HR: 11:05h
AN: SH41C-04 INVITED     [PDF]
TI: LASCO/SMEI Potential Joint Observations
AU: * Howard, R A
EM: russ.howard@nrl.navy.mil
AF: Naval Research Laboratory Naval Research Laboratory, 4555 Overlook Ave., SW, Washington, DC 20375-5352 United States
AB: The SOHO LASCO complement of coronagraphs has observed many halo CMEs. A subset of these events is the source of geomagnetic storms. A major question is to understand the propagation of CMEs through the interplanetary medium and their interaction with the Earths environment. LASCO observes the lateral expansion of Earth directed CMEs and can only infer the speed in the direction of Earth. Thus, determination of the time of impact at Earth from LASCO observations requires an extrapolation from the near-Sun environment. Combining observations from instruments such as SMEI will enable the tracking of such events as they propagate toward Earth, providing reliable predictions of the time of impact. Comparing the measurements from LASCO with SMEI will permit a number of studies. For example, the volumetric electron density of CMEs can be tracked from the Sun to the vicinity of Earth assuming the velocity field. One study would be to determine the electron density of the leading edge of the CME. From LASCO observations, the frontal electron density decreased according to the expansion into a volume (declined by $R^{-3}$) and no sweeping up the ambient solar wind material could not be observed out to the edge of the C3 field (30 solar radii). We believe that this was because the electron density in the CME was much greater than the ambient and only became comparable to the ambient at the edge of C3. Thus SMEI observations should be able to detect if there is a snow plow effect occurs.
DE: 7513 Coronal mass ejections
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting