Modeling Non-Equilbirum Plasma Adam Foster
Definition CIE plasma: a plasma which is in collisional ionization equilibrium NEI plasma: a collisional plasma which is not in CIE
Ionization Balance dn ( z) =N e S(z 1 z) N (z 1) dt ( N e S(z z+ 1) + N e α( z z 1) + N H C (z z 1)) N ( z) + N e α( z+ 1 z) N ( z+ 1)+ N H C( z+ 1 z) N ( z+ 1)
Ionization Balance dn ( z) =N e S( z 1 z) N ( z 1) dt populating ( N e S ( z z+ 1) + Neα ( z z 1) + NHC ( z z 1) )N ( z) + N e α( z+ 1 z) N ( z+ 1) + N H C ( z+ 1 z) N (z+ 1 ) set dn ( z) =0 dt CIE ionbal: S( z 1 z) N ( z 1)+ α( z+ 1 z) N ( z+ 1)=( N e S(z z+ 1)+ N e α( z z 1)) N (z ) depopulating
CIE ionization balance
Non-Equilibrium Ionization Needs a source of hot or cold electrons. sudden adiabatic expansion & cooling shock heating Solar Flare Cas A Solar Flare
Ionization Balance dn ( z) =N e S( z 1 z) N ( z 1) dt ( N e S ( z z+ 1) + Ne α ( z z 1) + NHC ( z z 1) )N ( z) + N e α( z+ 1 z) N ( z+ 1) + N H C ( z+ 1 z) N (z+ 1 ) d N ( z) ( z) = N e A N dt Solve ionization fraction equations explicitly, see, e.g. matrix eigenvector method (Smith & Hughes 2010).
Timescales No difference noted at Net < 107 cm-3s (4 months @ 1cm-3) Equilibrium at Net>2x1012cm-3s (60,000 years @ 1cm-3)
Part 1 summary NEI plasma can exist over a wide range of timescales. It dramatically changes the set of ions visible in a typical temperature plasma
Emitting processes from NEI Plasma
Emitting processes from NEI Plasma
Excitation Ionization Recombination
Summary of relevant processes X +(z-1) X+z X+(z+1) Direct Ionization Excitation-autoionization Collisional excitation Dielectronic recombination Radiative Recombination
Ionizing Plasma Signifiers
Ionizing Plasma Signifiers
Ionizing Plasma Signifiers
Ionizing Plasma Signifiers ionizes
Fluorescence Yield Li-like 1s 2s2 Ar~z5 Aa~z2 ~ no fluorescence for light elements Gorczyca+ 2006 Ar ωk = Aa+ Ar
Yamaguchi+2014 Line Centroid shifts with Ion
Yamaguchi+2014 Line Centroid shifts with Ion
Recombining Plasma Line ratio shifts enhanced forbidden line Presence & enhancement of DR satellite lines. Low line intensities, n=3 1 transition reduced
Continuum Processes Driven By Brems Ne, Te RRC N 2-photon Nz+, ~Te (z+1)+, Te Ionizing Recombining Notes ~ Enhanced Shape truly representative of current Te Reduced (none) Enhanced Edges appear in recombining plasma ~ no effect ~ no effect Not useful as NEI diagnostic ~ Reduced
W49B T_init=3.2keV T_final=1.5keV Net=2x1010cm-3s
W49B 20ks SXS simulation RRC
NEI Modeling with AtomDB Calculate Ionbal Iion=N+z-1Neεion(Te) Iexc=N+zNeεexc(Te) Sum Spectrum! Irec=N+z+1Neεrec(Te)
Back to those processes Excitation Ionization Recombination
Show me the data! Level resolved recombination data: Badnell+ Level resolved fluorescence yield data: only for lowest 2-3 levels of some ions Inner shell excitation data: Rare! (Liang for Lilike) Inner shell ionization: Coulomb-Born-Exchange (Beigman 1996). Otherwise... nothing
Large scale data generation Fill in the blanks! Large scale FAC runs Inner shell excitation up to n=4 Inner shell ionization creating holes in n=1,2,3 shells Autoionization from all doubly excited levels Database size: 300Mb 18Gb.
~Fe XII Kα Kβ 6keV plasma ~Fe XVII Ni Kα Cr Fe XXV Kδ+ Ionizing Plasma Spectrum
Line ratio diagnostics 1s2 2s 1s 2s forbidden line regular ratios Recombine statistically greater 1s 2s 3P1 pop
Modeling a Recombining Plasma Ozawa+2009 Ozawa+2009 Quantity Ozawa AtomDB 3.0 kte 1.5keV 1.5keV Fe 4.44 2.43 Ni 10.9 3.63 norm 0.16 0.16
Summary on Features on NEI Real Te can still be obtained from brems. Recombining plasma show RRC egdes Ionizing plasmas will show inner shell heavy ion lines if they are hot enough (kt>2kev) Both ionization and recombination lead to an enhanced forbidden line Much room for improvement on the inner shell atomic data Models are available in XSPEC, SPEX etc.
NEI Models in XSPEC Nei: single time, single temperature snapshot emissivity. Rnei: same as vnei, but can specify initial temperature Pshock: Parallel shock. Multiple times in a single temperature Npshock: As pshock, but with separate ion and electron temperatures
Plug plug plug The beta4 version of NEI is available on the website. Works in all XSPEC models. Need to download updated beta data. www.atomdb.org