Coronal sources and in situ properties of the solar winds sampled by ACE during 1999-2008

Abstract

We identify the coronal sources of the solar winds sampled by the ACE spacecraft during 1999-2008, and examine the in situ solar wind properties as a function of wind sources. The standard two-step mapping technique is adopted to establish the photospheric footpoints of the magnetic flux tubes along which the ACE winds flow. The footpoints are then placed in the context of EIT 284~Å images and photospheric magnetograms, allowing us to categorize the sources into four groups: coronal holes (CHs), active regions (ARs), the quiet Sun (QS), and "Undefined". This practice also enables us to establish the response to solar activity of the fractions occupied by each kind of solar winds, and of their speeds and O${}^{7+}$/O${}^{6+}$ ratios measured in situ. We find that during the maximum phase, the majority of ACE winds originate from ARs. During the declining phase, CHs and ARs are equally important contributors to the ACE solar winds. The QS contribution increases with decreasing solar activity, and maximizes in the minimum phase when QS appear to be the primary supplier of the ACE winds. With decreasing activity, the winds from all sources tend to become cooler, as represented by the increasingly low O${}^{7+}$/O${}^{6+}$ ratios. On the other hand, during each activity phase, the AR winds tend to be the slowest and associated with the highest O${}^{7+}$/O${}^{6+}$ ratios, and the CH winds correspond to the other extreme, with the QS winds lying in between. Applying the same analysis method to the slow winds only, here defined as the winds with speeds lower than 500 km s${}^{-1}$, we find basically the same overall behavior, as far as the contributions of individual groups of sources are concerned. This statistical study indicates that QS regions are an important source of the solar wind during the minimum phase.

arXiv comment24 pages, 7 figures, accepted for publication in Solar Physics

References in corpus (9)

• Ionization balance for optically thin plasmas: rate coefficients for all atoms and ions of the elements H to Ni
• Full-Sun observations for identifying the source of the slow solar wind
• Automated Coronal Hole Detection using Local Intensity Thresholding Techniques
• Coronal hole boundaries evolution at small scales: II. XRT view Can small-scale outflows at CHBs be a source of the slow solar wind?
• Coronal hole boundaries at small scales: III. EIS and SUMER views
• Tracking Solar Active Region Outflow Plasma from its Source to the near-Earth Environment
• Characterization of the slow wind in the outer corona
• How Can Active Region Plasma Escape into the Solar Wind from below a Closed Helmet Streamer?
• Measurements of Outflow Velocities in On-Disk Plumes from EIS Hinode Observations

Cited by in corpus (15)

• Diagnosing solar wind origins using in-situ measurements in the inner heliosphere
• Upflows in the upper solar atmosphere
• Charge States and FIP Bias of the Solar Wind from Coronal Holes, Active Regions, and Quiet Sun
• Helium abundance and speed difference between helium ions and protons in the solar wind from coronal holes, active regions, and quiet Sun
• Active region contributions to the solar wind over multiple solar cycles
• Sources of The Slow Solar wind During the Solar Cycle 23/24 Minimum
• On the relation between transition region network jets and coronal plumes
• Visualizing and Interpreting Unsupervised Solar Wind Classifications
• Cross Helicity and the Helium Abundance as an in situ Metric of Solar Wind Acceleration
• On the transition from Slow to Fast Wind as Observed in Composition Observations
• The properties of small magnetic flux ropes inside the solar wind come from coronal holes, active regions, and quiet Sun
• Dynamics in the transition region beneath active region upflows viewed by IRIS
• The Evolution of Heavy Ion Abundances with Solar Activity
• Characterizing the Impact of Alfvén Wave Forcing in Interplanetary Space on the Distribution of near-Earth Solar Wind Speeds
• On the Regulation of the Solar Wind Helium Abundance by the Hydrogen Compressibility