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<p class="MsoNormal"><span style="font-size:11.0pt">Hello,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Yes, the SpitzerHighZ magnetic resistivity implementation is intended for ionized plasmas. It will still work for unionized, room temperature gases, but you should keep in mind that the values may not be physically
realistic.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">A perpendicular and parallel component for resistivity are calculated for anisotropic magnetic diffusion, however anisotropic magnetic diffusion is not yet fully implemented. So the code will use one or the
other based on the runtime parameter resistivityForm (the default value is “perpendicular”). You can use “parallel” if you like, but the SpitzerHighZ implementation is hard-coded to only be accurate for strongly magnetized hydrogen.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">What FLASH calls magnetic resistivity is actually, by default, the magnetic diffusivity in cm^2/s, when the unitSystem is unchanged from its default value of “none”. This is the recommended mode of operation
as we cannot guarantee that non-ideal MHD terms are implemented for other unit systems.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Hope that answers your questions!<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">--</span><span style="font-size:10.0pt;font-family:"Calibri",sans-serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif;color:#181A1B">Eddie Hansen</span><span style="font-size:10.0pt;font-family:"Calibri",sans-serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif;color:#181A1B">Applications Group Leader<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif;color:#181A1B">Flash Center for Computational Science</span><span style="font-size:10.0pt;font-family:"Calibri",sans-serif;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><b><span style="color:black">From:
</span></b><span style="color:black">flash-users <flash-users-bounces@flash.rochester.edu> on behalf of lizy <3287940670@qq.com><br>
<b>Date: </b>Monday, October 14, 2024 at 9:05 AM<br>
<b>To: </b>flash-users <flash-users@flash.rochester.edu><br>
<b>Subject: </b>[FLASH-USERS] Several questions about the Spitzer resistivity used in Flash<o:p></o:p></span></p>
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Dear Flash developer, hello<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;line-height:150%">
I have some questions about the Spitzer resistivity used in Flash, and I sincerely hope to receive your answers.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">1. Should Spitzer resistivity be applicable to completely ionized substances? So, is it unreasonable to study a metal that is driven from room temperature to a fully ionized state
(such as in zpinch)? After all, the temperature in the early stage was too low, and the ionization level was very low.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">2. The Spitzer resistivity expression I found is: η=1.03 × e − 4 Zbar ln ll/tele_eV * * 1.5 (ohm * m)<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">And you provided two resistors here, the original text in the program is as follows:<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">resPerpLoc = 8.21876126127e5*zbar*ll/tele_eV**1.5 !! In CGS -- Here tele has to be in eV<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">resPar = resPerpLoc/1.96<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">And there is the following annotation: This formula is only valid when the magnetic field is strong (and only for hydrogen).<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">2.1. Are the two resistivity values you provided the components of vertical current and horizontal current resistivity? If I want to calculate the <span style="font-size:10.0pt;font-family:"Times New Roman",serif"> Isotropic</span> aluminum
, should I only consider resPar? When the unit system is converted, is the conversion parameter in the flash documentation also the ratio between the parameter to be converted and resPar?<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">2.2. As mentioned above, can the resistivity formula you provided only calculate hydrogen? Are the coefficients in front of the Spitzer resistivity different for different substances?<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">2.3. The issue of unit system conversion. What I found is an MKS unit system, while the one provided in Flash should be in the form of UnitSystem="none", right? How does the coefficient
not match the parameters provided in the documentation? not be 4<span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#333333">π</span>/c^2,,or 1/<span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#333333">μ0</span><span style="font-size:10.0pt;font-family:"MS Gothic";color:#333333">？？？</span><o:p></o:p></p>
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<o:p> </o:p></p>
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