Study of the Kinematics and Plasma Properties of A Solar Surge Triggered due to Chromospheric Activity in AR11271

TL;DR

This study combines observations and numerical modeling to analyze a solar surge's kinematics, plasma properties, and triggering mechanism, revealing that chromospheric heating and thermal pulses can generate surge-like phenomena.

Contribution

It provides the first detailed observational and numerical analysis linking chromospheric heating to surge initiation and properties.

Findings

Surge reached 65 Mm height with 100 km/s velocity.

Average temperature of surge plasma was 2.0 MK.

Numerical model supports thermal pulse triggering mechanism.

Abstract

We observe a solar surge in NOAA AR11271 using SDO AIA 304 image data on 25 August, 2011. The surge rises vertically from its origin upto a height of 65 Mm with a terminal velocity of 100 km/s, and thereafter falls and fades gradually. The total life time of the surge was 20 min. We also measure the temperature and density distribution of the observed surge during its maximum rise, and found an average temperature and density of 2.0 MK and 4.1 x 109 cm-3, respectively. The temperature map shows the expansion and mixing of cool plasma lagging behind the hot coronal plasma along the surge. As SDO/HMI temporal image data does not show any detectable evidence of the significant photospheric magnetic field cancellation for the formation of the observed surge, we infer that it is probably driven by magnetic reconnection generated thermal energy in the lower chromosphere. The radiance (thus mass density) oscillations near the base of the surge are also evident, which may be the most likely signature of its formation by a reconnection generated pulse. In support of the present observational base-line of the triggering of the surge due to chromospheric heating, we devise a numerical model with conceivable implementation of VAL-C atmosphere and a thermal pulse as an initial trigger. We find that the pulse steepens into a slow shock at higher altitudes that triggers plasma perturbations exhibiting the observed features of the surge, e.g., terminal velocity, height, width, life-time, and heated fine structures near its base.