A Detailed Analysis of a Magnetic Island Observed by WISPR on Parker Solar Probe

TL;DR

This paper reports the identification and analysis of a faint magnetic island observed by WISPR on Parker Solar Probe, revealing its properties, formation mechanism, and evolution during its journey through the solar corona.

Contribution

It provides the first detailed physical analysis of a magnetic island observed by WISPR, highlighting its formation via reconnection and its dynamic shape evolution.

Findings

The magnetic island has an average velocity of 334 km/s and accelerates at -0.64 m/s².

The island's shape evolves from elliptical to circular, doubling in aspect ratio.

It is only visible in WISPR images, not in other coronagraph data, due to its faintness.

Abstract

We present the identification and physical analysis of a possible magnetic island feature seen in white-light images observed by the Wide-field Imager for Solar Probe (WISPR) on board the Parker Solar Probe (Parker). The island is imaged by WISPR during Parker's second solar encounter on 2019 April 06, when Parker was ~38 solar radii from the Sun center. We report that the average velocity and acceleration of the feature are approximately 334 km s and -0.64 m s-2. The kinematics of the island feature, coupled with its direction of propagation, indicate that the island is likely entrained in the slow solar wind. The island is elliptical in shape with a density deficit in its center, suggesting the presence of a magnetic guide field. We argue that this feature is consistent with the formation of this island via reconnection in the current sheet of the streamer. The feature's aspect ratio (calculated as the ratio of its minor to major axis) evolves from an elliptical to a more circular shape that approximately doubles during its propagation through WISPR's field of view. The island is not distinct in other white-light observations from the Solar and Heliospheric Observatory (SOHO) and the Solar Terrestrial Relations Observatory (STEREO) coronagraphs, suggesting that this is a comparatively faint heliospheric feature and that viewing perspective and WISPR's enhanced sensitivity are key to observing the magnetic island.