gli scienziati in genere ancora non possono stimare esattamente, però negli anni dato l'indebolirsi del campo magnetico, studi sulle rocce, ecc.., le stime sono passate da millenni o secoli a pochi anni fino a dire che potrebbe avvenire in qualsiasi momento
esempio (su AG trovi molti articoli sopra ti ho linkato i tag)
The scientists believe the shallow core field may play a role in determining whether the main field polarity flips while weakened or whether it recovers its strength without reversing. “Mapping this field during transitional states may hold the key to understanding what happens in Earth's core when the field weakens to a point where it can actually reverse,” Hoffman says.
Current evidence suggests we are now approaching one of these transitional states because the main magnetic field is relatively weak and rapidly decreasing, he says. While the last polarity reversal occurred several hundred thousand years ago, the next might come within only a few thousand years.
“Right now, historic records show that the strength of the magnetic field is declining very rapidly. From a quick back-of-the-envelope prediction, in 1,500 years the field will be as weak as it's ever been and we could go into a state of polarity reversal,” says Singer. “One broad goal of our research is to provide some predictive capability for what could happen and what could be the signs of the next reversal.”
Hoffman and Singer's research has been supported largely by grants from the National Science Foundation.
sembra che il processo segua una curva esponenziale e non lineare