Su Zhou, Xiaoli Luan, Shangchun Teng, Zhiwei Wang, Shengting Zhu
{"title":"Nonlinear Effects of Ring Current Protons: Impacts of EMIC Wave Amplitude, Frequency, and Propagation Angle","authors":"Su Zhou, Xiaoli Luan, Shangchun Teng, Zhiwei Wang, Shengting Zhu","doi":"10.1029/2024JA033593","DOIUrl":"https://doi.org/10.1029/2024JA033593","url":null,"abstract":"<p>Nonlinear cyclotron resonance is known to cause the scattering of ring current protons to deviate from the predictions of quasi-linear theory, when wave-induced motion dominates over adiabatic motion. This study employed a test-particle simulation to investigate the nonlinear processes of ring current protons and their dependence on the amplitude, frequency, and wave normal angle <i>ψ</i> of electromagnetic ion cyclotron (EMIC) waves. As the equatorial pitch angle α<sub>eq</sub> increases, proton motion becomes dominated by the wave's electromagnetic force and responds nonlinearly. When wave-induced motion and adiabatic motion become comparable, the superposition of nonlinear phase trapping and phase bunching leads to complex oscillations in both the test-particle advection and diffusion coefficients. The nonlinear behavior becomes pronounced when the wave amplitude increases significantly. As the wave frequency increases, EMIC waves can nonlinearly interact with lower energy protons (i.e., <i>E</i><sub>k</sub> < 10 keV). Furthermore, oblique EMIC waves tend to produce less significant nonlinear behavior compared to parallel EMIC waves. Increasing the wave normal angle causes the nonlinear regime (i.e., the number of protons responding nonlinearly) in the E<sub>k</sub>−α<sub>eq</sub> plane to shrink, and the regime changes discontinuously with respect to α<sub>eq</sub>. We propose that the characteristics of EMIC waves significantly influence the nonlinear behavior of ring current protons and should be considered in the wave-particle interacting processes.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 3","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143595156","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}
P. Dazzi, K. Issautier, N. Meyer-Vernet, P. Henri, M. M. Martinović
{"title":"Quasi-Thermal Noise Spectroscopy in Magnetized Space Plasma: Theory and Model","authors":"P. Dazzi, K. Issautier, N. Meyer-Vernet, P. Henri, M. M. Martinović","doi":"10.1029/2024JA033325","DOIUrl":"https://doi.org/10.1029/2024JA033325","url":null,"abstract":"<p>The quasi-thermal noise measured by an electric antenna is routinely used to characterize space plasmas, mainly measuring the electrons' properties. To employ this diagnostic technique, instrumental models are required to turn the instrumental output into physically meaningful measurements. Such models have been developed mainly under the assumption that no magnetic field is present in the plasma. This limit case is not met in planetary magnetospheres, for example, Earth, Mercury. The latter is the objective of the European Space Agency/Japan Aerospace Exploration Agency BepiColombo mission, that has a dedicated quasi-thermal noise experiment. The aim of this work is to extend the current state-of-the-art in quasi-thermal noise modeling by taking into account the magnetic field, therefore providing a plasma diagnostic in this magnetized regime. To achieve this goal, we developed a model for the quasi-thermal noise in a magnetized plasma. We explore four cases: for a Maxwellian and double Maxwellian electron distributions, both in the collisionless limit and in the presence of weak electron-neutral collisions. Our model is validated against known behaviors of the magnetized quasi-thermal noise spectrum, including: the characteristic frequency of maxima and minima, the modulation from the antenna spinning around the magnetic field, the electron temperature(s) influence. We explored parameter ranges that were not accessible to previous quasi-thermal noise models, in particular the high magnetization regime. The model we developed will enable using quasi-thermal noise experiments for the diagnostic of magnetospheric space plasmas, including but not limited to the Hermean and terrestrial magnetospheres, with foreseen applications to future space missions.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 3","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143595157","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}
Neethal Thomas, Antti Kero, Ilkka Virtanen, Satonori Nozawa, Norihito Saito
