## Wednesday, December 17, 2008

### A giant breach in Earth's magnetic field

First, see:
NASA HTML, NASA video, Anthony Watts
They seem to be puzzled by a lot of things about the interactions between the Sun's and Earth's magnetic fields. Various changes differ from their expectations by an order of magnitude, and so on. At any rate, there seem to be a lot of effects that depend on the relative orientation of the magnetic fields.

One of five THEMIS probes that study these issues

We normally say that the solar activity has an 11-year periodicity but the even and odd cycles differ by the sign of the magnetic field and their effects on the Earth may differ due to the Earth's own magnetic field. So the underlying periodicity is 22 years. In fact, a 20+ year temperature (or related) signal has been observed in tree rings. It was puzzling because people thought that only the absolute value of the Sun's magnetic field should matter, and the latter had a 11-year periodicity.

However, already in 2007, we mentioned a paper about a possible role of interstellar dust as a climate driver: this dust was proposed to realize the 22-year cycles. Something of this sort is probably happening. It is not exactly clear which of the effects related to the magnetic fields and magnetic storms and auroras etc. are going to be crucial for the temperature.

At any rate, I find it likely that a proper understanding of the flow of charged particles - not only cosmic rays - and their interactions with the magnetic fields is going to be important for a proper understanding of climate variability. And be sure that the periodic effects with the 22-year period are not the only ones that will exist and matter.

In closely related news, the Earth's ionosphere dropped to a new, unexpected low.

Via Solar Cycle 24 and Watts Up With That