Coronal Hole Properties in Solar Cycle 24: Plasma Behavior in the Weakest Period of Solar Activity Over the Last Half Century

Coronal holes, regions of low temperature and density in the solar corona which coincide with open and mostly unipolar magnetic field lines, are the primary source of the fast component of the solar wind. I have conducted a systematic study of the properties of coronal holes from 2007 to February 2014. As part of my study, I have created a catalog of 691 coronal holes, the largest in existence for the current solar cycle, cycle 24. For 363 of these coronal holes, I have characterized the proton density, speed, and temperature of the associated solar wind streams measured at 1 AU. For 189 wind streams, I have also been able to collect the ratio of alpha particle to proton number density in the wind. A comparison of these properties has shown that there is an anti-correlation between wind density and speed (higher densities correspond to lower wind speeds), and correlations between wind temperature and alpha to proton number density ratios and speed (higher wind speeds correspond to higher temperatures and larger alpha to proton number density ratios). In addition, a study of the relationship between area and magnetic field strength for the coronal holes of these past seven years has revealed that smaller coronal hole areas correspond to larger magnetic field strengths. I have also found that coronal holes with higher magnetic field strengths produce lower wind speeds, while coronal holes with larger areas generate higher wind stream velocities.