Research Highlights

doi:10.1038/nindia.2014.6 Published online 16 January 2014

Tracking variations in solar radiation

Researchers have gained new insights into the variations in solar radiation by comparing regions of high magnetic activity1 in the Sun's corona with regions of lower magnetic activity1 . The insights will have far-reaching implications as variations in the solar radiation are known to affect the Earth's climate.

The Sun is the energy source that generates motion in the Earth's atmosphere and hence controls the weather and climate on Earth. Any variation in the amount of solar energy at the Earth's surface will therefore change the climate. Though studies have correlated variations in solar activity and changes in climate, none has provided a clear description of how they are linked.

The researchers captured images of solar activity variations in regions of the Sun that have strong magnetic fields, as well as cooler, darker coronal regions of low-density plasma and regions with lower magnetic activity known as the quiet Sun. The images were taken by extreme-ultraviolet telescopes onboard PROBA-2 (a small satellite launched by the European Space Agency) and NASA's Solar Dynamics Observatory.

The researchers found that the active regions greatly affect fluctuations in solar irradiance. At extreme-ultraviolet wavelengths, the quiet Sun is the greatest contributor to the solar irradiance, contributing up to 63% of the total intensity. In contrast, active regions contribute about 10% of the intensity. Feature extraction allowed them to use extreme-ultraviolet telescopes to measure irradiance fluctuations and to quantify the contribution of each part to the spectral solar irradiance in the extreme-ultraviolet region, as observed using a calibrated radiometer.


  1. Kumara, S. T. et al. Segmentation of coronal features to understand the solar EUV and UV irradiance variability. Astron. Astrophys. 561, A9 (2014) doi: 10.1051/0004-6361/201322137  | Article | ADS |