58 citations · 194 across the 12 of their papers we have counts for
13 papers
Quantifying the effect of passband on observations in the Ca II K line
Ajay Kumar Yadav, Theodosios Chatzistergos, Natalie Krivova +33
Full-disk observations of the Sun in the Ca II K line have been carried out since the late 19th century at various observatories worldwide. These long-term records of solar activit…
Observations of the formation of a proto-spot in a pre-existing field environment
Mariarita Murabito, Ilaria Ermolli, Salvo L. Guglielmino +2
Bipolar emerging flux regions (EFRs) form active regions (ARs) that generally evolve in a pre-existing magnetic environment in the solar atmosphere. Reconfiguration of the small- a…
Estimation of Polar Magnetic Fields using Ca II K Polar Network as a Proxy
Dibya Kirti Mishra, Bibhuti Kumar Jha, Theodosios Chatzistergos +3
The polar magnetic field plays a crucial role in the solar dynamo model and contributes to predicting future solar cycles. However, continuous and direct measurements of this polar…
Ca II K Polar Network Index of the Sun: A Proxy for Historical Polar Magnetic Field
Dibya Kirti Mishra, Bibhuti Kumar Jha, Theodosios Chatzistergos +4
The Sun's polar magnetic field is pivotal in understanding solar dynamo processes and forecasting future solar cycles. However, direct measurements of the polar field is only avail…
The Extreme Space Weather Event of 1872 February: Sunspots, Magnetic Disturbance, and Auroral Displays
Hisashi Hayakawa, Edward W. Cliver, Frédéric Clette +19
We review observations of solar activity, geomagnetic variation, and auroral visibility for the extreme geomagnetic storm on 1872 February 4. The extreme storm (referred to here as…
Butterfly Diagram and Other Properties of Plage Areas from Kodaikanal Ca II K Photographs Covering 1904-2007
Bibhuti Kumar Jha, Theodosios Chatzistergos, Dipankar Banerjee +4
Ca II K observations of the Sun have a great potential for probing the Sun's magnetism and activity, as well as for reconstructing solar irradiance. The Kodaikanal Solar Observator…
Differential Rotation of the Solar Chromosphere: A Century-long Perspective from Kodaikanal Solar Observatory Ca II K Data
Dibya Kirti Mishra, Srinjana Routh, Bibhuti Kumar Jha +5
Chromospheric differential rotation is a key component in comprehending the atmospheric coupling between the chromosphere and the photosphere at different phases of the solar cycle…
Analysis of full disc Ca II K spectroheliograms III. Plage area composite series covering 1892-2019
Theodosios Chatzistergos, Ilaria Ermolli, Natalie A. Krivova +16
We derive the plage area evolution over the last 12 solar cycles employing data from all Ca II K archives available publicly in digital form known to us, including several as yet u…
Magnetohydrodynamic Non-linearities in Sunspot Atmospheres: Chromospheric Detections of Intermediate Shocks
S. J. Houston, D. B. Jess, R. Keppens +8
The formation of shocks within the solar atmosphere remains one of the few observable signatures of energy dissipation arising from the plethora of magnetohydrodynamic waves genera…
Analysis of full disc Ca II K spectroheliograms. II. Towards an accurate assessment of long-term variations in plage areas
Theodosios Chatzistergos, Ilaria Ermolli, Natalie A. Krivova +1
Reconstructions of past irradiance variations require suitable data on solar activity. The longest direct proxy is the sunspot number, and it has been most widely employed for this…
Plasma flows and magnetic field interplay during the formation of a pore
I. Ermolli, A. Cristaldi, F. Giorgi +5
We studied the formation of a pore in AR NOAA 11462. We analysed data obtained with the IBIS at the DST on April 17, 2012, consisting of full Stokes measurements of the Fe I 617.3…
Effects of unresolved magnetic field on Fe I 617.3 and 630.2 nm line shapes
Serena Criscuoli, Ilaria Ermolli, Han Uitenbroek +1
The contribution of the quiet Sun to solar irradiance variability, due either to changes of the solar effective temperature or to the presence of unresolved magnetic field, is stil…
Line shape effects on intensity measurements of solar features: Brightness correction to SoHO MDI continuum images
S. Criscuoli, I. Ermolli, D. Del Moro +4
Continuum intensity observations obtained with the Michelson Doppler Imager (MDI) on-board the SoHO mission provide long time series of filtergrams that are ideal for studying the…