The 2800-MHz solar radio minimum of February 1976

Abstract

The total daily 2800-MHz solar flux observed at Algonquin Radio
Observatory, Lake Traverse, Ontario, during the recent sunspot minimum
has been analyzed for simultaneously occurring values of the basic quiet
sun and of the slowly varying component (SVC). Values of 67.5 and 2.7
solar flux units (sfu), respectively, were found to have occurred in
February 1976. Previous radio minima were in July 1964, with values of
67.2 and 4.9 sfu, and January 1954, with values of 65.0 and 3.1 sfu. The
basic quiet-sun levels for 1976 and 1954 appeared intermittently several
months before the two-parameter minima, while in 1964 the basic quiet
sun appeared only once, for a duration of three days. The average values
of the fluctuating SVC for twelve months centered on the minima of 1954,
1964 and 1976 were 8.0, 6.8, and 15.4 sfu, respectively. The high value
in 1976 corresponds to the highest sunspot minimum in 250 years of
sunspot records, according to Waldmeier (1977).