Influence of coronal hole morphology on the solar wind speed at Earth

Abstract

It has long been known that the high-speed stream (HSS) peak velocity at Earth directly depends on the area of the coronal hole (CH) on the Sun. Different degrees of association between the two parameters have been shown by many authors. In this study, we revisit this association in greater detail for a sample of 45 nonpolar CHs during the minimum phase of solar cycle 24. The aim is to understand how CHs of different properties influence the HSS peak speeds observed at Earth and draw from this to improve solar wind modeling. The characteristics of the CHs of our sample were extracted based on the Collection of Analysis Tools for Coronal Holes (CATCH) which employs an intensity threshold technique applied to extreme-ultraviolet (EUV) filtergrams. We first examined all the correlations between the geometric characteristics of the CHs and the HSS peak speed and duration at Earth, for the entire sample. The CHs were then categorized in different groups based on morphological criteria, such as the aspect ratio, the orientation angle and the geometric complexity, a parameter which is often neglected when the formation of the fast solar wind at Earth is studied. Our results, confirmed also by the bootstrapping technique, show that all three aforementioned morphological criteria play a major role in determining the HSS peak speed at 1 AU. Therefore, they need to be taken into consideration for empirical models that aim to forecast the fast solar wind at Earth based on the observed CH solar sources.

arXiv commentAccepted by the Astronomy & Astrophysics journal

References in corpus (14)

• Origins of the Ambient Solar Wind: Implications for Space Weather
• Origins of the slow and the ubiquitous fast solar wind
• Verification of high-speed solar wind stream forecasts using operational solar wind models
• Statistical Analysis and Catalog of Non-polar Coronal Holes Covering the SDO-era using CATCH
• Are Solar Active Regions with Major Flares More Fractal, Multifractal, or Turbulent than Others?
• Turbulence in the Solar Atmosphere: Manifestations and Diagnostics via Solar Image Processing
• 3-Phase Evolution of a Coronal Hole, Part I: 360° remote sensing and in-situ observations
• Parameters of the Magnetic Flux inside Coronal Holes
• The Dependence of the Peak Velocity of High-Speed Solar Wind Streams as Measured in the Ecliptic by ACE and the STEREO satellites on the Area and Co-Latitude of their Solar Source Coronal Holes
• A statistical study of long-term evolution of coronal hole properties as observed by SDO
• How the area of solar coronal holes affects the properties of high-speed solar wind streams near Earth -- An analytical model
• Expansion of High Speed Solar Wind Streams from Coronal Holes through the Inner Heliosphere
• Statistical Approach on Differential EmissionMeasure of Coronal Holes using the CATCH Catalog
• On the Dependency between the Peak Velocity of High-speed Solar Wind Streams near Earth and the Area of Their Solar Source Coronal Holes

Cited by in corpus (2)

• On the short term stability and tilting motion of a well-observed low-latitude solar coronal hole
• Investigating the Relationship Between Physical Properties and Spatial Irregularities at Coronal Hole Boundaries