Journal of Geophysical Research: Space Physics最新文献

{"title":"Generation of FTE Signatures by the Kelvin–Helmholtz Instability","authors":"Yu-Lun Liou,&nbsp;Katariina Nykyri,&nbsp;Xuanye Ma,&nbsp;Shiva Kavosi","doi":"10.1029/2024JA033541","DOIUrl":"https://doi.org/10.1029/2024JA033541","url":null,"abstract":"<p>Magnetic reconnection and the Kelvin–Helmholtz instability (KHI) are the two fundamental processes in planetary magnetospheres that can lead to plasma, momentum, and energy transport across the magnetospheric boundary. Flux Transfer Events (FTEs), being characterized by the bipolar variation of the magnetic normal component, are often considered to be generated by magnetic reconnection. However, several possible mechanisms can also give rise to FTE-like features in the boundary layer and potentially mislead observational analysis; the KHI is one such candidate. Using two-dimensional magnetohydrodynamics (MHD) simulations, we examine and categorize the signatures observed by several virtual satellites as they pass through the Kelvin–Helmholtz waves along different trajectories. We have shown that the bipolar signatures were identified during the satellite's passage across the spine region and the leading/trailing edge of the KH vortex. The duration of bipolar signatures was also shown to vary depending not only on where the satellite trajectory intersects with the vortices, but also on the density asymmetry on both sides of boundary which in turn affects the relative motion between the vortices and satellite. Further, slight adjustments to the projection angle of the magnetic field are also applied in the simulations, as the signatures of the KHI are very sensitive to the in-plane magnetic field component. These results can be used as diagnostics when analyzing spacecraft data to help distinguish KHI-created signatures from FTE.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 4","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143877816","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Global Ionospheric F Region Parameters From GNSS-POD Limb Measurements: Evaluations and Comparisons With Two Empirical Models - IRI-2020 and NeQuick-2","authors":"Nimalan Swarnalingam,&nbsp;Dong L. Wu,&nbsp;Dieter Bilitza,&nbsp;Daniel J. Emmons,&nbsp;Cornelius Csar Jude H. Salinas,&nbsp;Artem Smirnov,&nbsp;Yenca Migoya-Orue","doi":"10.1029/2024JA033466","DOIUrl":"https://doi.org/10.1029/2024JA033466","url":null,"abstract":"<p>An optimal estimation (OE) technique has recently been developed for <i>F</i> region electron density (Ne) using Global Navigation Satellite System (GNSS) limb sounding on low Earth orbit (LEO) satellites (COSMIC-2, Spire, and FengYun-3). This method provides unprecedented spatiotemporal sampling for global monthly Ne climatology within 100–500 km in 2 hr intervals. The global dataset, collected during mid to moderately high solar activity, is compared with leading models: IRI-2020 and NeQuick-2. Diurnal variations in summer, winter, and equinoctial months are examined for the F2-layer peak, as well as the topside and bottomside of the <i>F</i> region. The observed and modeled NmF2 and hmF2 show good agreement during the daytime, but discrepancies appear with NeQuick-2 at night. The OE-retrieved dataset reveals distinct interhemispheric differences in topside scale height between the summer and winter hemispheres, which are not adequately captured by models. The estimated topside scale heights in IRI-2020 are <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>20–30 km higher than observations on regional scale, but this difference decreases to <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>12–20 km on global scale. In the bottomside, the agreement between observations and models varies significantly between daytime and nighttime conditions. During the daytime, the global bottomside thicknesses derived from OE-retrieved profiles agree within 10 km with the IRI-2020, but they are <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>10–15 km higher than NeQuick-2. The nighttime thicknesses differ substantially, with deviations reaching up to <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>30 km compared to IRI-2020 and <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>45 km compared to NeQuick-2. As models face challenges due to lack of reliable measurements, especially in the topside and bottomside, improvements in GNSS-LEO observing techniques can provide more accurate and comprehensive data to characterize the global ionosphere.