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Recent simulation studies using the RAM‐SCB model showed that proton precipitation contributes significantly to the total energy flux deposited into the subauroral ionosphere thereby affecting the magnetosphere‐ionosphere coupling. In this study, we use the BATS‐R‐US + RAM‐SCB model to understand the evolution of ElectroMagnetic Ion Cyclotron (EMIC) waves in the inner magnetosphere, their correspondence to the proton precipitation into the subauroral ionosphere, and to assess the performance of the model in reproducing the EMIC wave‐particle interactions. During the 27 May 2017 storm, Arase and RBSP‐A satellites observed typical signatures of EMIC waves in the inner magnetosphere. Within this interval, Defense Meteorological Satellite Program (DMSP) and National Oceanic and Atmospheric Administration (NOAA)/MetOp satellites observed significant proton precipitation in the dusk‐midnight sector. Simulation results show that H‐ and He‐band EMIC waves are excited within regions of strong temperature anisotropy near the plasmapause. The simulated growth rates of EMIC waves show a similar trend to that of the EMIC wave power observed by the Arase and RBSP‐A satellites, suggesting that the model can reproduce the EMIC wave activity qualitatively. The simulated H‐band waves in the dusk sector are stronger than He‐band waves possibly due to the presence of excess protons in the boundary conditions obtained from the BATS‐R‐US code. The precipitating proton fluxes reproduced by the simulation with EMIC waves are found to agree reasonably well with the DMSP and NOAA/MetOp satellite observations. It is suggested that EMIC wave scattering of ring current ions can account for proton precipitation observed by the DMSP and MetOp satellites during the 27 May 2017 storm. Plain Language Summary: During geomagnetic storms, plasma waves are generated in the Earth's magnetosphere. Among these waves, ElectroMagnetic Ion Cyclotron (EMIC) waves can scatter protons from the ring current, causing them to precipitate into the subauroral ionosphere. Such precipitation not only affects the midlatitude ionosphere but also impacts the dynamics of the magnetosphere. Understanding the origin of magnetospheric plasma waves and how they interact with the magnetospheric populations, along with their subsequent impact on the ionosphere, is crucial for predicting space weather accurately. In our study, we combined ground and satellite observations with simulations using the BATS‐R‐US + RAM‐SCB to investigate EMIC wave‐particle interactions in the inner magnetosphere and the resulting proton precipitation during the 27 May 2017 storm. We found that EMIC waves were excited in the dusk‐midnight sector during the storm's main phase, within the regions of strong temperature anisotropy. The simulations reproduced the proton precipitation observed in the dusk‐midnight sector by the Defense Meteorological Satellite Program /National Oceanic and Atmospheric Administration MetOP satellites fairly well. The model qualitatively captured the growth of the EMIC waves during the storm and showed that the EMIC waves, by scattering the ring current, were responsible for the proton precipitation into the dusk‐midnight sector during the storm. Key Points: ElectroMagnetic Ion Cyclotron (EMIC) wave activity and proton precipitation were observed simultaneously in the dusk‐midnight sector during the 27 May 2017 stormThe BATS‐R‐US + RAM‐SCB model can capture the EMIC wave growth during the storm qualitativelyThe EMIC wave scattering of ring current ions can account for the proton precipitation in the dusk‐midnight sector during the storm [ABSTRACT FROM AUTHOR]

The importance of ElectroMagnetic Ion Cyclotron (EMIC) ultra-low-frequency (ULF) waves (and their Pc1 counterparts) is connected to their critical role in triggering energetic particle precipitation from the magnetosphere to the conjugated ionosphere via pitch angle scattering. In addition, as a prominent element of the ULF zoo, EMIC/Pc1 waves can be considered a perfect tool for the remote diagnosis of the topologies and dynamic properties of near-Earth plasmas. Based on the availability of a comprehensive set of instruments, operating on the ground and in the top-side ionosphere, the present case study provides an interesting example of the evolution of EMIC propagation to both ionospheric hemispheres up to the polar cap. Specifically, we report observations of Pc1 waves detected on 30 March 2021 under low Kp, low Sym-H, and moderate AE conditions. The proposed investigation shows that high-latitude ground magnetometers in both hemispheres and the first China Seismo-Electromagnetic Satellite (CSES-01) at a Low Earth Orbit (LEO) detected in-synch Pc1 waves. In strict correspondence to this, energetic proton precipitation was observed at LEO with a simultaneous appearance of an isolated proton aurora at subauroral latitudes. This supports the idea of EMIC wave-induced proton precipitation contributing to energy transfer from the magnetosphere to the ionosphere. [ABSTRACT FROM AUTHOR]

