Journal of Geophysical Research: Space Physics最新文献

{"title":"The Energization and Escape of Cold Ions in Dayside Magnetopause Magnetic Reconnection","authors":"Heng Zhang,&nbsp;Bin-Wen Ge,&nbsp;Zhi-Lin Zhu,&nbsp;Kang Zhou,&nbsp;Zhuo-Hui Li,&nbsp;Qing-He Zhang,&nbsp;Hui-Jie Liu,&nbsp;Bin-Bin Tang,&nbsp;Wen-Ya Li","doi":"10.1029/2024JA033535","DOIUrl":"https://doi.org/10.1029/2024JA033535","url":null,"abstract":"<p>At the Earth's dayside magnetopause, a cold ion population of ionospheric or plasmasphere origin is commonly observed at the magnetospheric side. In this study we use a 2.5D Particle-in-Cell simulation to investigate the energization of cold ions in the separatrix near X-line and the escape process. And we identify observation events made by the Magnetospheric Multiscale mission, which provide evidence of the acceleration mechanism of cold ions in separatrix. We track the trajectories of cold ions and conduct an analysis, discovering that the cold ions exhibit a positive drift velocity in the vertical direction of the current sheet and <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>E</mi>\u0000 <mo>+</mo>\u0000 <msub>\u0000 <mi>v</mi>\u0000 <mrow>\u0000 <mi>c</mi>\u0000 <mi>i</mi>\u0000 </mrow>\u0000 </msub>\u0000 <mo>×</mo>\u0000 <mi>B</mi>\u0000 <mo>≠</mo>\u0000 <mn>0</mn>\u0000 </mrow>\u0000 <annotation> $mathbf{E}+{mathbf{v}}_{ci}times mathbf{B}ne 0$</annotation>\u0000 </semantics></math> in the separatrix, so the cold ions undergo demagnetized motion. The analysis results show that the Hall electric field accelerates the cold ions, and it is followed by gyrations around the magnetic field, which results in the velocity distribution function of cold ions near the separatrix exhibits a ring-like distribution. Both simulation results and observations indicated that cold ions in the asymmetric magnetic reconnection separatrix region near the X-line undergo significant acceleration owing to the effects of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>E</mi>\u0000 <mo>×</mo>\u0000 <mi>B</mi>\u0000 </mrow>\u0000 <annotation> $mathbf{E}times mathbf{B}$</annotation>\u0000 </semantics></math>, where Hall electric field and the magnetic field parallel to the current sheet play the primary roles during this process. Although magnetic reconnection opens a channel for cold ion escape, the escape is limited, and we first predict the quantification of the escape rate of the cold ions, approximately <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>0.2</mn>\u0000 <mi>%</mi>\u0000 </mrow>\u0000 <annotation> $0.2%$</annotation>\u0000 </semantics></math>. The escape of cold ions from the magnetosphere to the magnetosheath is challenging and rare.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 2","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143431691","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":"Spatial Variation of Polarization Ellipticity for Transionospheric HF Radio Waves Observed by RRI on e-POP/Swarm-E","authors":"E. C. Kalafatoglu Eyiguler,&nbsp;K. Pandey,&nbsp;G. C. Hussey,&nbsp;D. W. Danskin,&nbsp;R. G. Gillies,&nbsp;A. W. Yau","doi":"10.1029/2024JA032822","DOIUrl":"https://doi.org/10.1029/2024JA032822","url":null,"abstract":"<p>The Radio Receiver Instrument (RRI) on Enhanced Polar Outflow Probe (e-POP) onboard CASSIOPE/Swarm-E can detect transionospheric radio waves from ground-based transmitters. The RRI crossed-dipoles were slewed toward the Natural Resources Canada (NRCan) Ottawa transmitter during 10 experiments in April 2016 and 2017 to determine the polarization characteristics of the transionospheric HF radio waves. Six experiments were during geomagnetically quiet intervals and four during unsettled ionospheric conditions. The detected radio waves exhibit elliptical to circular polarized states over a broad region, extending <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 <mn>30</mn>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> ${sim} 30{}^{circ}$</annotation>\u0000 </semantics></math> beyond the theoretical range for aspect angle <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>(</mo>\u0000 <mrow>\u0000 <mn>90</mn>\u0000 <mo>°</mo>\u0000 <mo>±</mo>\u0000 <mn>10</mn>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <mo>)</mo>\u0000 </mrow>\u0000 <annotation> $(90{}^{circ}pm 10{}^{circ})$</annotation>\u0000 </semantics></math> northward of the transmitter. In accordance with magnetoionic theory, the radio waves are mostly linear when the radio wave propagation direction and the geomagnetic field are antiparallel, which occurs to the south of the transmitter. During unsettled ionospheric conditions, the ellipticity magnitude can take on any value between <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>−</mo>\u0000 <mn>45</mn>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> ${-}45{}^{circ}$</annotation>\u0000 </semantics></math> and <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>45</mn>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> $45{}^{circ}$</annotation>\u0000 </semantics></math> whereas during quiet conditions, the ellipticity magnitude has a variation within <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>±</mo>\u0000 <mn>15</mn>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> $pm 15{}^{circ}$</annotation>\u0000 </semantics></math>. Dominant regions of O- and X-mode waves, derived from a power distribution model, hint at a plausible explanation for the observed variations in ellipticity magnitude and rotation sense of radio waves.