To analyze this solar cycle set, NRL researchers have studied the uniquely long-term and comprehensive CME observations obtained by the National Aeronautics and Space Administration (NASA) sponsored and NRL's SSD-developed and -operated Large Angle Spectrometric Coronagraph (LASCO) coronagraph aboard the NASA-European Space Agency (ESA) Solar and Heliospheric Observatory (SOHO) mission.
The continuous operation of the LASCO coronagraph since 1996 has resulted in the longest and most complete database of CME properties ever assembled. The CME properties such as size, speed, mass, and kinetic energy have been measured and catalogued for 13,587 CMEs (as of December 2009) from 130,000 calibrated LASCO images. This unique database was compiled by SSD researchers Drs. Angelos Vourlidas, Russell Howard, and outside collaborators. Their data analysis, soon to be reported in the Astrophysical Journal, provides a robust understanding of the dynamic properties of CMEs and their long-term trends, information important for understanding the geoeffective potential of CMEs and improving space weather forecasting capabilities.
Among the most important results of the study by the research team are:
- CMEs become fully developed only at solar distances of about 10-15 solar radii which will require a corresponding field of view (FOV) specification for future operational coronagraphs used for space weather forecasting.
- Not every solar plasma ejection qualifies as a CME. A large number of ejections disappear within the LASCO FOV (30 solar radii) possibly leading to misidentifications with in-situ observations at Earth.
- There is a surprising and abrupt drop in the average CME mass and CME ejection rate by a factor of 10 within 4 months in mid-2003.
- After mid-2003, CMEs exhibit a six-month periodic behavior while their average mass steadily decreases to about 4x less than the previous minimum. When compared with similar, but intermittent, observations in previous solar cycles, the average CME mass seems to exhibit a downward trend beginning in the mid-1970s.
Reader Comments
to our Newsletter