The mechanisms of the production of vibrationally excited NO and N2 molecules at the altitudes of the middle atmosphere of the Earth during high‐energetic proton precipitation on 20 January 2005 are considered. The study of vibrational populations N2(X1Σg+,v′ > 0) during high‐energetic proton precipitation has shown different principal mechanisms in the N2(X1Σg+,v′ > 0) excitation. First, the excitation by secondary electrons is principal for vibrational levels v′ = 1−10. Second, it is obtained that intramolecular electron energy transfer process in N2(A3Σu+)+N2 collisions dominates in vibrational excitation of high vibrational levels v′ = 20−30. It is shown that the chemical reaction of metastable atomic nitrogen with molecular oxygen is the main production mechanism of vibrationally excited NO(X2Π,v > 0) and of the radiation of 5.3 and 2.7 μm infrared emissions at these altitudes. The calculated intensities of the 5.3 μm emission are compared with experimental data from SABER instrument on TIMED spacecraft received at the time of the proton precipitation. The role of VV′‐processes in the radiation of 5.3 μm infrared emission is discussed. Plain Language Summary: The Ground Level Enhancement on 20 January 2005 is the strongest event of precipitation of energetic protons in the Earth's atmosphere. We study molecular processes at the altitudes of the middle atmosphere during the precipitation. Special attention is paid to a modeling of vibrational kinetics of molecular nitrogen N2 and nitric oxide NO. The influence of electronically excited states of N2 and NO molecules on the vibrational kinetics is considered. The intensities of NO 5.3 and 2.7 μm infrared emissions are calculated. The calculated intensities of the 5.3 μm emission are compared with experimental data from SABER instrument on TIMED spacecraft received at the time of the proton precipitation. Key Points: Vibrational kinetics of NO and N2 in the middle atmosphere during high‐energetic proton precipitation is consideredIntramolecular and intermolecular electron energy transfers are taken into account in calculations of vibrational populations of moleculesIt is shown that there is a dependence of calculated vibrational populations on atmospheric altitude [ABSTRACT FROM AUTHOR]

• Atmospheric variability leads to noise in TEC response to proton precipitation. • Atmosphere driven noise of TEC disturbances has UT variation. • Such noise strongly change during the solar proton event. • Atmospheric variability mask ionospheric response to space weather events. • Likelihood of ionospheric afterstorm effects decreases due to atmospheric variability. The purpose of this study is to investigate the role of internal atmospheric variability in the detection of ionospheric response to precipitating protons of solar and magnetospheric origin during 17–23 January 2005. For this purpose, we analyzed the results of ensemble runs of the whole atmosphere model EAGLE. We confirmed that the proton precipitation produces (directly and indirectly) significant TEC (Total Electron Content) enhancements at different latitudes. However, we also showed that internal atmospheric variability can strongly mask the forced signal, especially its after-effects, which can lead to false interpretation if only one model realization is considered. The ensemble standard deviation, or an atmospheric noise level, in TEC has a clear UT variation and spatial distribution, which defines the derivability of the signal depending on the time and the region of the forced effects. The noise itself is also affected by the increased ionization from protons, but its behavior is nonlinear and depends on the latitude, spectrum of the event and its time of occurrence. We conclude that studies of the ionospheric response to various space weather phenomena require the application of whole atmosphere models in ensemble mode to ensure statistical significance of the obtained results and a reliable interpretation of the observational data. [ABSTRACT FROM AUTHOR]

The importance of ElectroMagnetic Ion Cyclotron (EMIC) ultra-low-frequency (ULF) waves (and their Pc1 counterparts) is connected to their critical role in triggering energetic particle precipitation from the magnetosphere to the conjugated ionosphere via pitch angle scattering. In addition, as a prominent element of the ULF zoo, EMIC/Pc1 waves can be considered a perfect tool for the remote diagnosis of the topologies and dynamic properties of near-Earth plasmas. Based on the availability of a comprehensive set of instruments, operating on the ground and in the top-side ionosphere, the present case study provides an interesting example of the evolution of EMIC propagation to both ionospheric hemispheres up to the polar cap. Specifically, we report observations of Pc1 waves detected on 30 March 2021 under low Kp, low Sym-H, and moderate AE conditions. The proposed investigation shows that high-latitude ground magnetometers in both hemispheres and the first China Seismo-Electromagnetic Satellite (CSES-01) at a Low Earth Orbit (LEO) detected in-synch Pc1 waves. In strict correspondence to this, energetic proton precipitation was observed at LEO with a simultaneous appearance of an isolated proton aurora at subauroral latitudes. This supports the idea of EMIC wave-induced proton precipitation contributing to energy transfer from the magnetosphere to the ionosphere.

