Cosmic-Ray Intensity and Geomagnetism

A high resolution authigenic 10Be/9Be record of geomagnetic moment variations over the last 300 ka from sedimentary cores of the Portuguese margin

“…As shown in Figure 5, the averaged 10 Be/ 9 Be ratios plotted against averaged paleointensity values yields a simple exponential best-fit relationship, analogous to the Elsasser algorithm [2]:…”

“…Composed primarily of high energy protons and -particles, the cosmic-ray flux entering the magnetosphere is deflected by Lorentz forces. Cosmogenic production rate is thus proportional to the galactic cosmic ray flux and inversely proportional to the solar activity and the Earth's magnetic field intensity [1][2][3][4]. Measurements of cosmogenic radionuclides with different half-lives in lunar samples and in meteorites having different irradiation histories [5], and in marine sediments [6] and manganese crusts [7] yield to the conclusion that the average galactic cosmic ray flux was fairly constant on time-scales of millions of years.…”

The ~ 2400-year cycle in atmospheric radiocarbon concentration: bispectrum of <sup>14</sup><i>C</i> data over the last 8000 years

“…Variations in the atmospheric concentration of 14 C are the result of changes in the Earth's dipole moment (Elsasser et al, 1956;O'Brien, 1979;Lal, 1988), strengthening or weakening of solar activity (Stuiver and Quay, 1980;Bard et al, 1997) and parameters of radiocarbon exchange system (Oeschger et al, 1975;Siegenthaler et al, 1980;Stocker and Wright, 1996;Goslar et al, 1999). Variability of the 14 C Correspondence to: V. A. Dergachev (v.dergachev@pop.ioffe.rssi.ru) concentration is proved by experimental research, see (e.g.…”

“…Charvátová (2000) suggests to a possible relation of the ∼ 2400-year period be a similar one discovered in radiocarbon series. O'Brien (1979) and Elsasser et al (1956) discussed the principles of action of the geomagnetic field on the production rate of radiocarbon. As the number of 14 C nuclei formed in the Earth's atmosphere is proportional to µ(t) −0.52 , where µ(t) is the Earth's magnetic dipole moment, it is possibile to explain the change of amplitude of the ∼ 210-year cycle by geofield forcing, see Damon and Linick (1986).…”

Changes in cosmic ray cut-off rigidities due to secular variations of the geomagnetic field

“…Assuming the geomagnetic ®eld to be that due to a centred dipole, Elsasser et al (1956) and later Castagnoli and Lal (1980), have used the StoÈ rmer cuto rigidity to estimate the changes in the production rate of radiocarbon due to variation of the dipole moment. However, the e ect of variations in the non-dipole part of the geomagnetic ®eld on the incoming cosmic ray¯ux also needs to be studied in order to examine the possibility, raised by Creer (1988), of the persistent presence of a strong drifting quadrupole ®eld maintaining a small axially asymmetric input of 14 g against atmospheric mixing.…”