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 2","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143431690","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":"Frequency-Drifting Plasmaspheric Hiss Events Triggered by Three Consecutive Substorms in the Earth's Magnetosphere","authors":"Siyang Yi,&nbsp;Nigang Liu,&nbsp;Jiang Yu,&nbsp;Kun Li,&nbsp;Jun Cui","doi":"10.1029/2024JA033590","DOIUrl":"https://doi.org/10.1029/2024JA033590","url":null,"abstract":"<p>Whistler-mode waves are frequently observed electromagnetic emissions in planetary space. In the Earth's magnetosphere, the generation processes of whistler-mode waves within the high-density plasmasphere, referred to as plasmaspheric hiss, remain an open question. Here, based on the Van Allen Probes data, we report plasmaspheric hiss events triggered by three consecutive substorms within an interval of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>10 hr. These plasmaspheric hiss waves span a wide spatial region from post-midnight to prenoon (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>1</mn>\u0000 <mo>&lt;</mo>\u0000 </mrow>\u0000 <annotation> $1&lt; $</annotation>\u0000 </semantics></math>MLT<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>&lt;</mo>\u0000 <mn>12</mn>\u0000 </mrow>\u0000 <annotation> ${&lt; } 12$</annotation>\u0000 </semantics></math>), with varying intensity, frequency coverage, and propagation characteristics, yet share a similar frequency-drifting feature characterized by an increasing lower cutoff frequency over timescales exceeding 1 hr. Our analyses indicate that energy-dispersive injected electrons associated with the three substorms excite frequency-drifting whistler-mode waves in the outer plasmasphere around dawn, which subsequently propagate through the plasmasphere with the frequency-drifting feature retained. These events elucidate the direct link between substorm injection and plasmaspheric hiss, providing observational evidence for the excitation of hiss waves inside the plasmasphere by substorm injections.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 2","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143423517","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":"Nonlinear Interaction of the Lunar Tide M2 and the Diurnal Variation of Electron Density in the Ionosphere","authors":"Klemens Hocke,&nbsp;Nicholas M. Pedatella,&nbsp;Yosuke Yamazaki","doi":"10.1029/2024JA033482","DOIUrl":"https://doi.org/10.1029/2024JA033482","url":null,"abstract":"&lt;p&gt;Ground-based observations of time series of ionospheric electron density indicated the existence of spectral components at the periods of the lunar tidal constituents &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{O}}_{1}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; (25.82 hr) and &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mtext&gt;MK&lt;/mtext&gt;\u0000 &lt;mn&gt;3&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${text{MK}}_{3}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; (8.18 hr). It was unclear whether these variations are excited by &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{O}}_{1}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; and &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mtext&gt;MK&lt;/mtext&gt;\u0000 &lt;mn&gt;3&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${text{MK}}_{3}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; tides propagating from the surface into the ionosphere or if the variations are due to a nonlinear interaction of the semidiurnal lunar tide &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;M&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{M}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; with the diurnal variation of ionization (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;S&lt;/mi&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{S}}_{1}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;). A simulation was performed with the NSF National Center for Atmospheric Research thermosphere-ionosphere-mesosphere electrodynamics general circulation model (TIME-GCM). In the stratosphere at the lower boundary of TIME-GCM, the signal of the atmospheric semidiurnal lunar tide &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;M&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{M}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; is introduced. T","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 2","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033482","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143423518","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":"Excitation of Upper-Hybrid and Whistler-Mode Waves by Electron Velocity Ring Distribution","authors":"Sang-Yun Lee,&nbsp;Peter H. Yoon","doi":"10.1029/2024JA033285","DOIUrl":"https://doi.org/10.1029/2024JA033285","url":null,"abstract":"<p>The