Journal of Geophysical Research: Space Physics最新文献

{"title":"Correlation of Slow and Fast Electron Holes With Local Ion Distribution Minimum","authors":"Yue Dong,&nbsp;Zhigang Yuan,&nbsp;Shiyong Huang,&nbsp;Xiongdong Yu,&nbsp;Zuxiang Xue,&nbsp;Honghong Wu,&nbsp;Dedong Wang,&nbsp;C. J. Pollock,&nbsp;R. B. Torbert,&nbsp;J. L. Burch","doi":"10.1029/2024JA033646","DOIUrl":"https://doi.org/10.1029/2024JA033646","url":null,"abstract":"<p>Although the theory of electron holes has a 60-year history, whether fast and slow electron holes may share a common origin remains enigmatic. Here, with observations of Magnetospheric Multiscale spacecraft, we report that slow electron holes are accompanied with ion beams while fast electron holes are not. The velocity of slow holes is observed to vary with the local ion beam intensity and have the potential to be accelerated. Simulations demonstrate that ion distribution with a distinct beam constrains the velocity of electron holes into slow holes with stable electric field amplitudes while a weak beam fails to confine the hole's velocity but accelerates them through ion repulsion into fast holes with amplitude decay. Therefore, we speculate that the fast and slow electron holes may share a common origin and their subsequent behavior is determined by different ion distributions.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 5","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144085257","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":"Ionospheric and Thermospheric Response to the 13 June 2022 M-Class Solar Flare","authors":"A. W. Stephan,&nbsp;R. R. Meier,&nbsp;S. L. England,&nbsp;T. J. Immel","doi":"10.1029/2024JA033526","DOIUrl":"https://doi.org/10.1029/2024JA033526","url":null,"abstract":"<p>On 13 June 2022, an M3-class solar flare erupted at 03:00 UT that lasted nearly eight hours, causing increased ionization and shortwave radio blackouts. Here, we combine measurements made by the NASA Ionospheric Connections Explorer (ICON) mission to assess the evolution of the ionosphere-thermosphere system in response to this flare. We find that increased solar extreme ultraviolet (EUV) radiation during the flare did increase O⁺ plasma in the region that was directly exposed to the flare, but this effect was moderated by thermospheric perturbations as evidenced by a decrease in column O/N₂ (ΣO/N₂) that accompanied the sequence of events. Larger increases in O⁺ were seen in the same region the day after the flare as the non-impulsive, long-term solar EUV irradiance continued to increase and the thermospheric ΣO/N₂ recovered. When energetic particles arrived 3 days after the event, the ionospheric impact was delayed by about a day compared to the thermospheric changes. Changes in ΣO/N₂ inferred from far ultraviolet airglow are also strongly correlated with relative changes in atomic oxygen independently determined by simultaneous ICON measurements of EUV airglow. These results demonstrate the magnitude, duration, and complexity of change that even moderate M-class flares can generate in the ionosphere and thermosphere.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 5","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144085511","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":"Impact of E-Region Plasma Turbulence on Formation and Evolution of SAID/STEVE","authors":"Joaquín Díaz Peña,&nbsp;Joshua Semeter,&nbsp;Matthew Zettergren,&nbsp;Yukitoshi Nishimura,&nbsp;Michael Hirsch,&nbsp;Meers Oppenheim,&nbsp;Yakov Dimant,&nbsp;Brian M. Walsh","doi":"10.1029/2025JA033808","DOIUrl":"https://doi.org/10.1029/2025JA033808","url":null,"abstract":"<p>Subauroral Ion Drift (SAID) channels and Strong Thermal Emission Velocity Enhancement (STEVE) phenomena are distinct features of ionospheric dynamics that are accompanied by strong electric field forcing that is related to plasma turbulence in the E-region. This study investigates the role of the Farley-Buneman Instability (FBI) in modulating SAID and related phenomena, focusing on its impact on the evolution of extreme SAID channels. Using the Geospace Environment Model of Ion-Neutral Interactions (GEMINI), we incorporate macroscopic effects of FBI-induced turbulence in the form of anomalous electron heating and non-linear current density. Results demonstrate that FBI-induced turbulence produces a significant dampening effect on SAID channel velocity growth by increasing E-region conductance and density. This effect alters the electric field dynamics and moderates the extreme velocities characteristic of SAID channels. These findings underscore the critical role of including turbulence-driven processes in predictive models, advancing our understanding of magnetosphere-ionosphere coupling and space weather phenomena. This work is understood as missing physics that would increase the dampening effect, such as inelastic collisions and excitation of resonant cross-sections in electron neutral collisions, yet introduces itself as a starting point and an appeal to further improve.