Journal of Geophysical Research: Space Physics最新文献

{"title":"Solar Activity Effects on the Near-Earth Space Regions During the Descending Phase of Solar Cycle 24","authors":"Zhaohai He,&nbsp;Jiyao Xu,&nbsp;Lei Dai,&nbsp;Suping Duan,&nbsp;Hong Gao,&nbsp;Guojun Wang,&nbsp;Ilan Roth,&nbsp;Chi Wang","doi":"10.1029/2024JA032860","DOIUrl":"https://doi.org/10.1029/2024JA032860","url":null,"abstract":"<p>The solar cycle includes multi-scale variations in the near-Earth space regions including plasmasphere, inner radiation belt (IRB), ionosphere, mesosphere and lower thermosphere (MLT). We present a thorough analysis of the extent of solar cycle effect on those four regions by using mesospheric and thermospheric geopotential height and temperature from SABER on TIMED, ionospheric hmF2 from Chinese Meridian Project, high-energy protons in IRB and electron density in plasmasphere from Van Allen Probes within 2013–2018 intervals. By analyzing evolutions of these quantities, we find that entire IRB, ionosphere and MLT region shrink at solar minimum and stretch at solar maximum by ∼10³, 50–10², and 1 km scales, respectively, while plasmapause shows an opposite trend. Fourier spectra of these quantities have been investigated by Lomb–Scargle periodogram. The mid-term periodic oscillations (13.5-day, 45-day, and 52-day) have been observed in MLT region, matching well with plasmapause locations and geomagnetic indices, which have not been observed in solar EUV radiation and IRB. This may indicate that those oscillations facilitate energy exchange and mass transportation between MLT region and plasmasphere due to magnetic storms and substorms. The oscillation periods of higher energy (102.6 MeV) in IRB have not been observed in MLT region except for annual variations. The impact of higher energy protons on MLT regions may not be significant, although they could penetrate deeper into MLT region. Our results reveal relationships between some quantities and solar cycle multi-scale modulation, which may provide assistance and monitors for mass transportation in the near-Earth space regions.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 11","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142665064","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":"Nocturnal Sporadic Cusp-Type Layer (Esc) Resulting From Anomalous Excess Ionization Over the SAMA Region During the Extreme Magnetic Storm on 11 May 2024","authors":"L. C. A. Resende,&nbsp;Y. Zhu,&nbsp;A. M. Santos,&nbsp;R. A. J. Chagas,&nbsp;C. M. Denardini,&nbsp;C. Arras,&nbsp;L. A. Da Silva,&nbsp;P. A. B. Nogueira,&nbsp;S. S. Chen,&nbsp;V. F. Andrioli,&nbsp;J. Moro,&nbsp;J. R. Costa,&nbsp;H. Li,&nbsp;C. Wang,&nbsp;Z. Liu","doi":"10.1029/2024JA033167","DOIUrl":"https://doi.org/10.1029/2024JA033167","url":null,"abstract":"<p>Digisonde data showed a peculiar behavior in the nighttime lower ionosphere over Cachoeira Paulista (CXP, 22.7°S, 45°W, dip ∼35°), a low-latitude station located inside the South American Magnetic Anomaly (SAMA) during the main phase of the extreme magnetic storm on 11 May 2024. The E region appeared in observational data at high altitudes after sunset, which is unexpected. In sequence, it performed an unusual descending movement due to the disturbed electric field. The extra ionization responsible for forming the nocturnal E layer is due to the precipitation (EPP) of low energic (&lt;30 keV) particles. Moreover, a diurnal cusp-type Es layer (Es_c) appeared simultaneously, which has never been reported in the literature at such hours. Thus, the results further suggest that the EPP may have caused an oscillation in the thermosphere, forming the Es_c usually seen in the daytime. Therefore, this study shows the different mechanisms acting together during this magnetic storm, creating a daytime ionosphere after sunset over the SAMA region, as confirmed by observational data and simulations.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 11","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142665091","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":"Near-Real-Time Identification of the Source of Ionospheric Disturbances","authors":"B. Maletckii,&nbsp;E. Astafyeva","doi":"10.1029/2024JA032664","DOIUrl":"https://doi.org/10.1029/2024JA032664","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <p>The ionosphere is characterized by a large number of disturbances generated in response to a wide range of phenomena, including natural hazards, space weather and man-made events. Identification of the origin of ionospheric disturbances (ID), especially in real or near-real-time (NRT), is an extremely difficult task, and it is one of the most interesting fundamental scientific questions. In this paper we present, for the first time, an approach for an automatic and NRT-compatible detection and recognition of the source of ionospheric disturbances in time series of total electron content (TEC) measured by the Global Navigation Satellite Systems (GNSS) method. The main idea is (a) to analyze main characteristics (such as spatio-temporal features and frequency content) of ID generated by known sources, and (b) in NRT, to rapidly examine ID's features, and, based on this information, recognize their source. Currently, our database contains TEC data series with response to earthquakes, volcanic eruptions, tornadoes, explosions, rocket launches, equatorial plasma bubbles and geomagnetic storms. Our developments are important for the future assessment of natural hazards from the ionosphere, and also for NRT Space Weather nowcast and applications. Also, our work presents important information about the physical properties of ID of different origins.