Proton Precipitation Research Articles

Ionospheric Modulation by EMIC Wave‐Driven Proton Precipitation: Observations and Simulations

AbstractProtons of tens of keV can be resonantly scattered by electromagnetic ion cyclotron (EMIC) waves excited in the magnetosphere, resulting in proton precipitation down to the upper atmosphere. In this study, we report for the first time the ionospheric height‐dependent ionization in response to EMIC‐associated isolated proton aurora (IPA) using simultaneous space‐borne and ground‐based measurements. On 06 March 2019, the Polar Orbiting Environmental Satellites observed significant proton precipitation in the dusk sector (MLT ∼ 19), while ground‐based magnetometers detected a clear signature of EMIC waves. Meanwhile, the conjugated all sky imager captured an IPA and the nearby Poker Flat incoherent scatter radar (PFISR) showed enhanced electron density in the E region, suggesting a potential consequence of the EMIC wave‐driven proton precipitation. The Global Airglow model simulations confirmed the dominant impact of proton precipitation on the ionosphere and agreed well with PFISR observations. This study confirmed physical links from the magnetosphere to the ionosphere through EMIC‐driven proton precipitation.

First 3D hybrid-Vlasov global simulation of auroral proton precipitation and comparison with satellite observations

The precipitation of charged particles from the magnetosphere into the ionosphere is one of the crucial coupling mechanisms between these two regions of geospace and is associated with multiple space weather effects, such as global navigation satellite system signal disruption and geomagnetically induced currents at ground level. While precipitating particle fluxes have been measured by numerous spacecraft missions over the past decades, it often remains difficult to obtain global precipitation patterns with a good time resolution during a substorm. Numerical simulations can help to bridge this gap and improve the understanding of mechanisms leading to particle precipitation at high latitudes through the global view they offer on the near-Earth space system. We present the first results on auroral (0.5–50 keV) proton precipitation within a 3-dimensional simulation of the Vlasiator hybrid-Vlasov model. The run is driven by southward interplanetary magnetic field conditions with constant solar wind parameters. We find that on the dayside, cusp proton precipitation exhibits the expected energy–latitude dispersion and takes place in the form of successive bursts associated with the transit of flux transfer events formed through dayside magnetopause reconnection. On the nightside, the precipitation takes place within the expected range of geomagnetic latitudes, and it appears clearly that the precipitating particle injection is taking place within a narrow magnetic local time span, associated with fast Earthward plasma flows in the near-Earth magnetotail. Finally, the simulated precipitating fluxes are compared to observations from Defense Meteorological Satellite Program spacecraft during driving conditions similar to those in the simulation and are found to be in good agreement with the measurements.

The Electronic Kinetics of Molecular Nitrogen and Molecular Oxygen in the Earth’s Middle Atmosphere during the GLE Events of Solar Cycle 23

Based on models of the electronic kinetics of triplet and singlet states of molecular nitrogen andsinglet states of molecular oxygen for the Earth’s middle atmosphere, we calculated the intensity profiles ofthe bands of the first and second positive N2 systems, the Lyman–Birge–Hopfield N2 bands, and the infraredO2 bands in the case of precipitation of high-energy protons during the GLE65, GLE67, GLE69, and GLE70events of solar cycle 23. Calculations have shown that almost over the entire interval of altitudes of 20–80 km,there is a significant contribution from the processes of quenching some electronically excited states of N2and O2 during molecular collisions. The kinetics of O2 singlet states at the altitudes of the middle atmosphereduring proton precipitation is considered taking into account both direct excitation by high-energy particlesand intermolecular processes of electron excitation transfer

Observations of Mercury's Plasma Sheet Horn: Characterization and Contribution to Proton Precipitation

AbstractThe Mercury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) spacecraft was the first spacecraft to orbit the planet Mercury. Previous analysis of MESSENGER data has established that of all the planets in the solar system, Mercury's magnetosphere is the most like Earth's, dominated by the Dungey cycle in its dynamic response of the magnetosphere to solar wind forcing. In this work, we identify and describe for the first time Mercury's northern plasma sheet horn—a Dungey cycle feature key to plasma precipitation. We find three possible geometries for potential horn observation by MESSENGER and describe a case study of each. Two additional case studies are presented with geometries particularly favorable to estimating plasma precipitation within the horns. Estimates of proton precipitation flux are performed, which show precipitation levels on the order of 107 per cm2 per second, on the same order of magnitude as the estimated proton precipitation flux in the dayside cusp despite the higher average energy of the protons in the horn. Potential paths for future study of the horns are discussed.