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 5","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144085512","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 a Disconnection Event and Other Large-Scale Disturbances in the Ion Tail of Comet C/2022 E3 (ZTF)","authors":"A. Wellbrock,&nbsp;G. H. Jones","doi":"10.1029/2024JA033623","DOIUrl":"https://doi.org/10.1029/2024JA033623","url":null,"abstract":"<p>We analyze five large-scale tail disturbances in comet C/2022 E3 (ZTF)'s ion tail using images from astrophotographers, tracking specific features within the tail to determine their speeds. We employ a heliosphere model to estimate when the comet crossed the heliospheric current sheet (HCS). One event displays a distinct ion tail gap, suggesting that this was a disconnection event likely caused by magnetic reconnection associated with an HCS crossing. The tracked feature within the detached tail section exhibited increased acceleration under the influence of the solar wind compared to the still-attached portion of the tail. The other observed disturbances appear consistent with partial magnetic field rotations, and associated changes in the viewing geometry of the cross-tail current sheet, with some events also potentially linked to an interplanetary coronal mass ejection. We discuss typical time scales required for cometary ion tails to reach ambient solar wind speeds. Our results confirm that measured speeds of specific features within the visible part of ion tails tend to be considerably slower than the ambient solar wind that flows past the comet. An analysis of ion tail orientation can also provide speed estimates; however, these tend to align with typical solar wind speeds external to the tail and differ from the observed speeds of material within the tail. We discuss these methods and propose that the orientation of the ion tail is primarily controlled by the ambient solar wind flow outside the draped ion tail structure and is mostly unaffected by conditions within the ion tail.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 5","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033623","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144074571","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":"Study of Double-Pulse Magnetic Structure During Decoupling Expansion of Debris Plasma","authors":"Ziming Wang,&nbsp;Ye Dong,&nbsp;Mengmeng Song,&nbsp;Zhaohui Liu,&nbsp;Wei Yang,&nbsp;Qiang Sun,&nbsp;Wenbin Wu,&nbsp;Zhekai Luo,&nbsp;Hantian Zhang,&nbsp;Qianhong Zhou","doi":"10.1029/2024JA033641","DOIUrl":"https://doi.org/10.1029/2024JA033641","url":null,"abstract":"<p>The decoupling expansion of debris plasma refers to the process where debris plasma generated by a high-altitude nuclear explosion (HANE) slips through the ambient plasma. Unlike the coupled expansion of the debris plasma and ambient plasma, decoupling expansion leads to a smaller magnetic cavity and wider debris dispersal. This significantly alters the magnetic field structures within hundreds of kilometers around the HANE center and even the artificial radiation belt at higher altitude. In this paper, the evolution mechanism of the double-pulse magnetic structure is investigated by simulating the decoupling expansion process of super- Alfvénic debris plasma using a two-dimensional hybrid model. It is found that the rapidly formed azimuthal electron current generates a debris magnetic pulse (the initial magnetic pulse), which remains attached to the expanding debris shell. Subsequently, the spatially nonmonotonically varying ambient ions velocity, characterized by an initial increase followed by a decrease, aggregates ambient ions to gradually form an ambient magnetic pulse (the second magnetic pulse). This study provides essential insights into the magnetic field evolution during the decoupling expansion and the interaction between debris and ambient plasma.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 5","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144074548","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":"Thermospheric Disturbance Observed by Triple Ionosphere PhotoMeter Onboard the Chinese Meteorological Satellite FY3E During 10–11 May 2024 Storm","authors":"Qian Song,&nbsp;Qian Ye,&nbsp;Xiaoxin Zhang,&nbsp;Tian Mao","doi":"10.1029/2024JA033386","DOIUrl":"https://doi.org/10.1029/2024JA033386","url":null,"abstract":"<p>The Triple Ionospheric PhotoMeter (TriIPM) carried on the newly launched early morning FY3E meteorological satellite measures the spectral radiances of the Earth's far ultraviolet airglow in atomic oxygen 135.6 nm (OI 135.6 nm) and N₂ Lyman-Birge-Hopfield (N₂ LBH) bands. In this paper, the TriIPM instrument data are used for the first time to record the thermospheric O/N₂ ratio variations during geomagnetic storms through the case study of the superstorm on 10–11 May 2024. The variations of the TriIPM O/N₂ ratio and the ionospheric peak density at F2 layer (NmF2) derived from the modified IRI2016 model are also compared to explore the relationship between the storm-time thermospheric and ionospheric responses. Our results show that the TriIPM O/N₂ ratio depletion extends down to the equator in the Northern Hemisphere during the main phase of the storm period. The TriIPM O/N₂ ratio depletion shows a good quantitative agreement with the NmF2 depletion within the disturbed region at a local time period between 1100 and 1900 LT. The good agreement between the TriIPM O/N₂ ratio and NmF2 indicates that the new satellite TriIPM instrument may provide a good opportunity for understanding how the thermosphere-ionosphere system responds to geomagnetic storms.