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Florian Mekhaldi

Paleo-perspective on solar variability

The extent to which the sun exerts an influence on climate is a widely debated matter, as are the mechanisms involved. We can obtain a unique long-term perspective on solar activity through the study of cosmogenic radionuclides, e.g. 10Be, 14C, 36Cl.These radionuclides are produced by the nuclear cascade triggered when cosmic-rays enter the atmosphere. The Earth is partially shielded from galactic cosmic-rays by the heliomagnetic and the geomagnetic fields, the strengths of which vary from decadal to millennial time scales. Therefore, radionuclides carry the signal of solar activity which is then stored in environmental archives such as ice cores, tree rings and sediments.


My project

Throughout my Ph.D., I will mainly focus on 10Be in laminated lacustrine sediments. Such highly-resolved records offer temporal advantages in comparison to ice cores (due to the thinning of ice) and to tree rings (due to the shorter half-life of 14C). The potential of sediment records, which has yet to be thoroughly employed, will help us to provide information on three different axes. 1) We will hopefully be able to reconstruct past short-term solar variability (e.g. the ‘11-yr’ cycle) at timescales not reached before. 2) Varved sediments will allow us to investigate sun-climate relationships with no uncertainties in the timing between the different solar and climate proxies. 3) Determining a common signal of 10Be in both ice cores and lake sediments will contribute to synchronizing these different archives and thereby complement information on leads and lags of past climate changes.

I am also very interested in studying the possible magnitudes and the occurrence frequency of paleo-superflares - still using radionuclides.

Under the main supervision of Prof. Raimund Muscheler (LU).


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E-mail: florian.mekhaldi [at]

Doctoral student

Quaternary Sciences

+46 46 222 78 81