For centuries, Arctic sky watchers have occasionally reported strange sounds filling the air as Northern Lights danced overhead. Hisses, crackles, and even loud "claps" have been heard and recorded. Are they real? Evan Ludes of South Dakota is a believer. On Nov. 4th, he heard strange sounds after a Cannibal CME hit Earth's magnetic field, sparking a strong geomagnetic storm: "After pulling off the highway to observe the pulsing green aurora, I shut off my car engine and heard buzzing and chirping," says Ludes. "At first I thought the noise was being created by birds, which would have been very unusual for the middle of the night. Upon further investigation, the sound seemed to be emanating from nearby power lines or barbed wire fencing." Everyone's heard buzzing near power lines before, but in this case the sounds were modulated by events in the sky. "The noise seemed to be synced with quick pulses of auroral light," says Ludes. "It was bizarre." Aurora sounds are controversial. Despite innumerable reports over the years, researchers have struggled to explain the phenomenon and sometimes suggested that they might be imaginary. Recently, however, Prof. Emeritus Unto K. Laine of Finland's Aalto University has shown that at least some of the sounds are real. Using arrays of microphones in Finland, he has recorded instances of "geomagnetic thunder." The chirps Ludes recorded seem to be a different type of noise, but perhaps no less authentic. Advice to observers with visible aurora: The next time a geomagnetic storm erupts, don't just look. Try listening as well.
You mentioned 20m PSK, a reply said 17m and 15m were open. When the Maximum Usable Frequency (MUF) is above 20m, your signal will go farther with less Effective Radiated Power (ERP, combination of Antenna gain and TX watts). There is not much PSK on 17m or 15m (plenty of FT8, listen for it) but call CQ and look at RBNs like PSKreporter. Solar storms: space WX is just like regular weather, the forecasts have many variables, predictions are sometimes wrong.