</p>\u0000 </section>\u0000 </div>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 11","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA032664","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664982","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":"The Curvature of TEC as a Proxy for Ionospheric Amplitude Scintillation","authors":"K. Meziane,&nbsp;A. M. Hamza,&nbsp;P. T. Jayachandran","doi":"10.1029/2024JA033226","DOIUrl":"https://doi.org/10.1029/2024JA033226","url":null,"abstract":"&lt;p&gt;Fluctuations in the ionospheric electron density cause distortions in the Global Navigation Satellite Systems (GNSS) signals recorded on the ground. The examination of these distortions reveal some of the physical conditions under which the electron density fluctuations develop as well as their physical characteristics. Several studies have investigated the correlation between the rate of change of the total electron content &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;(&lt;/mo&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;R&lt;/mi&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mi&gt;T&lt;/mi&gt;\u0000 &lt;mi&gt;I&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;mo&gt;)&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $(ROTI)$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; and amplitude and phase scintillation indices &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;4&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${S}_{4}$&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;mi&gt;σ&lt;/mi&gt;\u0000 &lt;mi&gt;Φ&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${sigma }_{{Phi }}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, respectively. These studies stipulate that &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;R&lt;/mi&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mi&gt;T&lt;/mi&gt;\u0000 &lt;mi&gt;I&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $ROTI$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; could be used as a proxy for scintillation indices. The link between the scintillation indices and the variations in &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;T&lt;/mi&gt;\u0000 &lt;mi&gt;E&lt;/mi&gt;\u0000 &lt;mi&gt;C&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $TEC$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; is investigated both theoretically and empirically. Our study shows that the second derivative (the Laplacian) of the &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;T&lt;/mi&gt;\u0000 &lt;mi&gt;E&lt;/mi&gt;\u0000 &lt;mi&gt;C&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $TEC$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; provides a better diagnosis of the nature of the interaction of trans-ionospheric radio signals with ionospheric irregularities. In the refractive case, the second derivative of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;T&lt;/mi&gt;\u0000 &lt;mi&gt;E&lt;/mi&gt;\u0000 &lt;mi&gt;C&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $TEC$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; fluctuations vanish","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 11","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664760","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":"Lower-Hybrid Wave-Induced Plasma Mixing Related to Kelvin-Helmholtz Vortices During Southward IMF","authors":"K. A. Blasl,&nbsp;A. Settino,&nbsp;R. Nakamura,&nbsp;H. Hasegawa,&nbsp;T. K. M. Nakamura,&nbsp;M. Hosner","doi":"10.1029/2024JA033152","DOIUrl":"https://doi.org/10.1029/2024JA033152","url":null,"abstract":"<p>We examine characteristics of the boundaries of 11 Kelvin-Helmholtz vortex crossings observed by MMS on 23 September 2017 under southward IMF conditions. At both the leading and trailing edges, boundary regions of mixed plasma are observed together with lower-hybrid wave activity. We found that thicker boundary regions feature a higher number of sub-ion scale current sheets, of which only one shows clear reconnection signatures. Moreover, the lower-hybrid waves along the vortex spine region are identified as an effective mechanism for plasma transport with an estimated diffusion coefficient of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>D</mi>\u0000 <mo>≈</mo>\u0000 <mn>1</mn>\u0000 <msup>\u0000 <mn>0</mn>\u0000 <mn>9</mn>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> $Dapprox 1{0}^{9}$</annotation>\u0000 </semantics></math> <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msup>\u0000 <mi>m</mi>\u0000 <mn>2</mn>\u0000 </msup>\u0000 <mo>/</mo>\u0000 </mrow>\u0000 <annotation> ${mathrm{m}}^{2}/$</annotation>\u0000 </semantics></math>s. Comparisons with 3D simulations performed under the same conditions as the MMS event suggest that the extension of the boundary regions as well as the number of current sheets are related to different evolutionary stages of the vortices. Such observations can be explained by changes in the upstream magnetic field conditions.