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 4","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143877815","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characteristics of Energy-Latitude Dispersed Electron Precipitation Driven by EMIC Waves","authors":"Ruoxian Zhou,&nbsp;Xiao-Jia Zhang,&nbsp;Anton V. Artemyev,&nbsp;Didier Mourenas,&nbsp;Vassilis Angelopoulos","doi":"10.1029/2024JA033501","DOIUrl":"https://doi.org/10.1029/2024JA033501","url":null,"abstract":"<p>The resonant interaction of relativistic electrons and electromagnetic ion cyclotron (EMIC) waves significantly contributes to electron depletion in the outer radiation belts, resulting in their precipitation into Earth's atmosphere. While these interactions can effectively cause electron losses, their efficacy is influenced by various equatorial plasma and magnetic field characteristics, which are not always reliably measured in the wave source region. To gain a deeper understanding of the interaction between EMIC waves and electrons, we conduct a statistical analysis of low-altitude observations of dispersed electron precipitation induced by EMIC waves. Combining near-equatorial measurements from THEMIS, we show that the energy-latitude (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>L</mi>\u0000 </mrow>\u0000 <annotation> $L$</annotation>\u0000 </semantics></math>-shell) dispersion can be attributed to equatorial density and magnetic field gradients within the EMIC source region. By comparing properties of near-equatorial EMIC wave measurements and low-altitude precipitation measurements, we demonstrate that effective electron losses during these dispersion events are intimately associated with plasmasphere density gradients, well equatorward from the plasma sheet inner edge.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 4","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143877813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Separating DP1 and DP2 Current Pattern Contributions to Substorm-Like Intensifications in SML","authors":"C. J. Lao,&nbsp;C. Forsyth,&nbsp;M. P. Freeman,&nbsp;J. W. Gjerloev","doi":"10.1029/2024JA033592","DOIUrl":"https://doi.org/10.1029/2024JA033592","url":null,"abstract":"<p>Substorms have been identified from negative bays in the AL/SML index, which traces the minimum northward ground magnetic deflection at auroral latitudes, produced by enhancements of the westward electrojet. For substorms, negative bays are caused by the closure of the Substorm Current Wedge through the ionosphere, typically localized to the nightside and centered around 23-00 magnetic local time (MLT). In this case, the equivalent current pattern that causes the magnetic deflections is given the name Disturbance Polar (DP) 1. However, negative bays may also form when the westward electrojet is enhanced by increased convection, driving Pedersen and Hall currents in the auroral zone. Convection enhancements also strengthen the eastward electrojet, monitored by AU/SMU index. In this case, the equivalent current pattern that produces the magnetic deflections is called DP2. Unlike other substorm identification methods, the Substorm Onsets and PHases from Indices of the Electrojets technique by Forsyth et al. (2015), https://doi.org/10.1002/2015ja021343 attempts to distinguish between the DP1 and DP2 enhancements that cause substorm-like SML bays. Despite this, we find evidence that between 1997 and 2019 up to 59% of the 30,329 events originally identified as substorms come from enhancements of DP2 on top of the 2,627 convection enhancement events already identified. We explore ways to improve substorm identification using auroral indices to fully separate the DP1 and DP2 bays but conclude that there is insufficient information in the auroral indices to achieve this. In reality, any “substorm” list is a list of magnetic enhancements, auroral enhancements, etc., which may or may not correspond to substorm activity and should be treated that way.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 4","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033592","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143877818","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Estimating Electron Temperature and Density Using Van Allen Probe Data: Typical Behavior of Energetic Electrons in the Inner Magnetosphere","authors":"D. Rasinskaite,&nbsp;C. E. J. Watt,&nbsp;C. Forsyth,&nbsp;A. W. Smith,&nbsp;C. J. Lao,&nbsp;S. Chakraborty,&nbsp;J. C. Holmes,&nbsp;G. L. Delzanno","doi":"10.1029/2024JA033443","DOIUrl":"https://doi.org/10.1029/2024JA033443","url":null,"abstract":"&lt;p&gt;The Earth's inner magnetosphere contains multiple electron populations influenced by different factors. The cold electrons of the plasmasphere, warm plasma that