Electron Flux Research Articles

Towards a complete description of the reaction mechanisms between nitrenium ions and water.

Nitrenium ions are intermediates in the metabolic routes producing the highly carcinogenic nitrosamines and binding to DNA molecules. The reaction mechanism of nitrenium molecules with explicit water molecules is sensibly dependent on the number of waters: when a second molecule is involved, it acts as a catalyst for the reaction, lowering intrinsic activation barriers regardless of the substituent. For all cases, the reaction force constants and reaction electron flux indicate highly synchronous reactions for . Conversely, for highly non-synchronous reactions are obtained, involving two separate proton transfers happening early and late in the reaction path. As a test case, for the simplest reactions, orbital interactions within the NBO paradigm, bond orders, and their derivatives indicate that each individual proton transfer is highly synchronous. Molecular geometries were optimized and characterized at the B3LYP/6-311++G(d, p) level. Intrinsic reaction coordinates were calculated. CCSD(T) single point energies with the same basis were computed on all stationary points. The reaction force, reaction force constant, and reaction electron flux are used to study the evolution of the reacting systems. Natural bond orbitals are used to understand the primitive changes driving the reaction.

Predicting the Energetic Proton Flux with a Machine Learning Regression Algorithm

The need for real-time monitoring and alerting systems for space weather hazards has grown significantly in the last two decades. One of the most important challenges for space mission operations and planning is the prediction of solar proton events (SPEs). In this context, artificial intelligence and machine learning techniques have opened a new frontier, providing a new paradigm for statistical forecasting algorithms. The great majority of these models aim to predict the occurrence of an SPE, i.e., they are based on the classification approach. This work is oriented toward the successful implementation of onboard prediction systems, which is essential for the future of space exploration. We present a simple and efficient machine learning regression algorithm that is able to forecast the energetic proton flux up to 1 hr ahead by exploiting features derived from the electron flux only. This approach could be helpful in improving monitoring systems of the radiation risk in both deep space and near-Earth environments. The model is very relevant for mission operations and planning, especially when flare characteristics and source location are not available in real time, as at Mars distance.

Sirtuin-dependent reversible lysine acetylation of the o-succinylbenzoyl-coenzyme A synthetase of Bacillus subtilis.

Reversible lysine acylation (RLA) is a conserved posttranslational modification that cells of all domains of life use to regulate the biological function of proteins, some of which have enzymatic activity. Many AMP-forming organic acid:CoA ligases are regulated via acylation in prokaryotes and eukaryotes. Here, we report the acetylation of the o-succinylbenzoyl-CoA synthetase (EC 6.2.1.26) of Bacillus subtilis (BsMenE) by the GCN5-related acetyltransferase (GNAT) AcuA enzyme of this bacterium. BsMenE is part of the metabolic pathway that assembles menaquinone (MK), an essential component of the electron transport chain in B. subtilis. We demonstrate that the active-site lysine 471 (K471) of BsMenE is acetylated specifically by BsAcuA, and that acetylated BsMenE (BsMenEAc) is deacetylated by the NAD+-dependent sirtuin (BsSrtN) of this bacterium. The in vivo analyses performed in this study were done in an Escherichia coli ΔmenE strain because the enzymatic activity of MenE is essential in B. subtilis, but not in E. coli. The use of a heterologous system allowed us to assess the effect of acetylation on BsMenE function under MK-dependent growth conditions. Based on our in vivo data, we suggest that regulation of BsMenE by RLA reduces MK production, negatively affecting the growth rate and yield of the culture.IMPORTANCEReversible lysine acylation (RLA) is a posttranslational modification used by all cells to rapidly control the biological function of proteins. Herein, we identify an acetyltransferase and deacetylase in the soil bacterium Bacillus subtilis that can modify/demodify an enzyme required for the synthesis of menaquinone (MK), an essential electron carrier involved in respiration in cells of all domains of life. Based on our data, we suggest that under some as-yet-undefined physiological conditions, B. subtilis modulates MK biosynthesis, which changes the flux of electrons through the electron transport chain of this bacterium. To our knowledge, this is the first example of control of respiration by RLA.

