G. Stenberg Wieser, M. André, H. Nilsson, N. Edberg, M. Persson, S. Rojas Mata, M. Mihalikova, H. Gunell, A. Bader, Y. Futaana
{"title":"Estimating the Possible Ion Heating Caused by Alfvén Waves at Venus","authors":"G. Stenberg Wieser, M. André, H. Nilsson, N. Edberg, M. Persson, S. Rojas Mata, M. Mihalikova, H. Gunell, A. Bader, Y. Futaana","doi":"10.1029/2024JA032865","DOIUrl":"https://doi.org/10.1029/2024JA032865","url":null,"abstract":"<p>In the Earth's magnetosphere wave-particle interaction is a major ion energization process, playing an important role for the atmospheric escape. A common type of ion heating is associated with low-frequency broadband electric wave fields. For such waves the energy is not concentrated to a certain narrow frequency range and exhibits no peaks or dips in a power spectrum. If there are enough fluctuations close to the ion gyrofrequency the electric field may still come in resonance with gyrating ions and heat them perpendicular to the background magnetic field. We perform a proof-of-concept study to investigate if this heating mechanism may contibute significantly to the energization of planetary ions also in the induced magnetosphere of Venus. We assume Alfvénic fluctuations and estimate the electric field spectral density based on magnetic field observations. We find typical estimated electric spectral densities of a few <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msup>\u0000 <mrow>\u0000 <mo>(</mo>\u0000 <mtext>mV/m</mtext>\u0000 <mo>)</mo>\u0000 </mrow>\u0000 <mn>2</mn>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> ${(text{mV/m})}^{2}$</annotation>\u0000 </semantics></math>/Hz close to Venus. This corresponds to a heating rate of a few eV/s. We consider an available interaction time of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math> 300 s and conclude that this mechanism could increase the energy of an oxygen ion by about a keV. Observed thermal energies are in the range 100–1,000 eV and thus, resonant wave heating may also be important at Venus.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 12","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA032865","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142860597","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}
Hai-Sheng Zhao, Li-Ming Wang, Zheng-Wen Xu, Jie Feng, Yuan-Yuan Zhang, Hai-Ying Li, Yong Wang, Cheng Wang
{"title":"Improved Computerized Ionospheric Tomography Based on GPS and PALSAR Data","authors":"Hai-Sheng Zhao, Li-Ming Wang, Zheng-Wen Xu, Jie Feng, Yuan-Yuan Zhang, Hai-Ying Li, Yong Wang, Cheng Wang","doi":"10.1029/2024JA033087","DOIUrl":"https://doi.org/10.1029/2024JA033087","url":null,"abstract":"<p>Due to factors such as the uneven distribution of ground receiving stations and the lack of effective observation rays, Global Positioning System (GPS)-based computerized ionospheric tomography (CIT) is typically of low quality and requires additional data sources. Recently, Faraday rotation angle (FRA) retrieval using the Phased Array L-band Synthetic Aperture Radar (PALSAR) full-pol data have emerged as a reliable technique for ionospheric detection. Similar to the total electron content (TEC), the FRA is the integral effect of the electron density and geomagnetic field, with the geomagnetic field being accurately estimated by the International Geomagnetic Reference Field (IGRF) model. Therefore, this paper proposes a 3-D secondary CIT algorithm by integrating PALSAR and GPS data: first, the product of the electron density values obtained from GPS-based CIT and the magnitude of geomagnetic field in corresponding voxel obtained from IGRF is used as the initial value. Then, the iterative algorithm is improved by using the FRA obtained from PALSAR data, rather than TEC, as the input for the second iteration, avoiding the approximation error caused by converting FRA into TEC. The geomagnetic field information is then separated by using the IGRF model, and the reconstructed spatial distribution is finally obtained. Experimental verification shows that the FRA can compensate for the lack of GPS observation rays to a certain extent and improve the accuracy of the reconstructed electron density. The results also indicate that the PALSAR can provide an effective and feasible data source for CIT.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 12","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142860546","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}
Kedeng Zhang, Hui Wang, Jing Liu, Huimin Song, Xuanqing Liu
