scholarly journals A Study of Variations in Correlation Between Rotation Residual and Meridional Velocity of Sunspot Groups

Solar Physics ◽  
2021 ◽  
Vol 296 (10) ◽  
Author(s):  
J. Javaraiah
Keyword(s):  
Meridional Velocity ◽  
Sunspot Groups

Sunspot Groups as Tracers of Sub-Surface Processes

2000 ◽  
Vol 179 ◽  
pp. 155-160
Author(s):  
M. H. Gokhale
Keyword(s):  
Magnetic Flux ◽  
Indian Institute ◽  
Surface Processes ◽  
The Sun ◽  
Global And Local ◽  
Sunspot Groups

AbstractData on sunspot groups have been quite useful for obtaining clues to several processes on global and local scales within the sun which lead to emergence of toroidal magnetic flux above the sun’s surface. I present here a report on such studies carried out at Indian Institute of Astrophysics during the last decade or so.

scholarly journals Wings of the butterfly: Sunspot groups for 1826–2015

2017 ◽  
Vol 599 ◽  
pp. A131 ◽  
Author(s):  
R. Leussu ◽  
I. G. Usoskin ◽  
V. Senthamizh Pavai ◽  
A. Diercke ◽  
R. Arlt ◽  
...  
Keyword(s):  
Sunspot Groups

scholarly journals Solar flare forecasting using sunspot-groups classification and photospheric magnetic parameters

2010 ◽  
Vol 6 (S273) ◽  
pp. 446-450 ◽  
Author(s):  
Yuan Yuan ◽  
Frank Y. Shih ◽  
Ju Jing ◽  
Haimin Wang
Keyword(s):  
Solar Flare ◽  
Neutral Line ◽  
Forecasting Accuracy ◽  
Magnetic Parameters ◽  
Forecasting Method ◽  
Total Gradient ◽  
Strong Gradient ◽  
Classification Information ◽  
Year 2000 ◽  
Sunspot Groups

AbstractIn this paper, we investigate whether incorporating sunspot-groups classification information would further improve the performance of our previous logistic regression based solar flare forecasting method, which uses only line-of-sight photospheric magnetic parameters. A dataset containing 4913 samples from the year 2000 to 2005 is constructed, in which 2721 samples from the year 2000, 2002 and 2004 are used as a training set, and the remaining 2192 samples from the year 2001, 2003 and 2005 are used as a testing set. Experimental results show that sunspot-groups classification combined with total gradient on the strong gradient polarity neutral line achieve the highest forecasting accuracy and thus it testifies sunspot-groups classification does help in solar flare forecasting.

scholarly journals Observational evidence in favor of scale-free evolution of sunspot groups

2018 ◽  
Vol 618 ◽  
pp. A183
Author(s):  
A. Shapoval ◽  
J.-L. Le Mouël ◽  
M. Shnirman ◽  
V. Courtillot
Keyword(s):  
Weibull Distribution ◽  
Power Law ◽  
Large Range ◽  
Scale Free ◽  
Self Organized ◽  
Self Organized Criticality ◽  
Spatio Temporal ◽  
Computational Procedures ◽  
Definition Of ◽  
Sunspot Groups

Context. The hypothesis stating that the distribution of sunspot groups versus their size (φ) follows a power law in the domain of small groups was recently highlighted but rejected in favor of a Weibull distribution. Aims. In this paper we reconsider this question, and are led to the opposite conclusion. Methods. We have suggested a new definition of group size, namely the spatio-temporal “volume” (V) obtained as the sum of the observed daily areas instead of a single area associated with each group. Results. With this new definition of “size”, the width of the power-law part of the distribution φ ∼ 1/Vβ increases from 1.5 to 2.5 orders of magnitude. The exponent β is close to 1. The width of the power-law part and its exponent are stable with respect to the different catalogs and computational procedures used to reduce errors in the data. The observed distribution is not fit adequately by a Weibull distribution. Conclusions. The existence of a wide 1/V part of the distribution φ suggests that self-organized criticality underlies the generation and evolution of sunspot groups and that the mechanism responsible for it is scale-free over a large range of sizes.

scholarly journals Deep Intraseasonal Variability in the Central Equatorial Atlantic

