The Earth’s core magnetic field acts as a protective shield against solar wind and galactic cosmic rays, playing an important role in determining space weather conditions. Harmful effects of space weather in particular to modern technology increase the importance of understanding the effectiveness of the shielding, especially because the geomagnetic dipole field strength continues to decrease since the beginning of systematic measurements. Over geological times, geomagnetic excursions represent dramatic declines of the magnetic field intensity. During these events, Earth loses much of the geomagnetic shielding and suffers an increase in radiation exposure. However, little is known about space climate conditions during such extreme events. This study addresses the effects of long-term magnetic field variations and in particular geomagnetic excursions on the terrestrial magnetosphere and space climate conditions, using the first global reconstruction of the geomagnetic field over the past 100 ka (GGF100k model), and more detailed models of the Laschamp excursion that happened ~41 ka ago (LSMOD models) developed at GFZ.
The production rate of cosmogenic radionuclides, such as 10Be, in the atmosphere is influenced by the shielding from both the geomagnetic and the heliospheric magnetic field, the latter being determined by solar activity. Solar and geomagnetic modulations interact and play different roles depending on time scales. Regarding solar activity variations, very little is known beyond direct measurements of solar activity (past ~400 yrs) and reconstructions over the Holocene (past ~10 ka). We will seek to reconstruct the long-term solar variability using the 100 ka geomagnetic field model and a global dataset of 10Be cosmogenic isotope records. Integrated production rates of in situ produced radionuclides are essential in Earth’s surface exposure dating applications. The results obtained for the long-term variations in magnetospheric and heliospheric field shieldings will be used to study the implications for in situ radionuclide production rates and possible inferences for paleoclimate studies.
GFZ “Topic Innovation” Fond