Proton Precipitation in Mercury's Northern Magnetospheric Cusp

AbstractIon precipitation onto Mercury's surface through its magnetospheric cusps acts as a source of planetary atoms to both Mercury's exosphere and magnetosphere. Through the process of ion sputtering, solar wind ions (∼95% protons) impact the surface regolith and liberate material, mostly as neutral atoms. We have identified 2760 northern magnetospheric cusp crossings throughout the MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) mission, based on enhancements in proton flux observed by the Fast Imaging Plasma Spectrometer (FIPS). We find cusp crossings spanning 50–85° in magnetic latitude with a geometric center typically at 60–70°. The cusp center is stable about its average but its latitudinal extent varies orbit‐to‐orbit. The mean latitude weakly depends on the magnitude of the interplanetary magnetic field (IMF), dropping by about 1.3° magnetic latitude for each increase of 10 nT in IMF strength. We have used these identified cusp boundaries to estimate the flux of protons which will precipitate onto Mercury's surface. We find an average proton precipitation flux of 1.0 × 107 cm−2 s−1, ranging 3.3 × 104–6.2 × 108 cm−2 s−1, and that this flux can vary substantially between subsequent 10‐s measurements. We also tabulated the peak precipitation fluxes for each cusp crossing. They range 9.8 × 104–1.4 × 109 cm−2 s−1, with a mean of 3.7 × 107 cm−2 s−1. We find strong dependencies on the local time of the cusp crossing as well as on Mercury's orbit around the Sun, which warrant further investigation.

On the green isolated proton auroras during Canada thanksgiving geomagnetic storm

The existence of detached/isolated auroral structures in the subauroral ionosphere has been recognized and studied for decades. One major subset of such detached auroras is the so-called “isolated proton aurora” (IPA). IPA is characterized by substantial hydrogen emissions and thus inferred to be proton aurora, but is also accompanied by other emission lines. In particular, IPA is usually dominated by 557.7 nm green-line emissions in optical luminosity. To date, there is still a lack of dedicated spectrographic study and detailed comparison among structures in different emission lines of IPA. The intensity ratios between the 557.7 nm and hydrogen emissions in IPA have not been well established from concurrent observations or theoretical models. In this study, we report an IPA event during ∼0245–0345 UT on 12 October 2021, the Canada Thanksgiving storm night. Using multi-station, multi-wavelength optical instruments, including the Transition Region Explorer (TREx) spectrograph, we investigate the evolution and spectrographic properties of the IPA. In-situ and ground magnetometer data show evidence of electromagnetic ion cyclotron (EMIC) waves associated with the passage of IPA, supporting a causal link between the EMIC wave and the proton precipitation. The precipitating proton energies are estimated to range between a few keV and a few tens of keV according to the IPA emission heights inferred from triangulation analyses. Via careful examination of the spectral intensities and the elevation-angle profiles of the 557.7, 427.8, and 486.1 nm emissions based on the spectrograph data, we conclude that the 557.7 nm emissions contained in the IPA were unlikely to owe their source to energetic electron precipitation from the magnetosphere, but were the byproduct of the proton precipitation. The intensity ratio between the 557.7 nm (427.8 nm) and the 486.1 nm emissions of the IPA are confined within a relatively narrow range around ∼26 (∼4), which may serve as validation tests for existing and developing proton transport models.

Dependence of the global dayside reconnection rate on interplanetary magnetic field By and the earth’s dipole tilt

In the recent years, significant attention has been given to the combined effect of Interplanetary Magnetic Field (IMF) duskward component (By) and dipole tilt on the global magnetosphere-ionosphere system response. Numerous studies have pointed out that when the Earth’s magnetic dipole is tilted away from the Sun (negative dipole tilt during northern winter), and IMF has a positive By component, the effects on ionospheric currents, particle precipitation, ionospheric convection, and average size of the auroral oval, is significantly more enhanced, compared to when IMF By is negative. Furthermore, this IMF By polarity effect reverses when Earth’s dipole is tilted in the opposite direction. The underlying cause has remained unclear. Our analysis shows that substorms tend to be stronger during the same IMF By and dipole tilt polarity combination. Taken together with earlier results showing also more frequent substorms during the same conditions, our observations suggests that when IMF By and dipole tilt have opposite signs, there is a more efficient global dayside reconnection rate. We also show analysis of the occurrence frequency of periods of Steady Magnetospheric Convection, substorm onset latitude, and the isotropic boundary of proton precipitation, that are all consistent with our conclusion that the combination of IMF By and dipole tilt polarity affect the global dayside reconnection rate.

