Observations of CMEs from SOHO/LASCO R.A. Howard, R.A. Howard E.O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DCSearch for more papers by this authorG.E. Brueckner, G.E. Brueckner E.O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DCSearch for more papers by this authorO.C. St. Cyr, O.C. St. Cyr Computational Physics, Inc, Fairfax, VASearch for more papers by this authorD.A. Biesecker, D.A. Biesecker School of Physics and Space Research, University of Birmingham, Birmingham, UKSearch for more papers by this authorK.P. Dere, K.P. Dere E.O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DCSearch for more papers by this authorM.J. Koomen, M.J. Koomen Sachs-Freeman Associates, Landover, MDSearch for more papers by this authorC.M. Korendyke, C.M. Korendyke E.O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DCSearch for more papers by this authorP.L. Lamy, P.L. Lamy Laboratoire D'Astronomie Spatiale, Marseille, FranceSearch for more papers by this authorA. Llebaria, A. Llebaria Laboratoire D'Astronomie Spatiale, Marseille, FranceSearch for more papers by this authorM.V. Bout, M.V. Bout Laboratoire D'Astronomie Spatiale, Marseille, FranceSearch for more papers by this authorD.J. Michels, D.J. Michels E.O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DCSearch for more papers by this authorJ.D. Moses, J.D. Moses E.O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DCSearch for more papers by this authorS.E. Paswaters, S.E. Paswaters Interferometrics, Inc, Chantilly, VASearch for more papers by this authorS.P. Plunkett, S.P. Plunkett School of Physics and Space Research, University of Birmingham, Birmingham, UKSearch for more papers by this authorR. Schwenn, R. Schwenn Max-Planck-Institut für Aeronomie, Katlenburg-Lindau, GermanySearch for more papers by this authorG.M. Simnett, G.M. Simnett School of Physics and Space Research, University of Birmingham, Birmingham, UKSearch for more papers by this authorD.G. Socker, D.G. Socker E.O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DCSearch for more papers by this authorS.J. Tappin, S.J. Tappin School of Physics and Space Research, University of Birmingham, Birmingham, UKSearch for more papers by this authorD. Wang, D. Wang Interferometrics, Inc, Chantilly, VASearch for more papers by this author R.A. Howard, R.A. Howard E.O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DCSearch for more papers by this authorG.E. Brueckner, G.E. Brueckner E.O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DCSearch for more papers by this authorO.C. St. Cyr, O.C. St. Cyr Computational Physics, Inc, Fairfax, VASearch for more papers by this authorD.A. Biesecker, D.A. Biesecker School of Physics and Space Research, University of Birmingham, Birmingham, UKSearch for more papers by this authorK.P. Dere, K.P. Dere E.O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DCSearch for more papers by this authorM.J. Koomen, M.J. Koomen Sachs-Freeman Associates, Landover, MDSearch for more papers by this authorC.M. Korendyke, C.M. Korendyke E.O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DCSearch for more papers by this authorP.L. Lamy, P.L. Lamy Laboratoire D'Astronomie Spatiale, Marseille, FranceSearch for more papers by this authorA. Llebaria, A. Llebaria Laboratoire D'Astronomie Spatiale, Marseille, FranceSearch for more papers by this authorM.V. Bout, M.V. Bout Laboratoire D'Astronomie Spatiale, Marseille, FranceSearch for more papers by this authorD.J. Michels, D.J. Michels E.O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DCSearch for more papers by this authorJ.D. Moses, J.D. Moses E.O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DCSearch for more papers by this authorS.E. Paswaters, S.E. Paswaters Interferometrics, Inc, Chantilly, VASearch for more papers by this authorS.P. Plunkett, S.P. Plunkett School of Physics and Space Research, University of Birmingham, Birmingham, UKSearch for more papers by this authorR. Schwenn, R. Schwenn Max-Planck-Institut für Aeronomie, Katlenburg-Lindau, GermanySearch for more papers by this authorG.M. Simnett, G.M. Simnett School of Physics and Space Research, University of Birmingham, Birmingham, UKSearch for more papers by this authorD.G. Socker, D.G. Socker E.O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DCSearch for more papers by this authorS.J. Tappin, S.J. Tappin School of Physics and Space Research, University of Birmingham, Birmingham, UKSearch for more papers by this authorD. Wang, D. Wang Interferometrics, Inc, Chantilly, VASearch for more papers by this author Book Editor(s):Nancy Crooker, Nancy CrookerSearch for more papers by this authorJo Ann Joselyn, Jo Ann JoselynSearch for more papers by this authorJoan Feynman, Joan FeynmanSearch for more papers by this author First published: 01 January 1997 https://doi.org/10.1029/GM099p0017Citations: 42Book Series:Geophysical Monograph Series AboutPDFPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShareShare a linkShare onFacebookTwitterLinked InRedditWechat Summary This chapter contains sections titled: Introduction LASCO Instrument Description Observations of CMES Discussion Citing Literature Coronal Mass Ejections, Volume 99 RelatedInformation