{"title":"D-Region Ion-Neutral Collision Frequency Observed by Incoherent Scatter Spectral Width Combined With LIDAR Measurements","authors":"Neethal Thomas, Antti Kero, Ilkka Virtanen, Satonori Nozawa, Norihito Saito","doi":"10.1029/2024JA033587","DOIUrl":"https://doi.org/10.1029/2024JA033587","url":null,"abstract":"<p>We have carried out a statistical study of neutral atmospheric parameters in the mesosphere-lower thermosphere (MLT) region, by utilizing simultaneous measurements from the EISCAT-VHF radar and sodium LIDAR collocated near Tromsø, Norway. This study focuses on the spectral width of the incoherent scatter (IS) signal, which is a function of ion-neutral collision frequency, ion temperature, (equal to neutral temperatures in the D-region), and ion mass. Using the neutral temperatures obtained from LIDAR and ion mass obtained using a chemistry model, we have estimated the ion-neutral collision frequency in 80–100 km altitudes by fitting a theoretical IS spectrum to the EISCAT-VHF measurements. These fitted ion-neutral collision frequencies are then compared with the standard model values obtained using MSIS neutral densities. The study shows that the current widely used model underestimates the ion-neutral collision frequency on average by <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>1.54</mn>\u0000 <mo>±</mo>\u0000 <mn>0.24</mn>\u0000 </mrow>\u0000 <annotation> $1.54pm 0.24$</annotation>\u0000 </semantics></math>. Also, the fitted ion-neutral collision frequencies showed large temporal variations due to neutral density fluctuations, which are absent in the MSIS model. The study demonstrates that these random neutral density fluctuations caused by atmospheric waves can heavily influence the IS spectral width measurements and, therefore, can have a significant impact on ISR analysis when fitting neutral temperatures. The study also demonstrates the presence of heavy cluster ions below 85 km. Large uncertainties in the ion mass make it further challenging to extract the neutral temperature from spectral width below 85 km. In light of these observations, the inherent limitations of inferring temperatures from IS spectral width in the MLT altitudes are discussed.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 3","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-03-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143581726","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":"Stormtime Evolution of the \u0000 \u0000 \u0000 \u0000 O\u0000 +\u0000 \u0000 \u0000 ${mathrm{O}}^{+}$\u0000 Density: Magnetoseismic Analysis of Van Allen Probes Data","authors":"Kazue Takahashi, Richard E. Denton, Peter Chi","doi":"10.1029/2024JA033657","DOIUrl":"https://doi.org/10.1029/2024JA033657","url":null,"abstract":"<p>Measurements of singly ionized oxygen (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msup>\u0000 <mi>O</mi>\u0000 <mo>+</mo>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> ${mathrm{O}}^{+}$</annotation>\u0000 </semantics></math>) ions in the inner magnetosphere during geomagnetic storms are important because the ions affect various magnetospheric processes. We apply a magnetoseismic technique to Van Allen Probes data to statistically determine the spatial and temporal development of the region of elevated <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msup>\u0000 <mi>O</mi>\u0000 <mo>+</mo>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> ${mathrm{O}}^{+}$</annotation>\u0000 </semantics></math> number density <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mfenced>\u0000 <msub>\u0000 <mi>n</mi>\u0000 <msup>\u0000 <mi>O</mi>\u0000 <mo>+</mo>\u0000 </msup>\u0000 </msub>\u0000 </mfenced>\u0000 </mrow>\u0000 <annotation> $left({n}_{{mathrm{O}}^{+}}right)$</annotation>\u0000 </semantics></math>, referred to as the oxygen torus, during geomagnetic storms. This study is motivated by previous studies that reported magnetic local time (MLT) localization of the torus to the morning side. In our study, we first determine the frequencies of the fundamental through third harmonics of toroidal standing Alfvén waves to estimate the mass density <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>(</mo>\u0000 <mi>ρ</mi>\u0000 <mo>)</mo>\u0000 </mrow>\u0000 <annotation> $(rho )$</annotation>\u0000 </semantics></math> and then use the electron density <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mfenced>\u0000 <msub>\u0000 <mi>n</mi>\u0000 <mi>e</mi>\u0000 </msub>\u0000 </mfenced>\u0000 </mrow>\u0000 <annotation> $left({n}_{mathrm{e}}right)$</annotation>\u0000 </semantics></math> derived from plasma wave spectra to define the average ion mass <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>M</mi>\u0000 <mi>i</mi>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${M}_{mathrm{i}}$</annotation>\u0000 </semantics></math> (=<span></span><math>\u0000 ","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 3","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033657","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143571413","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}