We investigate the proton precipitation caused by electromagnetic ion cyclotron (EMIC) waves and its impact on the ionosphere with the self‐consistent ring current‐atmosphere interactions model (RAM‐SCBE) coupled with an ionospheric particle transport model Global Airglow (GLOW). The EMIC wave diffusion process causes significant precipitation of tens of keV protons, particularly in the afternoon to midnight sector. These precipitating energetic protons further impact the ionosphere‐thermosphere and contribute to the ionization in the E/F regions. The integrated auroral conductance is significantly enhanced in the dusk‐to‐midnight sector. Although the EMIC waves do not directly interact with the ring current electrons, after the EMIC wave scattering included in the model, remarkable changes are found in the global distribution of precipitating electron flux. This means that the addition of proton precipitation driven by EMIC waves results in feedback effects on the ring current electron dynamics through the circulation system. Validation is also conducted by comparing the simulated precipitation flux and ionospheric electron density with observations. Key Points: The electromagnetic ion cyclotron (EMIC) wave diffusion process causes significant precipitation of tens of keV protons, particularly in the afternoon to midnight sectorEnergetic precipitating proton scattered by EMIC wave further impact ionosphere‐thermosphere and contribute to the ionization in E/F regionsEMIC waves produce large proton precipitation, changing ionospheric electrodynamics and feeding back to the magnetospheric dynamics [ABSTRACT FROM AUTHOR]

We report the concurrent observations of F‐region plasma changes and field‐aligned currents (FACs) above isolated proton auroras (IPAs) associated with electromagnetic ion cyclotron Pc1 waves. Key events on March 19, 2020 and September 12, 2018 show that ground magnetometers and all‐sky imagers detected concurrent Pc1 wave and IPA, during which NOAA POES observed precipitating energetic protons. In the ionospheric F‐layer above the IPA zone, the Swarm satellites observed transverse Pc1 waves, which span wider latitudes than IPA. Around IPA, Swarm also detected the bipolar FAC and localized plasma density enhancement, which is occasionally surrounded by wide/shallow depletion. This indicates that wave‐induced proton precipitation contributes to the energy transfer from the magnetosphere to the ionosphere. Plain Language Summary: Electromagnetic ion cyclotron (EMIC) wave is known to precipitate energetic protons into the Earth's atmosphere via pitch angle scattering. Observations from ground‐based magnetometers, all‐sky imagers, and low Earth orbit satellites have shown that the precipitating protons scattered by EMIC waves can generate proton aurora isolated at a subauroral latitude. This kind of aurora is called isolated proton aurora (IPA, or detached proton auroral arc). In the present paper, we report the observations of concurrent Pc1 wave, proton precipitation, ionospheric perturbation, field‐aligned currents (FACs), and IPA using data from ground instruments, and from the Swarm and NOAA POES satellites. The observations show that the latitudinal (L‐shell) size of EMIC wave at Swarm altitude is larger than that of the IPA. We also investigated the effects of proton precipitation on the ionospheric F‐layer from Swarm satellite data, and found localized plasma density enhancement and FAC near the central IPA region. Our results demonstrate that the EMIC‐driven proton precipitation contributes to the energy transfer from the magnetosphere to the ionosphere. Key Points: We report the concurrent observations of Pc1 wave, proton precipitation, ionospheric perturbation, field‐aligned current, and isolated proton aurora (IPA)Pc1 waves over the ionospheric F‐layer and IPA over the E‐layer show different latitudinal widthsProton precipitation can cause localized plasma density enhancement, which is occasionally surrounded by wide/shallow density depletion [ABSTRACT FROM AUTHOR]

We evaluate the location, extent, and energy range of electron precipitation driven by ElectroMagnetic Ion Cyclotron (EMIC) waves using coordinated multisatellite observations from near‐equatorial and Low‐Earth‐Orbit (LEO) missions. Electron precipitation was analyzed using the Focused Investigations of Relativistic Electron Burst Intensity, Range and Dynamics (FIREBIRD‐II) CubeSats, in conjunction either with typical EMIC‐driven precipitation signatures observed by Polar Orbiting Environmental Satellites (POES) or with in situ EMIC wave observations from Van Allen Probes. The multievent analysis shows that electron precipitation occurred in a broad region near dusk (16–23 MLT), mostly confined to 3.5–7.5 L‐shells. Each precipitation event occurred on localized radial scales, on average ∼0.3 L. Most importantly, FIREBIRD‐II recorded electron precipitation from ∼200 to 300 keV to the expected ∼MeV energies for most cases, suggesting that EMIC waves can efficiently scatter a wide energy range of electrons. Plain Language Summary: ElectroMagnetic Ion Cyclotron (EMIC) waves occur in the Earth's magnetosphere and are excited during injections of hot ions from the magnetotail toward Earth. EMIC waves are known to cause precipitation of ∼MeV electrons into the upper atmosphere, which can lead to enhancements of ionization and chemical reactions, but some studies suggest that this energy can extend down to a few hundred keV as well. In this study, we focus on identifying the location, extent and energy range of electron precipitation driven by EMIC waves by analyzing multiple events using coordinated multisatellite observations. We found that energetic electron precipitation primarily occurred on the duskside and within ∼7.5 Earth Radii (RE). The precipitation was localized radially (on average ∼0.3 RE), and the energy range of precipitation extended from at least ∼200–300 keV up to ∼MeV. Our findings are important to understand the effects of EMIC waves on energetic electron precipitation, including their dependence on location, extent, and energy. Key Points: Conjunctions between FIREBIRD‐II and RBSP or POES with clear EMIC‐driven precipitation signatures are analyzedFIREBIRD‐II systematically observed EMIC‐driven electron precipitation with an energy range extending from ∼200 to 300 keV up to ∼1 MeVElectron precipitation occurred in a broad region (16–23 MLT, L < 7.5), but the extent per event was highly localized (on average ∼0.3 L) [ABSTRACT FROM AUTHOR]

