Astrophysical Jets : what can we learn from Solar Ejections?

Ejections from the Sun can be observed with a higher resolution than in any other astrophysical object: can we build up on solar results and apply them to astrophysical objects? Aim of this work is to establish whether there is any analogy between solar ejections and ejections in microquasars and AGNs. Briefly reviewing jets properties from these objects and from the Sun, we point out some characteristics they share and indicate research areas where cross-breeeding between astrophysical and solar research is likely to be productive. Preliminary results of this study suggest, for instance, that there may be an analogy between blobs created by tearing instability in current sheets (CSs) associated with solar coronal mass ejections (CMEs) and quasi periodic ejections of plasma associated with large radio outbursts in microquasars.

💡 Research Summary

The paper investigates whether the detailed physics of solar eruptions can inform our understanding of jets in microquasars and active galactic nuclei (AGN). By exploiting the unparalleled spatial and temporal resolution of solar observations—particularly of coronal mass ejections (CMEs) and the associated current sheets (CSs)—the authors identify a set of common physical ingredients that appear to operate across vastly different mass and length scales.

Solar CMEs are shown to generate thin, elongated current sheets in which the tearing‑mode instability repeatedly fragments the sheet into a chain of magnetic islands, or plasmoids. These plasmoids (often called “blobs”) are observed in EUV, soft X‑ray, and radio data as discrete, high‑density structures that accelerate from a few hundred to several thousand kilometres per second. Their formation period, size, and velocity are governed by the local plasma β, the current density, and the reconnection rate, all of which can be measured or inferred from solar instrumentation.

In microquasars such as GRS 1915+105 and Cyg X‑1, large radio outbursts are frequently accompanied by quasi‑periodic ejections of compact plasma condensations. These ejections appear on timescales of seconds to minutes, exhibit synchrotron spectra consistent with freshly accelerated electrons, and are often coincident with hard X‑ray spikes that signal rapid magnetic reconnection near the black‑hole accretion disk. Similar, though less temporally resolved, episodic features are seen in AGN jets (e.g., knot formation in M87 or 3C 273) where VLBI imaging reveals moving bright spots that can be interpreted as plasmoids traveling down the jet.

The authors argue that the tearing‑mode fragmentation of a reconnecting current sheet provides a natural, scale‑invariant mechanism for producing these episodic blobs. In the solar context, the instability is triggered when the Lundquist number exceeds a critical value, leading to a cascade of plasmoids whose spacing and growth follow a power‑law distribution. By applying the same MHD framework to the relativistic, high‑magnetisation environments of microquasars and AGN, one can predict analogous plasmoid chains whose observable signatures would be the quasi‑periodic radio flares and moving VLBI knots.

Key insights include: (1) the current sheet is the universal site of energy conversion, regardless of whether the background plasma is solar coronal material or relativistic jet plasma; (2) the characteristic timescale of plasmoid formation scales with the Alfvén crossing time of the sheet, which itself scales with system size and magnetic field strength, providing a simple scaling law that links seconds‑scale solar events to hour‑scale microquasar events and year‑scale AGN phenomena; (3) high‑resolution solar MHD and kinetic simulations, already validated against spacecraft data, can be directly transplanted to model jet reconnection zones, offering a predictive tool for jet variability; (4) upcoming facilities such as the Square Kilometre Array (SKA) and the Athena X‑ray observatory will deliver the temporal resolution needed to test these predictions in extragalactic sources.

The paper concludes by outlining a research roadmap: (i) coordinated multi‑wavelength campaigns that monitor solar CMEs, microquasar outbursts, and AGN jet knots simultaneously, enabling cross‑comparison of plasmoid statistics; (ii) systematic parameter studies that map the dependence of tearing‑mode growth rates on relativistic effects, guide‑field strength, and plasma composition; (iii) development of a unified scaling framework that translates solar reconnection rates into jet‑scale reconnection rates, thereby bridging the gap between heliophysics and high‑energy astrophysics. By fostering this cross‑disciplinary dialogue, the authors anticipate that the rich phenomenology of solar eruptions will become a laboratory for deciphering the universal physics of astrophysical jets.