Coronal dimmings are closely related to the footpoints of coronal mass ejections (CMEs) and, as such, offer information about CME origins and evolution. In this paper, we investigate the relationship between CME and dimming properties. In particular, we compare CME quantities for events with and without associated dimmings. We find that dimming-associated CMEs, on average, have much higher speeds than non-dimming-associated events. In fact, CMEs without an associated dimming do not appear to travel faster than 800 km s−1, i.e., the fast solar wind speed. Dimming-associated events are also more likely to be associated with flares, and those flares tend to have the highest magnitudes. We propose that each of these phenomena is affected by the energy available in the source region. Highly energetic source regions produce fast CMEs that are accompanied by larger flares and visible dimmings, while less energetic source regions produce slow CMEs that are accompanied by smaller flares and may or may not have dimmings. The production of dimmings in the latter case may depend on a number of factors including initiation height of the CME, source region magnetic configuration, and observational effects. These results have important implications for understanding and predicting CME initiations.

We report on a statistical analysis of 96 CME-associated EUV coronal dimmings between 1998 and 2000. We investigate the size and location of the events and characterize how these events evolve with time. The durations typically range from 3 to 12 hr. The dimmings appear most frequently within the belt of active regions (20 degrees-50 degrees latitude). Dimming events are generally symmetric in latitude and longitude with some tendency to be broader in latitude. The temporal profiles of most events are characterized by a sharp rise and a gradual recovery. Although the majority of cases are well fit by a single recovery slope, a large minority of events have a two-part decay with an initial decaying slope that is similar in magnitude to the rising slope and a secondary, flatter, decay lasting several hours.

Unlike most comets seen at larger heliocentric dis- tances, sungrazing comets seen near perihelion are often observed over a wide range of phase angles in a short time. The phase angle of the Marsden group comet C/1999 U2 changed by nearly 120 over 37 hours. Furthermore, many are seen at high phase angles where forward scattering is very important. The few comets that have been seen at large phase angles, including C/1976 V1 West, 96P/Machholz 1, and C/2006 P1 Mc- Naught, have shown dramatic brightening. Studies by Kolokolova et al. (1) and Marcus (2) have quantified the phase dependence of brightness due to scattering off dust in the coma, showing a gentle increase due to backscat- tering (phase angle < 30 ), a strong forward-scattering surge (phase angles > 100 ), and a relatively flat curve in between. We apply phase corrections based on the work by Kolokolova et al. (1) and Marcus (2) to the lightcurves of the Kreutz, Marsden, Kracht, and Meyer comet groups which account for more than 90% of all comets observed by SOHO. Unsurprisingly, the phase effect is seasonal, varying with the geometry of each group. Depending on when they reach perihelion, phase angle affects the apparent slope of the brightening and fading, the appar- ent time and heliocentric distance of peak brightness, and even the detectability for comets near the limiting magni- tude of SOHO. We correct the SOHO discovery rates and analyze how accounting for phase changes the size dis- tributions (and thus the implied total masses) of the sun- grazing families. We also investigate the implications of the phase angle difference between comets observed by SOHO and the STEREO-A and B satellites in the dis- covery statistics. This research was supported by NASA Planetary At- mospheres grant NNG06GF29G.

