arXiv subjects

Olga A. Panasenco

Publications and source records attributed to Olga A. Panasenco.

3 recordsLinked to original sources

arXiv2026

Coronal Mass Ejections from the Young Sun: Deceleration-Powered Solar Energetic Particles as a Self-Extinguishing Forcing of the Early Earth

At $\sim$3.9~Ga (stellar age $\sim$0.6~Gyr), the young Sun was far more magnetically active than today. It launched $\sim$$10^2$ large, fast coronal mass ejections (CMEs) per year into a denser, more magnetized wind. We follow these eruptions to Earth's atmosphere with a semi-analytic model chain. We find that a CME launched at $v_0\sim3\text{--}4\e{3}\unit{km\,s^{-1}}$ dissipates $ΔE_k\sim6\e{25}\unit{J}$ as it decelerates, an amount set only by its launch and final speeds. Diffusive shock acceleration converts $\sim$10\% of this energy into solar energetic particles (SEPs), whose deposition depth depends mainly on a spectral break energy $E_b$. We show that the stronger field moves the Alfvén surface, inside which the magnetic field controls the wind, from $\sim$10--25$\,\Rsun$ to $\sim$40--60$\,\Rsun$, so CME shocks deliver over ten times the particle fluence of flares. Because the forcing is powered by deceleration, it follows the measured wind history ($\dot M\propto t^{-2.3}$) and declines as $\sim t^{-3}$. It was $\sim$50--100 times stronger at 3.9~Ga than at 2~Ga and several hundred times today's level. This decline, strongest when the Sun was faintest, is what greenhouse solutions of the faint young Sun (FYS) problem usually impose by hand. The magnitude is small: SEP-driven $\mathrm{N_2O}$ adds at most a few $\unit{W\,m^{-2}}$ to a 20--40$\unit{W\,m^{-2}}$ greenhouse requirement, and only if a fractal organic haze extends its lifetime. Counting energy deposited below a survival level near 1~hPa, we find the particles fix $\sim$$4\e{10}$--$4\e{11}\unit{mol\,N\,yr^{-1}}$, which could supply prebiotic feedstock to surface pools. The largest uncertainties are $E_b$, the event rate, the survival depth, and the $\mathrm{N_2O}$ lifetime.

astro-ph.SR↗

arXiv2026

Axial-Dipole and Equatorial-Dipole Coronal Holes: Congruent Magnetic Geometry, Divergent Evolution

While the Sun's polar fields reverse, the axial dipole is weak and low-latitude coronal holes are common. Equatorial-dipole coronal holes (EDCHs) appear when the equatorial dipole is strong, forming at its magnetic poles, similar to the axial-dipole coronal holes (ADCHs) of minimum. Not every low-latitude hole qualifies: the 2024 maximum was quadrupole-led. Parker Solar Probe found fast wind from an EDCH deeply sub-Alfvénic at $9.9\,R_\odot$, at only $60\%$ of an asymptotic speed matching polar wind, which is usually thought to accelerate faster. We ask whether coronal structure predicts this, using potential-field models of synthetic and observed fields at three cycle phases. We show that pure axial and equatorial dipoles are exactly congruent, with the same open areas and core expansion factors, so any difference must arise from orientation relative to the differential-rotation pattern or from the surrounding multipoles. We find that ADCHs are stationary, sustained by converging meridional flow, whereas EDCHs depend on an equatorial dipole that active-region emergence builds and flux transport dismantles: over $18$-day sequences the axial-dipole strength at minimum is steady to $1\%$, while the equatorial dipole varies by $21\%$ at maximum and $8\%$ in the declining phase. Most open flux in EDCHs expands less than in ADCHs, but their boundaries are pseudostreamer-dominated, with non-monotonic expansion. Despite these differences, magnetic geometry alone does not predict slower acceleration in EDCHs; we argue that any real difference points to extended heating by reflection-driven Alfvén-wave turbulence, perhaps fed differently at those boundaries, which potential-field models cannot capture.

astro-ph.SR↗

arXiv2026

Bifurcations in the Heliosphere: Global-scale Coronal Pseudostreamer Evolution and the Creation of Secondary Heliospheric Current Sheets

The heliospheric current sheet (HCS) is the boundary between open magnetic fields of opposite polarity in the solar wind that connect back to their respective open flux regions in the corona. The HCS is often described as a disc-like sheet warped by the combined effects of the inclination of the magnetic equator on the Sun, solar rotation, and solar wind expansion. The HCS is an extension of the helmet streamer belt-the closed-flux region resulting from the global dipole component of the observed photospheric magnetic field. In the absence of a strong dipole, a dominant quadrupole can result in two separate HCSs. Here we report on a set of idealized, axisymmetric solar wind simulations designed to study the transition of the single-HCS corona and inner heliosphere into a multiple-HCS configuration, run with the WindPredict-AW PLUTO MHD code. We systematically vary the relative strengths of the dipole/quadrupole contributions to the global field and show this results in the formation of a large-scale, closed-flux pseudostreamer that interacts with the ambient solar wind. We find that when the dipole and quadrupole magnitudes are approximately equal, our model corona can oscillate between a one- and two-HCS configuration on the timescale of days-to-weeks. We characterize the plasma dynamics of the transition of a global-scale pseudostreamer into a localized, secondary helmet-streamer belt with its own HCS surrounding a newly-opened, opposite-polarity coronal hole. We discuss the implications of our results for solar cycle evolution and the dynamic coupling of the highly structured corona and inner heliosphere.

astro-ph.SR↗