An Empirical Model of the Proton Isotropic Boundary (IB)

AbstractAt mid‐ and high‐latitudes, energetic protons of magnetospheric origin precipitate down to the upper atmosphere, manifested as one of the most important coupling processes between the ionosphere and magnetosphere. The equatorward boundary of the energetic proton precipitation, or called isotropic boundary (IB), is usually believed to coincide with the boundary in the magnetosphere where field line curvature scattering of protons transits from strong to weak. In this study, we statistically examine the global distribution of the IB for 39 and 115 keV ring current protons as detected by the NOAA/Polar Operational Environmental Satellites in 2013–2018 and propose an empirical model of the IB as a function of solar wind conditions, magnetic local time, and geomagnetic activity index. The IB is well ordered by SYM‐H index and interplanetary magnetic field Bz, moving to lower latitudes with more negative SYM‐H index and Bz values, and with larger AE index and solar wind pressure. Energy dispersions of the IB are also explored, consistent with the scenario of field curvature scattering in the magnetosphere. This empirical model can be used as an indirect measure of the strength of the magnetospheric stretching and may be applied in magnetosphere‐ionosphere mapping studies.

Comparison of Weekly Variations in the Electrical Conductivity of the Lower Edge of the Ionosphere during Solar Proton Precipitations on September 29 and October 19, 1989

Comparison of Weekly Variations in the Electrical Conductivity of the Lower Edge of the Ionosphere during Solar Proton Precipitations on September 29 and October 19, 1989

The data for "Chain effects from EMIC waves, proton precipitation, and down to ionospheric responses"

The data for "Chain effects from EMIC waves, proton precipitation, and down to ionospheric responses"

The data for "Ionospheric modulation by EMIC wave driven proton precipitation: observations and simulations"

The data for "Ionospheric modulation by EMIC wave driven proton precipitation: observations and simulations"

Miniature ion analyzer for applications in space weather monitoring

This article presents the results of development and testing of a simple and compact ion energy-mass analyzer. PICA (Plasma Ion Compact Analyzer) is designed as a solution for solar wind measurements, polar proton precipitation monitoring and as a miniature solution for various space plasma experiments. We introduce general ideas that lead to the development of a simple and low-cost instrument and review several operating plasma instruments. After we address our previous results in modeling a possible scheme of the instrument and indicate improvements based on the results of previous research. We introduce the details of computer modeling of an improved for space application model, the results of prototype tests and flight configuration unit preformance. During the tests we checked the energy and mass resolutions of the laboratory prototype (ΔE/E = 4% M/ΔM = 4–8). All parameters were checked for the energy range of the upper boundary of 5 keV owing to the limitations of our equipment. The analytical characteristics of the instrument allow for distinguishing the fluxes of protons and alpha particles and monitoring the main parameters of the solar wind. The flight configuration of the instrument and can be placed on 3U CubeSATs.

Coexistence of Martian Proton Aurorae and Proton Cyclotron Waves during the Enhancement of Solar Wind Activity

Due to the lack of a global magnetic field, the charge exchange process between the solar wind protons and Martian hydrogen corona is of critical importance to Mars’ atmosphere. The energetic neutral atoms and pickup H+ produced during this process can further excite proton aurorae and proton cyclotron waves (PCWs) in the near-Mars space, for which the observational evidence however remains very limited. Here we report a particular event to show that the PCWs and proton aurorae were simultaneously recorded by the Mars Atmosphere and Volatile EvolutioN spacecraft during 10 consecutive orbits. As the byproducts of the charge exchange process, these two phenomena are found to be highly correlated in both space and time, with the correlation coefficient >0.7 between the auroral emissions and PCW amplitudes. Moreover, the wave and ultraviolet measurements show clearly that both the PCWs and proton aurora events tend to occur more frequently and intensively within the stream interaction region, as being strongly modulated by the solar wind activity. Our results indicate that the solar wind can directly transport energy and particles into the near-Mars environment, leading to the simultaneous enhancements of plasma wave activity and proton precipitation, which therefore helps comprehend the significant role of the solar wind activity and charge exchange process in driving the energy budget to the Martian upper atmosphere.

The data for "Evidences of the chain effect from EMIC wave-driven proton precipitation to ionospheric ionization"

The data for "Evidences of the chain effect from EMIC wave-driven proton precipitation to ionospheric ionization"

Effects of EMIC Wave‐Driven Proton Precipitation on the Ionosphere

AbstractWe 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.

