List of Figures

View Image Figure 1:
Timeline of the history of spacecraft relevant to CME study. Image adapted from Howard (2011b).
View Image Figure 2:
Evolution of a “classic” CME observed by the LASCO C2 coronagraph on 2 June 1998. Note the circular structures just above the prominence, suggesting a flux rope. Image reproduced with permission from Plunkett et al. (2000), copyright by Springer.
View Image Figure 3:
a) Snapshot map of a radio CME at a frequency of 164 MHz at the time of maximum flux. The background emission from the Sun has been subtracted. Time variable radio emission from a noise storm is present to the northwest (upper right). The brightness of the CME is saturated in the corona because the map has been clipped at a level of 0.04 SFU beam–1, corresponding to a brightness temperature of 2.6 × 105 K. The radio CME is visible as a complex ensemble of loops extended out to the southwest (lower right). Also shown is the spectral index measured at four locations in the radio CME. b) Flux spectra measured at the four points shown in (a). All flux measurements have been normalized to SFU N−be1am, where Nbeam is the 164 MHz beam. Model spectra are also shown. Image reproduced with permission from Bastian et al. (2001).
View Image Figure 4:
Examples of a variety of halo CME observations, clockwise: a frontside full halo (arrow shows likely source near Sun center); a backside full halo; a partial halo; and an asymmetric full halo. Image reproduced with permission from Gopalswamy et al. (2003a).
View Image Figure 5:
Images of the same Earth-directed CME obtained from three different viewing locations within an hour: a) from STEREO/COR2-B on 3 April 2010 at 11:39 UT, b) from LASCO/C2 at 10:55 UT, and c) from STEREO/COR2-A on the same day at 11:08 UT. At this time (April 2010) the STEREO spacecraft were approximately 70° in longitude from the Sun-Earth line and ∼ 140° from each other. The different appearances of this same CME observed at around the same time demonstrate the need to consider perspective in measuring CME properties.
View Image Figure 6:
Daily SOHO LASCO CME rates for Cycle 23 (thin curves: smoothed per month, thick curves: smoothed over 13 months) from 1997 – 2006. These have been extracted using CACTus (red) and the CDAW CME Catalog (blue). As reference, the daily and smoothed monthly sunspot number have been overplotted in gray (produced using the SIDC-Royal Observatory of Belgium). The CME rates have been adjusted to accommodate for duty cycle. Image reproduced with permission from Robbrecht et al. (2009a), copyright by IOP.
View Image Figure 7:
LASCO CME occurrence rate (left) and mean speed (right) from 1996 to 2011 averaged over Carrington rotations. The large spike in CME speed is due to highly energetic CMEs that erupted in the late 2003 period. Image adapted from Gopalswamy (2010b), updated by S. Yashiro (2011).
View Image Figure 8:
The LASCO CME rate smoothed over 13 Carrington rotations and compared with the solar sunspot number. Arrows indicate the two maxima in CME rate and sunspot number. Large data gaps occurred during June 1998 to February 1999. Image reproduced with permission from Gopalswamy (2004), copyright by Springer.
View Image Figure 9:
Daily CME rate for 2010 – 2011 in the context of the rate through recent solar minimum. CME data sources: LASCO = manual online CDAW catalog (black - NRL, CUA) and our counts since January 2010 (light blue); SEEDS = automatic catalog (dotted red) courtesy J. Zhang and J. Bannick (GMU); CACTus = automatic catalog courtesy E. Robbrecht & B. Bourgoignie (SIDC); STEREO COR1 = manual catalog (green) courtesy C. St. Cyr (NASA) and H. Xie (CUA); Sunspot number (SSN – dark blue is current, dotted blue is predicted) from NOAA SWPC. CDAW and SEEDS rates are for CME widths > 20. CDAW, SEEDS, and SSN plots are 13-month, COR1 6-month, and 2010 LASCO counts 6-week running averages. Image courtesy T. Kuchar.
View Image Figure 10:
Daily CME rate vs. SSN both averaged per year. The asterisks refer to rates for Cycle 23 derived from CACTUS (see Table 1). Its absolute scale is shown on the right y-axis. The daily CME rates derived by Webb and Howard (1994) are plotted with diamonds. Its absolute scale is shown on the left y-axis. A scaling factor of ∼ 4.7 applies between the CACTus and the Webb and Howard rates. Image reproduced with permission from Robbrecht et al. (2009a), copyright by IOP.
View Image Figure 11:
Latitudes of LASCO CMEs (filled circles) with known solar surface associations (identified from microwave prominence eruptions) plotted vs time, by Carrington Rotation number. The dotted and dashed curves represent the tilt angle of the heliospheric current sheet in the northern and southern hemispheres, respectively; the solid curve is the average of the two. The up and down arrows denote the times when the polarity in the north and south solar poles, resp., reversed. Note that the high latitude CMEs and PEs are confined to the solar maximum phase and their occurrence is asymmetric in the northern and southern hemispheres. PEs at latitudes below 40° may arise from active regions or quiescent filament regions, but those at higher latitudes are always from the latter. Image adapted from Gopalswamy (2004); Gopalswamy et al. (2010a), updated by S. Yashiro (2011).
