Transient artifacts in a flare observed by the Helioseismic and Magnetic Imager on the Solar Dynamics Observatory

TL;DR

This study investigates transient artifacts in solar flare observations by HMI on SDO, using GONG++ data and PASCAL correction to distinguish real signals from instrumental artifacts, enhancing the reliability of flare analysis.

Contribution

The paper demonstrates how GONG++ observations with PASCAL correction can validate and complement HMI flare data, addressing instrumental artifact concerns.

Findings

HMI blueshift signatures are artifacts, not real plasma motions.

GONG++ with PASCAL confirms redshifts at flare footpoints.

Proper data correction improves flare transient analysis.

Abstract

The Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) provides a new tool for the systematic observation of white-light flares, including Doppler and magnetic information as well as continuum. In our initial analysis of the highly impulsive \gamma-ray flare SOL2010-06-12T00:57 (Mart'{\i}nez Oliveros et al., Solar Phys., 269, 269, 2011), we reported the signature of a strong blueshift in the two footpoint sources. Concerned that this might be an artifact due to aliasing peculiar to the HMI instrument, we undertook a comparative analysis of Global Oscillations Network Group (GONG++) observations of the same flare, using the PArametric Smearing Correction ALgorithm (PASCAL) algorithm to correct for artifacts caused by variations in atmospheric smearing. This analysis confirms the artifactual nature of the apparent blueshift in the HMI observations, finding weak redshifts at the footpoints instead. We describe the use of PASCAL with GONG++ observations as a complement to the SDO observations and discuss constraints imposed by the use of HMI far from its design conditions. With proper precautions, these data provide rich information on flares and transients.