We report the first observation of plasma density oscillations coherent with magnetic Pc1 waves. Swarm satellites observed compressional Pc1 wave activity in the 0.5–3 Hz band, which was coherent with in situ plasma density oscillations. Around the Pc1 event location, the Antarctic Neumayer Station III (L ~ 4.2) recorded similar Pc1 events in the horizontal component while NOAA‐15 observed isolated proton precipitations at energies above 30 keV. All these observations support that the compressional Pc1 waves at Swarm are oscillations converted from electromagnetic ion cyclotron (EMIC) waves coming from the magnetosphere. The magnetic field and plasma density oscillate in‐phase. We compared the amplitudes of density and magnetic field oscillations normalized to background values and found that the density power is much larger than the magnetic field power. This difference cannot be explained by a simple magnetohydrodynamic (MHD) model, although steep horizontal/vertical gradients of background ionospheric density can partly reconcile the discrepancy. Plain Language Summary: Electromagnetic ion cyclotron (EMIC) wave is known to be generated in the inner magnetosphere in the ultralow frequency (ULF) Pc1 range (0.2–5 Hz). The EMIC Pc1 waves propagate as shear Alfvén mode from the magnetospheric source toward the ionosphere. On arriving at ionospheric altitudes, they undergo mode conversion to the compressional Alfvén mode due to the Hall conductivity. According to the ideal magnetohydrodynamics (MHD) theory, the compressional ULF wave can be accompanied by density perturbation of ionospheric plasmas. In this paper, we report the first observation of ionospheric plasma density oscillations driven by EMIC Pc1 waves based on the observation by the Swarm satellites. Simple MHD equations cannot fully explain the amplitude and phase relationship between plasma density and magnetic Pc1 pulsations, while steep horizontal/vertical gradients of background ionospheric plasma density may in part reconcile the discrepancy. Key Points: We report the first observation of ionospheric plasma density oscillation correlated with electromagnetic ion cyclotron (EMIC) Pc1 waveSimple MHD theory cannot explain the observed amplitude and phase relationships between the plasma density oscillation and the Pc1 waveThe EMIC Pc1 wave was also accompanied by localized proton precipitation [ABSTRACT FROM AUTHOR]

Satellite measurements have revealed significant enhancement of 5.3‐μm nitric oxide (NO) emission during shock‐led interplanetary coronal mass ejections. Great discrepancies in modeled neutral density occur during these events and may be attributed to the abnormally high NO cooling. Meanwhile, the relative significance of protons, soft electrons, and keV‐electrons to NO emission is yet to be well determined. The goal of this study is to identify the contribution of electron and proton precipitations to the thermospheric NO cooling by using the Defense Meteorological Satellite Program (DMSP) data. The observed energetic electrons and protons (0.1–30.2 keV) during 36 shock‐led interplanetary coronal mass ejection events in 2002–2010 are binned into geomagnetic grids to provide statistical distributions of the particle precipitation for polar regions. The distributions are incorporated into the Global Ionosphere‐Thermosphere Model. The results show that electrons play a dominant role to NO cooling, but protons are also important and contribute to up to a quarter of NO cooling by electrons and ions combined. NO cooling enhancement during the events is proportional to the level of energy flux and is dominated by the electrons in the energy band of 1.4–3.1 keV. Both total electron content (TEC) and NO cooling enhance at the source regions, but they have different lifetime and correlation with the particle precipitations. Generally, NO cooling and TEC enhancements have a positive correlation with the precipitating energy. Cross correlation shows that particle precipitations have more instantaneous impact on TEC while it takes longer for the atmosphere to heat up for cooling to proceed. Key Points: Electrons play a dominant role, but protons also contribute around a quarter of the total NO cooling enhancement during geo‐effective ICMEsElectrons of 1.4–30.2 keV are main contributors to NO cooling enhancement during geo‐effective eventsTime lags for maximal correlation with electron precipitating energy flux are 1–6 hr longer for NO cooling than for TEC [ABSTRACT FROM AUTHOR]

