The Structure and Dynamics of the Upper Chromosphere and Lower Transition Region as Revealed by the Subarcsecond VAULT Observations

TL;DR

This paper presents high-resolution VAULT observations of the solar upper chromosphere and transition region, revealing new insights into their structure and dynamics, and synthesizes current knowledge to guide future Ly-a solar studies.

Contribution

It provides the first sub-arcsecond Ly-a images of the solar transition region and synthesizes recent analyses to enhance understanding of this interface.

Findings

First sub-arcsecond Ly-a images of the transition region

New insights into the structure and dynamics of the upper chromosphere

Guidance for future Ly-a telescope design and observations

Abstract

The Very high Angular resolution ULtraviolet Telescope (VAULT) is a sounding rocket payload built to study the crucial interface between the solar chromosphere and the corona by observing the strongest line in the solar spectrum, the Ly-a line at 1216 {\AA}. In two flights, VAULT succeeded in obtaining the first ever sub-arcsecond (0.5") images of this region with high sensitivity and cadence. Detailed analyses of those observations have contributed significantly to new ideas about the nature of the transition region. Here, we present a broad overview of the Ly-a atmosphere as revealed by the VAULT observations, and bring together past results and new analyses from the second VAULT flight to create a synthesis of our current knowledge of the high-resolution Ly-a Sun. We hope that this work will serve as a good reference for the design of upcoming Ly-a telescopes and observing plans.