scholarly journals Stellar activity, differential rotation, and exoplanets

2010 ◽  
Vol 6 (S273) ◽  
pp. 89-95 ◽  
Author(s):  
A. F. Lanza
Keyword(s):  
Time Series ◽  
Differential Rotation ◽  
Solar Irradiance ◽  
Giant Planet ◽  
Total Solar Irradiance ◽  
Short Term ◽  
Stellar Activity ◽  
Transiting Planets ◽  
Spot Model ◽  
Spot Activity

AbstractThe photospheric spot activity of some of the stars with transiting planets discovered by the CoRoT space experiment is reviewed. Their out-of-transit light modulations are fitted by a spot model previously tested with the total solar irradiance variations. This approach allows us to study the longitude distribution of the spotted area and its variations versus time during the five months of a typical CoRoT time series. The migration of the spots in longitude provides a lower limit for the surface differential rotation, while the variation of the total spotted area can be used to search for short-term cycles akin the solar Rieger cycles. The possible impact of a close-in giant planet on stellar activity is also discussed.

Data Fusion of Total Solar Irradiance Composite Time Series Using 40 years of Satellite Measurements: First Results 

2021 ◽  
Author(s):  
Jean-Philippe Montillet ◽  
Wolfgang Finsterle ◽  
Werner Schmutz ◽  
Margit Haberreiter ◽  
Rok Sikonja
Keyword(s):  
Time Series ◽  
Data Fusion ◽  
Solar Irradiance ◽  
Total Solar Irradiance ◽  
Maunder Minimum ◽  
The Sun ◽  
Climate Reconstructions ◽  
The Earth ◽  
First Results ◽  
The Difference

<p><span>Since the late 70’s, successive satellite missions have been monitoring the sun’s activity, recording total solar irradiance observations. These measurements are important to estimate the Earth’s energy imbalance, </span><span>i.e. the difference of energy absorbed and emitted by our planet. Climate modelers need the solar forcing time series in their models in order to study the influence of the Sun on the Earth’s climate. With this amount of TSI data, solar irradiance reconstruction models  can be better validated which can also improve studies looking at past climate reconstructions (e.g., Maunder minimum). V</span><span>arious algorithms have been proposed in the last decade to merge the various TSI measurements over the 40 years of recording period. We have developed a new statistical algorithm based on data fusion.  The stochastic noise processes of the measurements are modeled via a dual kernel including white and coloured noise.  We show our first results and compare it with previous releases (PMOD,ACRIM, ... ). </span></p>

Short-term variability of experimental ultraviolet and total solar irradiance in Southeastern Spain

2011 ◽  
Vol 45 (28) ◽  
pp. 4815-4821 ◽  
Author(s):  
M. Antón ◽  
J.E. Gil ◽  
A. Cazorla ◽  
J. Fernández-Gálvez ◽  
I. Foyo-Moreno ◽  
...  
Keyword(s):  
Solar Irradiance ◽  
Total Solar Irradiance ◽  
Short Term ◽  
Southeastern Spain ◽  
Short Term Variability

scholarly journals Solar Noise in 40-year long Total Solar Irradiance Composite Time Series

2021 ◽  
Author(s):  
Jean-Philippe Montillet ◽  
Wolfgang Finsterle ◽  
Gael Kermarrec ◽  
Rok Sikonja ◽  
Margit Haberreiter ◽  
...  
Keyword(s):  
Time Series ◽  
Solar Irradiance ◽  
Total Solar Irradiance

Solar Noise in 40-year long Total Solar Irradiance Composite Time Series

2021 ◽  
Author(s):  
Jean-Philippe Montillet ◽  
Wolfgang Finsterle ◽  
Gael Kermarrec ◽  
Margit Haberreiter ◽  
Rok Sikonja ◽  
...  
Keyword(s):  
Time Series ◽  
Solar Irradiance ◽  
Total Solar Irradiance

scholarly journals Time series Doppler imaging using STELLA

2008 ◽  
Vol 4 (S259) ◽  
pp. 427-428
Author(s):  
Michael Weber ◽  
Klaus G. Strassmeier ◽  
Thomas Granzer
Keyword(s):  
Time Series ◽  
Differential Rotation ◽  
Stellar Surface ◽  
Doppler Imaging ◽  
Stellar Activity ◽  
Giant Star ◽  
Preliminary Results ◽  
The Core

AbstractOne of the core programs of the STELLA robotic observatory is to monitor the stellar activity on a sample of stars using Doppler imaging. We present first preliminary results of the rapidly rotating, single giant star HD 31993 from the first two years of operation. We confirm the presence and orientation of differential rotation on the stellar surface.

scholarly journals The total solar irradiance during the recent solar minimum period measured by SOHO/VIRGO

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
W. Finsterle ◽  
J. P. Montillet ◽  
W. Schmutz ◽  
R. Šikonja ◽  
L. Kolar ◽  
...  
Keyword(s):  
Time Series ◽  
Data Fusion ◽  
Solar Irradiance ◽  
Total Solar Irradiance ◽  
Data Driven ◽  
Combine Data ◽  
Fusion Algorithm ◽  
Heliospheric Observatory ◽  
Dual Channel ◽  
The Individual

AbstractVarious space missions have measured the total solar irradiance (TSI) since 1978. Among them the experiments Precision Monitoring of Solar Variability (PREMOS) on the PICARD satellite (2010–2014) and the Variability of Irradiance and Gravity Oscillations (VIRGO) on the mission Solar and Heliospheric Observatory, which started in 1996 and is still operational. Like most TSI experiments, they employ a dual-channel approach with different exposure rates to track and correct the inevitable degradation of their radiometers. Until now, the process of degradation correction has been mostly a manual process based on assumed knowledge of the sensor hardware. Here we present a new data-driven process to assess and correct instrument degradation using a machine-learning and data fusion algorithm, that does not require deep knowledge of the sensor hardware. We apply the algorithm to the TSI records of PREMOS and VIRGO and compare the results to the previously published results. The data fusion part of the algorithm can also be used to combine data from different instruments and missions into a composite time series. Based on the fusion of the degradation-corrected VIRGO/PMO6 and VIRGO/DIARAD time series, we find no significant change (i.e $$-0.17\pm 0.29$$ - 0.17 ± 0.29  W/m$$^2$$ 2 ) between the TSI levels during the two most recent solar minima in 2008/09 and 2019/20. The new algorithm can be applied to any TSI experiment that employs a multi-channel philosophy for degradation tracking. It does not require deep technical knowledge of the individual radiometers.

scholarly journals Total Solar Irradiance Variations: The Construction of a Composite and its Comparison with Models

1998 ◽  
Vol 185 ◽  
pp. 89-102 ◽  
Author(s):  
Claus Fröhlich ◽  
Judith Lean
Keyword(s):  
Time Series ◽  
Time Scales ◽  
Solar Irradiance ◽  
Total Solar Irradiance

Measurements of the total solar irradiance (TSI) during the last 18 years from spacecraft are reviewed. Corrections are determined for the early measurements made by the HF radiometer within the ERB experiment on NIMBUS7 and the factor to refer ACRIM II to the ACRIM I irradiance scale. With these corrections a composite TSI is constructed for the period from 1978-1997. This time series is compared with a model that combines a magnetic brightness proxy with observed sunspot darkening and explains nearly 90% of the observed short and longterm variance. Possible, but still unverified degradation of the radiometers hampers conclusions about irradiance changes on decadal time scales and longer.

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