Current

Current work

Recent papers

Systematic non-thermal velocity increase preceding soft X-ray flare onset.

The Astrophysical Journal, 2025.

Chromospheric dynamics and turbulence regulate the solar FIP effect.

Philosophical Transactions of the Royal Society A, accepted.

Coordination

Solar Orbiter, Hinode, and IRIS

Co-observation coordinator, 2024-present.

IRIS

Planner, 2024-2025.

Dataset

Hinode/EIS Solar Flare Footpoint Non-Thermal Velocity Dataset (2011-2024)

Zenodo, 2025.

Observing time

JVLA S-band programme

PI for observations on the correlation between solar abundances and F10.7 radio emission.

Joint observations with GREGOR, SST, IRIS, and Hinode.

CV

Brief CV

Publications

Selected publications

1. 2026 · First author

   Chromospheric dynamics and turbulence regulate the solar FIP effect

   To, Andy S. H., Laming, J. M., Reep, J., Finley, A. J.

   Philosophical Transactions of the Royal Society A · accepted for publication (2026)

   Accepted ADS abstract Summary

   Summary

   Coronal elemental abundance patterns (FIP bias) encode chromospheric physics. Coupling HYDRAD chromospheric simulations with the ponderomotive-force code FIPpy, we show the ponderomotive model remains viable under dynamic heating, while acoustic flux and turbulence strongly reshape fractionation: very low acoustic flux lets thermal velocities dominate and produce unusual element ordering, whereas turbulence—including enhanced turbulence in flares—suppresses fractionation and may explain weaker FIP bias observed during flares.

2. 2025 · First author

   Systematic non-thermal velocity increase preceding soft X-ray flare onset.

   To, Andy S. H., Burden, A., Baker, D., Eklund, H., Brooks, D. H., Hayes, L. A., Martínez-Sykora, J., Testa, P., Reep, J., Janvier, M., Imada, S., Hernandez Camero, J., Long, D. M., Mihailescu, T., Weberg, M. J.

   The Astrophysical Journal, 993, 102 (2025)

   ADS abstract Summary

   Summary

   Using a Hinode/EIS catalogue of 1,449 flares from 2011-2024, this paper measures how EUV non-thermal velocities evolve before soft X-ray flare onset across C-, M-, and X-class events. It finds that line broadening typically begins 4-25 minutes before GOES start in C and M flares, with earlier and more extended precursor behaviour in many eruptive M-class events.

3. 2024 · First author

   Spatially resolved plasma composition evolution in a solar flare – The effect of reconnection outflow.

   To, Andy S. H., Brooks, D. H., Imada, S., French, R. J., van Driel-Gesztelyi, L., Baker, D., Long, D. M., Ashfield, W., Hayes, L. A.

   Astronomy & Astrophysics, 691, A95 (2024)

   ADS abstract Summary

   Summary

   This paper tracks FIP bias through the 2017 September 10 X8.2 flare using 12 Hinode/EIS rasters and two abundance diagnostics. It finds persistent high-FIP-bias plasma near loop tops and near-photospheric values at footpoints, consistent with mixing between reconnection-downflow plasma and chromospheric evaporation.

4. 2023 · First author

   Understanding the Relationship between Solar Coronal Abundances and F10.7 cm Radio Emission.

   To, Andy S. H., James, A. W., Bastian, T. S., van Driel-Gesztelyi, L., Long, D. M., Baker, D., Brooks, D. H., Lomuscio, S., Stansby, D., Valori, G.

   The Astrophysical Journal, 948, 121 (2023)

   ADS abstract Summary

   Summary

   This paper tests why the Sun-as-a-star correlation between coronal composition and F10.7 becomes nonlinear during higher activity. Using coordinated JVLA, Hinode/EIS, and SDO observations, it shows that strong magnetic concentrations and gyroresonance above sunspots alter the local relationship between radio flux and coronal abundance.

5. 2021 · First author

   The Evolution of Plasma Composition during a Solar Flare.

   To, Andy S. H., Long, D. M., Baker, D., Brooks, D. H., van Driel-Gesztelyi, L., Laming, J. M., Valori, G.

   The Astrophysical Journal, 911, 86 (2021)

   ADS abstract Summary

   Summary

   Using Hinode/EIS observations of a small flare, this paper compares abundance diagnostics before and during the event. It finds a strong flare-time increase in the Ca XIV/Ar XIV ratio while Si X/S X remains comparatively unchanged, and discusses how flare heating and chromospheric plasma injection may affect different diagnostics.

A fuller publication record is available on the publications page, through the ADS library, ORCID, and the PDF CV.

Activities

Teaching, supervision, and service