{"title":"The Significant Enhanced Quiet-Time Equatorial Ionization Anomaly by the Intense Solar Flare on 06 September 2017","authors":"Kedeng Zhang, Hui Wang, Jing Liu, Huimin Song, Xuanqing Liu","doi":"10.1029/2024JA033264","DOIUrl":"https://doi.org/10.1029/2024JA033264","url":null,"abstract":"<p>On 06 September 2017, two X-class intense solar flare cases (X2.2 and X9.3) are observed. The X2.2/X9.3 case starts at 0857/1153 UT and peaks at 0910/1202 UT. The latter one is the most powerful event in recent decades and the more “geoeffective.” Using the total electron content (TEC) from the Global Navigation Satellite System, the Thermosphere-Ionosphere Electrodynamic General Circulation Model, the enhanced equatorial ionization anomaly (EIA) during the intense “geoeffective” X9.3 solar flare are investigated in this work. The observed and modeled TEC indicate that the daytime plasma is obviously enhanced by the solar flares. The model results show that the significant enhancement in EIA due to solar flare has a maximum density of 6.63 × 10<sup>11</sup> m<sup>−3</sup> at pre-noon sector. It has a maximum increase in the percentage of 26.59%. Four areas of enhanced and two areas of reduced electron density are found, forming a butterfly-like structure. Based on the term analysis of ion continuity equation, the rate of chemical production during daytime is considerably strengthened, with an average magnitude of 7.37 cm<sup>−3</sup>s<sup>−1</sup>. The roles of ambipolar diffusion are positive at almost all local time (LT) of EIA, except for the post-dusk sector. The daytime eastward electric field is weakened by an average intensity of 0.12 mV/m, preventing the formation of enhanced EIA. The effects of the disturbed horizontal winds (major: meridional winds) have an obvious hemispheric asymmetry.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 12","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142860574","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}
Jacob Fruchtman, Jasper Halekas, Francis G. Eparvier, Jacob Gruesbeck, Christian Mazelle, David Mitchell
{"title":"Application of a Scale Normalization Technique for High Resolution Analysis of the Magnetosheath at Mars","authors":"Jacob Fruchtman, Jasper Halekas, Francis G. Eparvier, Jacob Gruesbeck, Christian Mazelle, David Mitchell","doi":"10.1029/2024JA033166","DOIUrl":"https://doi.org/10.1029/2024JA033166","url":null,"abstract":"<p>In order to study spatial distributions of global magnetosheath structures, physicists often rely upon spatial binning, whereby space is divided into cells, each filled with the average value of all spacecraft measurements within that cell. The traditional binning schema utilizes a fixed Cartesian grid of cube bins. The morphology of the magnetosheath's boundaries are not fixed, however, but driven by upstream and planetary conditions. Therefore, the spatial structures are not fixed in Cartesian space, and thus a Cartesian binning technique will produce a highly coarse grained spatial distribution. We propose an alternative binning technique utilizing a scale normalized dimensionless coordinate system defined in terms of magnetosheath morphology. To demonstrate the efficacy of this technique, we apply a basic implementation to the Martian system. We are thereby able to achieve a high-resolution spatial mapping of bow shock and magnetosheath processes and resolve spatial structures that are washed out when binned traditionally. In particular, we can resolve the shock overshoot, analyze the dominant forces acting at the shock, and obtain fine-scale distributions of the bulk ion plasma magnetosheath forces and thermalization mechanisms. Magnetic tension and magnetic pressure gradient are compared. The ion pressure divergence at the shock is found to significantly vary in line with the solar wind temperature anisotropy. The dependency of the mirror mode instability on location and Mach number, and its implications for thermalization processes in the small Martian magnetosheath are investigated.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 12","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033166","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142860447","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}
Y. C. Jiang, Z. Z. Chen, J. Yu, J. Wang, X. M. Liu, J. Cui, J. B. Cao, A. J. Ren, X. L. Ding
