An alternative theory of magnetic flux tubes in strong fields via axion origin photons

TL;DR

The paper proposes an axion-based alternative to the solar dynamo, where axion-origin photons mediate energy transport in strongly magnetized flux tubes and drive sunspot cycles. It integrates Parker-Biermann cooling and the Ettingshausen-Nernst effect with axion-photon oscillations near the tachocline, positing anticorrelated 11-year variations between ADM density and solar axion/photon flux. With three defining parameters—$B_{tacho} \sim 10^7$ G, $m_a \sim 3.2\times10^{-2}$ eV, and $m_{ADM} \sim 5$ GeV—the framework yields a universal van Ballegooijen-Fan-Fisher description of flux-tube rise and reconnection, accounting for rise times, flux budgets, Joy's law tilts, and the Gnevyshev-gap double maxima. The approach offers testable predictions linking solar axions and ADM dynamics to solar activity and potential Earth climate correlations, suggesting new avenues for detecting axions and probing DM in the solar environment.

Abstract

In our alternative theory, built around the coincidence of experimental and theoretical data, three "free" parameters -- the magnetic field in the tachocline of the order of ~10^7 G (see Fig.(A.1) and Eq.(A17) in V. D. Rusov et al. (2021)), the axion mass ma ~3.2*10^{-2} eV (see Eq. (11) in V. D. Rusov et al. (2021)), and the asymmetric dark matter (ADM) in the Universe with mADM ~5 GeV ((see V. D. Rusov et al. (2021); A. C. Vincent et al. (2016)) -- give a complete solution to the problem of the theory of magnetic flux tubes in strong fields with 11-year variations of axion-origin photons, which are caused by and anticorrelated to the 11-year variations in density of ADM, gravitationally captured on the Sun.

Figures (13)

