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Abstract This work identifies and characterizes magnetic structures, especially in terms of small‐scale magnetic flux ropes (SFRs), in the solar wind and magnetosheath across the Earth's bow shock. We investigate the differences between the properties of SFR structures in these regions immediately upstream and downstream of the bow shock by employing two data analysis methods: one based on wavelet transforms and the other based on the Grad‐Shafranov (GS) detection and reconstruction techniques. In situ magnetic field and plasma data from the Magnetospheric Multiscale and Time History of Events and Macroscale Interactions during Substorms missions are used to identify these coherent structures through the two approaches. We identify thousands of SFR event intervals with a range of variable duration over a total time period of 1,000 hr in each region. We report parameters associated with the SFRs such as scale size, duration, magnetic flux content, and magnetic helicity density, derived from primarily the GS‐based analysis results. These parameters are summarized through statistical analysis, and their changes across the bow shock are shown based on comparisons of their respective distributions. We find that in general, the distributions of various parameters follow power laws. The SFR structures seem to be compressed in the magnetosheath, as compared with their counterparts in the solar wind. A significant rotation in the ‐axis defining the orientation of the structures is also seen across the bow shock. We also discuss the implications for the elongation of the SFRs in the magnetosheath along one spatial dimension. 

Abstract We report recent findings for the magnetic field configurations of small‐scale magnetic flux ropes (SFRs) broadly defined and identified by using the Grad‐Shafranov‐based techniques for in situ measurements via the Parker Solar Probe (PSP), Solar Orbiter (SolO), and two Helios spacecraft. Since the current sheets were found to occur at boundaries of SFRs and/or inside SFRs at 1 AU via the partial variance increment (PVI) and the Grad‐Shafranov (GS) reconstruction technique by Pecora et al. (2019), we further examine such a co‐existence in this study by assessing the maximum PVI indices within SFR intervals using the above four spacecraft observations throughout the inner heliosphere (1 AU). Less than 15% of SFRs have maximum PVI indices exceeding a threshold value of 6 that is used to indicate a current sheet structure. Three representative events are selected to explain the most common situations. (a) Current sheets occur at SFR boundaries and near the center. Each could be a weak switchback feature in the time‐series profile of the gradually bipolar magnetic field rotations. (b) An SFR configuration is confirmed by both the measurement of counterstreaming electrons and the GS reconstruction result, despite that a large PVI value occurs near the SFR center which is due to an arbitrary kink instead of a current sheet. (c) A current sheet is falsely identified as an SFR where a significant PVI value (~7) occurs near the center. In the end, we discuss the necessity of using multi‐point spacecraft measurements to discern the structures associated with SFRs. 

Abstract The COVID-19 pandemic has profoundly impacted global economies and healthcare systems, revealing critical vulnerabilities in both. In response, our study introduces a sensitive and highly specific detection method for cDNA, leveraging Luminescence Resonance Energy Transfer (LRET) between upconversion nanoparticles (UCNPs) and gold nanoparticles (AuNPs), and achieves a detection limit of 242 fM for SARS-CoV-2 cDNA. This innovative sensing platform utilizes UCNPs conjugated with one primer and AuNPs with another, targeting the 5′ and 3′ ends of the SARS-CoV-2 cDNA, respectively, enabling precise differentiation of mismatched cDNA sequences and significantly improving detection specificity. Through rigorous experimental analysis, we established a quenching efficiency range from 10.4 % to 73.6 %, with an optimal midpoint of 42 %, thereby demonstrating the superior sensitivity of our method. Our work uses SARS-CoV-2 cDNA as a model system to demonstrate the potential of our LRET-based detection method. This proof-of-concept study highlights the adaptability of our platform for future diagnostic applications. Instrumental validation confirms the synthesis and formation of AuNPs, addressing the need for experimental verification of the preparation of nanomaterial. Our comparative analysis with existing SARS-CoV-2 detection methods revealed that our approach provides a low detection limit and high specificity for target cDNA sequences, underscoring its potential for targeted COVID-19 diagnostics. This study demonstrates the superior sensitivity and adaptability of using UCNPs and AuNPs for cDNA detection, offering significant advances in rapid, accessible diagnostic technologies. Our method, characterized by its low detection limit and high precision, represents a critical step forward in developing next-generation biosensors for managing current and future viral outbreaks. By adjusting primer sequences, this platform can be tailored to detect other pathogens, contributing to the enhancement of global healthcare responsiveness and infectious disease control. 

