~5 x 10 32 ergs. Summary: The 20 January 2005 CME dense structure is reproduced by the UCSD 3D tomography. This material has a mass of approximately 3 x 10 17 g. The associated forward shock reaches Earth 35 hours following the CME initiation and this too can be recon- structed crudely from the SMEI data as it passes Earth.