magnetospheres of the Earth and other magnetized planets are replete with high-frequency fluctuations, which are sometimes accompanied by multiple-harmonic electron cyclotron waves, and lower frequency waves of the whistler-mode type. Such waves are presumed to be excited by energetic electrons trapped in the dipolar magnetic field, the so-called loss-cone electrons, the electron ring distribution being a highly idealized example. The present paper investigates the stability of electron ring distribution with respect to the excitation of quasi-electrostatic upper-hybrid wave instability as well as the quasi-electromagnetic whistler mode instability that operates near electron cyclotron frequency. By employing a two-dimensional particle-in-cell numerical simulation, it is demonstrated that the relatively early dynamics is dominated by the upper-hybrid wave instability, but over a longer time period it is the whistler mode instability that ultimately determines the final relaxed state. The simulation results are interpreted with the quasilinear theoretical framework.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 2","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143404424","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":"Observations of Energetic O+ Ions With Strong Velocity Shear in the Low Latitude Boundary Layer During an Intense Storm Main Phase","authors":"Suping Duan,&nbsp;Anxin Zhang,&nbsp;Lei Dai,&nbsp;Yuntian Hou,&nbsp;Zhaohai He,&nbsp;Chi Wang","doi":"10.1029/2024JA033127","DOIUrl":"https://doi.org/10.1029/2024JA033127","url":null,"abstract":"<p>Using particle and electromagnetic field data from Magnetospheric Multiscale Spacecraft (MMS), we investigate energetic O⁺ ion characteristics in the strong velocity shear regions in the dusk-side low-latitude boundary layer (LLBL) during the main phase of an intense storm on 13 October 2016. In the large velocity reversal regions, O⁺ ion number density is very high, N_o+ ∼ 0.3 cm⁻³. The pitch angle distributions of these energetic O⁺ ions vary distinctly across different energy ranges. The pitch angles of the lower energetic (3–10 keV) O⁺ ions are mostly less than 45° and show a quasi-parallel distribution. Conversely, the pitch angles of the higher energetic (20–40 keV) O⁺ ions are dominantly in the range from 45 to 135°, suggesting a quasi-perpendicular distribution. The quasi-parallel distribution of lower energetic O⁺ ions implies that these O⁺ ions are outflow along the magnetic field line from the dayside high-latitude ionosphere. Intense electric fields in the strong shear flow region can accelerate O⁺ ions to higher energy, altering their motion from along the magnetic field to the transverse direction in the dusk-side LLBL. Our studies present evidence for strong shear flow in the dusk-side LLBL driving energetic O⁺ ions to traverse the magnetic field motion. The quasi-perpendicular distribution of higher energetic O⁺ ions, in the inner edge of the dusk-side LLBL, may provide a new source of ring current energetic particles during the main phase of the intense storm.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 2","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143404468","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":"Equatorial Ionization Anomaly X-Pattern Occurrences Observed by the GOLD Mission During Its First 5 Years","authors":"R. E. Daniell,&nbsp;R. W. Eastes,&nbsp;C. R. Martinis,&nbsp;D. K. Karan","doi":"10.1029/2024JA033299","DOIUrl":"https://doi.org/10.1029/2024JA033299","url":null,"abstract":"<p>The Global-scale Observations of Limb and Disk (GOLD) mission has provided an unusual array of upper atmosphere observations from a geostationary platform, including the behavior of the low latitude nighttime ionosphere. One of the features observed by GOLD is the formation of an X-pattern in the Equatorial Ionization Anomaly when its crests collapse near the magnetic equator. This paper discusses the X-patterns that were observed during the first 5 years of the GOLD mission (2018–2023). This catalog reveals that X-pattern occurrences are more frequent during low solar activity, and appear to be driven by changes in the normal low latitude zonal winds. In the longitude region observed by GOLD (approximately 75°W–5°E) they occurred exclusively during the September Equinox-December Solstice-March Equinox seasons, and they were more likely to occur near 45°W longitude, near the point where the geomagnetic equator crosses the geographic equator in the western hemisphere.