Tuesday, September 9, 2014

Space Weather Today

LONG DURATION FLARE AND EARTH-DIRECTED CME

     Earlier today, the magnetic canopy of sunspot AR2158 erupted, producing an explosion that lasted more than 6 hours. The flare peaked on Sept. 9th at 00:30 UT with a classification of M4 on the Richter Scale of Solar Flares. Long-duration flares tend to produce bright CMEs, and this one was no exception. Coronagraphs onboard the Solar and Heliospheric Observatory observed a CME racing out of the blast site at nearly 1,000 km/s (2.2 million mph). ... from Spaceweather.com




Consider the following:

AR2158

     There is a system for numbering active regions. An active region can contain one or more spots. The National Oceanic and Atmospheric Administration (NOAA) numbers active regions consecutively as they are observed on the Sun. According to David Speich at NOAA, an active region must be observed by two observatories before it is given a number (a region may be numbered before its presence is confirmed by another observatory if a flare is observed to occur in it, however). 
     The present numbering system started on January 5, 1972, and has been consecutive since then. An example of an active region "name" is "AR5128" (AR for Active Region) or "NOAA Region 5128". Since we only see active regions when they are on the side of the Sun facing the Earth, and the Sun rotates approximately once every 27 days (the equator rotates faster than the poles), the same active region may be seen more than once (if it lasts long enough). In this case the region will be given a new number. Hence, a long-lived active region may get several numbers.
     On June 14, 2002, active region number 10000 was reached. For practical, computational reasons, active region numbers continue to have only four digits. Therefore, the sequence of numbers is 9998, 9999, 0000, 0001, and so on. Active region number 10030, for example, is AR0030. This region will often simply be referred to as region number 30, with 10030 implied.

... as explained by NASA Heliophysics Division

No comments:

Post a Comment

Back to the Top