scholarly journals The response of the equatorial ionosphere to fast stream solar coronal holes during 2008 deep solar minimum over Indian region

2016 ◽  
Vol 121 (1) ◽  
pp. 841-853 ◽  
Author(s):  
S. Sripathi ◽  
Ram Singh ◽  
S. Banola ◽  
Dupinder Singh ◽  
S. Sathish
Keyword(s):  
Solar Minimum ◽  
Coronal Holes ◽  
Equatorial Ionosphere ◽  
Indian Region ◽  
Solar Coronal

scholarly journals Spectral analysis of auroral geomagnetic activity during various solar cycles between 1960 and 2014

2016 ◽  
Vol 34 (12) ◽  
pp. 1159-1164 ◽  
Author(s):  
Pieter Benjamin Kotzé
Keyword(s):  
Spectral Analysis ◽  
Geomagnetic Activity ◽  
Solar Minimum ◽  
High Speed ◽  
Solar Rotation ◽  
Pearson Correlation ◽  
Coronal Holes ◽  
Rotation Period ◽  
Period Change ◽  
Solar Cycles

Abstract. In this paper we use wavelets and Lomb–Scargle spectral analysis techniques to investigate the changing pattern of the different harmonics of the 27-day solar rotation period of the AE (auroral electrojet) index during various phases of different solar cycles between 1960 and 2014. Previous investigations have revealed that the solar minimum of cycles 23–24 exhibited strong 13.5- and 9.0-day recurrence in geomagnetic data in comparison to the usual dominant 27.0-day synodic solar rotation period. Daily mean AE indices are utilized to show how several harmonics of the 27-day recurrent period change during every solar cycle subject to a 95 % confidence rule by performing a wavelet analysis of each individual year's AE indices. Results show that particularly during the solar minimum of 23–24 during 2008 the 27-day period is no longer detectable above the 95 % confidence level. During this interval geomagnetic activity is now dominated by the second (13.5-day) and third (9.0-day) harmonics. A Pearson correlation analysis between AE and various spherical harmonic coefficients describing the solar magnetic field during each Carrington rotation period confirms that the solar dynamo has been dominated by an unusual combination of sectorial harmonic structure during 23–24, which can be responsible for the observed anomalously low solar activity. These findings clearly show that, during the unusual low-activity interval of 2008, auroral geomagnetic activity was predominantly driven by high-speed solar wind streams originating from multiple low-latitude coronal holes distributed at regular solar longitude intervals.

Models for Solar Coronal Holes.

1978 ◽  
Author(s):  
George L. Withbroe
Keyword(s):  
Coronal Holes ◽  
Solar Coronal

Heating solar coronal holes

1991 ◽  
Vol 372 ◽  
pp. 719 ◽  
Author(s):  
E. N. Parker
Keyword(s):  
Coronal Holes ◽  
Solar Coronal

scholarly journals THE FIRST STRAY LIGHT CORRECTED EXTREME-ULTRAVIOLET IMAGES OF SOLAR CORONAL HOLES

2012 ◽  
Vol 749 (1) ◽  
pp. L8 ◽  
Author(s):  
Paul Shearer ◽  
Richard A. Frazin ◽  
Alfred O. Hero III ◽  
Anna C. Gilbert
Keyword(s):  
Extreme Ultraviolet ◽  
Coronal Holes ◽  
Stray Light ◽  
Solar Coronal

Periodic processes and plasma motions in solar coronal holes

2007 ◽  
Vol 51 (9) ◽  
pp. 773-779 ◽  
Author(s):  
N. I. Kobanov ◽  
A. A. Sklyar
Keyword(s):  
Coronal Holes ◽  
Periodic Processes ◽  
Solar Coronal

A 600-day periodicity in solar coronal holes

Nature ◽  
1992 ◽  
Vol 360 (6402) ◽  
pp. 322-324 ◽  
Author(s):  
P. S. Mclntosh ◽  
R. J. Thompson ◽  
E. C. Willock
Keyword(s):  
Coronal Holes ◽  
Solar Coronal

scholarly journals Soft X-ray emission as diagnostics for Maunder minimum stars

2011 ◽  
Vol 7 (S286) ◽  
pp. 346-349
Author(s):  
Katja Poppenhaeger ◽  
Jürgen H. M. M. Schmitt
Keyword(s):  
Low Temperature ◽  
Main Sequence ◽  
Coronal Holes ◽  
Maunder Minimum ◽  
Coronal Plasma ◽  
X Ray ◽  
Chromospheric Activity ◽  
Chromospheric Emission ◽  
Solar Coronal

AbstractThe identification of stars in a Maunder minimum state purely from their chromospheric emission (for example in Ca II lines) has proven to be difficult. Photospheric contributions, metallicities and possible deviations from the main sequence stage may lead to very low values of the traditional chromospheric activity indicators, while no Maunder minimum state may be present. X-ray observations can be a key tool for identifying possible Maunder minimum stars: We have detected very soft X-ray emission from low-temperature coronal plasma, similar to emission from solar coronal holes, in several stars with very low chromospheric activity indicators. The coronal properties inferred from X-ray observations can therefore yield a crucial piece of information to verify Maunder minimum states in stars.

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