Near-earth solar wind flows and related geomagnetic activity during more than four solar cycles (1963–2011)

¹ Code 661, NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771, USA
² CRESST and Department of Astronomy, University of Maryland, College Park, Maryland 20742, USA
³ School of Mathematics and Physics, University of Tasmania, Hobart, Tasmania, Australia

^* corresponding author: e-mail: ian.g.richardson@nasa.gov

Received: 27 February 2012
Accepted: 29 April 2012

Abstract

In past studies, we classified the near-Earth solar wind into three basic flow types based on inspection of solar wind plasma and magnetic field parameters in the OMNI database and additional data (e.g., geomagnetic indices, energetic particle, and cosmic ray observations). These flow types are: (1) High-speed streams associated with coronal holes at the Sun, (2) Slow, interstream solar wind, and (3) Transient flows originating with coronal mass ejections at the Sun, including interplanetary coronal mass ejections and the associated upstream shocks and post-shock regions. The solar wind classification in these previous studies commenced with observations in 1972. In the present study, as well as updating this classification to the end of 2011, we have extended the classification back to 1963, the beginning of near-Earth solar wind observations, thereby encompassing the complete solar cycles 20 to 23 and the ascending phase of cycle 24. We discuss the cycle-to-cycle variations in near-Earth solar wind structures and the related geomagnetic activity over more than four solar cycles, updating some of the results of our earlier studies.