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 5","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144074549","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":"Core-Halo Correlations of Solar Wind Electrons and Temperature Anisotropy Instabilities","authors":"S. M. Shaaban,&nbsp;S. Kennis,&nbsp;M. Lazar,&nbsp;V. Pierrard,&nbsp;S. Poedts","doi":"10.1029/2025JA033838","DOIUrl":"https://doi.org/10.1029/2025JA033838","url":null,"abstract":"<p>The properties of electrons in the heliospheric plasma are modulated by various factors, starting with the expansion and bimodal nature of the slow or fast solar wind, and continuing with the kinetic mechanisms of acceleration and energy exchange with small-scale plasma waves. The role of wave-particle interactions can be understood through rigorous kinetic modeling based on observational data. This paper presents a refined evaluation of the instabilities triggered by temperature anisotropy, that is, whistler and firehose instabilities, taking into account for the first time the correlations between the electron core and halo populations revealed by in situ observations. In establishing core-halo correlations, temperature anisotropies <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>(</mo>\u0000 <mi>A</mi>\u0000 <mo>)</mo>\u0000 </mrow>\u0000 <annotation> $(A)$</annotation>\u0000 </semantics></math> and plasma beta parameters <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mfenced>\u0000 <mrow>\u0000 <msub>\u0000 <mi>β</mi>\u0000 <mo>‖</mo>\u0000 </msub>\u0000 </mrow>\u0000 </mfenced>\u0000 </mrow>\u0000 <annotation> $left({beta }_{Vert }right)$</annotation>\u0000 </semantics></math> are of interest, as quantifiers of free (kinetic) energy at the origin of instabilities. These correlations incorporate the mutual effects of the electron populations and enable a realistic characterization of instabilities, in terms of either the core or the halo parameters. The instability thresholds can be significantly reduced under the mutual core-halo effects, and comparisons with observations prove the constraining role of self-generated instabilities, not only for the core but also for the halo electrons. The most relevant are the results for the slow solar wind, for which both the parameters and the core-halo correlations are less affected by the strahl component, which is otherwise more prominent in the fast wind. In high-speed winds, temperature anisotropies are more confined, most likely under a stronger effect of fluctuations generated by the electron strahl whose properties are not yet quantified to allow a similar analysis.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 5","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JA033838","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143944416","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":"Ducted Propagation of Whistler Mode Waves Observed by the Arase Satellite","authors":"Y. Ampuku,&nbsp;F. Tsuchiya,&nbsp;S. Kurita,&nbsp;Y. Kasaba,&nbsp;Y. Katoh,&nbsp;M. Fukizawa,&nbsp;Y. Miyoshi,&nbsp;I. Shinohara,&nbsp;Y. Kasahara,&nbsp;S. Matsuda,&nbsp;A. Kumamoto,&nbsp;A. Matsuoka,&nbsp;M. Kitahara,&nbsp;O. Santolík","doi":"10.1029/2024JA033359","DOIUrl":"https://doi.org/10.1029/2024JA033359","url":null,"abstract":"<p>Ducted propagation of whistler-mode waves has attracted attention as a process that explains how whistler-mode waves propagate to high latitudes, resulting in the loss of relativistic electrons to the atmosphere and changes in the upper atmosphere due to electron precipitation. However, few studies have compared the observed density ducts and wave propagation characteristics to theoretical predictions in detail, particularly for low-density ducts. We present four patterns of ducting modes as electron density increases or decreases, as observed by the Arase satellite. (a) Lower-band (LB) waves propagating along a high-density duct with small wave normal angles (WNAs), (b) LB waves propagating along a low-density duct with a wide distribution of WNAs up to above the Gendrin Angle, (c) LB waves propagating along a low-density duct with WNAs around the Gendrin Angle, and (d) upper-band waves propagating along a low-density duct with small WNAs. We derived the WNAs for these cases, and their characteristics were consistent with the ducting theory. Based on this theory, we calculated the frequency range in which the waves were likely to be trapped in the ducts. We compared this frequency range with the power spectra of the recorded whistler-mode waves and found consistency between the theory and observations. Furthermore, it is suggested that the WNAs for cases (b) and (c) have azimuthal distributions based on a comparison of the WNA analysis of the simple simulated waveforms and the observed data.