Results 241 to 250 of about 917 (261)

Velocity Oscillations in Active Sunspot Groups

Solar Physics, 1998
Time series of two-dimensional spectra were taken with the Gottingen 2D spectrometer at the VTT on Tenerife in 1996. They were investigated for Doppler velocities and velocity oscillations in small spots and pores of rapidly evolving sunspot groups. For the present measurements the magnetically insensitive lines Fe i 557.6 nm and Fe i 709.0 nm were ...
Balthasar, Horst, Martinez, Pillet V., Schleicher, Helmut, Wöhl, Hubertus   +3 more
openaire   +1 more source

Sunspot Groups as Tracers of Sub-Surface Processes

International Astronomical Union Colloquium, 2000
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.
openaire   +1 more source

Common evolution of adjacent sunspot groups

Solar Physics, 1993
The evolution of two adjacent bipolar sunspot groups is studied using Debrecen full-disc, white-light photoheliograms and Hα filtergrams as well as Meudon magnetograms. The proper motions of the principal preceding spots of both groups show quite similar patterns; the spots move along almost parallel tracks and change the direction of their motion on ...
L. van Driel-Gesztelyi, G. Csepura, I. Nagy, O. Gerlei, B. Schmieder, J. Rayrole, P. Démoulin   +6 more
openaire   +1 more source

Automated Detection of Sunspots and Sunspot Groups in Full-Disk Solar Images

2010
In this paper, a new adopted unsupervised segmentation technique is presented. This technique extracts both sunspots and sunspot groups from the solar disk as whole group that eases the automated sunspot group classification. MacIntosh Classification is used as standard to determine which group belongs to which class.
Sarab F. Majed, Mehmmood A. Abd, V. Zharkova   +2 more
openaire   +1 more source

Historical sunspot records

Living Reviews in Solar Physics, 2020
J M Vaquero, Arlt Rainer
exaly  

Hemispheric asymmetry of long-term sunspot activity: sunspot relative numbers for 1939–2019

Monthly Notices of the Royal Astronomical Society, 2022
L H Deng
exaly  

A GREAT SUNSPOT GROUP

Bulletin of the American Meteorological Society, 1928
openaire   +1 more source

Periodicity of sunspot activity in the modern solar cycles

Science Bulletin, 2013
K J Li
exaly  

Revisiting the Sunspot Number

Space Science Reviews, 2014
F Clette, Leif Svalgaard, J M Vaquero
exaly  

A note on the relationship between sunspot numbers and active days

Advances in Space Research, 2014
J M Vaquero
exaly