Solar spicule population properties inferred from IRIS Mg II k off-limb spectra using likelihood-free Bayesian inference
Abstract
Solar spicules are ubiquitous and strongly overlap in off-limb observations, which complicates the interpretation of individual events. We aim to infer population-level properties of spicules from IRIS Mg II k off-limb spectra using a forward model that explicitly accounts for line-of-sight superposition and instrumental effects. We constructed a stochastic 3D spicule-population model and synthesized Mg II k spectra with radiative transfer, including instrumental degradation and photon noise. We then constrained the hyperparameters that describe the underlying spicule population with likelihood-free Bayesian inference. This approach combines approximate Bayesian computation and an adaptive population Monte Carlo sampler, comparing observed and simulated datasets through principal-component summary statistics at five heights above the limb. The inferred posterior constrains effective population-level properties of the spicules that dominate the observed Mg II k variability and height dependence. These constraints provide a route to connect off-limb spectroscopy with forthcoming spectropolarimetric diagnostics of the chromosphere--corona interface.
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BibTeX
@misc{stepan2026solar,
title = {{Solar spicule population properties inferred from IRIS Mg II k off-limb spectra using likelihood-free Bayesian inference}},
author = {Jiri Stepan and Stanislav Gunar and Akiko Tei and Petr Heinzel},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.37811},
eprint = {2609.37811},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.37811},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Solar spicule population properties inferred from IRIS Mg II k off-limb spectra using likelihood-free Bayesian inference
AU - Jiri Stepan
AU - Stanislav Gunar
AU - Akiko Tei
AU - Petr Heinzel
PY - 2026
DA - 2026/10/20
PB - arXiv
DO - 10.48550/arxiv.2609.37811
UR - https://arxiv.org/abs/2609.37811
AB - Solar spicules are ubiquitous and strongly overlap in off-limb observations, which complicates the interpretation of individual events. We aim to infer population-level properties of spicules from IRIS Mg II k off-limb spectra using a forward model that explicitly accounts for line-of-sight superposition and instrumental effects. We constructed a stochastic 3D spicule-population model and synthesized Mg II k spectra with radiative transfer, including instrumental degradation and photon noise. We then constrained the hyperparameters that describe the underlying spicule population with likelihood-free Bayesian inference. This approach combines approximate Bayesian computation and an adaptive population Monte Carlo sampler, comparing observed and simulated datasets through principal-component summary statistics at five heights above the limb. The inferred posterior constrains effective population-level properties of the spicules that dominate the observed Mg II k variability and height dependence. These constraints provide a route to connect off-limb spectroscopy with forthcoming spectropolarimetric diagnostics of the chromosphere--corona interface.
ER -