<p>This study explores the complex behavior of ion-acoustic (IA) solitary waves (SWs) in unmagnetized collisionless plasmas composed of electrons, thermal positrons, and positive ions, with particular attention to the influence of electron drift velocity. By employing a fluid model and the reductive perturbation method (RPM), we retrieve the Korteweg-de Vries (KdV) equation, which describes the weakly nonlinear progression of such waves. The findings show the presence of two distinct IA modes, i.e., fast and slow. In the fast mode, KdV solitons occur within two different ranges of drift velocities (<InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13538_2025_1716_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="93" /> </InlineMediaObject> <EquationSource Format="TEX">$0<{{v}_{e}^{\prime}}\le 172$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>0</mn> <mo><</mo> <msubsup> <mi>v</mi> <mrow> <mi>e</mi> </mrow> <mo>′</mo> </msubsup> <mo>≤</mo> <mn>172</mn> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13538_2025_1716_Article_IEq2.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="62" /> </InlineMediaObject> <EquationSource Format="TEX">${{v}_{e}^{\prime}}\ge 199$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msubsup> <mi>v</mi> <mrow> <mi>e</mi> </mrow> <mo>′</mo> </msubsup> <mo>≥</mo> <mn>199</mn> </mrow> </math></EquationSource> </InlineEquation>), whereas for the slow mode, solitons appear when <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13538_2025_1716_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="62" /> </InlineMediaObject> <EquationSource Format="TEX">${{v}_{e}^{\prime}}\ge 223$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msubsup> <mi>v</mi> <mrow> <mi>e</mi> </mrow> <mo>′</mo> </msubsup> <mo>≥</mo> <mn>223</mn> </mrow> </math></EquationSource> </InlineEquation>. Numerical simulations indicate that the fast mode supports both compressive and rarefactive solitons, while the slow mode only supports compressive solitons. The study underscores the importance of distinct factors such as positron density <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13538_2025_1716_Article_IEq4.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="24" /> </InlineMediaObject> <EquationSource Format="TEX">$\left(\mu \right)$</EquationSource> <EquationSource Format="MATHML"><math> <mfenced close=")" open="("> <mi>μ</mi> </mfenced> </math></EquationSource> </InlineEquation>, electron drift velocity <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13538_2025_1716_Article_IEq5.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="28" /> </InlineMediaObject> <EquationSource Format="TEX">$\left({v}_{e}^{\prime}\right)$</EquationSource> <EquationSource Format="MATHML"><math> <mfenced close=")" open="("> <msubsup> <mi>v</mi> <mrow> <mi>e</mi> </mrow> <mo>′</mo> </msubsup> </mfenced> </math></EquationSource> </InlineEquation>, and temperature ratios of electron to positron <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13538_2025_1716_Article_IEq6.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="22" /> </InlineMediaObject> <EquationSource Format="TEX">$\left(\delta \right)$</EquationSource> <EquationSource Format="MATHML"><math> <mfenced close=")" open="("> <mi>δ</mi> </mfenced> </math></EquationSource> </InlineEquation> in determining the properties of solitons. The results offer valuable insights into space plasmas where similar plasma compositions and drift velocities can affect the transmission of IA waves in planetary ionospheres and interstellar spaces.</p>

Influence of Electron Drift Velocity on Ion-Acoustic Solitary Waves in Collisionless Electron–Positron-Ion Plasmas

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2025年2月13日

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Ranjan Das,
Bhargab Madhukalya,
Kamyar Hosseini,
Farzaneh Alizadeh,
Dumitru Baleanu

摘要

This study explores the complex behavior of ion-acoustic (IA) solitary waves (SWs) in unmagnetized collisionless plasmas composed of electrons, thermal positrons, and positive ions, with particular attention to the influence of electron drift velocity. By employing a fluid model and the reductive perturbation method (RPM), we retrieve the Korteweg-de Vries (KdV) equation, which describes the weakly nonlinear progression of such waves. The findings show the presence of two distinct IA modes, i.e., fast and slow. In the fast mode, KdV solitons occur within two different ranges of drift velocities ( $0<{{v}_{e}^{\prime}}\le 172$ $0 < v_{e}^{'} \leq 172$ and ${{v}_{e}^{\prime}}\ge 199$ $v_{e}^{'} \geq 199$ ), whereas for the slow mode, solitons appear when ${{v}_{e}^{\prime}}\ge 223$ $v_{e}^{'} \geq 223$ . Numerical simulations indicate that the fast mode supports both compressive and rarefactive solitons, while the slow mode only supports compressive solitons. The study underscores the importance of distinct factors such as positron density $\left(\mu \right)$ $(μ)$ , electron drift velocity $\left({v}_{e}^{\prime}\right)$ $(v_{e}^{'})$ , and temperature ratios of electron to positron $\left(\delta \right)$ $(δ)$ in determining the properties of solitons. The results offer valuable insights into space plasmas where similar plasma compositions and drift velocities can affect the transmission of IA waves in planetary ionospheres and interstellar spaces.