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.

[1] Fast coronal mass ejections (CMEs), X-class flares, solar energetic particle (SEP) events, and interplanetary shocks were abundantly observed during the episode of intense solar activity in late October and early November 2003. Most of the 80 CMEs originated from three active regions (NOAA ARs 484, 486, and 488). We compare the statistical properties of these CMEs with those of the general population of CMEs observed during cycle 23. We find that (1) the 2003 October-November CMEs were fast and wide on the average and hence were very energetic, (2) nearly 20 percent of the ultrafast CMEs (speed !2000 km s À1 ) of cycle 23 occurred during the October-November interval, including the fastest CME of the study period ($2700 km s À1 on 4 November 2003 at 1954 UT), (3) the rate of full-halo CMEs was nearly four times the average rate during cycle 23, (4) at least sixteen shocks were observed near the Sun, while eight of them were intercepted by spacecraft along the Sun-Earth line, (5) the CMEs were highly geoeffective: the resulting geomagnetic storms were among the most intense of cycle 23, (6) the CMEs were associated with very large SEP events, including the largest event of cycle 23. These extreme properties were commensurate with the size and energy of the associated active regions. This study suggests that the speed of CMEs may not be much higher than $3000 km s À1 , consistent with the free energy available in active regions. An important practical implication of such a speed limit is that the Sun-Earth travel times of CME-driven shocks may not be less than $0.5 day. Two of the shocks arrived at Earth in <24 hours, the first events in $30 years and only the 14th and 15th documented cases of such events since 1859.

Abstract.We compare the near-Sun and near-Earth mani•hstations of solar eruptions that occurred during November 1994 to June 1998. We compared white-light coronal mass ejections, metric type II radio bursts, and extreme ultraviolet wave transients (near the Sun) with interplanetary (IP) signatures such as decameter-hectometric type II bursts, kilometric type II bursts, IP ejecta, and IP shocks. We did a two-way correlation study to (1) suggesting that the shocks have a much larger extent than the drivers. Shocks originating from both limbs of the Sun arrived at Earth, contradicting earlier claims that shocks from the west limb do not reach Earth. These shocks also had good type II radio burst association. We provide an explanation •br the observed relation between metric, decameter-hectometric, and kilometric type II bursts based on the fast mode magnetosonic speed profile in the solar atmosphere.

The twin STEREO spacecraft were launched on October 26, 2006, at 00:52 UT from Kennedy Space Center aboard a Delta 7925 launch vehicle. After a series of highly eccentric Earth orbits with apogees beyond the moon, each spacecraft used close flybys of the moon to escape into orbits about the Sun near 1 AU. Once in heliospheric orbit, one spacecraft trails Earth while the other leads. As viewed from the Sun, the two spacecraft separate at approximately 44 to 45 degrees per year. The purposes of the STEREO Mission are to understand the causes and mechanisms of coronal mass ejection (CME) initiation and to follow the propagation of CMEs through the inner heliosphere to Earth. Researchers will use STEREO measurements to study the mechanisms and sites of energetic particle acceleration and to develop three-dimensional (3-D) time-dependent models of the magnetic topology, temperature, density and velocity of the solar wind between the Sun and Earth. To accomplish these goals, each STEREO spacecraft is equipped with an almost identical set of optical, radio and in situ particles and fields instruments provided by U.S. and European investigators. The SECCHI suite of instruments includes two white light coronagraphs, an extreme ultraviolet imager and two heliospheric white light imagers which track CMEs out to 1 AU. The IMPACT suite of instruments measures in situ solar wind electrons, energetic electrons, protons and heavier ions. IMPACT also includes a magnetometer to measure the in situ magnetic field strength and direction. The PLASTIC instrument measures the composition of heavy ions in the ambient plasma as well as protons and alpha particles. The S/WAVES instrument uses radio waves to track the location of CME-driven shocks and the 3-D topology of open field lines along which flow particles produced by solar flares. Each of the four instrument packages produce a small real-time stream of selected data for purposes of predicting space weather events at Earth. NOAA forecasters at the Space Environment

Abstract. Previously, the formation of the lunar wake was considered from a magnetohydrodynamic perspective. However, recent Wind particle and field observations suggest the lunar wake may be formed by kinetic processes: those microphysical processes not considered in an MHD formalism. Unfortunately, a full multidimensional and selfconsistent kinetic simulation of the lunar wake is beyond current means. However, some elements of the kinetic structure can be simulated via a simple one-dimensional electrostatic particle-in-cell simulation. We present a self-consistent simulation of a cross-sectional element of a plasma void. Essentially, wakeward directed ion beams are formed at the flanks of the simulated void, consistent with the Wind observations of counterstreaming ion beams in the wake region. These wakeward directed beams are generated by ambipolar electric fields formed at the wake edges. Other structures observed by Wind are also seen in the simulation, including an electrostatically turbulent central wake region that causes the wake to fill-in and a rarefaction wave emanating outward from the wake. IntroductionThe Wind spacecraft was launched in November 1994 as part of the Global Geospace Science (GGS) fleet, and thereafter followed a double-lunar swingby orbit to allow for long periods of solar wind study. This orbit was primarily designed for lunar gravitational assist to boost the spacecraft to increasing perigee. However, the moon also became a target of opportunity for scientific study [1970]. Unfortunately, these early investigations had relatively low resolution magnetometers, and did not have simultaneous particle distribution and plasma wave measurements. As a consequence, there was an understandable deemphasis on plasma kinetic effects since the fundamental measurements of such processes where not available. However, some debate over an MHD versus particle/kinetic lunar wake did occur, as described in the introduction of Spreiter et al. [1970]. Unfortunately, high-resolution particle and electric wave measurements were unavailable to aid in their discussion. 23,653