• Figure 1: An illustration of the main possible processes of a magnetically active star of the Sun type. (a) $\alpha$-effect, $\Omega$-effect and BL mechanism as components of the solar dynamo model. The $\Omega$-effect (blue) depicts the transformation of the primary poloidal field into a toroidal field by differential rotation. Regeneration of the poloidal field is then performed either by the $\alpha$-effect (top) or by the BL mechanism (yellow in the middle). In case of $\alpha$-effect, the toroidal field at the base of the convection zone is subject to cyclonic turbulence. In the BL mechanism, the main process of regeneration of the poloidal field (based on the $\Omega$-effect (blue)) is the formation of sunspots on the surface of the Sun from the rise of buoyant toroidal flux tubes from the base of the convection zone. The magnetic fields of these sunspots closest to the equator in each hemisphere diffuse and join, and the field due to the spots closer to the poles has a polarity opposite to the current that initiates rotation of the polarity. The newly formed polar magnetic flux is transported by the meridional flow to deeper layers of the convection zone, thereby creating a new large-scale poloidal field. Derived from Sanchez2014. (b) 11-year variations of sunspot magnetic fields as a component of the solar anti-dynamo. The formation of the thermomagnetic EN effect (see Spitzer1962Spitzer2006Rusov2015), emphasizes that this process is associated with the continuous transformation of toroidal field into poloidal one ($T \rightarrow P$ transformation), but not vice versa ($P \rightarrow T$). For this purpose, we note (seeRusovDarkUniverse2021) that the modulations of the ADM halo in the Galactic Center (GC), which is an indicator of the periods of S-stars, e.g. S-102 with a period of about 11 years, lead (via vertical density waves from the black hole to the solar neighborhood) to modulations of the ADM density, gravitationally trapped in the interior of the Sun. This means that anticorrelation modulations of the ADM density control the solar luminosity or sunspot cycles, in which the sunspot variations are identical to the 11-year variations of the magnetic flux tubes (see Section \ref{['sec-empty-tubes']}): maximum (red lines) and minimum (green-red lines).
• Figure 2: (a) Summary of astrophysical, cosmological and laboratory constraints on axions. Comprehensive axion parameter space, highlighting two main front lines of direct detection experiments: helioscopes (CAST CAST2017) and haloscopes (ADMX Asztalos2010, and RBF Wuensch1989 and microwave resonators Brubaker2017Zhong2018Braine2020Lee2020Backes2021). The astrophysical bounds from horizontal branch and massive stars are labeled "HB" Raffelt2008 and "Cepheids" Carosi2013, respectively, and there are also astrophysical hints (WD cooling hints, and HB hint). The QCD motivated models (KSVZ Kim1979Shifman1980) for axions lay in the yellow diagonal band. A plot of $g_{a\gamma}$ versus $m_a$ with the most stringent results (solid lines) and sensitivity perspectives (dashed lines) of observations and experiments directly comparable to the different phases of IAXO are shown, BabyIAXO, IAXO, and an upgraded version of IAXO, IAXO+. The yellow band denotes the region of the parameter space favoured by QCD axion models. The red star marks the values of the axion mass $m_a \sim 3.2 \cdot 10^{-2}~eV$ and the axion-photon coupling constant $g_{a\gamma} \sim 4.4\cdot 10^{-11}~GeV^{-1}$, which were first obtained experimentally (see RusovDarkUniverse2021). (b) $R$ parameter constraints, which compares the numbers of stars in the the horizontal branch (HB) and in the upper portion of the red giant branch (RGB), to helium mass fraction $Y$ and axion coupling $g_{a\gamma}$ (adopted from Ayala2014). The resulting bound on the axion ($g_{10} = g_{a\gamma} / (10^{-10}~GeV^{-1})$ is somewhere between rather conservative $0.5 < g_{10} < 0.8$ and most aggressive $0.35 < g_{10} < 0.5$Friedland2013. The red line marks the value of the axion–photon coupling constant $g_{a\gamma} \sim 4.5\cdot 10^{-11}~GeV^{-1}$ adopted from Eq. (2) in Ayala2014. The blue shaded area represents the bounds from Cepheids observation. The yellow star corresponds to $Y=0.254$ and the bounds from HB lifetime (yellow dashed line).
• Figure 3: Topological effects of magnetic reconnection inside the magnetic tubes with the "magnetic steps" (Fig. B.1 in RusovDarkUniverse2021). The left panel shows the temperature and pressure change along the radius of the Sun from the tachocline to the photosphere Bahcall1992, $L_{MS}$ is the height of the magnetic shear steps. At $R \sim 0.72~R_{Sun}$ the vertical magnetic field, which is developed from the horizontal part of the magnetic field (step) with the participation of the O-loop through the well-known Kolmogorov turbulent cascade (see Fig. \ref{['fig-Kolmogorov-cascade']}), reaches $B_z \sim 3600$ T, and the magnetic pressure $p_{ext} = B^2 / 8\pi \simeq 5.21 \cdot 10^{13}~erg/cm^3$Bahcall1992. The very cool regions along the entire convective zone caused by the Parker-Biermann cooling effect have the virtually zero internal gas pressure, i.e. the maximum magnetic pressure in the magnetic tubes. The narrow "purple" rings between the O-loop and the tube walls ($\rho_{ext} = \rho_{int}^0 \gg \rho_{int}$) with the Parker-Bierman cooling effect inside, are a very important result of the existence of convective heating $(dQ/dt)_2$ in Section \ref{['sec-heating']}.
• Figure 4: Kolmogorov turbulent cascade Kolmogorov1941Kolmogorov1968Kolmogorov1991 and primary magnetic reconnection (which differs sharply from the secondary (see Fig. \ref{['fig-lower-reconnection']}b) in the lower layers inside the unipolar magnetic tube (Fig. B.2 in RusovDarkUniverse2021). Common to these various turbulent systems is the presence of the inertial region of Kolmogorov, through which the energy is cascaded from large to small scales. In this case, dissipative mechanisms (as a consequence of the "primary" magnetic reconnection) overcome the turbulent energy during plasma heating.
• Figure 5: Sketch of primary or secondary magnetic reconnection near the tachocline. (a) The $\Omega$-loop forms a sunspot shadow (with photons of axion origin from O-loops associated with the primary reconnection) due to the indirect thermomagnetic EN effect in the tachocline, but without secondary reconnection; (b) The $\Omega$-loop with a spot in the presence of secondary reconnection, but without photons of axion origin (see b,c); the pink arrows show the upward convective flow between the "legs" of the $\Omega$-loop as it rises from the tachocline to the visible surface of the Sun; (c) The $\Omega$-loop with secondary reconnection and without a sunspot; (d) The O-loop without spots and reconnection. Passing stages (a), (b), (c) (from left to right), the convection around the ascending $\Omega$-loop "closes" it at the base (d) and, thus, a free O-loop is formed, and the initial configuration of the azimuthal field is restored near the tachocline. The blue arrows show the motion of matter leading to the connection of the "legs" of the loop and their "flying away" from the surface of the Sun.