JonoThora: Psionics expansion (01a + 01b): content authored / LaTeX-restored per local submodule; lint-clean.

2026-05-11T20:54:03Z

Psionics expansion (01a + 01b): content authored / LaTeX-restored per local submodule; lint-clean.

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{{Audience_Sidebar
| difficulty = Introductory
| reading_time = 5 minutes
| prerequisites = [[Psionics_Primer]]; basic astronomy.
| if_too_advanced_see = [[Space_Weather]]
| if_you_want_the_math_see = [[Space_Weather]]
}}

== Summary ==

'''Solar cycles''' are the quasi-periodic variations in solar magnetic activity, most prominently the '''~ 11-year sunspot cycle''' first systematically recorded by Heinrich Schwabe in 1843. The cycle is now understood to be the half-period of the longer ~ 22-year '''Hale magnetic-polarity cycle'''. Cycles are numbered sequentially from the 1755 minimum (Cycle 1) through the current Cycle 25 (started December 2019).

The cycle drives [[Space_Weather|space-weather]] activity, modulates [[Geomagnetic_Field|geomagnetic-field]] variability, and through these channels influences the Earth's near-space EM environment.

== Cycle Structure ==

* '''Minimum''': low sunspot count; few flares / CMEs; quiet magnetosphere.
* '''Rising phase''': sunspot count increases; activity from low latitudes migrates equatorward over the cycle.
* '''Maximum''': peak sunspot count (typically 100-300); maximum flare / CME activity; frequent geomagnetic storms.
* '''Declining phase''': sunspot count falls; coronal-hole-driven recurring storms become dominant.

The mean cycle length is 11 years but individual cycles range from ~ 9 to ~ 14 years. Cycle '''amplitude''' (peak sunspot count) varies substantially: the Maunder Minimum (1645-1715) had essentially no sunspots; the late 20th century cycles were among the strongest in instrumental history.

== Hale Cycle ==

The ~ 22-year Hale cycle reflects '''magnetic-polarity reversal''' between successive 11-year cycles: the magnetic polarity of leading sunspots in each hemisphere reverses between cycles. Two successive 11-year cycles thus complete one Hale cycle.

== Effects on Earth ==

* '''Atmospheric heating''' (small): increased solar UV / EUV at maximum heats the upper atmosphere, slightly inflating the thermosphere.
* '''Cosmic-ray modulation''' (anti-correlated with cycle): strong solar wind during high-activity periods deflects galactic cosmic rays; ground-level cosmic-ray flux is highest at solar minimum.
* '''Climate effects''': contested. Total solar irradiance varies by only ~ 0.1% across the cycle, producing climate effects of similar order. Cosmic-ray modulation effects on cloud cover (Svensmark hypothesis) are debated.
* '''Space-weather frequency''': dramatically higher during cycle maximum.
* '''Ozone-layer variability''': solar UV modulation drives small (~ 1-3%) ozone variation tracking the cycle.

== Long-Term Variability ==

Beyond the 11/22-year cycles, longer-term modulations include:

* '''Gleissberg cycle''' (~ 87 years): amplitude modulation of successive 11-year cycles.
* '''Suess / de Vries cycle''' (~ 208 years).
* '''Hallstatt cycle''' (~ 2400 years).
* '''Grand minima''' (Maunder 1645-1715, Spörer ~ 1450-1550, Wolf ~ 1280-1350, Oort ~ 1010-1050): periods of suppressed activity lasting decades.

These long-term variations are derived from cosmogenic-isotope (¹⁴C, ¹⁰Be) records in tree rings and ice cores.

== Current Cycle Status ==

Cycle 25 (started December 2019) has been more active than predicted; peak now expected late 2024 - mid 2025. Cycle 24 (2008-2019) was the weakest cycle since Cycle 14 (early 20th century).

== Psionic Relevance ==

In the [[Psionics|psionic framework]], the solar cycle is the dominant '''long-timescale modulator''' of the Earth's near-space EM environment. Predicted ψ-field-mediated environmental-coupling effects should show solar-cycle modulation, providing one of the framework's longer-timescale empirical-test windows.

== See Also ==

* [[Space_Weather]]
* [[Geomagnetic_Field]]
* [[Geomagnetic_Indices_Kp_Dst]]
* [[Solar_Cycle_24]]
* [[Solar_Cycle_25]]

== External Links ==

* Wikipedia: Solar cycle
* SILSO (Sunspot Index and Long-term Solar Observations).
* NOAA Solar Cycle Progression.

== References ==

* Hathaway, D. H. (2015). "The solar cycle." ''Living Reviews in Solar Physics'' 12: 4.
* Usoskin, I. G. (2017). "A history of solar activity over millennia." ''Living Reviews in Solar Physics'' 14: 3.

[[Category:Psionics]]
[[Category:Environmental EM]]
[[Category:Solar Physics]]

Solar Cycles - Revision history

JonoThora: Psionics expansion (01a + 01b): content authored / LaTeX-restored per local submodule; lint-clean.