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Solar Physics

, Volume 198, Issue 2, pp 347–365 | Cite as

Spatial Distribution and Temporal Evolution of Coronal Bright Points

  • Jie Zhang
  • Mukul R. Kundu
  • Stephen M. White
Article

Abstract

We present a statistical study of the spatial distribution and temporal evolution of coronal bright points (BPs) by analyzing a continuous set of observations of a quiet-Sun region of size 780′′ × 780′′ over a period of 55 hours. The main data set consists of observations taken by EIT (the Extreme-ultraviolet Imaging Telescope on board the SOHO spacecraft) in its Fe xii 195 Å channel which is sensitive to coronal plasma of temperature ∼ 1.5 MK; we also use soft X-ray observations by SXT (Soft X-ray Telescope on the Yohkoh spacecraft) which is sensitive to coronal plasma of temperature > 2.5 MK. The flux histogram for all pixels in EIT 195 Å images indicates that BPs have a power law flux distribution extending down to a level of 3σ (σ, root mean square deviation) above the average flux of the quiet Sun, while the bulk quiet Sun has a Gaussian-like flux distribution. Using a 3σ intensity threshold, we find a spatial density of one BP per 90 Mm × 90 Mm area, or equivalently 800 BPs for the entire solar surface at any moment. The average size of a BP is 110 Mm2. About 1.4% of the quiet-Sun area is covered by bright points and the radiation from all BPs is only about 5% of that from the whole quiet Sun. Thus, the atmosphere above quiet-Sun regions is not energetically dominated by BPs. During the 55-hour period of EIT observations, we identify 48 full-life-cycle BPs which can be tracked from their initial appearance to final disappearance. The average lifetime of these BPs is 20 hours, which is much longer than the previously reported 8 hours based on Skylab X-ray observations (Golub et al., 1974). We also see shorter life times and smaller numbers of BPs in the soft X-ray images than in the EIT 195 Å observations, suggesting that the temperature of BPs is generally below 2 MK.

Keywords

Flux Distribution Coronal Plasma Short Life Time SOHO Spacecraft Coronal Bright Point 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Kluwer Academic Publishers 2001

Authors and Affiliations

  • Jie Zhang
    • 1
  • Mukul R. Kundu
    • 1
  • Stephen M. White
    • 1
  1. 1.Center for Earth Observing and Space Research, Institute for Computational ScienceGeorge Mason UniversityFairfaxU.S.A

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