How does the critical torus instability height vary with the solar cycle?
arXiv:2409.02695 · doi:10.3847/1538-4357/ad77a0
Abstract
The ideal magnetohydrodynamic torus instability can drive the eruption of coronal mass ejections. The critical threshold of magnetic field strength decay for the onset of the torus instability occurs at different heights in different solar active regions, and understanding this variation could therefore improve space weather prediction. In this work, we aim to find out how the critical torus instability height evolves throughout the solar activity cycle. We study a significant subset of HMI and MDI Space-Weather HMI Active Region Patches (SHARPs and SMARPs) from 1996-2023, totalling 21584 magnetograms from 4436 unique active region patches. For each magnetogram, we compute the critical height averaged across the main polarity inversion line, the total unsigned magnetic flux and the separation between the positive and negative magnetic polarities. We find the critical height in active regions varies with the solar cycle, with higher (lower) average critical heights observed around solar maximum (minimum). We conclude this is because the critical height is proportional to the separation between opposite magnetic polarities, which in turn is proportional to the total magnetic flux in a region, and more magnetic regions with larger fluxes and larger sizes are observed at solar maximum. This result is noteworthy because, despite the higher critical heights, more CMEs are observed around solar maximum than at solar minimum.
Accepted to ApJ. 14 pages, 6 Figures, 1 Table
References in corpus (23)
- Torus instability
- Confined and ejective eruptions of kink-unstable flux ropes
- The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: SHARPs -- Space-weather HMI Active Region Patches
- VFISV: Very Fast Inversion of the Stokes Vector for the Helioseismic and Magnetic Imager
- Criteria for Flux Rope Eruption: Non Equilibrium versus Torus Instability
- Prediction of the strength and timing of sunspot cycle 25 reveal decadal-scale space environmental conditions
- Numerical simulations of fast and slow coronal mass ejections
- Critical decay index at the onset of solar eruptions
- Initiation and Early Kinematic Evolution of Solar Eruptions
- Initiation of Coronal Mass Ejections by Sunspot Rotation
- On-disc Observations of Flux Rope Formation Prior to its Eruption
- Critical Height of the Torus Instability in Two-Ribbon Solar Flares
- On the factors determining the eruptive character of solar flares
- An Observationally-Constrained Model of a Flux Rope that Formed in the Solar Corona
- Solar LImb Prominence CAtcher and Tracker (SLIPCAT): An Automated System and Its Preliminary Statistical Results
- SMARPs and SHARPs: Two Solar Cycles of Active Region Data
- Evaluating (and Improving) Estimates of the Solar Radial Magnetic Field Component from Line-of-Sight Magnetograms
- Torus-Stable Zone Above Starspots
- The role of flux cancellation in eruptions from bipolar active regions
- A comparative study between a failed and a successful eruption initiated from the same polarity inversion line in AR 11387
- A new trigger mechanism for coronal mass ejections: the role of confined flares and photospheric motions in the formation of hot flux ropes
- Where and how does a decay-index profile become saddle-like?
- Evolution of the critical torus instability height and CME likelihood in solar active regions