Abstract Flux transfer events (FTEs) are a type of magnetospheric phenomena that exhibit distinctive observational signatures from the in situ spacecraft measurements. They are generally believed to possess a magnetic field configuration of a magnetic flux rope and formed through magnetic reconnection at the dayside magnetopause, sometimes accompanied with enhanced plasma convection in the ionosphere. We examine two FTE intervals under the condition of southward interplanetary magnetic field (IMF) with a dawn‐dusk component. We apply the Grad‐Shafranov (GS) reconstruction method to the in situ measurements by the Magnetospheric Multiscale (MMS) spacecraft to derive the magnetic flux contents associated with the FTE flux ropes. In particular, given a cylindrical magnetic flux rope configuration derived from the GS reconstruction, the magnetic flux content can be characterized by both the toroidal (axial) and poloidal fluxes. We then estimate the amount of magnetic flux (i.e., the reconnection flux) encompassed by the area “opened” in the ionosphere, based on the ground‐based Super Dual Auroral Radar Network (SuperDARN) observations. We find that for event 1, the FTE flux rope is oriented in the approximate dawn‐dusk direction, and the amount of its total poloidal magnetic flux falls within the range of the corresponding reconnection flux. For event 2, the FTE flux rope is oriented in the north‐south direction. Both the FTE flux and the reconnection flux have greater uncertainty. We provide a detailed description about a formation scenario of sequential magnetic reconnection between adjacent field lines based on the FTE flux rope configurations from our results. 

Abstract Magnetic flux rope, a type of magnetic field structure in space plasmas, has been studied for decades through both observational and theoretical means. We provide a brief report on our recent modeling study of its magnetic field configuration based on in-situ spacecraft measurements, focusing on those made for large-scale flux ropes in the interplanetary space. We illustrate the complexity in its field-line topology by presenting two event studies employing a unique analysis method. In particular, we demonstrate the feasibility and challenges for the approach to use two or more in-situ spacecraft datasets. We discuss the implications of our results and offer some thoughts on further advancing the investigation of the nature of the magnetic flux rope. 

Abstract We reconstruct the morphology and kinematics of a series of small transients that erupted from the Sun on 2021 April 24 using observations primarily from Parker Solar Probe (PSP). These sequential small coronal mass ejections (CMEs) may be the product of a continuous reconnection at a current sheet, which is a macroscopic example of the more microscopic reconnection activity that has been proposed to accelerate the solar wind more generally. These particular CMEs are of interest because they are the first CMEs to hit PSP and be simultaneously imaged by it, using the Wide-field Imager for Solar Probe (WISPR) instrument. Based on imaging from WISPR and STEREO-A, we identify and model six discrete transients, and determine that it is the second of them (CME2) that first hits PSP, although PSP later more obliquely also encounters the third transient. Signatures of these encounters are seen in the PSP in situ data. Within these data, we identify six candidate magnetic flux ropes (MFRs), all but one of which are associated with the second transient. The five CME2 MFRs have orientations that are roughly consistent with PSP encountering the right-hand sides of roughly E-W oriented MFRs, which are sloping back toward the Sun. 

Abstract Understanding the mechanisms underlying the heating of the solar atmosphere is a fundamental problem in solar physics. In this paper, we present an overview of our research on understanding the heating mechanism of the solar active region atmosphere in chromosphere. We investigate Joule heating due to the dissipation of currents perpendicular to the magnetic field by the Cowling resistivity using a data-constrained analysis based on observational and tabulated theoretical/semi-empirical solar atmosphere model data. As target region, we focus on a sunspot umbral light bridge where we find that this heating mechanism plays an important role and is also highly dynamic. 

Abstract Using in situ measurements from the Parker Solar Probe and Wind spacecraft, we investigate the small-scale magnetic flux ropes (SFRs) and their properties inside stream interaction regions (SIRs). Within SIRs from ∼0.15 to 1 au, SFRs are found to exist in a wide range of solar wind speeds with more frequent occurrences after the stream interface, and the Alfvénicity of these structures decreases significantly with increasing heliocentric distances. Furthermore, we examine the variation of five corresponding SIRs from the same solar sources. The enhancements of suprathermal electrons within these SIRs persist at 1 au and are observed multiple times. An SFR appears to occur repeatedly with the recurring SIRs and is traversed by the Wind spacecraft at least twice. This set of SFRs has similarities in variations of the magnetic field components, plasma bulk properties, density ratio of solar wind alpha and proton particles, and unidirectional suprathermal electrons. We also show, through the detailed time-series plots and Grad–Shafranov reconstruction results, that they possess the same chirality and carry comparable amounts of magnetic flux. Lastly, we discuss the possibility for these recurring SFRs to be formed via interchange reconnection, maintain the connection with the Sun, and survive up to 1 au.