Natural disaster
A solar flare is a phenomenon where the Sun suddenly releases a great amount of solar radiation, much more than normal. Solar flares are unlikely to cause any direct injury, but can destroy electrical equipment. The potential of solar storms to cause disaster was seen during the 1859 Carrington event, which disrupted the telegraph network, and the March 1989 geomagnetic storm which blacked out Quebec. Some major known solar flares include the X20 event on August 16, 1989, and a similar flare on April 2, 2001. The most powerful flare ever recorded occurred on November 4, 2003 (estimated at between X40 and X45).
Astrophysical X-ray source
Solar flares usually follow the solar cycle. CORONAS-F was launched on July 31, 2001 to coincide with the 23rd solar cycle maximum.
The solar flare of October 29, 2003 apparently showed a significant degree of linear polarization (> 70% in channels E2 = 40-60 keV and E3 = 60-100 keV, but only about 50% in E1 = 20-40 keV) in hard X-rays, but other observations have generally only set upper limits.
Coronal loops form the basic structure of the lower corona and transition region of the Sun. These highly structured and elegant loops are a direct consequence of the twisted solar magnetic flux within the solar body. The population of coronal loops can be directly linked with the solar cycle, it is for this reason coronal loops are often found with sunspots at their footpoints. Coronal loops populate both active and quiet regions of the solar surface. The Yohkoh Soft X-ray Telescope (SXT) observed X-rays in the 0.25-4.0 keV range, resolving solar features to 2.5 arc seconds with a temporal resolution of 0.5–2 seconds. SXT was sensitive to plasma in the 2-4 MK temperature range, making it an ideal observational platform to compare with data collected from TRACE coronal loops radiating in the EUV wavelengths.