Heliospheric Weather Expert Service Centre - Statistical Products

CME Statistics

Distribution with HEEQ Longitude

When making use of CME event lists it is important to understand the caveats associated with the collection of the data. The figure below shows the distribution of events as a function of HEEQ longitude (solid line) together with statistical uncertainty (dotted lines) based on the H-ESC forecast centre (provide by the Met Office) identification and characterisation of CMEs. These events are based on SOHO/LASCO coronagraph observations made from the L1 location.


For a statistically significant sample, without selection effects, a uniform distribution would be expected. From the figure it is clear that there is a strong observational bias. This is anticipated since the identification of CMEs, particularly weak ones, is easier from limb observations than observer directed (or anti-directed), halo type, events. The observational bias is expected to reduce for larger, more space weather relevant, events but the current H-ESC CME event list does not yet contain sufficient such events to demonstrate this.

Distribution of CME speed

The CME speed is estimated from analysis of SOHO/LASCO coronagraph images. The histogram below shows the distribution of H-ESC identified CMEs as a function of their speed. The Mean and Median speeds are also displayed.

Distribution of CME width

The CME width is estimated from analysis of SOHO/LASCO coronagraph images. The histogram below shows the distribution of H-ESC identified CMEs as a function of their width. The Mean and Median speeds are also displayed.

Comparison of CME width to speed

This comparison shows the determined width of the CME as a function of the calculated speed. Generally we expect that faster CMEs will be broader in their extent.

SWE Portal > H-ESC > HPARC > HPARC/ST > CME

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