Nonlinear properties of the Pc1 geomagnetic pulsations with anomalous (magnetosonic) dynamic spectrum are studied. The nonlinear properties of the waves are reflected in the emergence of ponderomotive force proportional to the squared amplitude of the waves. Just as in the case of the Alfven waves, at small values of parameter ν0 = ω/ωci0 < 0.4 (ratio of the carrier frequency to proton gyrofrequency in the equatorial plane), the ponderomotive force leads to the modification of the background plasma through increasing its density towards the equator. At ν0 > 0.4, plasma is expelled from the equator towards the higher latitudes. The dependence of the nonlinear modification of background plasma for the different parameters of the magnetosphere is studied. [ABSTRACT FROM AUTHOR]

Abstract: We present model results of the interaction of proton and hydrogen atom precipitation with the Martian atmosphere. We use a kinetic Monte Carlo model developed earlier for the analysis of the Analyzer of Space Plasmas and Energetic Atoms (ASPERA‐3) Mars Express data. With the availability of Mars Atmosphere and Volatile Evolution Mission in situ measurements, not only the flux of protons incident on the atmosphere but also their degradation along the orbit may now be described. The comparison of the simulations with data collected with the Solar Wind Ion Analyzer shows that the Monte Carlo model reproduces some of the measured features. The results of comparison between simulations and measurements of the proton fluxes at low altitudes make it possible to infer the efficiency of charge exchange between solar wind and the extended hydrogen corona if the value of the magnetic field is measured simultaneously. We also find that the induced magnetic field plays a very important role in the formation of the backscattered flux and strongly controls its magnitude. At the same time, discrepancies between the modeled and the measured energy spectra of the backscattered protons are pointed out. We suggest that some of the physical processes controlling the upward flux are not fully understood or that the data processing of the measured backscattered proton flux should be improved. [ABSTRACT FROM AUTHOR]

Space weather events may adversely affect high frequency (HF) radio propagation, hence the ability to provide nowcasting and forecasting of HF radio absorption is key for industries that rely on HF communications. This paper presents methods of assimilating 30 MHz radio absorption measurements into two types of ionospheric polar cap absorption (PCA) model to improve their performance as nowcasting tools. Type 1 models calculate absorption as m times the square root of the flux of solar protons above an energy threshold, Et. Measurements from 14 riometers during 94 solar proton events (1995–2010) are assimilated by optimising the day and night values of m by linear regression. Further non-linear optimisations are demonstrated in which parameters such as Et are also optimised and additional terms characterise local time and seasonal variations. These optimisations reduce RMS errors by up to 36%. Type 2 models incorporate altitude profiles of electron and neutral densities and electron temperatures. Here the scale height of the effective recombination coefficient profile in the D-region is optimised by regression. Furthermore, two published models of the rigidity cut-off latitude (CL) are assessed by comparison with riometer measurements. A small improvement in performance is observed by introducing a 3-h lag in the geomagnetic index Kp in the CL models. Assimilating data from a single riometer in the polar cap reduces RMS errors below 1 dB with less than 0.2 dB bias. However, many high-latitude riometers now provide absorption measurements in near-real time and we demonstrate how these data may be assimilated by fitting a low-order spherical harmonic function to both the measurements and a PCA model with optimised parameters.

The ionic detergent sodium deoxycholate (SDC) is compatible with in-solution tryptic digestion and LC-MS/MS-based shotgun proteomics by virtue of being easy to separate from the peptide products via precipitation in acidic buffers. However, it remains unclear whether unique human peptides co-precipitate with SDC during acid treatment of complex biological samples. In this study, we demonstrate for the first time that a large quantity of unique peptides in human blood plasma can be co-precipitated with SDC using an optimized sample preparation method prior to shotgun proteomic analysis. We show that the plasma peptides co-precipitated with SDC can be successfully recovered using a sequential re-solubilization and precipitation procedure, and that this approach is particularly efficient at the extraction of long peptides. Recovery of peptides from the SDC pellet dramatically increased overall proteome coverage (>60 %), thereby improving the identification of low-abundance proteins and enhancing the identification of protein components of membrane-bound organelles. In addition, when we analyzed the physiochemical properties of the co-precipitated peptides, we observed that SDC-based sample preparation improved the identification of mildly hydrophilic/hydrophobic proteins that would otherwise be lost upon discarding the pellet. These data demonstrate that the optimized SDC protocol is superior to sodium dodecyl sulfate (SDS)/urea treatment for identifying plasma biomarkers by shotgun proteomics. [ABSTRACT FROM AUTHOR]

