ARLA/CLUSTER: Ciclo Solar 24 continua em queda, mínimo previsto para 2020 ou 2021.

[João Costa > CT1FBF]

Solar Cycle 24

SARL News carries an article in which *Jim Kennedy, KH6/K6MIO* reports that
the current Solar Cycle 24 is continuing its downward trend.

For several years now, the Sun's northern and southern hemispheres continue
to have separate minds about their relative rates of descent. The southern
hemisphere index is now rather close to zero, while the northern index,
though tracking downward, has started from a higher level.

In the meantime, during March 2017, there were no sunspots for 16 days in
either hemisphere. There was a total of 23 days with fewer than 30 daily
sunspots. All the indications are that we will be seeing even longer
periods of blank Sun over the next few years.

There continue to be expectations that the upcoming Cycle 25 will be
noticeably weaker than Cycle 24. It seems likely that, when it does clearly
begin to move upward from the probably long minimum, it will be slow in
rising.

It is interesting to compare Cycle 12 (1878 - 1890) with Cycle 24. Although
Cycle 12 was somewhat weaker than Cycle 24, it shows a lot of the same
general characteristics of Cycle 24 rise and fall profile.
It is reasonable to think that the official Cycle 24 minimum will occur
sometime in 2020 or 2021.

Many solar professionals are predicting Cycle 25 to have an overall maximum
in the 60s. That would be nearly half of Cycle 24 maximum.

Fonte: The South African Radio League <http://www.sarl.org.za/Default.asp>
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