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 2","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033299","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143404467","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":"Quantifying Meridional Advection in the Auroral E-Region For a Range of Geomagnetic Activity Levels","authors":"Rafael Mesquita,&nbsp;Stephen R. Kaeppler,&nbsp;Roger Varney,&nbsp;Ashton Reimer,&nbsp;Robert F. Pfaff,&nbsp;John Craven,&nbsp;Mark Conde,&nbsp;Irfan Azeem,&nbsp;Patrick Dandenault","doi":"10.1029/2024JA032952","DOIUrl":"https://doi.org/10.1029/2024JA032952","url":null,"abstract":"<p>The high-latitude E-region wind forcing has been studied extensively at large scales, but studies in auroral-oval-width scales are still sparse. In the auroral region, where the magnetospheric forcing is in the scale size of the aurora, winds can be forced to hundreds of meters per second in the auroral acceleration channel. This can result in large advective accelerations, where even a moderate cross-channel neutral wind could move momentum outside the acceleration channel through advection. In this paper, we use sounding rocket data from Alaska to estimate the meridional advective acceleration of horizontal momentum and other forcing terms for different geomagnetic activity levels. We used the Poker Flat Incoherent Scatter Radar measurements of F-region plasma drifts and E-region electron densities to calculate the magnetospheric Lorentz forcing (MLF). We interpret our results in terms of the gradient wind solution presented in recent study by Larsen et al. (2022, https://www.doi.org/10.1029/2021JA029936). We found that the magnitude of the advective acceleration and MLF generally increase with the sampled geomagnetic conditions in the non-storm time Quiet to Active range. We concluded that while a correlation between advection and geomagnetic activity is indicated but not the only factor at work with our results, the meridional advection can disturb the gradient balance and influence the neutral winds in both zonal and meridional directions. We also show that it is crucial to account for the time evolution of forcing of winds in the scale of 100–1,000s of kilometers when examining aurora-related events.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 2","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA032952","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143404471","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":"Enhancing Scientific Capacity in Africa – A Report on the 2023 International Space Weather Initiative School and the African Geophysical Society Annual Conference","authors":"Chigomezyo M. Ngwira,&nbsp;Endawoke Yizengaw,&nbsp;Nat Gopalswamy,&nbsp;Antti Pulkkinen,&nbsp;Prospery Simpemba","doi":"10.1029/2024JA033447","DOIUrl":"https://doi.org/10.1029/2024JA033447","url":null,"abstract":"<p>Natural hazards, such as weather in space and the terrestrial environment, have the potential to disrupt critical technologies and infrastructures that contribute to national security and economic advancement. Enhancing our understanding of natural hazards is a central part to developing mitigation strategies to avert their impact on technological assets and/or infrastructure. With the support of the broader scientific community, the International Space Weather Initiative (ISWI) and the African Geophysical Society (AGS) successfully organized two international events in September–October 2023, namely, the ISWI space weather school and the AGS Annual Conference. Both events were locally hosted by the Physics Society of Zambia in Lusaka, Zambia. This paper is a summary report of the two events, highlighting efforts focused on advancing scientific research in Africa. The report also outlines some of the major challenges faced and discusses key considerations for organizing future meetings.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 2","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033447","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143404470","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":"VLF Transmitter Signals Observed by the Cluster Spacecraft Over a Wide Range of Latitudes","authors":"F. Němec,&nbsp;O. Santolík,&nbsp;J. M. Albert","doi":"10.1029/2024JA033621","DOIUrl":"https://doi.org/10.1029/2024JA033621","url":null,"abstract":"<p>Very low frequency transmitter signals can penetrate through the ionosphere and propagate in the inner magnetosphere, being observed by spacecraft instruments with sufficient frequency resolution and range. We use 23 years of measurements performed by the Waves of High frequency and Sounder for Probing of Electron density by Relaxation instrument on board the four Cluster spacecraft at frequencies up to 80 kHz to investigate the observed wave intensities. The transmitter signals are about an order of magnitude more intense during the night than during the day, and they are apparently confined within the plasmasphere. The extensive latitudinal coverage of the measurements allows us to investigate frequency cut-offs observed in the transmitter spectra. These are mostly in line with nonducted propagation, but occasional partial ducting seems to be necessary to explain signals spanning otherwise inaccessible regions. Finally, we compare the observed intensity patterns with the calculations of Starks et al. (2020), https://doi.org/10.1029/2019ja027029. Although overall agreement is obtained, the observed wave intensities tend to be a factor of about 2–3 lower than the calculated intensities.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 2","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033621","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143396775","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}