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Solar Wind and Coronal Bright Points Inside Coronal Holes  

Nina Karachik   Submitted: 2011-06-21 08:44

Observations of 108 coronal holes (CHs) from 1998-2008 were used to investigate the correlation between fast solar wind (SW) and several parameters of CHs. Our main goal was to establish the association between coronal bright points (CBPs; as sites of magnetic reconnection) and fast SW. Using in situ measurements of the SW, we have connected streams of the fast SW at 1 AU with their source regions, CHs. We studied a correlation between the SW speed and selected parameters of CHs: total area of the CH, total intensity inside the CH, fraction of area of the CH associated with CBPs, and their integrated brightness inside each CH. In agreement with previous studies, we found that the SW speed most strongly correlates with the total area of the CHs. The correlation is stronger for the non (de)projected areas of CHs (which are measured in image plane) suggesting that the near-equatorial parts of CHs make a larger contribution to the SW measured at near Earth orbit. This correlation varies with solar activity. It peaks for periods of moderate activity, but decreases slightly for higher or lower levels of activity. A weaker correlation between the SW speed and other studied parameters was found, but it can be explained by correlating these parameters with the CH's area. We also studied the spatial distribution of CBPs inside 10 CHs. We found that the density of CBPs is higher in the inner part of CHs. As such, results suggest that although the reconnection processes occurring in CBPs may contribute to the fast SW, they do not serve as the main mechanism of wind acceleration.


Authors: Nina V. Karachik and Alexei A. Pevtsov
Projects: SoHO-EIT

Publication Status: Published in ApJ
Last Modified: 2011-06-21 13:47
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Solar Cycle 23 in Coronal Bright Points  

Nina Karachik   Submitted: 2011-04-21 11:48

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: Sattarov, Isroil; Pevtsov, Alexei A.; Karachik, Nina V.; Sherdanov, Chori T.; Tillaboev, A. M.
Projects: SoHO-EIT

Publication Status: Published in Solar Physics
Last Modified: 2011-04-22 06:33
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Rotation of Solar Corona from Tracking of Coronal Bright Points  

Nina Karachik   Submitted: 2011-04-21 11:44

An automated procedure for identification of coronal bright points is applied to selected EIT images observed at various phases of the solar cycle. The procedure finds about 400 bright points on a single EIT image observed at 195 Å. The positions of the bright points are tracked to study the profile of solar rotation in the solar corona. It is shown that the rotation of coronal bright points closely follows the latitudinal rotation profile of the underlying photospheric magnetic field. It is also demonstrated that coronal features situated at the same heliographic coordinates but different heights in the corona may exhibit different rotation rates.


Authors: Karachik Nina, Pevtsov Alexei A. and Sattarov Isroil
Projects: SoHO-EIT

Publication Status: Published in The Astrophysical Journal
Last Modified: 2011-04-22 06:33
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Formation of Coronal Holes on the Ashes of Active Regions  

Nina Karachik   Submitted: 2011-04-20 15:14

We investigate the formation of isolated non-polar coronal holes (CHs) on the remnants of decaying active regions (ARs) at the minimum/early ascending phase of sunspot activity. We follow the evolution of four bipolar ARs and measure several parameters of their magnetic fields including total flux, imbalance, and compactness. As regions decay, their leading and following polarities exhibit different dissipation rates: loose polarity tends to dissipate faster than compact polarity. As a consequence, we see a gradual increase in flux imbalance inside a dissipating bipolar region, and later a formation of a CH in place of more compact magnetic flux. Out of four cases studied in detail, two CHs had formed at the following polarity of the decaying bipolar AR, and two CHs had developed in place of the leading polarity field. All four CHs contain a significant fraction of magnetic field of their corresponding AR. Using potential field extrapolation, we show that the magnetic field lines of these CHs were closed on the polar CH at the North, which at the time of the events was in imbalance with the polar CH at the South. This topology suggests that the observed phenomenon may play an important role in transformation of toroidal magnetic field to poloidal field, which is a key step in transitioning from an old solar cycle to a new one. The timing of this observed transition may indicate the end of solar cycle 23 and the beginning of cycle 24.


Authors: Nina Karachik, Alexei A. Pevtsov, and Valentyna I. Abramenko
Projects: SoHO-EIT

Publication Status: Published in the Astrophysical Journal
Last Modified: 2011-04-21 01:35
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Abstracts by Author
Solar Wind and Coronal Bright Points Inside Coronal Holes
Solar Cycle 23 in Coronal Bright Points
Rotation of Solar Corona from Tracking of Coronal Bright Points
Formation of Coronal Holes on the Ashes of Active Regions

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