EIT Observations of Coronal Mass Ejections

[EIT 304 A pair]

A CME with an eruptive prominence
well observed from the ground

[H-alpha linb patrol image] [H-alpha linb patrol image] [H-alpha linb patrol image]
HAO MLSO
H alpha
limb movie
(1.1 Mbyte)
SOHO EIT
Fe XII 195 Å
movie
0.25 Mbyte
SOHO EIT
Fe XII difference
movie
6.5 Mbyte

All movies are QuickTime with MPEG-4 compression. Requires a href = "http://www.apple.com/quicktime/download/">QuickTime 6.5 or higher for Mac OS X or Windows.


A CME without a flare

Click on thumbnail for full-resolution image

[GIF movie icon] On 1999 September 20, EIT observed a large-scale eruptive filament near central meridian. the filament exhibited significant, large-scale twist-up (not unravelling), or at least the transfer of helicity from small to filament-long scales.

Perhaps the most intriguing feature of this filament eruption is that it was evidently involved in a halo CME but apparently had no associated flare (unless, of course, you consider the post-CME loops to be a flare). This appears to be at least a single case of a CME without a flare.


Another CME without a flare

Click on thumbnail for full-resolution image

[GIF movie icon] On 1999 September 23, EIT observed a large-scale eruptive filament from the southwest quadrant of the disk, from the same region as our first example of a "flareless CME" (something Hugh Hudson refers to as an oxymoron).

This event may not be a perfect example, since it is preceded (by about 4 hours) by a backside CME from the southeast limb, and at roughly the same time as the backside CME, a "mini-CME" (tiny loop brightening, small puff dimming, and runtish arcade) in a prominent EUV bright point in the NW quadrant. One could argue that a "global coronal disturbance" unites all three events somwhow, and that that disturbance is initiated by a flare that is conveniently located on the backside of the Sun.

I find that inherently implausible, though, since the distance between the mini-CME and the eruptive filament site is only half a solar radius or so, and a wave propagating between the two would only be moving at around 24 km/s, an order of magnitude slower than we know CME-related waves travel in the corona seen in the EIT 195 Å channel.

There is no GOES event at the time of this eruptive, but there is a LASCO CME, moving quite rapidly, visible in the C2 images shortly after the eruption seen in EIT.

So one man's oxymoron may be another man's paradigm.


SOHO's first post-recovery halo CME!!

Shortly after EIT recorded its first image in over three months, EIT observed its first post-recovery earth-directed CME. The filament was situated on the Solar meridian north of disk center, and erupted at approximately 02:30 UT on 15 October 1998. During this period, EIT was obtaining full-resolution, full-frame images at an average cadence of 12 - 13 minutes.

The image below on the left is an EIT image taken at 23:59 UT on the 14th of October, showing the location of filament. The image on the right is a LASCO C3 image of the halo CME, taken at 14:37 UT on 15 October. The EIT image has been rotated by 53 degrees to correct for the SOHO's angle at the time, so Solar North corresponds to the top of the image. However, the LASCO image has not been rotated (it is tilted 53 degrees counterclockwise, so Solar North points to the upper left). The bright dot with the line through it spanning the top of the image is Venus (to fully understand why Venus looks that way in a C3 image, refer to Dr. SOHO's answer to this question.

Pre-event Filament is rising, fading Still fading
It finally erupts Arcades forming Strong, two-ribbon
flare visible

A Javascript Movie of this event shows the evolution really well. Movies and images of the LASCO coronagraph's observations of the halo CME are available at ftp://lasco-www.nrl.navy.mil/pub/lasco/halo/981015/.


The CME/Moreton wave of Thanksgiving Day, 1997 (1997/11/27)

[GIF movie icon] 1997 November 27, 13:11 - 14:19 UT (Note that all times are ~ 1 m earlier than marked.)

The following pages are available for the use of our collaborators in analyzing individual events. Nothing in these pages is citable without an approved EIT data analysis proposal.

A well-observed halo CME: 1997 October 23

SOHO-LASCO and -EIT, as well as
Yohkoh SXT, observed a halo CME originating near central meridian on 1997 October 23. Because LASCO and EIT had the benefit of the SUMER telemetry that week, EIT was obatining full-resolution, full-frame images at an average cadence of 12 - 13 minutes.

Pre-event Filament motion Filament gone
Dimming grows ...and grows Arcade still visible

Note that the filament visibility descriptions in the table refer to Fe XII 195 Å observations only.

[GIF movie icon] A GIF movie of closeups from the EIT full-field, full-resolution CME watch, covering 1997 October 23, 12:13 - 18:57 UT.

If you're interested in analyzing these data, please contact Joe Gurman or another member of the EIT consortium.


Moreton waves: The "ground track" of a CME

Note: See the official International Solar-Terrestrial Physics (ISTP) program Sun-Earth Connections event page for this event (lots more detail on prediction criteria, other measurements, &c.)

Here are a few EIT Moreton waves, examined in far less detail than are those treated in Barbara Thompson's pages on the event of 1997 April 7.

Moreton waves from AR 8088, 1997 September 23

In addition to an event late on 1997 September 23 that went off primarily southeastward and produced a clear CME in LASCO, there were two remarkable events on 1997 September 24:

Click on the thumbnail for a full-sized image.

ImageTime (UT)
02:51 UT
11:08 UT

I've jacked up the contrast in a rectangular area containing the active region and the Moreton wave front to make the latter easier to see.

We estimate the speed of the 02:51 UT event as at least 300 km s-1.

QuickTime movieMPEG movieDescription
[Movie icon] [Movie icon] Full-disk EIT Fe XII 195 Å movie, 1997 September 23 - 24
[Movie icon] [Movie icon] Closeup of NOAA AR 8088 and vicinity
Click on one of the movie icons to view the movie.

All movies are ~ 800 - 900 Kbyte in length.


Mini-CME's?

EIT has observed a number of small darkenings reminiscent of CME's but originating not in active regions but in bright points. Are these the same phenomenon on a smaller scale? You be the judge (before you have to be the referee).

Regular, economy size CME's


Web curator: Joseph B. Gurman
Responsible NASA official: Joseph B. Gurman, Facility Scientist, Solar Data Analysis Center
joseph.b.gurman@gsfc.nasa.gov
+1 301 286-4767

NASA Goddard Space Flight Center
Solar Physics Branch / Code 682
Greenbelt, MD 20771

Last revised 2004 February 24 - J.B. Gurman