Coronal mass ejection transients observed with the white light coronagraph on Skylab are found to be associated with several other forms of solar activity. There is a strong correlation between such mass ejection transients and chromospheric Ha activity, with three-quarters of the transients apparently ...... o/ originating m or near active regions. We infer that 4(1~ of transients are associated with flares, 30 ,o are associated with eruptive prominences solely (without flares), and more than 70~ are associated with eruptive prominences or filament disappearances (with or without flares). Nine of ten flares which displayed apparent mass ejections of Ha-emitting material from the flare site could be associated with coronal transients. Within each class of activity, the more energetic events are more likely to be associated with an observable mass ejection.

More than 30 instances of sudden mass ejections from the sun were observed with the white light coronagraph experiment aboard Skylab during the first 118 days of the mission. Typically, these ejections appear as large magnetic loops rooted at the sun, yet expanding outward through the solar corona at speeds of the order of 400 km s−1. The loops always appear to retain their magnetic connection to the sun. Eighteen of these ejections were associated with active and eruptive prominences and surges; only three ejections appear to have been flare initiated. Associations with ground‐detected metric wavelength type 2 and 4 radio bursts occur for about 30% of these events; however, ground‐detected type 2 and 4 radio bursts originating near the limb are almost invariably accompanied by coronagraph‐observed ejections. Pressure or MHD waves run out ahead of the transient material ejecta; at times these waves can be detected by their effects on nearby coronal structures. For one event, that of August 10, 1973, we make the following estimates: (1) mass content, 4 × 1015 grams; (2) mass flow rate, 1.1 × 1012 grams s−1; (3) energy content, 8.4 × 1030 ergs; and (4) energy flow rate, 7.7 × 1026 ergs s−1. Locally, this represents a significant mass and energy input to the solar wind; we suggest that the ejections are the coronal counterparts of nonrecurrent (including shocks) solar wind disturbances detected near the orbit of the earth.

Abstract. We report the properties of all the 841 coronal mass ejections (CMEs) observed by the Solar and Heliospheric Observatory (SOHO) Large Angle Spectroscopic Coronagraph (LASCO) C2 and C3 white-light coronagraphs from January 1996 through June 1998, and we compare those properties to previous observations by other similar instruments. Both the CME rate and the distribution of apparent locations of CMEs varied during this period as expected based on previous solar cycles. The distribution of apparent speeds and the fraction of CMEs showing acceleration were also in agreement with earlier reports. The pointing stability provided by an L-1 orbit and the use of CCD detectors have resulted in superior brightness sensitivity for LASCO over earlier coronagraphs; however, we have not detected a significant population of fainter (i.e., low mass) CMEs. The general shape of the distribution of apparent sizes for LASCO CMEs is similar to those of earlier reports, but the average (median) apparent size of 72 ø (50 ø ) is significantly larger. The larger average apparent size is predominantly the result of the detection of a population of partial and complete halo CMEs, at least some of which appear to be events with a significant longitudinal component directed along the SunEarth line, either toward or away from the Earth. Using full disk solar images obtained by the Extreme ultraviolet Imaging Telescope (EIT) on SOHO, we found that 40 out of 92 of these events might have been directed toward the Earth, and we compared the timing of those with the Kp geomagnetic storm index in the days following the CME. Although the "false alarm" rate was high, we found that 15 out of 21 (71%) of the Kp _> 6 storms could be accounted for as SOHO LASCO/EIT frontside halo CMEs. If we eliminate three Kp storms that occurred following LASCO/EIT data gaps, then the possible association rate was 15 out of 18 (83%). IntroductionThe dynamic processes taking place in the rarified atmosphere of our nearest star are sufficient motivation for many researchers to examine the Sun, the hellosphere, and planetary magnetospheres as plasma physics laboratories. But recent research connecting severe geomagnetic disturbances directly with coronal mass ejections from the Sun [e.g., Gosling, 1993] has renewed interest in a more systemic approach to the arcane specialties of solar and space physics (e.g., collection of This manuscript describes recent observations of coronal mass ejections near the Sun. These sporadic ejections of material through the Sun's atmosphere into interplanetary space can be detected remotely (both by imaging and by inference) at many wavelengths across the electromagnetic spectrum (e.g., X ray, EUV, Ha, and radio). Also the plasma, particle, and magnetic properties of ejected material can be measured in situ in the heliosphere. However, the phrase "coronal mass The understanding of the origin, observation, and effects of CMEs has benefited from significant effort during the past 25 years, and the reader is directed to any of the r...

The outward speeds of mass ejection events observed with the white light coronagraph experiment on Skylab varied over a range extending from less than 100kms -I to greater than 1200 km s -1. For all events the average speed within the field of view of the experiment (1.75 to 6 solar radii) was 470 km s -I. Typically, flare associated events (Importance 1 or greater) traveled faster (775 km s -j) than events associated with eruptive prominences (330 km s 1); no flare associated event had a speed less than 360 km s 1, and only one eruptive prominence associated event had a speed greater than 600 km s 1. Speeds versus height profiles for a limited number of events indicate that the leading edges of the ejecta move outward with constant or increasing speeds.Metric wavelength type II and IV radio bursts are associated only with events moving faster than' about 400kms t; all but two events moving faster than 500kms i produced either a type II or IV radio burst or both. This suggests that the characteristic speed with which MHD signals propagate in the lower (1.1 to 3 solar radii) corona, where metric wavelength bursts are generated, is about 400 to 500 km s -t. The fact that the fastest mass ejection events are almost always associated with flares and with metric wavelength type II and IV radio bursts explains why major shock wave disturbances in the solar wind at 1 AU are most often associated with these forms of solar activity rather than with eruptive prominences.