Coastal <i>Synechococcus</i> strains can exploit low oxygen habitats

We found that PhycoErythrin-rich <i>Synechococcus</i> achieved faster growth rates (µ), across the spectral bandwidths from 405 – 730 nm, under 2.5 µM [O<sub>2</sub>], characteristic of Oxygen Minimum Zones (OMZs), than under 250 µM [O<sub>2</sub>], whereas PhycoCyanin-rich strain showed generally similar µ under 2.5 and 250 µM [O<sub>2</sub>]. For PhycoCyanin- and PhycoErythrin-rich <i>Synechococcus</i>, µ showed also positive linear responses to both Phycobiliproteins:Chlorophyll <i>a</i>, and to cumulative diel PSII electron flux, although the relations vary across strain and [O<sub>2</sub>]. Electron transport downstream of Photosystem II was generally higher for both PhycoCyanin- and PhycoErythrin-rich strains under 250 µM [O<sub>2</sub>], since cyanobacteria show strong capacity for electron flow away from PSII to O<sub>2</sub>, particularly under excess excitation. Even though electron transport was faster under 250 µM [O<sub>2</sub>], the PhycoErythrin-rich strain showed a higher growth yield of electron transport under 2.5 µM [O<sub>2</sub>]. PhycoErythrin-rich <i>Synechococcus</i> are currently typically found at greater depths, and lower light, than are PhycoCyanin-rich strains, but we suggest that the PhycoErythrin-rich strains are actually limited to lower light by an interaction between light and full air-saturated [O<sub>2</sub>]. In expanding Oxygen Minimum Zones PhycoErythrin-rich strains will likely exploit higher light niches, across a wider spectral range.

The modified 6-chromanol SUL-238 protects against accelerated vascular aging in vascular smooth muscle Ercc1-deficient mice

Introduction: Vascular aging is marked by increased mitochondrial reactive oxygen species (ROS) production, which leads to decreased nitric oxide (NO)-mediated vasodilation. Loss of NO can be partially compensated by endothelium-derived hyperpolarization (EDH), which partly relies on increased mitochondrial Ca2+ release to maintain vascular dilation. Thus, intervention in mitochondria may target both NO and EDH signaling to alleviate aging-related vascular dysfunction. DNA damage by mitochondrial ROS is an important cause of organismal aging. Previous work showed that local vascular Ercc1 knockout dramatically accelerates vascular aging. The aim of the study was to investigate the effect of chronic treatment with the modified 6-chromanol, SUL-238, an inhibitor of mitochondrial reverse electron flux and ROS, in a mouse model of accelerated vascular smooth muscle aging induced by DNA repair endonuclease Ercc1 knockout (SMC-KO). Aim: The aim of the study was to investigate the effect of chronic treatment with the modified 6-chromanol, SUL-238, an inhibitor of mitochondrial reverse electron flux and ROS, in a mouse model of accelerated vascular smooth muscle aging induced by DNA repair endonuclease Ercc1 knockout (SMC-KO). Methods: SMC-KO mice and healthy wild-type littermates received SUL-238 (90 mg/kg/day) in drinking water from 12 to 22 weeks of age. At the age of 21 weeks, arterial stiffness was measured in vivo with echography and they were euthanized at the age of 22 weeks. Ex vivo vascular function was assessed in wire myography setups and mitochondrial function of the thoracic aorta was assessed using a seahorse assay. Results: SMC-KO mice showed reduced EDH-mediated vasodilation, elevated arterial stiffness, and increased elastin breaks at 22 weeks of age compared to their wild-type littermates. SUL-238 improved EDH, thus restoring aortic and mesenteric relaxation in SMC-KO mice. Furthermore, the number of elastin breaks was reduced and arterial stiffness normalized after treating SMC-KO mice with SUL-238. Mitochondrial respiration measured in the aorta was not different between the groups. Conclusion: Chronic treatment with SUL-238 alleviates features of vascular aging, including decreased vasodilation and increased arterial stiffness. SUL-238 seems to have a more general effect on aging rather than involving a direct coupling between mitochondrial function and vascular signaling. SUL-238 is the first small-molecule drug reported to increase EDH after chronic treatment.

