From June 21st until Sept 22nd, the sun was blank more than 89% of the time.
During the entire season only 6 tiny sunspots briefly appeared and not a single significant solar flare was detected during this extreme quiet period. This is a sign that Solar Minimum is underway and probably near its deepest point.
For 2019 overall (January through September), the sun has been blank 72% of the time, comparable to annual averages during the century-class Solar Minimum of 2008 (73%) and 2009 (71%).
The current Solar Minimum appears to be century-class as well, meaning you have to go back to the beginnning of the 20th century to find lulls in solar activity this deep.
But, “Solar Minimum” is not boring
During this phase of the solar cycle, the sun’s magnetic field weakens, allowing cosmic rays to enter the solar system. This doses astronauts and possibly air travelers with extra radiation.
The sun also dims, especially at extreme ultraviolet wavelengths, causing the upper atmosphere to cool and collapse. Space junk accumulates in Earth orbit as a result.
Finally, streams of solar wind punch through the sun’s weakening magnetic field, lashing Earth with gaseous material that can cause geomagnetic storms.
Interestingly, the summer of 2019 also brought us a sign that Solar Minimum is coming to an end. One of the numbered sunspots that briefly appeared on July 7th had a reversed magnetic polarity:
According to Hale’s Law, sunspots switch polarities from one solar cycle to the next. This small summertime sunspot was +/- instead of the usual -/+, marking it as a member of the next solar cycle, Solar Cycle 25.
Solar cycles always mix together at their boundaries. We can expect to see more new-cycle sunspots in the months ahead as Solar Cycle 24 dies out and Solar Cycle 25 slowly comes to life.
Solar Cycle 25 is predicted to peak with solar maximum occurring between 2023 and 2026, and with a sunspot range of 95 to 130. This is well below the average number of sunspots, which typically ranges from 140 to 220 sunspots per solar cycle. Let see what is going to happen, then. Meanwhile, keep your eyes to the sky and enjoy space events!