Plasmoid-trapped Condensation Associated with a Transient Thermal Instability–Like Process in Chromospheric Magnetic Reconnection
6 affiliations
- 1Yunnan Observatories
- 2Yunnan Key Laboratory of Solar Physics and Space Science
- 3University of Chinese Academy of Sciences
- 4Indian Institute of Geomagnetism
- 5Peking University
- 6State Key Laboratory of Solar Activity and Space Weather
Abstract
We perform high-resolution 2.5D single-fluid magnetohydrodynamic (MHD) simulations to explore the development of cool, dense structures within plasmoids during chromospheric magnetic reconnection. The model incorporates temperature-dependent ionization degrees of hydrogen and helium, resulting in improved diffusivities and viscosity, as well as adequate radiative cooling. The numerical results show that the plasma is significantly hot, with temperatures reaching several tens of thousands of Kelvin in newly developed plasmoids in the low initial plasma- β cases, β ₀ = 0.05. Later, the localized accumulation of plasma and decreasing temperature result in an explosive, much stronger radiative cooling process. Radiative cooling peaks over the temperature range of 8000–20,000 K. The co-spatial density enhancement, substantial radiative cooling, shorter radiative cooling timescales, and a significant temperature decrease support the existence of thermal instability–like condensation within the plasmoids. Similar cool, dense structures are identified in all low- β ₀ cases at different chromospheric altitudes, suggesting that this occurrence is not limited to a single chromospheric layer. In contrast, in the high initial plasma- β , β ₀ = 0.5 case, the maximum temperature inside the dense plasmoids is only about 8000 K. Therefore, the radiative cooling has never entered the explosive increasing stage, and the thermal-instability-like condensation does not happen. These findings reveal that plasmoid-trapped condensation may develop in chromospheric reconnection once radiative losses become self-amplifying under low- β ₀ conditions.
Related
- Bifrost spectral inversions. Fast non-LTE solar chromospheric diagnostics from 3D simulations
- TESS flares and chromospheric variability in the Pleiades, the Hyades, and Praesepe
- Cross-layer coupling in active-region upflows: Statistical connections between photospheric magnetic field, chromospheric activity, and coronal blueshifts
- The variable mass-loss in low-mass red giant stars. Chromospheric motion across stellar evolution in 47 Tuc
- Chromospheric fluxes from the Ca II infrared triplet in M dwarfs. A homogeneous catalog from CARMENES spectra
BibTeX
@article{zafar2026plasmoidtrapped,
title = {{Plasmoid-trapped Condensation Associated with a Transient Thermal Instability–Like Process in Chromospheric Magnetic Reconnection}},
author = {Abdullah Zafar and Lei Ni and Samrat Sen and Yuhao Chen and Mohamed Sedik and Mehdi Yousefzadeh and Jun Lin},
journal = {The Astrophysical Journal},
year = {2026},
month = sep,
doi = {10.3847/1538-4357/aea6d5},
url = {https://iopscience.iop.org/article/10.3847/1538-4357/aea6d5},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Plasmoid-trapped Condensation Associated with a Transient Thermal Instability–Like Process in Chromospheric Magnetic Reconnection
AU - Abdullah Zafar
AU - Lei Ni
AU - Samrat Sen
AU - Yuhao Chen
AU - Mohamed Sedik
AU - Mehdi Yousefzadeh
AU - Jun Lin
PY - 2026
DA - 2026/09/30
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/aea6d5
UR - https://iopscience.iop.org/article/10.3847/1538-4357/aea6d5
AB - We perform high-resolution 2.5D single-fluid magnetohydrodynamic (MHD) simulations to explore the development of cool, dense structures within plasmoids during chromospheric magnetic reconnection. The model incorporates temperature-dependent ionization degrees of hydrogen and helium, resulting in improved diffusivities and viscosity, as well as adequate radiative cooling. The numerical results show that the plasma is significantly hot, with temperatures reaching several tens of thousands of Kelvin in newly developed plasmoids in the low initial plasma- β cases, β ₀ = 0.05. Later, the localized accumulation of plasma and decreasing temperature result in an explosive, much stronger radiative cooling process. Radiative cooling peaks over the temperature range of 8000–20,000 K. The co-spatial density enhancement, substantial radiative cooling, shorter radiative cooling timescales, and a significant temperature decrease support the existence of thermal instability–like condensation within the plasmoids. Similar cool, dense structures are identified in all low- β ₀ cases at different chromospheric altitudes, suggesting that this occurrence is not limited to a single chromospheric layer. In contrast, in the high initial plasma- β , β ₀ = 0.5 case, the maximum temperature inside the dense plasmoids is only about 8000 K. Therefore, the radiative cooling has never entered the explosive increasing stage, and the thermal-instability-like condensation does not happen. These findings reveal that plasmoid-trapped condensation may develop in chromospheric reconnection once radiative losses become self-amplifying under low- β ₀ conditions.
SN - 0004-637X
SN - 1538-4357
ER -