Science

I browsed through my copy of QST magazine yesterday. QST is the publication of the American Radio Relay League, an amateur radio (ham radio) organization. In it, I read an interesting scientific hypothesis explaining the dearth of sunspots we have seen over the past several years. The theory holds that plasma currents deep inside the sun may have interfered with the formation of sunspots and prolonged the solar minimum.

Later in the article, there is mention of a secondary consequence of the minimum in that “space junk” can remain in low Earth orbit due to the upper atmosphere collapsing. You can read this very interesting article at this link.

NASA-sponsored research has resulted in the first computer model that explains the recent period of decreased solar activity during the sun’s 11-year cycle.

This recent solar minimum, a period characterized by a lower frequency of sunspots and solar storms, was the deepest observed in almost 100 years. The solar minimum has repercussions on the safety of space travel and the amount of orbital debris our planet accumulates.

. . .

During this deep solar minimum, the sun’s magnetic field weakened, allowing cosmic rays to penetrate the solar system in record numbers, making space a more dangerous place to travel. At the same time, the decrease in ultraviolet radiation caused Earth’s upper atmosphere to cool and collapse.

As a consequence space debris stopped decaying and started accumulating in Earth orbit due to decreased atmospheric drag. These effects demonstrate the importance of understanding the entire solar cycle, during both minimum and maximum.

Emphasis added.

This is an interesting article on the SOHO website. The speeding of the internal plasma circulation is connected with the deepest solar minimum in a century.

One of the outstanding questions facing solar physicists is the origin of the solar magnetic cycle: What drives the 11-year sunspot cycle? We have just passed an extended and deep minimum, unlike any in the past 100 years. The late onset of the new solar cycle (#24) and the unusually deep minimum between cycles 23 and 24 took all experts by surprise, which suggests that there is a fundamental lack in our understanding of the origin of the solar activity cycle.

Image: Artist’s concept of the Sun’s meridional circulation, a large scale flow that transports solar plasma from the equator to the poles and back like a giant conveyor belt. Credit: Science@NASA

The Sun’s meridional circulation is a massive flow pattern within the Sun that transports hot plasma near the surface from the solar equator to the poles and back to the equator in the deeper layers of the convection zone, similar to a “conveyor belt”. The flow is rather slow, with typical speeds of 10-15 m/s (20 to 30 mph). The structure and strength of this meridional flow is believed to play a key role in determining the strength of the Sun’s polar magnetic field, which in turn determines the strength of the sunspot cycles. One class of dynamo models predicts that a stronger meridional flow produces weaker polar fields, whereas another class of models predicts stronger polar fields (and a shorter sunspot cycle) for the same flow. [more]