contributes to the ring current, and the relativistic plasma of the radiation belts often seem to behave independently. Using omni-directional flux and energy measurements from the HOPE and Magnetic Electron Ion Spectrometer instruments aboard the Van Allen Probes, we provide a detailed density and temperature description of the inner magnetosphere, offering a comprehensive statistical analysis of the entire Van Allen Probe era. While number density and temperature data at geosynchronous orbit are available, this study focuses on the warm plasma in the inner magnetosphere &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mfenced&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;mo&gt;&lt;&lt;/mo&gt;\u0000 &lt;msup&gt;\u0000 &lt;mi&gt;L&lt;/mi&gt;\u0000 &lt;mo&gt;∗&lt;/mo&gt;\u0000 &lt;/msup&gt;\u0000 &lt;mo&gt;&lt;&lt;/mo&gt;\u0000 &lt;mn&gt;6&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/mfenced&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $left(2&lt; {L}^{ast }&lt; 6right)$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;. Values of density and temperature are extracted by fitting energy and phase space density to obtain the distribution function. The fitted distributions are related to the zeroth and second moments to estimate the number density and temperature. Analysis has indicated that a two Maxwellian fit is sufficient over a wide range of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mi&gt;L&lt;/mi&gt;\u0000 &lt;mo&gt;∗&lt;/mo&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${L}^{ast }$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; and that there are two independent plasma populations. The more energetic population has a median number density of approximately &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;1.2&lt;/mn&gt;\u0000 &lt;mo&gt;×&lt;/mo&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;msup&gt;\u0000 &lt;mn&gt;0&lt;/mn&gt;\u0000 &lt;mn&gt;4&lt;/mn&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $1.2times 1{0}^{4}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;mn&gt;3&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{m}}^{-3}$&lt;/annotation&gt;\u0000 &lt;","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 4","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033443","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143877814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Metallic Ions Near the Moon: Impact of Solar Activity and Lunar Position","authors":"Mei-Yun Lin,&nbsp;Andrew R. Poppe","doi":"10.1029/2024JA033566","DOIUrl":"https://doi.org/10.1029/2024JA033566","url":null,"abstract":"<p>Metallic ions are commonly found in the cis-lunar environment, primarily produced through the neutral lunar exosphere. They become prevalent species of lunar pickup ions as the Moon moves through the solar wind upstream, magnetosheath, and magnetotail. Extensive studies on the composition of lunar pickup ions from the Lunar Atmosphere and Dust Environment Explorer and THEMIS-ARTEMIS missions have revealed the significant presence of ions with around 28 and 40 amu near the Moon, which are later identified as metallic species such as Al⁺, Si⁺ and K⁺ ions. However, while these studies have provided valuable insights, the abundance of metallic ions and their variations with the Moon's location and solar activity has yet to be understood. This study calculates the production and ionization rates of metallic ions based on in-situ THEMIS-ARTEMIS observations. Our analysis indicates that the magnetosphere effectively reduces the production of metallic neutrals and ions due to the reduction of ionization and sputtering rates. The statistical analysis of the 12-year data set further shows that the lunar pickup ion fluxes are not heavily reliant on solar activity, and the median values remain relatively consistent over time. Therefore, the source rates of metallic pickup ions are associated with the location of the Moon rather than being dependent on solar activity. The outflow rates of heavy ion species from the Moon are comparable with the molecular and metallic ion rates from Earth's ionosphere, suggesting their essential roles in the dynamics of heavy ions in Earth's terrestrial environment.