20 July 2024 - Mission Day: 10459 - DOY: 202

CME and Particle Storm

Caption: On 14 July 2000, a full halo coronal mass ejection (CME) was recorded by SOHO's LASCO/C2 coronagraph. Halo events are CMEs aimed toward (or away from) the Earth. As they loom larger and larger they appear to envelop the Sun, forming a halo around our star.

Just prior to this, an X-class solar flare had been recorded near the center of the solar disk by the spacecraft's Extreme-ultraviolet Imaging Telescope (EIT), observing the Sun in Fe XII at 195 Angstroms. In other words, the halo event was heading for Earth.

We have collected some of the images and movies from this spectacular event, including "observations" of the torrent of energetic particles that arrived about half an hour later. Such particle storms cause snow on the images as the cameras' electronic detectors are bombarded with high-energy particles.

More observations:

See also


The MeV electron and proton fluxes as measured by the COSTEP instrument onboard SOHO. The first high energy electrons were detected at 10:38 UT. The long lasting intensity-time profiles are characteristic for fast interplanetary shocks associated with halo CMEs propagating towards Earth. Time resolution of the measurements shown is one minute. Note the particle intensity decreases on July 15/16 when the CME passed over SOHO:

Click on the image to enlarge or try the 234K, PDF version


The flux of solar protons measured in SOHO/ERNE following the solar eruption on July 14, 2000. The histograms represent the proton fluxes in four energy channels (3.3-6.4, 6.4-13, 13-26 and 26-51 MeV). The first protons in the highest energy channel were detected at 10:55 UT. The maximum event fluxes are more than 1,000,0000 fold compared to the constant background flux from the Milky Way:

Click on the image to enlarge or try the 85K, PDF version


The solar wind proton speed registered by the CELIAS/PM sensor on SOHO during the time of passage of the shock wave driven by the CME. The speed after the shock is about twice the typical solar wind speed. Relatively large uncertainties are caused by the exceptionally high background produced by energetic flare particles:

Click on the image to download a 15K, PDF version of the plot.


The image below is a good example of how severely detectors can be influenced by high-energy particles from such events. The CDS (Coronal and Diagnostic Spectrometer) instrument on board SOHO was observing a totally different part of the sun than the flaring region. However, the observations taken during the particle shower were almost useless, and the sequence was in fact aborted as a precaution to avoid any damage to the instrument.

A movie showing the observation sequence has been prepared by Bill Thompson, and can be viewed here (MPEG), as well as a "cleaned up" version (MPEG) (using automated detection and removal of particle hits).



( 99K)
Higher resolution



Higher resolution

• European Site • US Site


Feedback & Comments: SOHO Webmaster

Last modification: July 27, 2020

SOHO is a project of international cooperation between