High frequency (HF) radio band is important for the long-range communications and over-the-horizon surveillance, particularly in the polar cap region where the ground infrastructure may be limited. However, the space weather events drastically affect the high frequency radio wave propagation so that the ability to provide now-casting and forecasting of HF radio wave absorption is important for users relying on the HF communications. During the space weather events such as solar proton events and X-ray flares the high-latitude ionosphere becomes a particularly efficient absorber of HF radio waves. There is therefore a need to develop accurate HF propagation prediction services. Absorption of the HF field caused by the X-ray flux, Solar Ultra-Violet flux and proton precipitations is investigated in this paper for the event of the solar flare observed on 11 April 2013. The effects of the X-ray flux and proton precipitations on the structure of the vertical and oblique ionograms for different latitudes are estimated. The simulation of the vertical and oblique ionograms was performed on the basis of the computational model of the ionosphere oriented to applications into the high frequency wave propagation problems. The absorption effects induced by the proton precipitations and X-ray flux are calculated according to the algorithm elaborated by Sauer and Wilkinson and D-region Absorption Model (D-RAP) available from the NOAA Space Weather Prediction Center. The simulated vertical and oblique ionograms with the absorption effects taken into account and the measured ionograms exhibit a fairly good similarity. [ABSTRACT FROM AUTHOR]

Data from a cluster of three THEMIS (Time History of Events and Macroscale Interactions during Substorms) spacecraft during February-March 2009 frequently provide an opportunity to construct local data-adaptive magnetospheric models, which are suitable for the accurate mapping along the magnetic field lines at distances of 6-9 Re in the nightside magnetosphere. This allows us to map the isotropy boundaries (IBs) of 30 and 80 keV protons observed by low-altitude NOAA POES (Polar Orbiting Environmental Satellites) to the equatorial magnetosphere (to find the projected isotropy boundary, PIB) and study the magnetospheric conditions, particularly to evaluate the ratio KIB (Rc=rc; the magnetic field curvature radius to the particle gyroradius) in the neutral sheet at that point. Special care is taken to control the factors which influence the accuracy of the adaptive models and mapping. Data indicate that better accuracy of an adaptive model is achieved when the PIB distance from the closest spacecraft is as small as 1-2 Re. For this group of most accurate predictions, the spread of KIB values is still large (from 4 to 32), with the median value KIB ~ 13 being larger than the critical value Kcr ~ 8 expected at the inner boundary of nonadiabatic angular scattering in the current sheet. It appears that two different mechanisms may contribute to form the isotropy boundary. The group with K ~ [4, 12] is most likely formed by current sheet scattering, whereas the group having KIB ~ [12, 32] could be formed by the resonant scattering of low-energy protons by the electromagnetic ion-cyclotron (EMIC) waves. The energy dependence of the upper K limit and close proximity of the latter event to the plasmapause locations support this conclusion. We also discuss other reasons why the K ~ 8 criterion for isotropization may fail to work, as well as a possible relationship between the two scattering mechanisms. [ABSTRACT FROM AUTHOR]

We study the precipitation of protons and alpha-particles onto the upper atmosphere of Venus, using particle data recorded by the Venus Express spacecraft inside the induced magnetosphere. Our investigations are limited to the dayside close to the terminator. We observe on average a net downward flux of protons, which originate partly from the planetary atmosphere and partly from the solar wind. We present median energy spectra of the precipitating protons divided into two energy ranges, 10–100 eV and 100 eV–30 keV. The total dayside precipitation of solar wind protons is estimated to be 3×10 22 s −1 , assuming only protons with energies above 500 eV will reach the exobase. Downgoing protons are frequently observed but only in 3% of the available data records we see He 2 + . These observations are made close to the induced magnetosphere boundary and we argue that at lower altitude the countrates for alpha-particles fall below detection limits. We estimate the precipitation of He 2 + onto the dayside exobase to be 1×10 21 s −1 , which is not enough enough to replace the helium escaping from the planet. [ABSTRACT FROM AUTHOR]

