Lower Solar Extreme Ultraviolet Irradiances During the Solar Cycle 23/24 Minimum
Abstract
The solar cycle 23/24 minimum in 2007-2010 is deeper and broader than recent cycle minima, and this minimum appears similar to the minima in the early 1900s. With the best-ever solar irradiance measurements from SOHO, SORCE, and TIMED, this minimum offers a unique opportunity to advance our understanding of secular (long-term) changes in the solar irradiance. A first task towards this goal is the comparison of the 2007-2009 irradiance results of this current minimum to the irradiance levels during the previous minimum in 1996. The solar extreme ultraviolet (EUV: 10-120 nm) irradiance is lower in 2008 than in 1996 by about 15%. There are uncertainties in these irradiance results because they depend strongly on understanding instrument degradation trends over 12 years. Nonetheless, the reduced solar EUV irradiance in 2008 are consistent with the reduced solar magnetic field and increase in low-latitude coronal holes during this current cycle minimum.
- Publication:
-
38th COSPAR Scientific Assembly
- Pub Date:
- 2010
- Bibcode:
- 2010cosp...38.1127W