. QST . ^ Fig. 3 — Example of a shortauroral opening beginning about5:50 Esterline-Augus recordof the signal from CedarRapids shows need for bands in early eveninghours. Blank spots on hour andhalf hour are 2-minute periodswhen transmitter is turned offautomatically. 12 QST for DIURNAL VARIATION OF CEDARRAPIOS SIGNALS PROPAGATEDBY AURORASEPT 1952 TO MAY 1954 ^ Fig. 4 — Good times for auroralpropagation are 6:00 and2:00 gation at any time of day appears in Fig. cases of auroral signals have been ob-served at almost every hour, but the phenomeno
. QST . ^ Fig. 3 — Example of a shortauroral opening beginning about5:50 Esterline-Augus recordof the signal from CedarRapids shows need for bands in early eveninghours. Blank spots on hour andhalf hour are 2-minute periodswhen transmitter is turned offautomatically. 12 QST for DIURNAL VARIATION OF CEDARRAPIOS SIGNALS PROPAGATEDBY AURORASEPT 1952 TO MAY 1954 ^ Fig. 4 — Good times for auroralpropagation are 6:00 and2:00 gation at any time of day appears in Fig. cases of auroral signals have been ob-served at almost every hour, but the phenomenonis chiefly a nighttime one. This curve emphasizesthe importance of observation just before supper-time. An interesting dip near midnight showsup, for which no explanation is here offered. Itshows that openings frequently continue intothe early morning hours, although they may dieout temporarily around midnight. There arealso cases of auroral openings after midnight notaccompanied by auroral signals earUer. _ The seasonal variation was plotted in Fig. 5by determining for each month the percentageof time that auroral propagation was of auroral propagation can be seen tooccur in March and October, vnth importantminima in December and June. A decrease canbe seen from 1952 to 195-t that is believed to beauthentic. This is attributed to the decrease inthe sunspot activity over the past few years,expected to reach a minimum some time in1954.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectradio, bookyear1915
