Time-Distance Imaging of Solar Far-Side Active Regions

TL;DR

This paper enhances solar far-side active region imaging by combining four- and five-skip time-distance helioseismology techniques, significantly improving image quality and reliability for space weather prediction.

Contribution

It introduces a new five-skip scheme and combines it with existing methods to improve the accuracy and clarity of solar far-side active region images.

Findings

Enhanced signal-to-noise ratio in far-side images

Reduced spurious signals in imaging results

Validated improvements with one year of solar data

Abstract

It is of great importance to monitor large solar active regions in the far-side of the Sun for space weather forecast, in particular, to predict their appearance before they rotate into our view from the solar east limb. Local helioseismology techniques, including helioseismic holography and time-distance, have successfully imaged solar far-side active regions. In this Letter, we further explore the possibility of imaging and improving the image quality of solar far-side active regions by use of time-distance helioseismology. In addition to the previously used scheme with four acoustic signal skips, a five-skip scheme is also included in this newly developed technique. The combination of both four- and five-skip far-side images significantly enhances the signal-to-noise ratio in the far-side images, and reduces spurious signals. The accuracy of the far-side active region imaging is also assessed using one whole year solar observation.