{"title":"Low-Frequency Whistler Waves Excited by Electron Butterfly Distributions in Turbulent Reconnection Outflow","authors":"Y. C. Jiang, Z. Z. Chen, J. Yu, J. Wang, X. M. Liu, J. Cui, J. B. Cao, A. J. Ren, X. L. Ding","doi":"10.1029/2024JA033250","DOIUrl":"https://doi.org/10.1029/2024JA033250","url":null,"abstract":"<p>Whistler waves, leading to electron scattering and energy transport, are frequently observed in magnetic reconnection. High-energy electrons produced by magnetic reconnection are expected to excite low-frequency whistler waves. However, the study on low-frequency whistler waves in magnetic reconnection is still quite scarce. Utilizing high-resolution data from the Magnetospheric Multiscale (MMS) mission, we provide observations of low-frequency whistler waves in a turbulent reconnection outflow. The quasi-antiparallel propagating whistler waves have power peaked at ∼0.1 <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>f</mi>\u0000 <mrow>\u0000 <mi>c</mi>\u0000 <mi>e</mi>\u0000 </mrow>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${f}_{ce}$</annotation>\u0000 </semantics></math> and wave number of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>k</mi>\u0000 <msub>\u0000 <mi>d</mi>\u0000 <mi>e</mi>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> $k{d}_{e}$</annotation>\u0000 </semantics></math> ∼0.43 in the plasma rest frame. It can be excited through the cyclotron resonance by the electron butterfly distributions, which can be interpreted by a model comprising the addition of electron beams hosting perpendicular anisotropy to electron isotropy distributions. The energy of resonant electrons is calculated as 1.06∼4.16 keV, the parts corresponding to lower frequency (<∼0.1<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>f</mi>\u0000 <mrow>\u0000 <mi>c</mi>\u0000 <mi>e</mi>\u0000 </mrow>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${f}_{ce}$</annotation>\u0000 </semantics></math>) falling into suprathermal energy range. Our study can promote the understanding of generation of whistler waves in magnetic reconnection.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 12","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142860448","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 Impacts of Thermospheric Circulation and Exospheric Transport on the Coupled System","authors":"S. E. Luettgen, E. K. Sutton, J. P. Thayer","doi":"10.1029/2024JA033116","DOIUrl":"https://doi.org/10.1029/2024JA033116","url":null,"abstract":"<p>The boundary between the thermosphere and exosphere is often given the simplified description of being a separation between highly collisional continuum mechanics and a collisionless domain. The realistic smooth transition through this space has historically presented a challenge to model as the assumptions used to simplify the Boltzmann equation in fluid models are invalidated at higher altitudes. A lack of rigorous modeling of the region limits the ability to understand the dynamics of light atmospheric species. This manuscript describes the dynamics present in a two-way coupled fluid-particle atmospheric model extending from the mesosphere through the exosphere with a smooth transition between fluid and particle domains. This model is used to examine the coupled nature of the thermosphere and exosphere using the fluid simulation TIME-GCM and the direct simulation Monte Carlo simulation Monaco. The coupled model allows for examination of the thermosphere circulation and exosphere transport mechanisms, as well as their impacts on the distribution of hydrogen. In this analysis, upper transport regions in the exosphere are revealed and distinguished from lower transport regions during June solstice. Furthermore, coupling allows TIME-GCM to account for effects of lateral exospheric transport of hydrogen, altering its upper boundary condition and consequentially the spatial distribution of hydrogen throughout the thermosphere. Finally, it is asserted that a self-consistent hydrogen exobase distribution is necessary to constrain other analytical extrapolation techniques used to predict the vertical hydrogen profile in the exosphere. Plasma interactions are excluded from this study to isolate neutral dynamics.