Observations of solar cosmic rays using cubesat nanosatellites

We discussed the possibilities of using cubesat nanosatellites for studying solar cosmic rays. SCR electron fluxes in the polar caps at an altitude of ~550 km were detected. The measurements were carried out with DeCoR scintillation detectors operated at several cubesats of Moscow State University during the solar cosmic ray event on September 6–21, 2022.

Comparison of interfacial injected energy between simulated lightning return stroke experiment and common Joule heat & Arc heat model application

A previous study has shown that the thermal damage of the Joule thermal arc heat transfer model is lighter than that of a natural lightning strike. Therefore, this paper focuses on the return stroke current and proposes an improved experimental method of simulated return damage without using arc-inducing wire. Combining the data with the inversion model of injected energy, the energy transfer characteristics of the samples are characterized. Furthermore, a data dimensionality reduction method based on multiple correlation coefficients is used to discuss the impact of the current peak/rise rate/wave tail time on the injected energy discrepancy. The results indicate a positive correlation between the current peak and current rise rate with the injected energy discrepancy. When the tail time exceeds 15 microseconds, the injected energy discrepancy decreases as the tail time increases. The thermal source characteristics of energy transfer during the return stroke process are determined. During the initial phase of the return stroke current, interfacial energy transfer includes contributions from ion enthalpy flux, Joule heating, and electronic enthalpy flux. When the tail time exceeds 15 microseconds, the contribution of ion enthalpy flux to the injected energy diminishes with increasing tail time.

Lightning-induced relativistic electron precipitation from the inner radiation belt.

The Earth's radiation belts are maintained by a number of acceleration, loss and transport mechanisms, and the electron fluxes at any given time are highly variable. Microbursts, which are rapid (sub-second) bursts of energetic electrons entering the atmosphere from the magnetosphere, are one of the key loss mechanisms controlling radiation belt fluxes. Such rapid bursts are typically observed from the outer radiation belt and driven by interactions with whistler mode chorus waves, but they can also occur in the inner belt and slot region, driven by lightning-generated whistlers. This lightning-induced electron precipitation is typically observed at 10s-100s keV, but here we present direct observations of this phenomenon at MeV energies. This unveils a coupling between near-Earth processes, such as lightning, and radiation belt processes, such as relativistic electron microbursts, bridging the gap between Earth weather and space weather.

Omnidirectional Energetic Electron Fluxes From 150 to 20,000 km: An ELFIN‐Based Model

AbstractThe strong variations of energetic electron fluxes in the Earth's inner magnetosphere are notoriously hard to forecast. Developing accurate empirical models of electron fluxes from low to high altitudes at all latitudes is therefore useful to improve our understanding of flux variations and to assess radiation hazards for spacecraft systems. In the present work, energy‐ and pitch‐angle‐resolved precipitating, trapped, and backscattered electron fluxes measured at low altitude by Electron Loss and Fields Investigation (ELFIN) CubeSats are used to infer omnidirectional fluxes at altitudes below and above the spacecraft, from 150 to 20,000 km, making use of adiabatic transport theory and quasi‐linear diffusion theory. The inferred fluxes are fitted as a function of selected parameters using a stepwise multivariate optimization procedure, providing an analytical model of omnidirectional electron flux along each geomagnetic field line, based on measurements from only one spacecraft in low Earth orbit. The modeled electron fluxes are provided as a function of ‐shell, altitude, energy, and two different indices of past substorm activity, computed over the preceding 4 hr or 3 days, potentially allowing to disentangle impulsive processes (such as rapid injections) from cumulative processes (such as inward radial diffusion and wave‐driven energization). The model is validated through comparisons with equatorial measurements from the Van Allen Probes, demonstrating the broad applicability of the present method. The model indicates that both impulsive and time‐integrated substorm activity partly control electron fluxes in the outer radiation belt and in the plasma sheet.

