Astronomy

We construct a systematic general-relativistic model of the spacetime generated by a slowly rotating, axially symmetric, self-gravitating clump of collisionless matter whose gravitational potential is of Miyamoto–Nagai type. The metric is taken in a three-function cylindrical gauge, , with the frame-dragging function $\omega$ added at the stationary level. We prove a no-go lemma of explicitly delimited scope (no pointwise relation can annihilate the off-diagonal Ricci component) and reduce the field equations, for a diagonal source, to an algebraic system for $b_{\rho },b_z$ valid wherever ${(\nabla W)}^2\ne 0$, $W=\rho e^{(a+c)/2}$. The integrability of the resulting quadrature is not automatic: we prove that the compatibility condition is exactly equivalent to the meridional matter-conservation equations—one combination of which is an identity, the other being the equation that determines the remaining metric function—and that at second order in it becomes the linear Poisson-type problem . A barotropy criterion shows that a prescribed flattened potential with strictly isotropic pressure is already inconsistent at the Newtonian level, whereas the Miyamoto–Nagai potential admits a globally physical anisotropic solution: density, meridional pressure and stress anisotropy follow in closed form, and , all of definite sign, so that $P_{\varphi }>P_m$ everywhere off the axis and the anisotropy vanishes identically in the spherical limit. Rotation is included to Hartle order: the dragging obeys a linear equation at all orders in our gauge, the second-order diagonal metric is degenerate under the dispersion–rotation partition of the azimuthal support, and the degeneracy is broken only by the gravitomagnetic sector; the fully rotational realization gives $v_{\varphi }/v_c$ in closed form, which is near-circular for thin discs. On this basis we assess detectability: the flattening layer is routinely observable, with a deflection anisotropy decaying anomalously slowly (as $A/b$); galactic frame dragging (∼${10}^{-3}$μas ${\mathrm{yr}}^{-1}$) is astrometrically hopeless, but the parity-odd rotational asymmetry of time delays between opposite-side images of strongly lensed transients, s, is detectable in principle given VLBI-grade (∼10 μas) astrometry, the threshold being at disc-galaxy velocities; in the compact regime the model yields falsifiable energy-condition bounds ( , ) and dragging frequencies in the QPO band.

Ground-based neutron monitor observations are essential for investigating long-term galactic cosmic ray (GCR) variability, but their measurements are significantly affected by geomagnetic shielding and atmospheric conditions. This study presents a comparative analysis of GCR observations from the Tashkent (Uzbekistan) and Almaty (Kazakhstan) neutron monitor stations to evaluate the combined effects of geomagnetic cutoff rigidity ($R_{\mathrm{c}}$) and atmospheric pressure. Long-term datasets were analyzed using station-specific barometric corrections and regression methods. The results show that the high-altitude Almaty station (3340 m; $R_{\mathrm{c}}\approx 6.4$–$6.7$ GV) is more sensitive to lower-energy cosmic rays than the lower-altitude Tashkent station (400–500 m; $R_{\mathrm{c}}\approx 7.3$–$7.5$ GV). A strong inverse relationship was found between atmospheric pressure and neutron monitor intensity, with barometric coefficients of for Almaty and for Tashkent. Correlation analysis of the atmospheric-pressure dependence yielded $R\approx 0.92$–$0.95$, whereas the multifactor regression analysis used for atmospheric correction yielded a coefficient of determination of $R^2\approx 0.97$. These findings demonstrate that station-specific atmospheric corrections and consideration of geomagnetic conditions significantly improve the accuracy of long-term neutron monitor observations for GCR and regional space-weather studies.

Subauroral geospace is a dynamic region. Its various features include Subauroral Polarization Streams (SAPS), hot and cold zones, and storm enhanced densities (SED). Previous studies have covered the nightside, leaving the dayside largely unexplored and poorly understood. This study investigates the prenoon and midday sectors, based on multi-instrument, multipoint observations. In the inner magnetosphere, the observed dayside SAPS’ development was set off by solar-wind flow pressure increases compressing the dayside magnetosphere in the equatorial plane and triggering earthward-directed hot plasma surges or particle injections in the coupled Alfvenic solar wind and dayside magnetosphere. The dayside SAPS developed in an inner-magnetosphere voltage generator and appeared sometimes within the cold zone where the isotropic ion temperature (Ti_‖ ≈ Ti_⊥) minimized and sometimes within the hot zone fueled by whistler-mode chorus waves locally enhancing the field-aligned temperature anisotropy (T_‖ > T_⊥) and providing localized plasma heating both via Landau damping and implicitly. In the ionosphere, the observed dayside SAPS’ development was unfolding in a prenoon eastward auroral electrojet (AEJ) scenario on the dawnside and in a midday westward AEJ scenario on the duskside. The observed dayside SAPS mapped down to the noontime SED plume base depicted by the total electron content maps.