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 12","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033116","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142860438","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":"Extreme Responses of the Ionospheric Radial Currents to the Main Phase of the Super Geomagnetic Storm on 10 May 2024","authors":"Hao Xia, Hui Wang, Kedeng Zhang","doi":"10.1029/2024JA033126","DOIUrl":"https://doi.org/10.1029/2024JA033126","url":null,"abstract":"<p>On 10 May 2024, a super geomagnetic storm occurred with a minimum Dst index of −412 nT. This study investigates the behavior of the ionospheric radial current (IRC) during the main phase of this storm using data from Swarm A and simulations from the Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIEGCM). At dawn, the IRC exhibits distinct temporal variations: a strong outward flow of 14 nA/m<sup>2</sup> between 18:00 and 20:00 UT and an inward flow of −15 nA/m<sup>2</sup> by 24:00 UT. At dusk, the IRC starts with an inward value of −6 nA/m<sup>2</sup> and rapidly reverses to an outward flow peaking at 15 nA/m<sup>2</sup> between 22:00 and 24:00 UT. The dawn-dusk asymmetry of the IRC is primarily influenced by the merging electric field (<i>E</i><sub><i>m</i></sub>). Increasing <i>E</i><sub><i>m</i></sub> penetrates to low latitudes, establishing an eastward (dusk) or westward (dawn) electric field and enhancing the outward (dusk) or inward (dawn) IRC through meridional Hall currents. Model results indicate that the strong polarity changes in dawn IRC are linked to local disturbed zonal winds (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mrow>\u0000 <mi>Δ</mi>\u0000 <mi>u</mi>\u0000 </mrow>\u0000 <mi>y</mi>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${{Delta }u}_{y}$</annotation>\u0000 </semantics></math>). Which are eastward at dawn and westward at other magnetic local times (MLT). The eastward/westward <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mrow>\u0000 <mi>Δ</mi>\u0000 <mi>u</mi>\u0000 </mrow>\u0000 <mi>y</mi>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${{Delta }u}_{y}$</annotation>\u0000 </semantics></math> generate outward/inward F-layer dynamo currents, driving the disturbed vertical electric field (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mrow>\u0000 <mi>Δ</mi>\u0000 <mi>E</mi>\u0000 </mrow>\u0000 <mi>z</mi>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${{Delta }E}_{z}$</annotation>\u0000 </semantics></math>) in opposite direction. The significant outward reversal of dusk ∆IRC could be attribute to the rapid enhancement of disturbed Pedersen conductivity (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mrow>\u0000 <mi>Δ</mi>\u0000 <mi>σ</mi>\u0000 </mrow>\u0000 <mi>p</mi>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${{Delta }sigma }_{p}$<","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 12","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142860449","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}
Y.-X. Hao, Y. Y. Shprits, J. D. Menietti, T. Averkamp, D. D. Wang, P. Kollmann, G. B. Hospodarsky, A. Drozdov, A. Saikin, E. Roussos, N. Krupp, R. B. Horne, E. E. Woodfield, S. J. Bolton
{"title":"Acceleration of Energetic Electrons in Jovian Middle Magnetosphere by Whistler-Mode Waves","authors":"Y.-X. Hao, Y. Y. Shprits, J. D. Menietti, T. Averkamp, D. D. Wang, P. Kollmann, G. B. Hospodarsky, A. Drozdov, A. Saikin, E. Roussos, N. Krupp, R. B. Horne, E. E. Woodfield, S. J. Bolton","doi":"10.1029/2024JA032735","DOIUrl":"https://doi.org/10.1029/2024JA032735","url":null,"abstract":"<p>An abundant multi-MeV electron population beyond the orbit of Io is required to explain the intense inner radiation belt (electrons <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>></mo>\u0000 <mn>50</mn>\u0000 </mrow>\u0000 <annotation> ${ >} 50$</annotation>\u0000 </semantics></math> MeV) at Jupiter and its synchrotron radiation. In order to better understand the synergistic effect of radial transport and local wave-particle interactions driven by whistler-mode waves on the formation of Jupiter's radiation belt, we perform 3-D Fokker-Planck simulations for Jovian energetic electrons with the Versatile Electron Radiation Belt code. An empirical model of Jovian whistler-mode waves updated with measurements from the Juno extended mission is used to quantify the local acceleration and pitch angle scattering. Resonant cyclotron acceleration by whistler-mode waves leads to significant enhancement in the intensity of electrons above 1 MeV in the middle magnetosphere. Radial diffusion is capable of transporting MeV electrons accelerated by outer-belt whistler-mode waves into the <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>M</mi>\u0000 <mo><</mo>\u0000 <mn>10</mn>\u0000 </mrow>\u0000 <annotation> $M< 10$</annotation>\u0000 </semantics></math> region, where they are further accelerated adiabatically to energies of about 10 MeV.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 12","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA032735","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142860218","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}
