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Mirabbos Mirkamalov

Publications and source records attributed to Mirabbos Mirkamalov.

2 recordsLinked to original sources

Relationship of ICME Composition Signatures with Solar Activity during 2009-2025

Coronal Mass Ejections (CMEs) are among the most energetic solar eruptions, expelling magnetized plasma from the corona into interplanetary space. Their interplanetary counterparts, known as Interplanetary Coronal Mass Ejections (ICMEs), retain distinct compositional signatures that reflect the physical conditions of their solar source regions. This study presents a statistical analysis of ICME composition dependence on solar activity during 2009--2025, covering Solar Cycle (SC) 24 and the ascending phase of SC~25 through its maximum, and compares the results with SC~23 studied by \citet{Song+etal+2021}. Using data from the Solar Wind Ion Composition Spectrometer (SWICS) aboard the Advanced Composition Explorer (ACE), we examined the average iron charge state ($\langle Q_{\rm Fe}\rangle$), ionic ratios (C$^{6+}$/C$^{5+}$ and O$^{7+}$/O$^{6+}$), and the elemental abundance ratio (Fe/O) for 307 ICMEs listed in the Richardson and Cane ICME catalog. The results show strong positive correlations of $\langle Q_{\rm Fe}\rangle$ ($r$~=~0.86) and O$^{7+}$/O$^{6+}$ ($r$~=~0.85) with the annual sunspot number (SSN), whereas C$^{6+}$/C$^{5+}$ exhibits a weak correlation ($r$~=~0.17) primarily due to SWICS~2.0 upper-end saturation truncation that suppresses the solar maximum signal, and Fe/O a moderate correlation ($r$~=~0.57). The Fe/O ratio, a proxy for the First Ionization Potential (FIP) effect, displayed elevated values during the maxima of both SC~24 and SC~25, suggesting enhanced elemental fractionation during periods of increased magnetic activity. Comparing with SC~23, we find that the overall solar cycle dependence of ICME composition persists across cycles, though with notable quantitative differences attributed to the different magnetic activity levels between cycles. These findings confirm that ICME compositional signatures are strongly modulated by the solar cycle.

astro-ph.SR↗

What Causes the Asymmetry of Conjugate Hard X-Ray Footpoints in Solar Flares?

Hard X-ray (HXR) emission in solar flares critically diagnoses nonthermal electron acceleration, transport, and precipitation. Observations commonly show asymmetric HXR photon fluxes between paired footpoints, whose physical origin remains debated, as the conventional magnetic mirroring mechanism often fails to explain the observed asymmetry. Here we performed rigorous statistical tests on the association between photospheric magnetic parameters within the HXR footpoint regions and the asymmetry of HXR production. We analyzed 103 time intervals taken from around the peaks of HXR bursts in 67 M- and X-class flares with a clear double-ribbon morphology observed by both the Ramaty High Energy Solar Spectroscopic Imager and the Solar Dynamics Observatory. We found that conjugate HXR footpoint sources are asymmetric in photon fluxes, maximum intensities, and sizes, but rather symmetric in mean intensities. The photon flux ratio of the stronger over weaker footpoint source shows a strong linear correlation with the size ratio and a nonlinear correlation with the maximum intensity ratio. The asymmetry of magnetic field strength and flux at the conjugate footpoints shows a positive correlation with the HXR asymmetry, contrary to what magnetic mirroring effects predict. Importantly, the asymmetry of unsigned photospheric vertical electric current (PVEC) exhibits a strong positive correlation with the HXR footpoint asymmetry. PVEC at HXR footpoints most likely maps the footprints of coronal current layers where flaring reconnections occur. This tight linkage suggests that the electric-current-associated physical processes, including reconnection-induced electric fields and current-driven micro-turbulence, are at work to modulate the production and precipitation of nonthermal electrons.

astro-ph.SR↗