A picture of a completely spotless sun captured this year. Spaceweather

Due to a drop in number of sunspots and the resulting decrease in total solar radiance (TSI) values, NASA launched a new sensor to study the dimming sun. Data from NASA’s Spaceweather website showed after a solar maximum 2012, which lasted till 2014, we have entered a solar minimum period in the solar cycle, which has caused the sun’s electromagnetic output to drop by 0.1 percent.

SpaceX launched a new sensor to the International Space Station named NASA's Total and Spectral Solar Irradiance Sensor (TSIS-1) on Dec. 15. It will add to the plethora of instruments dangling from the space station and help measure the TSI. It will also replace the aging SORCE spacecraft to aid in the study of the sun.

All past data showed we are heading towards the 11-year minimum in the sun’s cycle. In 2017, 96 days (27 percent) were without sunspots.

The TSI values last plunged to its low point in 2009. In fact, it marked the year with the lowest recorded electromagnetic activity from the sun, where 260 (71 percent) days of the 365 were spotless, since scientists started gathering data in 1978.

The Earth will reach peak spotlessness in 2018-2020. One thing that came to the attention of scientists since they started gathering TSI data is that the lowest point of every latest 11-year cycle, is lower than the lowest point of the previous cycle. The low in 2009 was the lowest since 1978 and if the 2020 readings are lower than the 2009 values, scientists from NASA can conclude our sun is dimming over time.

Across the entire electromagnetic spectrum, the sun’s output dropped nearly 0.1% compared to the solar maximum of 2012-2014.

Graph displaying TSI data. NASA's Spaceweather DATA

This graph released on NASA’s data website shows the TSI data since 1978. In the first graph, the daily average TSI is plotted in red. The red vertical bar on the left shows the total 0.3 percent fluctuation we have witnessed till now in the TSI. The black line indicates the average 0.09 percent of TSI over time and the yellow line at the bottom of the first graph shows the all-time low in 2009. The bottom plot records the annual sunspot numbers over time from the SIDC in Belgium .

The rise and fall of the sun’s luminosity is a natural part of the solar cycle. A change of 0.1 percent may not sound like much, but the sun deposits a lot of energy on the Earth, approximately 1,361 watts per square meter. Summed over the globe, a 0.1 percent variation in this quantity exceeds all of our planet’s other energy sources put together.

A 2013 NASA reports explained how this small change could affect the chemistry of Earth’s upper atmosphere and possibly alter regional weather patterns, especially in the Pacific.

It is already visible that as the magnetic activity of the sun decreases, influx of Galactic Cosmic Rays (GCR’s) increase. This has been observed by Helium balloon measurements over California.

The reason for this is that solar storm clouds, such as coronal mass ejections (CMEs), generally sweep aside incoming cosmic rays. During solar minimum, CMEs are very low and the effect of cosmic rays on Earth increases manifold.