View Image Figure 12:
Speed and width distributions of all CMEs (top) and wider CMEs (W ≥ 30°; bottom). The average width of wider CMEs is calculated using only those CMEs with W ≥ 30°. Image reproduced with permission from Gopalswamy et al. (2010a), copyright by Springer.
View Image Figure 13:
Apparent CME width distributions, displayed per year in log-log scale. The CACTus distribution corresponds to the red curve; the CDAW distribution is represented by the light blue curve. The distributions are not corrected for observing time. Image reproduced with permission from Robbrecht et al. (2009a), copyright by IOP.
View Image Figure 14:
The 3-D spatial location of the CME on 17 October 2008 at 14:08 UT as calculated using geometric localization. The CME appeared as a west-limb event in STEREO-A, as an east-limb event in STEREO-B, and as a halo CME by LASCO. The absence of space weather disturbances at Earth associated with the CME suggests that it was a backside halo event. The green quadrilaterals indicate the bounding volume of the CME as a whole; the blue quadrilaterals indicate the bounding volume of the leading-edge shell. The hash marks on the plots indicate the scale used; the distance between each mark is 1 R⊙. The viewing latitudes and longitudes on the plots refer to the observer’s position in HEEQ coordinates. The left plot is for an observer hovering over the west limb of the Sun; Earth is on the left-hand side of the plot. The center plot is for an observer at Earth. The right plot is for an observer looking down onto the north pole of the Sun; Earth is toward the bottom of the plot. Image reproduced with permission from de Koning et al. (2009), copyright by Springer.
View Image Figure 15:
Annual mean and median speeds of LASCO CMEs from 1996 – 2010. There are two peaks, the first near solar activity maximum and the second in 2003. Thus, high speeds were still prevalent during the early declining phase. Image adapted from Gopalswamy (2004), updated by S. Yashiro (2011).
View Image Figure 16:
Histograms of LASCO CME mass distribution (upper left), kinetic energy (upper right), and total mechanical energy (bottom left) for 7668 events. Also shown are the histograms for events reaching maximum mass < 7R ⊙ (dashed lines) and events reaching maximum mass 7 R ⊙ (dash-double dot). Not all detected CMEs have been included because mass measurements require: (i) a good background image, (ii) three consecutive frames with CMEs, and (iii) CMEs well separated from preceding CMEs. Image adapted from Vourlidas et al. (2010, 2011b), courtesy A. Vourlidas (2011).
View Image Figure 17:
Top: scatter plot of the logarithm of maximum CME mass vs. the height where it was measured. Two populations are present: CMEs reaching maximum mass < 7 R ⊙ and CME with maximum mass > 7R ⊙. Bottom: scatter plot of the logarithm of CME surface density (e cm–2) vs. height. The CME density is constant above ∼ 10 R ⊙. A histogram with 1 R ⊙ bins is calculated and the average density (asterisks) and in each bin is overploted. Note the small spread of the CME density values above ∼ 10 R⊙. Its average value is shown on the plot. The height spread is mostly due to the noise and flatness of the mass measurements at those heights which tend to shift around the height of the maximum mass. Image adapted from Vourlidas et al. (2010, 2011b), courtesy A. Vourlidas (2011).
View Image Figure 18:
Solar cycle dependence of the CME mass and kinetic energy. Top left: log CME mass. Top right: log CME mass density in g R–2. Middle left: log CME kinetic energy. Middle right: CME speed. All four plots show annual averages. Bottom panel: total CME mass per Carrington rotation. The data gaps in 1998 and the drop in 1999 are due to spacecraft emergencies. The plot is an update of Figures 14 and 1 in Vourlidas et al. (2010, 2011b) to include events to July 31, 2010, courtesy A. Vourlidas (2011).
View Image Figure 19:
LASCO C2 image from 4 January 2002 image of a Coronal Mass Ejection (CME) showing detail in the ejected material. The solar limb Sun is represented by the white circle. Available from SOHO online image gallery: External Linkhttp://sohowww.nascom.nasa.gov/gallery/bestofsoho.html.
Watch/download Movie Figure 20: (mpeg-Movie; 455 KB)
Movie: LASCO C3 images of lightbulb shaped CME on 27 February 2000. Classic three-part structure with outer shell, void and inner bright structure, in this case an erupting prominence. From SOHO online movie gallery: External Linkhttp://sohowww.nascom.nasa.gov/gallery/Movies/flares.html.
View Image Figure 21:
Schematic diagram of a disrupted magnetic field that forms in an eruptive process (Lin, 2004). Catastrophic loss of equilibrium, occurring in a magnetic configuration including a flux rope, stretches the closed magnetic field and creates a Kopp–Pneuman-type structure. This diagram is created by incorporating the traditional two-ribbon flare model (bottom), from Forbes and Acton (1996) with the CME model (top) of Lin and Forbes (2000). Colors denote the different hierarchies of plasma in the configuration. Image reproduced with permission from Lin (2004), copyright by Springer.