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 4","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143871641","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Interconnected Relationship Between Hydrogen and Protons During Martian Proton Aurora Activity: A Combined MAVEN Remote Sensing and In Situ Analysis","authors":"Andréa C. G. Hughes,&nbsp;Michael S. Chaffin,&nbsp;Edwin J. Mierkiewicz,&nbsp;Gina A. DiBraccio,&nbsp;Jasper Halekas,&nbsp;Sarah Henderson,&nbsp;Nicholas Schneider,&nbsp;Justin Deighan,&nbsp;Sonal Jain,&nbsp;Norberto Romanelli,&nbsp;Christina O. Lee,&nbsp;Majd Mayyasi,&nbsp;Ali Rahmati,&nbsp;Davin Larson,&nbsp;Shannon Curry","doi":"10.1029/2024JA032934","DOIUrl":"https://doi.org/10.1029/2024JA032934","url":null,"abstract":"<p>We compare observations of hydrogen (H) and protons associated with Martian proton aurora activity, co-evaluating remote sensing and in situ measurements during these events. Following the currently understood relationship between penetrating protons and H energetic neutral atoms (ENAs) in the formation of proton aurora, we observe an expected correlation between the H Lyman-alpha (Ly-<i>α</i>) emission enhancement (used herein as a proxy for H-ENAs) and penetrating proton flux. However, we also observe a notable spread in the trend between these two data sets. We find that this spread is contemporaneous with one of two major impacting events: high dust activity or extreme solar activity. Proton aurora events exhibiting a relative excess in penetrating proton flux compared to Ly-<i>α</i> enhancement tend to correspond with periods of high dust activity. Conversely, proton aurora events exhibiting a relative deficit of penetrating proton flux compared to Ly-<i>α</i> enhancement are qualitatively associated with periods of extreme solar activity. Moreover, we find that the largest proton aurora events occur during concurrent dust storm and solar events, primarily due to the compounding intensified increase in H column density above the bow shock. Finally, we present a simplified empirical estimate for Ly-<i>α</i> emission enhancement during proton aurora events based on the observed penetrating proton flux and a knowledge of local dust/solar activity at the time; this estimate provides a straightforward method for predicting auroral activity when direct observations are not possible or available. The results of this study advance our understanding of the interconnected relationship between H and protons during Martian proton aurora activity.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 4","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA032934","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143875548","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Low-Cost Monitoring of Energetic Particle Precipitation: Weather Balloon-Borne Timepix Measurements During the May 2024 Superstorm","authors":"L. Olifer,&nbsp;P. Manavalan,&nbsp;D. Headrick,&nbsp;S. Palmers,&nbsp;B. Harbarenko,&nbsp;J. Cai,&nbsp;J. Fourie,&nbsp;O. Bauer,&nbsp;I. R. Mann","doi":"10.1029/2024JA033626","DOIUrl":"https://doi.org/10.1029/2024JA033626","url":null,"abstract":"<p>Understanding energetic electron precipitation is crucial for accurate space weather modeling and forecasting, impacting the Earth's upper atmosphere and human infrastructure. This study presents a low-cost, low-mass, and low-power solution for high-fidelity analysis of electron precipitation events by measuring the resulting bremsstrahlung X-ray emissions. Specifically, we report on results from the flight of a radiation detector payload that utilized a silicon pixel read-out “Timepix” chip, and its successful utilization onboard a “burster” weather balloon. We launched this payload during the May 2024 superstorm, capturing high-resolution measurements of both background cosmic ray radiation as well as storm-time energetic electron precipitation. We further developed particle and radiation detection algorithms to separate bremsstrahlung X-rays from other particle species in the pixel-resolved trajectories as seen in the Timepix detector. The measurements revealed a distinctive four-peak structure in X-ray flux, corresponding to periodic four-minute-long bursts of energetic electron precipitation between 21:20 and 21:40 UT. This precipitation was also observed by a riometer station close to the balloon launch path, further validating balloon measurements and the developed X-ray identification algorithm. The clear periodic structure of the measured precipitation is likely caused by modulation of the electron losses from the radiation belt by harmonic Pc5 ultra-low frequency waves, observed contemporaneously on the ground. The study underscores the potential of compact, low-cost payloads for advancing our understanding of space weather. Specifically, we envision a potential use of such Timepix-based detectors in space science, for example, on sounding rockets or nano-, micro-, and small satellite platforms.