The Global Characteristics of Electrons Near the Inner Edge of the Inner Radiation Belt

AbstractEnergetic electrons around the inner edge of the inner radiation belt (L1.3) have not been studied to the extent of the rest of the inner belt and certainly not to that of the outer radiation belt. Yet, the behavior of electrons at the inner edge of the inner belt could improve our understanding of important dynamics deep within Earth's magnetosphere. Previous work has analyzed these electrons during either isolated events or via significantly limited statistical studies, and it remains unclear what the particular drivers of electron flux enhancements in this region may be. Here, we present a broad statistical study of electrons around the inner edge of the inner radiation belt, utilizing the 7‐year data set of the MagEIS particle detectors aboard both Van Allen Probes spacecraft. Moreover, we separate electron flux measurements into stably trapped and quasi‐trapped electrons and directly compare their behavior. We find both populations to be variable in L and energy, as well as showing a clear magnetic local time (MLT) asymmetry. Potential drivers are also explored, where we demonstrate an association between increased electron fluxes in this region and heightened solar wind speed, Sym‐H, dynamic pressure, southward IMF and most prominently with the AU and AL indices.

Reduction of the Downward Energy Flux of Nonthermal Electrons in the Solar Flare Corona due to Cospatial Return-current Losses

High-energy electrons carry much of a solar flare’s energy. Therefore, understanding changes in electron beam distributions during their propagation is crucial. A key focus of this paper is how the cospatial return current reduces the energy flux carried by these accelerated electrons. We systematically compute this reduction for various beam and plasma parameters relevant to solar flares. Our 1D model accounts for collisions between beam and plasma electrons, return-current electric-field deceleration, thermalization in a warm target approximation, and runaway electron contributions. The results focus on the classical (Spitzer) regime, offering a valuable benchmark for energy flux reduction and its extent. Return-current losses are only negligible for the lowest nonthermal fluxes. We calculate the conditions for return-current losses to become significant and estimate the extent of the modification to the beam’s energy flux density. We also calculate two additional conditions that occur for higher injected fluxes: (1) where runaway electrons become significant, and (2) where current-driven instabilities might become significant, requiring a model that self-consistently accounts for them. Condition 2 is relaxed and the energy flux losses are reduced in the presence of runaway electrons. All results are dependent on beam and cospatial plasma parameters. We also examine the importance of the reflection of beam electrons by the return-current electric field. We show that the interpretation of a number of flares needs to be reviewed to account for the effects of return currents.

Whistler wave scattering of energetic electrons past 90°

The consequences of a 90° barrier in the scattering of energetic electrons by whistler waves are explored with self-consistent two-dimensional particle-in-cell simulations. In the presence of a 90° scattering barrier, a field-aligned heat flux of energetic electrons will rapidly scatter to form a uniform distribution with pitch angles 0<θ<90° but with a discontinuous jump at θ=90° to a lower energy distribution of electrons with 90°<θ<180°. However, simulations reveal that such a distribution contains a large reservoir of free energy that is released to drive large-amplitude, oblique-propagating whistler waves (δB/B0∼0.1). As a result, energetic electrons near a pitch angle 90° experience strong resonance scattering. Nearly half of the energetic electrons in the positive parallel velocity plane cross the 90° barrier and diffuse to negative parallel velocities. Thus, the late-time electron velocity distribution becomes nearly isotropic. This result has implications for understanding the regulation of energetic particle heat flux in space and astrophysical environments, including the solar corona, the solar wind, and the intracluster medium of galaxy clusters.

