Evidence for Energy Supply by Active Region Spicules to the Solar Atmosphere

TL;DR

This study uses high-resolution solar observations to analyze active region spicules, revealing coherent oscillations and phase speeds that suggest they contribute to heating the solar atmosphere and supplying energy to the solar wind.

Contribution

It provides new evidence of coherent waves in spicules and quantifies their phase speeds, supporting their role in solar atmospheric heating and wind energy supply.

Findings

Detected coherent oscillations at around 5.5 mHz in spicules.

Measured phase speeds increasing from 250 to 425 km/s with height.

Identified dominant frequencies in the 2-8 mHz range.

Abstract

We investigate the role of active region spicules in the mass balance of the solar wind and energy supply for heating the solar atmosphere. We use high cadence observations from the Solar Optical Telescope (SOT) onboard the Hinode satellite in the Ca II H line filter obtained on 26 January 2007. The observational technique provides the high spatio-temporal resolution required to detect fine structures such as spicules. We apply Fourier power spectrum and wavelet analysis to SOT/Hinode time series of an active region data to explore the existence of coherent intensity oscillations. The presence of coherent waves could be an evidence for energy transport to heat the solar atmosphere. Using time series, we measure the phase difference between two intensity profiles obtained at two different heights, which gives information about the phase difference between oscillations at those heights as a function of frequency. The results of a fast Fourier transform (FFT) show peaks in the power spectrum at frequencies in the range from 2 to 8 mHz at four different heights (above the limb), while the wavelet analysis indicate dominant frequencies similar to those of the Fourier power spectrum results. A coherency study indicates the presence of coherent oscillations at about 5.5 mHz (3 min). We measure mean phase speeds in the range 250 to 425 km/s increasing with height.