Understanding the altitude distribution of particle precipitation forcing is vital for the assessment of its atmospheric and climate impacts. However, the proportion of electron and proton forcing around the mesopause region during solar proton events is not always clear due to uncertainties in satellite-based flux observations. Here we use electron concentration observations of the European Incoherent Scatter Scientific Association (EISCAT) incoherent scatter radars located at Tromsø (69.58° N, 19.23° E) to investigate the contribution of proton and electron precipitation to the changes taking place during two solar proton events. The EISCAT measurements are compared to the results from the Sodankylä Ion and Neutral Chemistry Model (SIC). The proton ionization rates are calculated by two different methods - a simple energy deposition calculation and the Atmospheric Ionization Model Osnabrück (AIMOS v1.2), the latter providing also the electron ionization rates. Our results show that in general the combination of AIMOS and SIC is able to reproduce the observed electron concentration within ±50% when both electron and proton forcing is included. Electron contribution is dominant above 90 km, and can contribute significantly also in the upper mesosphere especially during low or moderate proton forcing. In the case of strong proton forcing, the AIMOS electron ionization rates seem to suffer from proton contamination of satellite-based flux data. This leads to overestimation of modelled electron concentrations by up to 90% between 75-90 km and up to 100-150% at 70-75 km. Above 90 km, the model bias varies significantly between the events. Although we cannot completely rule out EISCAT data issues, the difference is most likely a result of the spatio-temporal fine structure of electron precipitation during individual events that cannot be fully captured by sparse in situ flux (point) measurements, nor by the statistical AIMOS model which is based upon these observations. [ABSTRACT FROM AUTHOR]

Some peculiarities of the source region of proton precipitations and electromagnetic ion-cyclotron waves on the dayside during magnetospheric compression are considered. Flashes of proton emission observed by the IMAGE satellite in the dayside sector equatorwards from the proton aurora oval are used to localize this region. The data from the LANL geostationary satellites, the projections of which during magnetospheric compression were within the proton emission flash, made it possible to find that the source region of the proton precipitations is usually located outside the plasmasphere. In periods of increased geomagnetic activity, this region is located closer to the Earth. Using NOAA satellite data, it is shown that in the dayside outer magnetosphere, precipitations of energetic protons with relatively low intensity are observed prior to magnetospheric compression. This fact shows that the conditions for the development of ion-cyclotron instability are fulfilled there. Magnetospheric compression leads to a sharp increase in the instability increment and, as a consequence, to a sharp growth in the fluxes of precipitating protons, exceeding the level needed for the registration of proton auroras on board the IMAGE satellite. [ABSTRACT FROM AUTHOR]

The simulation of the multi-beam ionograms in the polar cap region, assessing absorption effect is performed. It is reasonable to distinguish among four different mechanisms responsible for absorption: regular absorption due to solar UV illumination, absorption associated with energetic particles precipitation, absorption connected with X-rays flare and additional absorption in Auroral oval area. In this paper the absorption attributed to proton precipitations is envisaged. The computational model of the high-latitude ionosphere with irregularities oriented to application for the high frequency wave propagation problem was elaborated (Zaalov et al., 2005). A number of the quasi-vertical ionograms in the polar cap region were simulated on the basis of this model. A well-known algorithm (Sauer and Wilkinson, 2008) is applied for the absorption effects calculation. The simulated high-latitude ionograms with the absorption effect and the measured ionograms exhibit quite a good resemblance. This paper illustrates the importance of the understanding and taking into account the absorption effect in the presence of the various structural features in the polar ionosphere (in particular, patches of enhanced electron density) in interpreting ionosonde data. [ABSTRACT FROM AUTHOR]

Abstract: Observations of Energetic Neutral Atoms (ENAs) emitted from the proton aurora and from the equatorial ring current at tens to a few hundred of keV during the Halloween 2003 storm are presented. From the proton oval a large number of ENAs are spread over the polar cap making a contribution to the ion outflow. From the Ring Current (RC) ENAs are spread in all directions. The Storm Time Equatorial Belt (STEB) consists of ENAs observed around the geomagnetic equator at low L-values. Their source is RC protons existing at larger L-values. The number of observed ENAs is directly dependent on the amount of ions (protons) present in the RC along the line of sight. Thus the time variations of the STEB enable us to monitor the behavior of the RC. Based on observations of the STEB at six different local times we discuss the RC injection region, the drift of RC-particles through the evening/afternoon sector into the morning sector and the RC decay time during the storm recovery phase. The MLT variation of the STEB gives information about the symmetry and asymmetry of the RC with no interference from other current systems. The revealed RC-symmetry and asymmetry complement magnetic ground observations. [Copyright &y& Elsevier]

Positron annihilation lifetime studies (PAL) have been carried out on Al-Cu alloy, in order to get information about solute surroundings at the annihilation site. Exceedingly large numbers of positrons are found to annihilate at the matrix-Al2Cu precipitate interfaces. The defect structure of Al-Cu alloy with a variety of Cu concentrations is deduced from the PAL measurements at room temperature. The change of the average positron lifetime with different Cu concentrations (up to 25 wt. % Cu) has been discussed. PAL measurements revealed saturation trapping of positrons at large concentration of copper in the alloy, specifically in matrix-precipitate interface. Complementary techniques such as X-ray diffraction (XRD), scanning electron microscope (SEM), and Vickers hardness are used in the present work. The nucleation and growth of the Al2Cu particles lead to reduction in the positron lifetime and raising in the Vickers hardness. Hence, the hardness variation is qualitatively consistent with that of positron annihilation parameters. The information obtained from PAL studies provides direct observations of positron trapping at the misfit interfaces between the Al-rich matrix and the Al2Cu phase. [ABSTRACT FROM AUTHOR]

