Abstract.We describe an empirical model to predict the 1-AU •rrival of coronal mass ejections (CMEs). This model is based on an effective interplanetary (IP) acceleration described by Gopalswamy et al. [2000b] that the CMEs are subject to, as they propagate from the Sun to i AU. We have improved this model (1) by minimizing the projection effects (using data from spacecraft in quadrature) in determining the initial speed of CMEs, and (2) by allowing for the cessation of the interplanetary acceleration before i AU. The resulting effective IP acceleration was higher in magnitude than what was obtained from CME measurements from spacecraft along the Sun-Earth line. We evaluated the predictive capability of the CME arrival model using recent two-point measurements from the Solar and Heliospheric Observatory (SOHO), Wind, and ACE spacecraft. We found that The standard assumption that the CME is a rigid cone may not be correct. In fact, the predicted arrival times have a better agreement with the observed arrival times when no projection correction is applied to the SOHO CME measurements. The results presented in this work suggest that CMEs expand and accelerate near the Sun (inside 0.7 AU) more than our model supposes; these aspects will have to be included in future models.

The statistics improved during the 1980s as the SOLWIND (1979)(1980)(1981)(1982)(1983)(1984)(1985) and SMM (1980,(1984)(1985)(1986)(1987)(1988)(1989) However, there were relatively few systematic studies of acceleration. Despite its large 2.5-10 Rs field of view, the SOLWIND coronagraph had a low spatial resolution (-1.25 arc min) and revealed unambiguous accelerations for only a small number of particularly well observed events [Howard et 24,739

No abstract

In an examination of the Solwind coronagraph images obtained during the interval March 28, 1979, to December 31, 1981, we have identified 998 coronal mass ejections and recorded their structural classes, central latitudes, latitudinal spans, speeds, excess brightnesses, and relative importances. A statistical analysis revealed the following general results. (1) The properties of coronal mass ejections (CMEs) depended strongly on their structure. Curved front, halo, and complex CMEs were the most energetic, and single spike, streamer blowout, and diffuse fan CMEs were the least energetic. CMEs occurred over a wide range of position angles, broadly centered on the equator, and had an average angular span of 45°. The leading edge moved at an average of approximately 470 km/s, and the average ejected mass and kinetic energy were 4.1×1015 g and 3.5×1030 erg, respectively. The average CME proton flux at the equator at 1 AU was 2.2×107 cm−2 s−1 or approximately 5% of the measured in situ flux during 1971–1976. (2) During 1979–1981, the average occurrence rate was 1.8/day for all CMEs, 0.9/day for “major” CMEs, and 0.15/day for all CMEs that crossed the equator and had an angular span of at least 45°. (3) The temporal variations in the CME occurrence rate did not show an obvious persistent relation to the variations in the sunspot number on time scales ranging from 7 to 180 days. During 1979–1981 the maximum in the 180‐day average CME rate peaked in the second half of 1980, whereas the 180‐day average sunspot number peaked during the first half of 1980. The 180‐day average rate of fast CMEs (speeds of at least 800 km/s) had a monotonic increase that seemed to be more closely associated with the occurrence rate of large solar flares than with the variation of the sunspot number.

We examine the energetics of coronal mass ejections (CMEs) with data from the large-angle spectrometric coronagraphs (LASCO) on SOHO. The LASCO observations provide fairly direct measurements of the mass, velocity, and dimensions of CMEs. Using these basic measurements, we determine the potential and kinetic energies and their evolution for several CMEs that exhibit Ñux-rope morphologies. Assuming Ñux conservation, we use observations of the magnetic Ñux in a variety of magnetic clouds near the Earth to determine the magnetic Ñux and magnetic energy in CMEs near the Sun. We Ðnd that the potential and kinetic energies increase at the expense of the magnetic energy as the CME moves out, keeping the total energy roughly constant. This demonstrates that Ñux-rope CMEs are magnetically driven. Furthermore, since their total energy is constant, the Ñux-rope parts of the CMEs can be considered a closed system above D2 R _ .