Coupling between Geomagnetic Field and Earth's Climate System

*Natalya Kilifarska, Volodymyr Bakhmutov and Galyna Melnyk*

### **Abstract**

The idea about synchronized variations of geomagnetic field and climate appears in the middle of the twentieth century. Among others, one of the main reasons for its unpopularity is the missing mechanism of coupling between magnetic and nonmagnetic media. This chapter offers such a mechanism, consisting of a chain of relations transmitting the geomagnetic spatial-temporal variations down to the planetary surface. The first element of this chain is energetic particles propagating in Earth's atmosphere, whose density and depth of penetration are modulated by geomagnetic field. Thus, the non-dipolar geomagnetic irregularities are projected on the ionization layer in the lower atmosphere (known as Regener-Pfotzer maximum). This unevenly distributed ionization, in certain conditions (i.e. dry atmosphere), acts as a secondary source of ozone near the tropopause. Ozone at this level is of special importance due to its influence on the tropopause temperature and humidity, and consequently on the planetary radiation balance. Hence, the geomagnetic spatial and temporal variations are imprinted down to the surface, impacting the climate system and its regional structures. The chapter provides synthesized information about geomagnetic field variability, particles' propagation in Earth's atmosphere, ion-molecular reactions initiating ozone formation in the lower stratosphere, as well as evidence for its covariance with some atmospheric variables.

**Keywords:** geomagnetic variations, geomagnetic focusing of charged particles, lower stratospheric ozone, regionality of climate changes

### **1. Introduction**

The co-variability of paleomagnetic and paleoclimate time series has been found in many sedimentary records, e.g. [1] and references therein. Most of the reversals of geomagnetic field polarity and magnetic poles' excursions seem to appear in periods of cold climate [1, 2]. Other authors, however, announced that climatic cooling fairly well corresponds to episodes with a stronger geomagnetic field [3–5]. This controversy, together with objective difficulties for disentangling paleomagnetic from paleoclimate data – due to the high variability and climate dependence of marine sedimentation rates – determines the skepticism of the greater part of the scientific community regarding possible links between geomagnetic filed and climate.

On the other hand, time series based on contemporary instrumental measurements do not contain the ambiguity of paleo-data records. Based on the magnetic and climate measurements collected from the beginning of 1900 up to 2010, this chapter provides not only more evidence for existing coupling between geomagnetic field and climate system, but also offers a physically rational explanation and results supporting its validity.
