Open AccessGeomagnetic data reveal unusual nature of recent solar minimum
Author(s) -
Schultz Colin
Publication year - 2012
Publication title -
eos, transactions american geophysical union
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.316
H-Index - 86
eISSN - 2324-9250
pISSN - 0096-3941
DOI - 10.1029/2012eo140024
Subject(s) - earth's magnetic field , physics , solar wind , interplanetary magnetic field , heliospheric current sheet , solar cycle 22 , coronal mass ejection , solar cycle 23 , coronal hole , solar minimum , solar rotation , solar cycle , geophysics , magnetic field , astronomy , solar physics , quantum mechanics
Since the mid‐1800s, scientists have been systematically measuring changes in the Earth's magnetic field and the occurrence of geomagnetic activity. Such long‐term investigation has uncovered a number of cyclical changes, including a signal associated with 27‐day solar rotation. This is most clearly seen during the declining phase and minimum of each 11‐year solar cycle, when the Sun's magnetic dipole is sometimes tilted with respect to the Sun's rotational axis. With the Sun's rotation and the emission of solar wind along field lines from either end of the solar magnetic dipole, an outward propagating spiral‐like pattern is formed in the solar wind and the interplanetary magnetic field that can drive 27‐day, and occasionally 13.5‐day, recurrent geomagnetic activity. Recurrent geomagnetic activity can also be driven by isolated and semipersistent coronal holes, which can emit concentrated streams of solar wind.