Butyrate as a growth factor of Clostridium acetobutylicum

The butyrate biosynthetic pathway not only contributes to electron management and energy generation in butyrate forming bacteria, but also confers evolutionary advantages to the host by inhibiting the growth of surrounding butyrate-sensitive microbes. While high butyrate levels induce toxic stress, effects of non-toxic levels on cell growth, health, metabolism, and sporulation remain unclear. Here, we show that butyrate stimulates cellular processes of Clostridium acetobutylicum, a model butyrate forming Firmicute. First, we deleted the 3-hydroxybutyryl-CoA dehydrogenase gene (hbd) from the C. acetobutylicum chromosome to eliminate the butyrate synthetic pathway and thus butyrate formation. A xylose inducible Cas9 cassette was chromosomally integrated and utilized for the one-step markerless gene deletions. Non-toxic butyrate levels significantly affected growth, health, and sporulation of C. acetobutylicum. Upon deleting spo0A, the gene of the master regulator of sporulation, Spo0A, and followed by butyrate addition experiments, we conclude that butyrate affects cellular metabolism through both Spo0A-dependent and independent mechanisms. We also deleted the hbd gene from the chromosome of the asporogenous C. acetobutylicum M5 strain lacking the pSOL1 plasmid to examine the potential involvement of pSOL1 genes on the observed butyrate effects. Addition of the precursor of butyrate biosynthesis crotonate to the hbd deficient M5 strain was used to probe the role of butyrate biosynthesis pathway in electron and metabolic fluxes. Finally, we found that butyrate addition can enhance the growth of the non-butyrate forming Clostridium saccharolyticum. Our data suggest that butyrate functions as a stimulator of cellular processes, like a growth factor, in C. acetobutylicum and potentially evolutionarily related Clostridium organisms.

Rapid Transport of Energetic Electrons to Low L $L$‐Shells: The Key Role of Electric Fields

AbstractThe dynamics of the outer radiation belt are traditionally associated with wave‐particle resonant interactions, which provide local electron acceleration and losses through very low‐frequency waves, and electron radial transport by ultra‐low frequency waves. However, these processes cannot explain observations of rapid radial transport of energetic electrons (on a time‐scale of a couple of hours), deep into the inner magnetosphere (down to , mapping to magnetic latitude in the ionosphere). This transport is likely associated with strong convection electric fields forming around the plasmapause. To investigate these rapid, low‐latitude electron transport, we combine low‐altitude observations of energetic electron fluxes by the ELFIN CubeSats and DMSP satellites, SuperDARN measurements of ionospheric plasma flows (electric fields), and equatorial measurements of energetic electrons and electric fields by THEMIS. Our findings demonstrate that the rapid filling of the slot region by keV electrons is directly associated with electric field penetration to low latitudes (down to ). The proposed electron transport scenario, the direct penetration of energetic electrons by strong, localized electric fields, underscores the importance of ionosphere‐magnetosphere coupling in radiation belt dynamics.

Living Cell-Mediated Catalyst-Free Spontaneous Polymerization of Zwitterionic Methacrylates for Preparation of Probiotic-Loaded Hydrogels.

Living cell-mediated polymerization offers promising applications in biomaterials, yet its further biological utilization is hindered by the need for metal ions or radical initiators with available methods. In this study, we introduce a living cell-mediated polymerization that leverages the intrinsic metabolic activities of living cells to initiate and sustain free radical polymerization of zwitterionic methacrylates. The polymerization proceeded in the absence of transition metal catalysts, radical initiators, or light sources. The conversion of zwitterionic methacrylate strongly correlated with cellular activities and achieved a maximum conversion of 98% within 48 hours. Living cells efflux redox power across membranes through metabolism and that terminal electron fluxes are captured by zwitterionic methacrylates pre-assembled on the living cell surface to initiate radical polymerization reactions. The polymerization caused significant changes to the cell membrane surface and synthesized hydrogels with tailored mechanical properties. The polymer hydrogel obtained via probiotic E. coli Nissle 1917 was able to release the in-situ encapsulated molecules, which demonstrated living cell-mediated polymer hydrogel as a vehicle for the delivery of both cellular and molecular therapeutic agents. This research offered a green and efficient method for synthesizing bioactive materials and advancing the field of cellular therapeutics and drug delivery.

