Solar Cycle 24

Taking a totally non-scientific “chartist” view of the latest Hathaway prediction for Cycle 24 shows that the cycle is very compressed both horizontally and vertically. This compressions provides a far clearer view of the underlying “signal” with very little noise.

Image credit: Nasa

The “chartist” view is that Solar Maximum occurred at the end of 2011 and that Solar Minimum will occur at the end of 2014 or early 2015.

The longer term “chartist” view indicates declining solar activity until 2030.

The “chartist” fit between cycles 23 and 24 is surprisingly good.

The fit implies:

a) Sunspots are not a perfect proxy because the count doesn’t go negative.

b) The underlying solar “engine” is very mechanical:
b1) More “fuel” and the “engine” runs fast, long and noisy.
b2) Less “fuel” and the “engine” runs slow, short and smoothly.

c) The cyclical nature of the solar “engine” implies a cyclical “fuel” supply.

Planetary and galactic alignment [above and below the ecliptic] regulates the “fuel” supply via the Parker Spiral [heliospheric current sheet].

Parker Spiral
The Parker spiral is the shape of the Sun’s magnetic field as it extends through the solar system. Unlike the familiar shape of the field from a bar magnet, the Sun’s extended field is twisted into an arithmetic spiral by the magnetohydrodynamic influence of the solar wind. The shape is named after Eugene Parker, who predicted the solar wind and many of its associated phenomena in the 1950s.

The influence of the Sun’s spiral-shaped magnetic field on the interplanetary medium (solar wind) creates the largest structure in the Solar System, the heliospheric current sheet.

The Parker spiral shape of the solar wind changes the shape of the Sun’s magnetic field in the outer solar system: beyond about 10-20 astronomical units from the Sun, the magnetic field is nearly toroidal (pointed around the equator of the Sun) rather than poloidal (pointed from the North to the South pole, as in a bar magnet) or radial (pointed outward or inward, as might be expected from the flow of the solar wind if the Sun were not rotating). The spiral shape also greatly amplifies the strength of the solar magnetic field in the outer solar system.

The spiral shape is similar to the pattern produced by a spinning lawn sprinkler, for similar reasons: the solar wind travels outward from the Sun at a uniform rate, but an individual jet of solar wind from a particular feature on the Sun’s surface rotates with the solar rotation, making a spiral pattern in space. Unlike the jet from a sprinkler, the solar wind is tied to the magnetic field by MHD effects, so that magnetic field lines are tied to the material in the jet and take on an arithmetic spiral shape.

The Parker spiral may be responsible for the differential solar rotation, in which the Sun’s poles rotate more slowly (about a 35-day rotation period) than the equator (about a 27-day rotation period). The solar wind is guided by the Sun’s magnetic field and hence largely emanates from the polar regions of the Sun; the induced spiral shape of the field causes a drag torque on the poles due to the magnetic tension force.

During solar maximum the entire magnetic field of the sun flips, thus alternating the polarity of the field every solar cycle.

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