Signatures of photospheric convection throughout the solar atmosphere: the EVE Sun-as-a-star mHz continuum
Abstract
Convectively driven motions in the solar photosphere can generate broadband Doppler variability across the chromosphere, transition region and corona. Here we investigate this variability using "Sun-as-a-Star" observations from the Extreme Ultraviolet Variability Experiment (EVE) aboard the Solar Dynamics Observatory, constructing high signal-to-noise Doppler power spectra by incoherently averaging spectra from 3-hour sequences of the centroid wavelengths of emission lines that span wavelengths 35-104 nm. The spectra reveal a broad power-spectral continuum with two "Harvey" components, one of which extends to the Nyquist frequency at 50 mHz with a steep power-law tail. All emission lines have substantial power both above and below the nominal acoustic cutoff frequency at 5 mHz, but none of the power spectra show maxima corresponding to p-mode or chromospheric 3-minute oscillations. Lines formed in the corona, as compared with those of the chromosphere/transition region, have substantially less Doppler amplitude in the Harvey spectrum associated with granulation-scale convection. Based on the observed continuum, there is no evidence (in any of the 26 lines studied) for Kolmogorov turbulence, which predicts a flat continuum component with Doppler variance ~f^(-5/3) as a function of frequency f. The total inferred RMS velocities (>0.1 mHz) are roughly consistent with coronal microturbulence estimates from excess line widths. These observations provide the first clear detection of Sun-as-a-star EUV Doppler variability above ~10 mHz and demonstrate the potential of full-disk EUV spectroscopy to probe turbulent energy transport throughout a stellar atmosphere.
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BibTeX
@misc{hudson2026signatures,
title = {{Signatures of photospheric convection throughout the solar atmosphere: the EVE Sun-as-a-star mHz continuum}},
author = {Hugh Hudson and Anne-Marie Broomhall and Lyndsay Fletcher and David Graham and Sargam M. Mulay and Chris Osborne and Kirsty Williamson and Graham Woan},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2607.05108},
eprint = {2607.05108},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.05108},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Signatures of photospheric convection throughout the solar atmosphere: the EVE Sun-as-a-star mHz continuum
AU - Hugh Hudson
AU - Anne-Marie Broomhall
AU - Lyndsay Fletcher
AU - David Graham
AU - Sargam M. Mulay
AU - Chris Osborne
AU - Kirsty Williamson
AU - Graham Woan
PY - 2026
DA - 2026/09/25
PB - arXiv
DO - 10.48550/arxiv.2607.05108
UR - https://arxiv.org/abs/2607.05108
AB - Convectively driven motions in the solar photosphere can generate broadband Doppler variability across the chromosphere, transition region and corona. Here we investigate this variability using "Sun-as-a-Star" observations from the Extreme Ultraviolet Variability Experiment (EVE) aboard the Solar Dynamics Observatory, constructing high signal-to-noise Doppler power spectra by incoherently averaging spectra from 3-hour sequences of the centroid wavelengths of emission lines that span wavelengths 35-104 nm. The spectra reveal a broad power-spectral continuum with two "Harvey" components, one of which extends to the Nyquist frequency at 50 mHz with a steep power-law tail. All emission lines have substantial power both above and below the nominal acoustic cutoff frequency at 5 mHz, but none of the power spectra show maxima corresponding to p-mode or chromospheric 3-minute oscillations. Lines formed in the corona, as compared with those of the chromosphere/transition region, have substantially less Doppler amplitude in the Harvey spectrum associated with granulation-scale convection. Based on the observed continuum, there is no evidence (in any of the 26 lines studied) for Kolmogorov turbulence, which predicts a flat continuum component with Doppler variance ~f^(-5/3) as a function of frequency f. The total inferred RMS velocities (>0.1 mHz) are roughly consistent with coronal microturbulence estimates from excess line widths. These observations provide the first clear detection of Sun-as-a-star EUV Doppler variability above ~10 mHz and demonstrate the potential of full-disk EUV spectroscopy to probe turbulent energy transport throughout a stellar atmosphere.
ER -