Solar cycle 25 should be a repeat of our last eleven year cycle. For the next five years, though, high frequency radio propagation will definitely improve.
Well, it’s official. Solar cycle 25 is underway. Scientists have been modeling the Sun for years, but there are still many mysteries to solar processes and sunspots. One thing we hams and shortwave listeners do know for sure: more sunspots, more joy.
You may know that sunspots are regions of the Sun’s surface with reduced temperature caused by concentrations of the star’s magnetic field. Our Sun’s magnetic field varies over an eleven year cycle, as do the number of sunspots. We find that more sunspots appear at the peak of the cycle, and the their magnetic fields cook the ionosphere to strengthen shortwave radio propagation of signals. Our next peak will be in 2025, so dust off your shortwave gear.
Scientists have been studying sunspots for four hundred years. Ham radio operators began to understand the effect of sunspots on shortwave during the 1930’s. During my lifetime, cycle 19 which peaked in 1958 was great, and in the 1960’s led to the CB radio “skip craze”. Remember that?
More recently, the start of solar cycle 25 has led to concerns about “extreme space weather” in the popular press. Increased geomagnetic activity can cause communications blackouts, power outages and GPS malfunctions. In 1989, a geomagnetic storm (coronal mass ejection) caused Quebec's infamous hydro-electric distribution failure.
But, all in all, hams love sunspots.
Solar Cycle 25 Geomagnetic Storms
But, even with low sunspots like we have now, geomagnetic activity can cause radio blackouts. Shown above left is the moderate geomagnetic storm we experienced recently in late September. My ability to listen to shortwave stations above 7 MHz pretty much disappeared for the whole week.
You can easily spot increased geomagnetic activity by considering for increased auroral oval size in the north sky. Increased auroral activity leads to increased absorption of radio signals over polar paths in particular. Both sunspot activity and other solar phenomena can help or hurt on the shortwave bands.