Spectroscopic Studies of Limb Spicules. I. Radial and Turbulent Velocities

TL;DR

This study uses high-resolution spectroscopy to analyze limb spicules, revealing different velocity components and turbulence levels, which enhance understanding of their dynamic behavior.

Contribution

It provides detailed spectroscopic measurements of limb spicules, identifying multiple velocity components and turbulence, which were not previously characterized in such detail.

Findings

Fewer than half of spicules have Gaussian profiles.

Some spicules show asymmetric profiles with two Gaussian components.

Detected non-thermal turbulence velocities around 30 km/s.

Abstract

We made high-resolution spectroscopic observations of limb-spicules in H-alpha using the Vertical Spectrograph of Domeless Solar Telescope at Hida Observatory. While more than half of the observed spicules have Gaussian line-profiles, some spicules have distinctly asymmetric profiles which can be fitted with two Gaussian components. The faster of these components has radial velocities of 10 - 40 km/s and Doppler-widths of about 0.4 A which suggest that it is from a single spicule oriented nearly along the line-of-sight. Profiles of the slower components and the single-Gaussian type show very similar characteristics. Their radial velocities are less than 10 km/s and the Doppler-widths are 0.6 - 0.9 A. Non-thermal "macroturbulent" velocities of order 30 km/s are required to explain these width-values.