Filling Factors of Sunspots in SODISM Images

TL;DR

This paper introduces a new automated method for detecting sunspots in SODISM images, accurately calculating their filling factors, and cataloguing these factors in tabular form, which correlates well with existing data.

Contribution

It presents the first catalog of sunspot filling factors in SODISM images and a fully automated detection method with high recognition accuracy.

Findings

Sunspot detection rate of 97.6%

High correlation (99%) with SOHO data

Effective calculation of filling factors at 607nm wavelength

Abstract

Received: 1st December 2018; Accepted: 18th February 2019; Published: 1st April 2019 Abstract: The calculated filling factors (FFs) for a feature reflect the fraction of the solar disc covered by that feature, and the assignment of reference synthetic spectra. In this paper, the FFs, specified as a function of radial position on the solar disc, are computed for each image in a tabular form. The filling factor (FF) is an important parameter and is defined as the fraction of area in a pixel covered with the magnetic field, whereas the rest of the area in the pixel is field-free. However, this does not provide extensive information about the experiments conducted on tens or hundreds of such images. This is the first time that filling factors for SODISM images have been catalogued in tabular formation. This paper presents a new method that provides the means to detect sunspots on full-disk solar images recorded by the Solar Diameter Imager and Surface Mapper (SODISM) on the PICARD satellite. The method is a totally automated detection process that achieves a sunspot recognition rate of 97.6%. The number of sunspots detected by this method strongly agrees with the NOAA catalogue. The sunspot areas calculated by this method have a 99% correlation with SOHO over the same period, and thus help to calculate the filling factor for wavelength (W.L.) 607nm.