A theoretical study of mirror-point altitude variability due to geomagnetic field variations

GUTIERREZ FALCON, ALVARO R.; ELIAS, ANA G.; AMIT, HAGAY; ZOSSI, BRUNO S.

Nagoya

Workshop; PWING-ERG Conference (Particles and Waves in the INner magnetosphere using Ground-based network observations); 2021

ISEE, Nagoya University

The Earth?s intrinsic magnetic field has been weakening at ∼5% per century from at least 1840 mostly determined by the decrease in the dipolar magnetic moment component. This may point out an undergoing reversal or excursion, or maybe the possibility of a recovery without any extreme event. In any case, the global field intensity will very probably continue to decrease in the near future with a consequent weakening of our planet?s magnetic shield capacity. In the current dipole like geomagnetic field, where the field intensity gets stronger with increasing magnetic latitude, there exist points in the northern and southern hemisphere, called magnetic mirror points, where charged particles traveling along a field line bounce between them. This motion is one of the three cyclic motions of trapped particles in the magnetosphere. The mirror points altitude depends directly on the magnetic moment, which means that a magnetic decrease may induce an altitude lowering eventually reaching the atmosphere. A theoretical estimate of magnetic mirror points lowering rate due to the current geomagnetic field decrease is estimated and compared to the shrinking of the upper atmosphere due to greenhouse gases increase during the last 120 years.