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 4","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033626","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143875549","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Global and Sequential Imaging Observation of the Earth's Plasmasphere by PHOENIX Onboard EQUULEUS","authors":"Masaki Kuwabara,&nbsp;Kazuo Yoshioka,&nbsp;Reina Hikida,&nbsp;Go Murakami,&nbsp;Ichiro Yoshikawa,&nbsp;Shintaro Nakajima,&nbsp;Ryota Fuse,&nbsp;Yosuke Kawabata,&nbsp;Ryu Funase","doi":"10.1029/2024JA033389","DOIUrl":"https://doi.org/10.1029/2024JA033389","url":null,"abstract":"<p>The Plasmaspheric Helium ion Observation by Enhanced New Imager in eXtreme ultraviolet (PHOENIX) onboard EQUilibriUm Lunar-Earth point 6U Spacecraft (EQUULEUS) performed global imaging observations of the Earth's plasmasphere from a meridian view. PHOENIX is a normal-incidence telescope designed to observe He II emission at 30.4 nm, consisting of a mirror coated with molybdenum and silicon multilayers, a thin metallic filter made of aluminum and carbon, and a microchannel plate detector. This paper provides an overview of the PHOENIX instrument, its in-flight calibration, and initial results of Earth observations. During in-flight calibration, it was found that stray light affected the data when the phase angle between the line of sight and the Sun was small, but a method for its removal was developed using stray light observations. The calibration results confirmed that PHOENIX is optimized for He II observation, with a sensitivity of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>1.45</mn>\u0000 <mo>×</mo>\u0000 <msup>\u0000 <mn>10</mn>\u0000 <mrow>\u0000 <mo>−</mo>\u0000 <mn>2</mn>\u0000 </mrow>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> $1.45times {10}^{-2}$</annotation>\u0000 </semantics></math> cts/s/pix/Rayleigh for He II. It was also demonstrated that PHOENIX is capable of capturing global images of the Earth's plasmasphere with an angular resolution of less than 0.19° and a temporal resolution of less than 1.5 hr. In May 2023, PHOENIX successfully conducted imaging observations of the Earth's plasmasphere while EQUULEUS was on its way to the Earth-Moon Lagrange point 2, revealing the density structure along the dipole-shaped magnetic field lines. Furthermore, the shrinkage of the plasmasphere due to geomagnetic disturbances was captured. This marks the first global imaging of the Earth's plasmasphere using an ultra-small instrument.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 4","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033389","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143865948","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Observation of Large-Scale Traveling Ionospheric Disturbances in the Topside Ionosphere Using POD TEC From Multiple LEO Satellites Constellations","authors":"Pin-Hsuan Cheng,&nbsp;Y. Jade Morton","doi":"10.1029/2024JA033293","DOIUrl":"https://doi.org/10.1029/2024JA033293","url":null,"abstract":"<p>We present two case studies of large-scale traveling ionospheric disturbances (LSTIDs) triggered by the 23–24 April 2023 and the 10–12 May 2024 geomagnetic storms. The LSTIDs are observed in topside ionospheric total electron content (TEC) measurements obtained from precise orbit determination (POD) receivers onboard LEO satellites. The POD TEC data used in this work are from Spire Global, PlanetiQ, Meteorological Operational satellite-C (MetOp-C), TerraSAR-X/TanDEM-X (TSX/TDX), and COSMIC-2. The POD TEC captures the “frozen-in-time” wave structures of LSTIDs in the topside ionosphere (&gt;550 km altitude) due to its GNSS rays rapid scan velocity. During the April 2023 geomagnetic storm, we observed LSTIDs with a magnitude of ∼20 TEC unit in slant TEC (sTEC) over Antarctica and a LSTIDs with an apparent wavelength of 1,600 km over North America. For the May 2024 storm, the observed maximum sTEC disturbances were ∼35 TECu over the ocean near Antarctica and a LSTIDs with an apparent wavelength of ∼1,800 km over North America. To convert the sTEC to vertical TEC (vTEC), we applied Foelsche and Kirchengast mapping function with a centroid ionosphere effective height (IEH) to signals with zenith angle ≤50° and the Thin Layer Model mapping function with integral medium value IEH method for the signal with zenith angle &gt;50°. The POD vTEC are detrended and are compared with co-located ground-based GNSS TEC from Madrigal database. The results indicate that the POD TEC contributes a 11%–40% of the TEC disturbance magnitude of the LSTIDs observed from ground receivers.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 4","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143865949","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}