Open AccessHow Do Coronal Hole Storms Affect the Upper Atmosphere?
Author(s) -
Mannucci A. J.,
Tsurutani B. T.,
Solomon S. C.,
Verkhoglyadova O. P.,
Thayer J. P.
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 - 10.1029/2012eo080002
Subject(s) - coronal mass ejection , solar cycle 22 , solar minimum , solar irradiance , physics , atmospheric sciences , solar cycle 23 , solar cycle , solar maximum , coronal hole , sunspot , extreme ultraviolet , geomagnetic storm , astronomy , solar wind , plasma , magnetic field , optics , laser , quantum mechanics
The solar cycle, often described as an increase and decrease of solar activity with a period of about 11 years, can strongly affect Earth's thermosphere and ionosphere. Although the longest direct record of solar activity is based on sunspot number, a more quantifiable parameter is solar irradiance at extreme ultraviolet (EUV) wavelengths, which varies by more than a factor of 3 over the sunspot cycle. To first order, upper atmospheric variation is a result of changes in ionizing fluxes at EUV wavelengths. As the solar cycle passes its EUV peak and approaches minimum, the number of solar active regions declines, leading to a reduction and then a near absence of coronal mass ejections (CMEs)—episodic events of high‐energy bursts of solar plasma that cause geomagnetic storms at Earth. During the solar cycle's declining phase, coronal holes begin to occupy lower latitudes on the solar surface and fall in line with the ecliptic plane.