Earth's magnetic field protects us from the dangerous radiation of space, but it is not as permanent as we might believe. Scientists at the European Geosciences Union General Assembly present new information about an 'excursion' 41,000 years ago where our planet's magnetic field waned, and harmful space rays bombarded the planet. Earth's magnetic field cocoons our planet from the onslaught of cosmic radiation streaming through space while also shielding us from charged particles hurled outward by the sun. But the geomagnetic field is not stationary. Not only does magnetic north wobble, straying from true north (a geographically defined location), but occasionally, it flips. During these reversals, north becomes south, south becomes north, and in the process, the intensity of the magnetic field wanes. But there's also something called magnetic field excursions, brief periods in which the intensity of the magnetic field wanes and the dipole (or two magnetic poles) that we're familiar with can disappear, replaced with multiple magnetic poles. The Laschamps excursion that occurred around 41,000 years ago is among the best studied. It features a low magnetic field intensity that implies less protection for Earth's surface from harmful space rays. Periods of low magnetic field intensity could correlate to major upheavals in the biosphere. To see when cosmic rays were heavily bombarding Earth's surface, scientists can measure cosmogenic radionuclides in cores from both ice and marine sediment. These special isotopes are produced by the interaction between cosmic rays and Earth's atmosphere; they are born of cosmic rays, hence they are cosmogenic. Times of lower paleomagnetic field intensity - less shielding - should correlate to higher rates of cosmogenic radionuclide production in the atmosphere. Sanja Panovska, a researcher at GFZ Potsdam, Germany will present her findings about the relationship between paleomagnetic field intensity and... |