Y.-X. Hao, Y. Y. Shprits, J. D. Menietti, Z. Y. Liu, T. Averkamp, D. D. Wang, P. Kollmann, G. B. Hospodarsky, A. Drozdov, E. Roussos, N. Krupp, R. B. Horne, E. E. Woodfield, S. J. Bolton
{"title":"Jupiter's Whistler-Mode Belts and Electron Slot Region","authors":"Y.-X. Hao, Y. Y. Shprits, J. D. Menietti, Z. Y. Liu, T. Averkamp, D. D. Wang, P. Kollmann, G. B. Hospodarsky, A. Drozdov, E. Roussos, N. Krupp, R. B. Horne, E. E. Woodfield, S. J. Bolton","doi":"10.1029/2024JA032850","DOIUrl":"https://doi.org/10.1029/2024JA032850","url":null,"abstract":"<p>The spatial distribution of whistler-mode wave emissions in the Jovian magnetosphere measured during the first 45 perijove orbits of Juno is investigated. A double-belt structure in whistler-mode wave intensity is revealed. Between the two whistler-mode belts, there exists a region devoid of 100 s keV electrons near the magnetic equator at <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>9</mn>\u0000 <mo><</mo>\u0000 <mi>M</mi>\u0000 <mo><</mo>\u0000 <mn>16</mn>\u0000 </mrow>\u0000 <annotation> $9< M< 16$</annotation>\u0000 </semantics></math>. Insufficient source electron population in such an electron “slot” region is a possible explanation for the relatively lower wave activity compared to the whistler-mode belts. The wave intensity of the outer whistler-mode belt measured in the dusk-premidnight sector is significantly stronger than in the postmidnight-dawn sector. We suggest that the inherent dawn-dusk asymmetries in source electron distribution and/or auroral hiss emission rather than the modulation of solar cycle are more likely to result in the azimuthal variation of outer whistler-mode belt intensity during the first 45 Juno perijove orbits.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 12","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA032850","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142860219","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":"Altitudinal Variation of O+ Scale Height at the Equatorial Topside Ionosphere","authors":"Shunzu Gao, Chao Xiong, Ziyuan Zhu, Weijia Zhan, Alessio Pignalberi, Hong Zhang","doi":"10.1029/2024JA033033","DOIUrl":"https://doi.org/10.1029/2024JA033033","url":null,"abstract":"<p>Altitude variation of the topside ionospheric electron density or its scale height has been widely investigated in the past. However, as the oxygen ion (<i>O</i><sup><i>+</i></sup>) is an important indicator for separating the topside ionosphere and plasmasphere, the altitude variation of <i>O</i><sup><i>+</i></sup>, which has not been well investigated, is crucial to understand the topside ionosphere. In this study, we provided analysis on how the <i>O</i><sup><i>+</i></sup> scale height varies with altitude under different solar and geomagnetic activities, by using 12-year measurements from the incoherent scatter radar (ISR) located at Jicamarca. Constant scale height Chapman (CSC) as well as Linearly Varying Chapman (LVC) functions are used to reconstruct the <i>O</i><sup><i>+</i></sup> profile. The corresponding scale heights of <i>O</i><sup><i>+</i></sup> based on both approaches have been compared. The <i>O</i><sup><i>+</i></sup> profile derived from LVC function shows better agreement with the ISR measurements than that from CSC function. We found that the <i>O</i><sup><i>+</i></sup> scale height increases with increasing solar/geomagnetic activity, and its height gradient varies significantly with local time, reaching a maximum of 0.05 at sunrise (around 06:00 local time) and a minimum of about −0.08 at noon (around 12:00 LT). We further investigated possible drivers causing the <i>O</i><sup><i>+</i></sup> scale height variations at topside ionosphere, based on simulations from the SAMI2 physics-based model. The model results show that the solar extreme ultra-violet (EUV) radiation plays a key role in the positive gradient of <i>O</i><sup><i>+</i></sup> scale height observed around sunrise, while the vertical plasma drift caused by <b>E</b> <b>×</b> <b>B</b> significantly contributes to the negative gradient observed around noon.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"129 12","pages":""},"PeriodicalIF":2.6,"publicationDate":"2024-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142860163","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}