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 11","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033152","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142642121","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":"Simultaneous Observations of Mirror Mode Structures and Electromagnetic Ion Cyclotron Waves in the Earth's Outer Magnetosphere","authors":"Xiaoman Liu,&nbsp;Jiang Yu,&nbsp;Zuzheng Chen,&nbsp;Jing Wang,&nbsp;Aojun Ren,&nbsp;Liuyuan Li,&nbsp;Jun Cui,&nbsp;Jinbin Cao","doi":"10.1029/2024JA032951","DOIUrl":"https://doi.org/10.1029/2024JA032951","url":null,"abstract":"<p>Electromagnetic ion cyclotron (EMIC) waves and mirror mode structures respectively produced by the cyclotron and mirror instabilities are both generated by the temperature anisotropy of ions. However, whether these two instabilities can grow simultaneously in the magnetosphere is still unclear, as well as how they distribute if they can. In this paper, we first report an event of simultaneous observation of mirror mode structures and EMIC waves and then perform a statistical survey in the magnetosphere based on the measurements from Magnetospheric Multiscale (MMS) satellites. The event is observed in the duskside (MLT ∼ 18 hr) of Earth's outer magnetosphere (L ∼ 12) near the magnetic equator (MLAT ∼ 12°). The further linear instability analyses demonstrate that mirror mode structures and EMIC waves can be simultaneously and locally generated in the magnetosphere. The statistical results show that simultaneous mirror mode structures and EMIC waves are mainly distributed in the dawnside and duskside of the outer magnetosphere with slightly larger numbers in the dawnside but no significant differences in the proton number density, and plasma beta, proton temperature anisotropy, power-weighted wave frequency, and wave normal angle.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 11","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142642118","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":"On the Contribution of Latitude-Dependent ULF Waves to the Radial Transport of Off-Equatorial Relativistic Electrons in the Radiation Belts","authors":"Theodore E. Sarris,&nbsp;Xinlin Li,&nbsp;Hong Zhao,&nbsp;Weichao Tu,&nbsp;Kostis Papadakis,&nbsp;Stelios Tourgaidis,&nbsp;Wenlong Liu,&nbsp;Li Yan,&nbsp;Robert Rankin,&nbsp;Zheng Xiang,&nbsp;Yang Mei,&nbsp;Declan O’Brien,&nbsp;Benjamin Hogan,&nbsp;David Brennan,&nbsp;Robert E. Ergun,&nbsp;Vassilis Angelopoulos,&nbsp;Dimitris Baloukidis,&nbsp;Panagiotis Pirnaris","doi":"10.1029/2024JA032905","DOIUrl":"https://doi.org/10.1029/2024JA032905","url":null,"abstract":"<p>Ultra-low frequency (ULF) waves radially diffuse hundreds-keV to few-MeV electrons in the magnetosphere, as the range of drift frequencies of such electrons overlaps with the wave frequencies, leading to resonant interactions. Theoretically this process is described by analytic expressions of the resonant interactions between electrons and ULF wave modes in a background magnetic field. However, most expressions of the radial diffusion rates are derived for equatorially mirroring electrons and are based on estimates of the power of ULF waves that are obtained either from spacecraft close to the equatorial plane or from the ground but mapped to the equatorial plane. Based on recent statistical in situ observations, it was found that the wave power of magnetic fluctuations is significantly enhanced away from the magnetic equator. In this study, the distribution of the wave amplitudes as a function of magnetic latitude is compared against models simulating the natural modes of oscillation of magnetospheric field lines, with which they are found to be consistent. Energetic electrons are subsequently traced in 3D model fields that include a latitudinal dependence that is similar to measurements and to the natural modes of oscillation. Particle tracing simulations show a significant dependence of the radial transport of relativistic electrons on pitch angle, with off-equatorial electrons experiencing considerably higher radial transport, as they interact with ULF wave fluctuations of higher amplitude than equatorial electrons. These findings point to the need for incorporating pitch-angle-dependent radial diffusion coefficients in global radiation belt models.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 11","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA032905","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142641801","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":"Ionospheric Disturbances Observed Over the Peruvian Sector During the Mother's Day Storm (G5-Level) on 10–12 May 2024","authors":"Ram Singh,&nbsp;Danny E. Scipión,&nbsp;Karim Kuyeng,&nbsp;Percy Condor,&nbsp;Cesar De La Jara,&nbsp;Juan Pablo Velasquez,&nbsp;Roberto Flores,&nbsp;Edwar Ivan","doi":"10.1029/2024JA033003","DOIUrl":"https://doi.org/10.1029/2024JA033003","url":null,"abstract":"<p>This article presents the recent extreme and rare G5-level geomagnetic storm (Mother's Day Storm) effects on the equatorial and low-latitude ionosphere observed at the Peruvian sector by the Jicamarca (11.9°S, 76.8°W, magnetic dip 1°N) incoherent scatter radar and associated instruments. This storm was produced by multiple Earth-directed coronal mass ejections, which generated significant modifications in the Earth's