2018 ◽  
Vol 48 (12) ◽  
pp. 2851-2865 ◽  
Author(s):  
Franz Philip Tuchen ◽  
Peter Brandt ◽  
Martin Claus ◽  
Rebecca Hummels
Keyword(s):  
Intraseasonal Variability ◽  
Deep Ocean ◽  
Minor Role ◽  
Equatorial Atlantic ◽  
Near Surface ◽  
Velocity Fluctuations ◽  
Instability Waves ◽  
Vertical Mode ◽  
Tropical Instability Waves ◽  
Meridional Velocity

AbstractBesides the zonal flow that dominates the seasonal and long-term variability in the equatorial Atlantic, energetic intraseasonal meridional velocity fluctuations are observed in large parts of the water column. We use 15 years of partly full-depth velocity data from an equatorial mooring at 23°W to investigate intraseasonal variability and specifically the downward propagation of intraseasonal energy from the near-surface into the deep ocean. Between 20 and 50 m, intraseasonal variability at 23°W peaks at periods between 30 and 40 days. It is associated with westward-propagating tropical instability waves, which undergo an annual intensification in August. At deeper levels down to about 2000 m considerable intraseasonal energy is still observed. A frequency–vertical mode decomposition reveals that meridional velocity fluctuations are more energetic than the zonal ones for periods < 50 days. The energy peak at 30–40 days and at vertical modes 2–5 excludes equatorial Rossby waves and suggests Yanai waves to be associated with the observed intraseasonal energy. Yanai waves that are considered to be generated by tropical instability waves propagate their energy from the near-surface west of 23°W downward and eastward to eventually reach the mooring location. The distribution of intraseasonal energy at the mooring position depends largely on the dominant frequency and the time, depth, and longitude of excitation, while the dominant vertical mode of the Yanai waves plays only a minor role. Observations also show the presence of weaker intraseasonal variability at 23°W below 2000 m that cannot be associated with tropical instability waves.

scholarly journals Decoupling of ground level pressures observed in Italian volcanoes: are they driven by space weather geo-effectiveness?

2014 ◽  
Vol 57 (3) ◽  
Author(s):  
Paolo Madonia ◽  
Paolo Romano ◽  
Salvatore Inguaggiato
Keyword(s):  
Space Weather ◽  
Atmospheric Pressure ◽  
Pressure Field ◽  
Ground Level ◽  
Total Solar Irradiance ◽  
Weather Parameters ◽  
Sun Activity ◽  
Fft Analysis ◽  
Sunspot Groups

<p>Investigations on correlation drops between near-ground atmospheric pressures measured at sea level and at higher altitudes on Italian volcanoes have been carried out. We looked for perturbations of the atmospheric pressure field driven by volcanic activity, but not excluding possible external triggers for the observed anomalies. Decorrelations between atmospheric pressures measured at Stromboli Island in stations located at different altitudes (years 2002-10) have been analysed and compared with data from other volcanic (Vesuvius) and non volcanic (Mt. Soro) orographic structures. We investigated as their possible triggers volcanic, meteorological and space weather parameters, with particular attention to Total Solar Irradiance (TSI), Kp index and Forbush decreases. Pressure decorrelations seems to be driven by astronomic cycles, with maxima in summer and minima in winter. A further contribution was found, seemingly assignable to TSI anomalies, with correlation minima occurring 12 hours after these but only during phases of high Sun activity. Moreover, during the same phases a main periodicity of about 27 days in pressure decorrelations was revealed by FFT analysis. This period is the same of the Sun Carrington rotation, expressing the periodic reappearance of sunspot groups on Sun’s surface. The strong similarity between recurrences of sunspot number and atmospheric pressure anomalies further supports the role of the former as a possible trigger for the latter.</p>

scholarly journals Increasing Lifetime of Recurrent Sunspot Groups Within the Greenwich Photoheliographic Results

Solar Physics ◽  
2009 ◽  
Vol 262 (2) ◽  
pp. 299-313 ◽  
Author(s):  
R. Henwood ◽  
S. C. Chapman ◽  
D. M. Willis
Keyword(s):  
Sunspot Groups
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