Effects of polarization-reversed EMIC waves on the ring current dynamics

It is widely believed that the electromagnetic ion cyclotron (EMIC) waves play an important role in influencing the radiation belt and ring current dynamics. Most studies investigated the effects or characteristics of EMIC waves assuming their left-handed polarization. However, recent studies found that the polarization reversal, which occurs at higher latitudes along the wave propagation path, can change the wave-induced pitch angle diffusion coefficients. Whether such a polarization reversal can influence the global ring current dynamics remains unknown. In this study, we investigate the ring current dynamics and proton precipitation loss in association with the polarization reversed EMIC waves using the Ring current - Atmosphere interactions Model (RAM). The results indicate that the polarization reversal of H-Band EMIC waves truly can decrease the scattering rates of protons of 10 to 50 keV or > 100 keV by comparing with the scenario where the EMIC waves are considered as purely left-handed polarized. Additionally, it is found that the global ring current intensity and proton precipitation can be slightly affected by the polarization reversal, especially during the prestorm and recovery phase, but the effects are not that large during the main phase. This is probably because the H-Band EMIC waves contribute to the proton scattering loss primarily at E < 10 keV, an energy range that is not strongly affected by the polarization reversal.

Relativistic Electron Precipitation Near Midnight: Drivers, Distribution, and Properties

AbstractWe analyze the drivers, distribution, and properties of the relativistic electron precipitation (REP) detected near midnight by the Polar Orbiting Environmental Satellites (POES) and Meteorological Operational (MetOp) satellites, critical for understanding radiation belt losses and nightside atmospheric energy input. REP is either driven by wave‐particle interactions (isolated precipitation within the outer radiation belt), or current sheet scattering (CSS; precipitation with energy dispersion), or a combination of the two. We evaluate the L‐MLT distribution for the identified REP events in which only one process evidently drove the precipitation (∼10% of the REP near midnight). We show that the two mechanisms coexist and drive precipitation in a broad L‐shell range (4–7). However, wave‐driven REP was also observed at L &lt; 4, whereas CSS‐driven REP was also detected at L &gt; 7. Moreover, we estimate the magnetotail stretching during each REP event using the magnetic field observations from the Geostationary Operational Environmental Satellite (GOES). Both wave‐particle interactions and CSS drive REP in association with a stretched magnetotail, although CSS‐driven REP potentially shows more pronounced stretching. Wave‐driven REP events are localized in L shell and often occur on spatial scales of &lt;0.3 L. Using either proton precipitation (observed by POES/MetOp during wave‐driven REP) as a proxy for electromagnetic ion cyclotron (EMIC) wave activity or wave observations (from GOES and the Van Allen Probes) at the conjugate event location, we find that ∼73% wave‐driven REP events are associated with EMIC waves.

Modeling of Diffuse Auroral Emission at Mars: Contribution of MeV Protons

AbstractThe Solar Energetic Particle and imaging ultraviolet spectrograph (IUVS) instruments onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft discovered diffuse aurora that span across the nightside of Mars due to the interaction of solar energetic particles (SEPs) with the Martian atmosphere. However, it is unclear whether the diffuse aurora originates from energetic electrons or protons. We have developed a Monte Carlo model to calculate the limb intensity profile of the CO2+ ultraviolet doublet (UVD) due to precipitation of energetic electrons and protons with energy ranges from 100 eV to 100 keV and from 50 keV to 5 MeV, respectively. We used electron and proton fluxes observed by MAVEN during the December 2014 SEP event and the September 2017 SEP event. Our results showed that proton‐induced CO2+ UVD emission has a lower peak altitude than electron‐induced CO2+ UVD emission. The calculated peak altitudes of the CO2+ UVD limb profiles are 76 and 68 km in the December 2014 event and the September 2017 event, respectively. Extending the energy to 500 keV for electrons and 20 MeV for protons further improved our comparison to the IUVS observations. We have succeeded in reproducing peak altitudes and shapes of the observed CO2+ UVD limb profiles using the SEP flux observed by MAVEN. This was possible by taking into account the contribution of energetic protons, indicating that both energetic electrons and protons contribute to producing the observed diffuse aurora.

Luminescence of Molecular Nitrogen and Molecular Oxygen in the Earth’s Middle Atmosphere During the Precipitation of High-Energy Protons

Luminescence of Molecular Nitrogen and Molecular Oxygen in the Earth’s Middle Atmosphere During the Precipitation of High-Energy Protons

Isolated Proton Aurora Driven by EMIC Pc1 Wave: PWING, Swarm, and NOAA POES Multi‐Instrument Observations

AbstractWe 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.