Living Cell‐Mediated Catalyst‐Free Spontaneous Polymerization of Zwitterionic Methacrylates for Preparation of Probiotic‐Loaded Hydrogels

Living cell‐mediated polymerization offers promising applications in biomaterials, yet its further biological utilization is hindered by the need for metal ions or radical initiators with available methods. In this study, we introduce a living cell‐mediated polymerization that leverages the intrinsic metabolic activities of living cells to initiate and sustain free radical polymerization of zwitterionic methacrylates. The polymerization proceeded in the absence of transition metal catalysts, radical initiators, or light sources. The conversion of zwitterionic methacrylate strongly correlated with cellular activities and achieved a maximum conversion of 98% within 48 hours. Living cells efflux redox power across membranes through metabolism and that terminal electron fluxes are captured by zwitterionic methacrylates pre‐assembled on the living cell surface to initiate radical polymerization reactions. The polymerization caused significant changes to the cell membrane surface and synthesized hydrogels with tailored mechanical properties. The polymer hydrogel obtained via probiotic E. coli Nissle 1917 was able to release the in‐situ encapsulated molecules, which demonstrated living cell‐mediated polymer hydrogel as a vehicle for the delivery of both cellular and molecular therapeutic agents. This research offered a green and efficient method for synthesizing bioactive materials and advancing the field of cellular therapeutics and drug delivery.

Impact of EMIC Waves on Electron Flux Dropouts Measured by GPS Spacecraft: Insights From ELFIN

AbstractAlthough the effects of electromagnetic ion cyclotron (EMIC) waves on the dynamics of the Earth's outer radiation belt have been a topic of intense research for more than 20 years, their influence on rapid dropouts of electron flux has not yet been fully assessed. Here, we make use of contemporaneous measurements on the same ‐shell of trapped electron fluxes at 20,000 km altitude by Global Positioning System (GPS) spacecraft and of trapped and precipitating electron fluxes at 450 km altitude by Electron Losses and Fields Investigation (ELFIN) CubeSats in 2020–2022, to investigate the impact of EMIC wave‐driven electron precipitation on the dynamics of the outer radiation belt below the last closed drift shell of trapped electrons. During six of the seven selected events, the strong 1–2 MeV electron precipitation measured at ELFIN, likely driven by EMIC waves, occurs within 1–2 hr from a dropout of relativistic electron flux at GPS spacecraft. Using quasi‐linear diffusion theory, EMIC wave‐driven pitch angle diffusion rates are inferred from ELFIN measurements, allowing us to quantitatively estimate the corresponding flux drop based on typical spatial and temporal extents of EMIC waves. We find that EMIC wave‐driven electron precipitation alone can account for the observed dropout magnitude at 1.5–3 MeV during all events and that, when dropouts extend down to 0.5 MeV, a fraction of electron loss may sometimes be due to EMIC waves. This suggests that EMIC wave‐driven electron precipitation could modulate dropout magnitude above 1 MeV in the heart of the outer radiation belt.