magnetic field, leading to the Sym-H of ∼−518 nT. On the dayside, due to the strong eastward penetration electric field, vertical plasma drift and equatorial electrojet (EEJ) enhanced for 2–3 hr and remained consistent at values of ∼95 m/s and 260 nT between 1700 and 1900 UT (1200 and 1400 LT). At the same time, vertical E <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>×</mo>\u0000 </mrow>\u0000 <annotation> ${times} $</annotation>\u0000 </semantics></math> B plasma drift uplifted the equatorial ionosphere, producing the dusk-side super plasma fountain and transferring electron density to higher latitudes. A huge increase (∼1,325%) in electron density (from 11 to 142 TECu) is observed at low and mid-latitudes from ∼20°S to 50°S between 2000 and 0400 UT (1500–2300 LT). The strong westward penetration electric field suppressed pre-reversal enhancement, leading to downward plasma drift (∼−96 m/s) at around 2400 UT (1900 LT). Overnight, vertical plasma drift fluctuated between ±90 m/s, and the combined effect of penetration and disturbance dynamo electric fields caused a significant increase (∼530 km) in ionospheric virtual height. In the main and early recovery phase, consistent short- and long-duration electric field disturbances persisted for approximately 30 hr, with periods of ∼48 and 90 min.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 11","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142641802","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":"Dawn-Dusk Asymmetry of the Magnetopause Distance Under the Parker Spiral Configuration of the IMF","authors":"B. Janda,&nbsp;F. Němec,&nbsp;Z. Němeček,&nbsp;J. Šafránková","doi":"10.1029/2024JA033181","DOIUrl":"https://doi.org/10.1029/2024JA033181","url":null,"abstract":"<p>The dawn-dusk asymmetry of the magnetopause radial distance under the Parker (and ortho-Parker) configuration of the interplanetary magnetic field (IMF) is investigated. An extensive data set of about 50,000 magnetopause crossings identified in the data from the THEMIS A-E, Magion 4, Geotail, and Interball-1 satellites is used for this purpose. It is shown that the magnetopause radial distances are larger at the side where the IMF is quasi-parallel to the bow shock normal than at the side where IMF is quasi-perpendicular to the bow shock normal. The effect is more significant at the flanks than close to the subsolar point. This introduces a significant asymmetry of the magnetopause shape, with the difference in the magnetopause radial distances being as large as about one Earth radius beyond the terminator. The experimental results are confirmed by a global magnetohydrodynamic (MHD) model, demonstrating that the asymmetry can be explained by MHD effects, without considering foreshock transients. This MHD model is further used to investigate the evolution of individual pressure components across the magnetopause and contrast them in quasi-parallel and quasi-perpendicular cases.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 11","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033181","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142642001","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":"A Statistical Examination of the Spatial Correlations of HF Ionospheric Absorption Signatures Using the GO-Canada Riometer Network","authors":"R. G. Gillies,&nbsp;E. Spanswick,&nbsp;S. Skone","doi":"10.1029/2023JA032082","DOIUrl":"https://doi.org/10.1029/2023JA032082","url":null,"abstract":"<p>A network of 30-MHz riometers distributed across Canada have been monitoring auroral absorption for decades. Electron precipitation can cause enhanced densities to develop below ∼100 km where the higher neutral density can cause absorption of High Frequency (HF) signals. Modeling D-region absorption accurately can be challenging due to the large distances between riometer monitoring sites. It is of interest to develop an understanding of the typical scale sizes of these regions for assimilation in ionospheric models. Using the entire network of GO-Canada riometers, auroral absorption events may be monitored as they develop through a wide MLT sector. By examining correlations between sites, proxies for the scale sizes of absorption regions may be estimated. It was found that the sizes of the absorbing regions in the zonal direction are on the order of 900 km. Conversely, the characteristic scale sizes of the regions in the meridional direction were ∼700 km. These results are consistent with the general magnetospheric structure which sees higher energy electrons primarily present in the nightside transition region, and ring current. This creates a natural limit in latitudinal correlations, while the spread in longitude is likely connected to the size of precipitation regions in MLT. Our results also show significant spread in scale sizes in both directions from a few hundred to several thousand km. In this paper, we summarize these results in terms of the observed trends in high energy electron precipitation spatial and temporal scales and discuss future work to connect these scales to magnetospheric drivers.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 11","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023JA032082","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142642276","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}