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Maybe a Solar Minimum Can Be Too Deep for 160 Meters

11/02/2016

Propagation observer Carl Luetzelschwab, K9LA, recently offered some “deep thoughts” on the Top Band Reflector. As he explained, while less geomagnetic field activity heading into winter bodes favorable 160-meter propagation, more galactic cosmic rays entering our atmosphere could become a factor.

“The Sun’s magnetic field is weakening, probably to the lowest levels in our lifetimes,” Luetzelschwab said ini an October 27 post. “With a weak solar magnetic field, more galactic cosmic rays will be able to get into Earth’s atmosphere. We are now seeing unprecedented high neutron counts (neutrons are one of the byproducts of cosmic rays). Since galactic cosmic rays are mostly very energetic protons, they can get down to low atmospheric altitudes, causing collisional ionization in the D region and lower E region.”

He said a cursory estimate using cosmic ray ionization rates confirms greater ionization in the lower atmosphere, and 160 meters is not too tolerant of more absorption.

“Many of us think that ‘solar min is solar min is solar min,’” Luetzelschwab said, “but maybe a solar minimum can be too deep for 160 meters.” He said a good question to ask in the early 2020s may be “How was 160 meters?” Only time will tell, he suggested. — Thanks to the ARRL Contest Update



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