Conditions for the occurrence of intense fluxes of energetic electrons at L<1.2 associated with solar activity and solar wind parameters

We present the results of a statistical study of transient enhancements of electrons with energies >30 keV at low drift shells in the quasi-trapped region (forbidden zone) at the geomagnetic equator. Using data from low-altitude NOAA/POES and MetOp satellites, we have compiled a catalog of events with forbidden energetic electron (FEE) enhancements for the period from 1998 to 2023. Statistical analysis of FEE events has revealed solar-cyclic, as well as seasonal and diurnal variations in the occurrence of FEE enhancements. We have examined the correlation of the annual frequency of FEE events with solar activity, solar wind parameters, and geomagnetic activity. Strong correlations have been found with the F10.7 index of solar activity (radio emission flux) as well as with the Alfvén Mach number (solar wind parameter). An interpretation of the obtained results is proposed which is based on the mechanism of electrical drift and radial transport of electrons from Earth’s inner radiation belt to the quasi-trapped region (L<1.2). The key factor for the operation of the mechanism is the effective penetration of the electric field to low latitudes when a significant difference in the conductivity of the high-latitude ionosphere occurs in the illuminated and unilluminated sectors of local time under conditions of weakening auroral activity.

Optical properties of ZnWO4 ceramics obtained by radiation synthesis

One of the promising methods for producing ceramics from tungstate metals of the MWO4 composition is ra- diation synthesis using powerful electron fluxes. Due to the unique properties of radiation, it was possible to significantly accelerate the synthesis process. It has been demonstrated that ZnWO4 ceramics can be synthe- sized by acting on an electron flux with an energy from 1.4 to 2.5 MeV and a high power density of 10– 25 kW/cm2. In this regard, studies of the optical properties of ceramic samples of zinc tungstate ZnWO4 ob- tained by this method were carried out. The morphology of the surface, X-ray diffraction spectra and optical properties of ZnWO4 ceramics obtained by radiation synthesis were studied. X-ray diffraction measurements and EDX analysis confirmed the formation of zinc tungstate ceramics ZnWO4 as a result of radiation synthe- sis. The absorption, luminescence, and luminescence excitation spectra of synthesized samples were meas- ured. Luminescence spectra of a reference single crystal sample were also measured. X-ray diffraction con- firmed the formation of zinc tungstate (ZnWO4) as a result of radiation synthesis. The luminescent spectra of the synthesized sample coincide with the spectra of crystalline ZnWO4. A comparison of the luminescence spectra of a synthesized ceramic sample and a monocrystalline reference sample measured under different op- tical excitation conditions shows significant differences in the luminescence spectra of the synthesized sample and the reference sample and indicates possible various defects present in the compared samples.

The April 2023 SYM‐H = −233 nT Geomagnetic Storm: A Classical Event

AbstractThe 23–24 April 2023 double‐peak (SYM‐H intensities of −179 and −233 nT) intense geomagnetic storm was caused by interplanetary magnetic field southward component Bs associated with an interplanetary fast‐forward shock‐preceded sheath (Bs of 25 nT), followed by a magnetic cloud (MC) (Bs of 33 nT), respectively. These interplanetary structures were led by a coronal mass ejection erupted from the Sun in association with an M1.7 X‐ray flare. At the center of the MC, the plasma density exhibited an order of magnitude decrease, leading to a sub‐Alfvénic solar wind interval for ∼2.1 hr. Ionospheric Joule heating accounted for a significant part (∼81%) of the magnetospheric energy dissipation during the storm main phase. Equal amount of Joule heating in the dayside and nightside ionosphere is consistent with the observed intense and global‐scale DP2 (disturbance polar) currents during the storm main phase. The sub‐Alfvénic solar wind is associated with disappearance of substorms, a sharp decrease in Joule heating dissipation, and reduction in electromagnetic ion cyclotron wave amplitude. The shock/sheath compression of the magnetosphere led to relativistic electron flux losses in the outer radiation belt between L* = 3.5 and 5.5. Relativistic electron flux enhancements were detected in the lower L* ≤ 3.5 region during the storm main and recovery phases. Equatorial ionospheric plasma anomaly structures are found to be modulated by the prompt penetration electric fields. Around the anomaly crests, plasma density at ∼470 km altitude and altitude‐integrated ionospheric total electron content are found to increase by ∼60% and ∼80%, with ∼33% and ∼67% increases in their latitudinal extents compared to their quiet‐time values, respectively.