View Image Figure 22:
Histograms of “source” longitudes of halo CMEs. Image reproduced with permission from Webb (2002).
View Image Figure 23:
Erupting prominence, dimming regions and arcade associated with a fast CME on 12 September 2000. Top: SOHO EIT 195 Å running-difference images; bottom: CME leading edge and erupting prominence (EP) seen in SOHO LASCO C2 images. Image reproduced with permission from Tripathi et al. (2004), copyright by ESO.
View Image Figure 24:
A filament eruption and post-eruption arcade near Sun center on 17 February 2000 (top). It was associated with a symmetrical LASCO halo CME (bottom). Image reproduced with permission from Tripathi et al. (2004), copyright by ESO.
View Image Figure 25:
Locations of associated solar surface activity related to CMEs that produce major (Dst ≤ − 100 nT) geomagnetic storms (left) and large SEP events (right). The circle sizes represent the significance of the resultant event (Gopalswamy, 2010b).
View Image Figure 26:
A very fast CME with flux-rope structure followed by a narrow ray on 18 – 20 November 2003. The ray also shows evidence of bursty reconnection in the current sheet (bottom panels). Image reproduced with permission from Lin et al. (2005).
View Image Figure 27:
A LASCO “Light-bulb CME” on 23 March 1998 (see Ciaravella et al., 2003a). The UVCS slit at 1.5 R⊙ reveals hot Fe XVIII emission trailing the CME, an expected spectroscopic signature of a current sheet. Image courtesy A. Ciaravella.
View Image Figure 28:
Coronal synoptic maps from the SMM C/P coronagraph showing the white light emission at a height of 3.4R ⊙ over the east (top) and west (bottom) limb. The coronal streamer belt is evident on these maps. Narrow vertical streaks on the maps indicate CMEs. These were first called “bugles” by Hundhausen (1993), since streamer-blowout CMEs appear on synoptic maps as vertical streaks usually preceded by brightening and widening streamers. Such bugle shapes are left-facing on synoptic maps because time runs from right to left. The locations and widths of all CMEs on this rotation are marked by dashed boxes. Image adapted from Hundhausen (1993), courtesy J. Burkepile, NCAR/HAO.
View Image Figure 29:
Sequence showing the three-dimensional evolution of the coronal magnetic field via the kink instability model. The heavy blue/green lines represent the kinked flux rope, which erupts through the overlying strapping magnetic field (red). This field is pushed aside during this process. Image reproduced by permission from Fan (2005), copyright by AAS.
View Image Figure 30:
Schematic drawing of modeled flux rope on 15 May 1997, including estimate of its dimensions and orientation with respect to the ecliptic plane; the axis of the cloud lay nearly in the ecliptic plane and pointed toward the east. Also drawn is the Sun-Earth line at time of cloud passage by Wind near the L1 point. Image reproduced with permission from Webb et al. (2000b), copyright by AGU.
View Image Figure 31:
A composite all-sky image from SMEI taken in February 2003. An equal-area Hammer–Aitoff projection centered on the Sun with North and South ecliptic poles at top and bottom. The dark circle is a zone of exclusion 20° in radius usually centered on the Sun. The inset box shows a large, loop CME in May 2003 superimposed on the all-sky image. CMEs can only be detected in the SMEI data by careful subtraction of backgrounds that include particle contamination because of its Earth orbit (for details see, e.g., Webb et al., 2006).
Watch/download Movie Figure 32: (avi-Movie; 10682 KB)
Movie: Orbit difference images of an Earthward halo from SMEI. Halo was visible as an arc over ≥ 150° of sky (arrows). Blacked-out areas are due to shuttering of bright sunlight and CCD noise from particles in Coriolis’ 840 km circular Earth orbit.
View Image Figure 33:
The fields of view of the STEREO SECCHI HI telescopes flanking that of the SOHO/LASCO C3 instrument. The SECCHI EUVI, COR1, and COR2 telescopes are Sun-pointed like LASCO but the COR2 field extends to only half that of C3. Image adapted from Harrison et al. (2008).
Watch/download Movie Figure 34: (mpeg-Movie; 28364 KB)
Movie: Combined views from all of the STEREO SECCHI telescopes during a series of CMEs in early April 2010. The bottom panels show the ST-B and ST-A views of the EUVI disk, COR1 and COR2 imagers out to 15 R⊙, and the upper set shows the HI-1 and -2 fields viewing east (left, HI-A) and west (right, HI-B) of the Sun beyond the EUVI, COR1, COR2 set shown to scale. From the online data at: External Linkhttp://secchi.nrl.navy.mil/index.php?p=movies.
Watch/download Movie Figure 35: (avi-Movie; 70269 KB)
Movie: STEREO/HI2-A images following the latest data processing pipeline for SECCHI (DeForest et al., 2011).