The bow shock has been studied so far, mostly as a boundary that influences the particles that are incident from the upstream region (of solar origin). In this paper, we provide, for the first time, observational evidence from the energetic-particle-experiment and the charged-particle-measurement-experiment instruments onboard the IMP-8 spacecraft, showing that ions leaking from the magnetosphere, during storms or substorms, are affected by the quasi-perpendicular (Q-P) bow shock and can be temporally trapped just downstream from the shock in a magnetic configuration opposite to the magnetic mirror. The observations from three representative event periods examined in this paper suggest that magnetospheric energetic (>50 keV) ions show general flows along the field lines in the direction from the magnetosheath toward the interplanetary space, in both sides of the shock (up- and downstream), and characteristic cross-field anisotropic distributions just downstream from the shock, consistent with a "trapped population." In a series of successive bow-shock crossings within several hours, the IMP-8 spacecraft observed intensity gradients toward the magnetosheath, which strongly suggest a spatial modulation of magnetospheric ion fluxes at the Q-P bow shock. Highest peaks of ion intensities and a very hard spectrum (j ∝ E-0.4) in the energy range between ∼100 and 400 keV were observed just at the shock front, which suggest acceleration of magnetospheric particles during their temporal trapping at the bow shock. The observations near the Earth's bow shock examined in this paper are well explained in terms of the shock drift acceleration (SDA) theory for magnetospheric particles reaching the bow shock. The phenomenon discussed here, an apparent temporal trapping—and acceleration—of escaped magnetospheric ions at the Earth's bow shock, appears to be an important mechanism that influences the particle distributions near the Earth's bow shock and may have important applications to other shocks in our solar system (planetary, heliospheric, interplanetary, and corotating shock waves) and the interstellar medium (supernova shocks). [ABSTRACT FROM AUTHOR]

Abstract: This brief review summarizes recent findings related to particle precipitation associated with electromagnetic ion–cyclotron (EMIC) waves seen on the ground as geomagnetic Pc1 and IPDP pulsations. Particle precipitation signatures of ion–cyclotron interaction are described as revealed from low-altitude satellite measurements of the energetic proton fluxes as well as from observations of the proton aurora. As a result, localized proton precipitation patterns situated equatorward of the isotropy boundary are disclosed. One of the patterns is a proton precipitation spot in the morning sector, presumably mapped onto plasmapause; another one is an elongated region of the precipitation, presumably mapped onto the plasmaspheric plume. Clear evidence of the pitch-angle scattering associated with the ion–cyclotron wave activity is found near the equatorial plane in the region conjugated with the localized proton precipitation at low altitude. Thus, the revealed precipitation patterns determine the location of the region of intense pitch-angle scattering of energetic protons, and, therefore, their observations can be used to monitor the region of the ion–cyclotron interaction and to study its origin and properties. Some examples of such application of the low-altitude observations of energetic particles are described. [Copyright &y& Elsevier]

Abstract: A one-dimensional time-dependent model has been used to calculate the production and loss of minor components of the middle atmosphere during solar proton precipitations in October 2003. We used the solar proton fluxes measured on the GOES-11 spacecraft to estimate the rates of ion–electron pair, odd-nitrogen and odd-hydrogen production. Our calculations show that the production of odd-hydrogen causes the ozone depletion by the factor 2 and more at the altitudes higher than 55km. This depletion is in an agreement with measurements of O3 altitude profiles made on POAM-3 satellite. [Copyright &y& Elsevier]

Using a partial reflection technique, there were experimentally investigated changes in the electron density, N, in the ionospheric D-region at the time of solar proton events, spe. Increasing by more than 50-100% in the electron density in the lower D-region of the ionosphere (∼70-80 km) was observed during several tens of minutes. Estimations of changes in the ionization rate were made. On the basis of the experimental data on electron density changes over the proton precipitation periods, corresponding flows were estimated, being ∼106-107m-2sec-. [ABSTRACT FROM AUTHOR]

Focuses on a study which was conducted to establish the relationship between new prescriptions for proton pump inhibitors and recorded upper gastrointestinal morbidity within a large computerized general practitioner database. Findings which indicate that oesophagitis was the commonest recorded indication in 1991; Conclusion in relation to morbidity associated with new prescriptions of the inhibitors. INSET: Key messages.