The Solar Terrestrial Relations Observatory (STEREO) is primarily a solar and interplanetary research mission, with one of the natural applications being in the area of space weather. The obvious potential for space weather applications is so great that NOAA has worked to incorporate the real-time data into their forecast center as much as possible. A subset of the STEREO data will be continuously downlinked in a real-time broadcast mode, called the Space Weather Beacon. Within the research community there has been considerable interest in conducting space weather related research with STEREO. Some of this research is geared towards making an immediate impact while other work is still very much in the research domain. There are many areas where STEREO might contribute and we cannot predict where all the successes will come. Here we discuss how STEREO will contribute to space weather and many of the specific research projects proposed to address STEREO space weather issues. The data which will be telemetered down in the Space Weather Beacon is also summarized here. Some of the lessons learned from integrating other NASA missions into the forecast center are presented. We also discuss some specific uses of the STEREO data in the NOAA Space Environment Center.

[1] In the paper ‘‘Major geomagnetic storms (Dst 100 nT) generated by corotating interaction regions’’ by I. G. Richardson et al. (Journal of Geophysical Research, 111, A07S09, doi:10.1029/2005JA011476, 2006), there are several typographical errors. In Figures 1, 2, 3, 4, and 7, the y component of the solar wind electric field (Ey) is plotted with the incorrect sign. Signed values of Ey referred to in the text and given in Table 1 also have the incorrect sign. As stated in the second paragraph of section 2, the ‘‘Ey’’ panel shows the value of VxBz. However, this is equal to Ey, not Ey (assuming that VxBz VzBx in the solar wind). JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, A12105, doi:10.1029/2007JA012332, 2007 Click Here for Full Article

Seventy‐nine major geomagnetic storms (minimum Dst ≤ −100 nT) observed in 1996 to 2004 were the focus of a “Living with a Star” Coordinated Data Analysis Workshop (CDAW) in March 2005. In nine cases, the storm driver appears to have been purely a corotating interaction region (CIR) without any contribution from coronal mass ejection‐related material (interplanetary coronal mass ejections (ICMEs)). These storms were generated by structures within CIRs located both before and/or after the stream interface that included persistently southward magnetic fields for intervals of several hours. We compare their geomagnetic effects with those of 159 CIRs observed during 1996–2005. The major storms form the extreme tail of a continuous distribution of CIR geoeffectiveness which peaks at Dst ∼ −40 nT but is subject to a prominent seasonal variation of ∼40 nT which is ordered by the spring and fall equinoxes and the solar wind magnetic field direction toward or away from the Sun. The O'Brien and McPherron (2000) equations, which estimate Dst by integrating the incident solar wind electric field and incorporating a ring current loss term, largely account for the variation in storm size. They tend to underestimate the size of the larger CIR‐associated storms by Dst ∼ 20 nT. This suggests that injection into the ring current may be more efficient than expected in such storms. Four of the nine major storms in 1996–2004 occurred during a period of less than three solar rotations in September to November 2002, also the time of maximum mean IMF and solar magnetic field intensity during the current solar cycle. The maximum CIR‐storm strength found in our sample of events, plus additional 23 probable CIR‐associated Dst ≤ −100 nT storms in 1972–1995, is (Dst = −161 nT). This is consistent with the maximum storm strength (Dst ∼ −180 nT) expected from the O'Brien and McPherron equations for the typical range of solar wind electric fields associated with CIRs. This suggests that CIRs alone are unlikely to generate geomagnetic storms that exceed these levels.