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 5","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JA033359","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143944417","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 the Impact of Whistler Waves Near the Lunar Surface Through Observational Data","authors":"Abdul Waheed,&nbsp;Zeyu An,&nbsp;Yifan Wu,&nbsp;Shangchun Teng,&nbsp;Hui Zhang,&nbsp;A. V. Artemyev,&nbsp;Xin Tao","doi":"10.1029/2024JA033628","DOIUrl":"https://doi.org/10.1029/2024JA033628","url":null,"abstract":"<p>Whistler waves are electromagnetic emissions widely observed in space plasma, and recent observational studies have confirmed their existence near the lunar surface. These waves can significantly affect the incoming plasma, causing electron heating or density depletion. However, the wave-particle interaction between the incoming solar wind and whistler waves near the lunar surface has yet to be thoroughly investigated. In this study, we employ automated methods to identify whistler wave events and investigate their statistical properties using 4 years of ARTEMIS mission data. We find that the occurrence rate and intensity of these waves are influenced by lunar magnetic field anomalies and the lunar orbital locations. To further quantify the effects of these waves, we calculate the quasi-linear diffusion coefficient based on the statistical properties of whistler mode waves near the lunar surface. Our findings indicate that these waves have intense pitch angle scattering effects on energetic electrons <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>(</mo>\u0000 <mrow>\u0000 <mn>10</mn>\u0000 <mo>−</mo>\u0000 <mn>1000</mn>\u0000 <mtext>eV</mtext>\u0000 </mrow>\u0000 <mo>)</mo>\u0000 </mrow>\u0000 <annotation> $(10-1000text{eV})$</annotation>\u0000 </semantics></math>. This study improves our understanding of the interaction between waves and particles within the plasma environment near the lunar surface.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 5","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143944500","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":"Differential Response of Nitric Oxide Radiative Cooling to Moderate and Intense Geomagnetic Storms: Insights From Superposed Epoch Analysis","authors":"Dayakrishna Nailwal,&nbsp;M. V. Sunil Krishna,&nbsp;Alok Kumar Ranjan","doi":"10.1029/2024JA033693","DOIUrl":"https://doi.org/10.1029/2024JA033693","url":null,"abstract":"<p>Geomagnetic storms have been a subject of significant interest due to their potential impact on Earth’s upper atmosphere. Nitric oxide (NO) radiative emission is a key feature that can help in understanding and assessing the storm-time response of the Earth’s upper atmosphere. This study attempts to provide a unified and comprehensive understanding of the storm-time response of NO radiative cooling to geomagnetic storms of different strengths and durations by using the superposed epoch analysis method. The satellite-based observations of NO radiative cooling at 5.3 <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>μ</mi>\u0000 </mrow>\u0000 <annotation> ${upmu }$</annotation>\u0000 </semantics></math>m during thirty geomagnetic storms have been analyzed using the superposed epoch analysis. Based on the response time of nitric oxide infrared radiative flux (NOIRF) to reach its peak value, the storms are categorized into three classes. The findings reveal that the response time of NO to a geomagnetic storm is linked to the duration of its main phase. In the case of a long-duration main-phase geomagnetic storm, the response is faster, and it is typically earlier than that during a storm with a short-duration main phase. To understand the behavior of NO during various geomagnetic storms, the temperature and compositional data from the Thermosphere Ionosphere Electrodynamic General Circulation Model (TIEGCM) simulations are used to calculate the NOIRF. The calculated NOIRF shows a good agreement with temporal variations compared to the Sounding of the Atmosphere using Broadband Emission Radiometry observations. The combined results of superposed epoch analysis and TIEGCM conclude that the duration of the main phase of a geomagnetic storm significantly affects the NO density, temperature, and response time of NOIRF.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 5","pages":""},"PeriodicalIF":2.6,"publicationDate":"2025-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143930452","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}