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Ambipolar diffusion

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52: 232:. As the electrons leave the initial volume, they will leave behind a positive charge density of ions, which will result in an outwardly-directed electric field. This field will act on the electrons to slow them down and on the ions to speed them up. The net result is that both ions and electrons stream outward at the 332:
where the fractional ionization is very low (one part per million or less), neutral particles only rarely encounter charged particles, and so are not entirely hindered in their collapse (note that now is dynamical collapse, not free fall) into a
303: 230: 163:. If the ions are relatively cold, their thermal velocity will be small. The thermal velocity of the electrons will be fast due to their high temperature and low mass: 468: 388:
Zweibel, Ellen G. (2015). "Chapter 11 Ambipolar Diffusion". In Lazarian, Alexander; de Gouveia Dal Pino, Elisabete M.; Melioli, Claudio (eds.).
407: 148:. The latter will in turn create an electric field that can alter the transport of one or both species in such a way that they become equal. 73: 354: 316:
of neutral particles from plasma, for example in the initial stage of star formation. The neutral particles in this case are mostly
99: 239: 166: 77: 156: 62: 305:, which is much smaller than the electron thermal velocity, but usually much larger than the ion thermal velocity. 81: 66: 488: 345:
In the case of ionic crystals, the fluxes of the diffusing species are also coupled due to the electroneutrality
321: 313: 394:. Astrophysics and Space Science Library. Vol. 407. Berlin, Heidelberg: Springer Berlin Heidelberg. 328:) and electrons, which are tied to the interstellar magnetic field and therefore resist collapse. In a 424: 447: 403: 233: 132:, so naively one would expect one species to be transported faster than the other, whether by 31: 324:
if they were not collisionally coupled to the plasma. The plasma is composed of ions (mostly
439: 395: 160: 121: 117: 472: 329: 374: 145: 113: 35: 389: 482: 451: 425:"Definitions of terms for diffusion in the solid state (IUPAC Recommendations 1999)" 309: 51: 399: 141: 137: 443: 133: 27: 23: 317: 129: 325: 34:(such as electrons and positive ions) due to their interaction via an 159:.) Both electrons and ions will stream outward with their respective 152: 334: 151:
The simplest example is a plasma localized in an unmagnetized
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or some other process. If such differential transport has a
116:, ambipolar diffusion is closely related to the concept of 298:{\displaystyle c_{s}\approx {\sqrt {k_{B}T_{e}/m_{i}}}} 225:{\displaystyle v_{e}\approx {\sqrt {k_{B}T_{e}/m_{e}}}} 16:
Drift between charged and neutral particles in a plasma
242: 169: 312:, "ambipolar diffusion" refers specifically to the 423:Kizilyalli, M.; Corish, J.; Metselaar, R. (1999). 297: 224: 8: 469:Mathematical analysis of ambipolar diffusion 80:. Unsourced material may be challenged and 287: 278: 272: 262: 256: 247: 241: 214: 205: 199: 189: 183: 174: 168: 100:Learn how and when to remove this message 320:molecules in a cloud that would undergo 366: 128:are different from those acting on the 144:, then it results in a change of the 7: 78:adding citations to reliable sources 14: 475: (archived November 7, 2013) 391:Magnetic Fields in Diffuse Media 355:Earth's ambipolar electric field 50: 1: 157:Inertial confinement fusion 124:, the forces acting on the 505: 400:10.1007/978-3-662-44625-6 375:"Definition of AMBIPOLAR" 26:of positive and negative 444:10.1351/pac199971071307 322:gravitational collapse 299: 226: 300: 227: 240: 167: 74:improve this section 20:Ambipolar diffusion 295: 222: 409:978-3-662-44624-9 293: 220: 110: 109: 102: 32:electrical charge 496: 489:Plasma phenomena 456: 455: 438:(7): 1307–1325. 429: 420: 414: 413: 385: 379: 378: 371: 304: 302: 301: 296: 294: 292: 291: 282: 277: 276: 267: 266: 257: 252: 251: 231: 229: 228: 223: 221: 219: 218: 209: 204: 203: 194: 193: 184: 179: 178: 161:thermal velocity 105: 98: 94: 91: 85: 54: 46: 504: 503: 499: 498: 497: 495: 494: 493: 479: 478: 473:Wayback Machine 465: 463:Further reading 460: 459: 432:Pure Appl. Chem 427: 422: 421: 417: 410: 387: 386: 382: 373: 372: 368: 363: 351: 343: 330:molecular cloud 283: 268: 258: 243: 238: 237: 210: 195: 185: 170: 165: 164: 118:quasineutrality 106: 95: 89: 86: 71: 55: 44: 17: 12: 11: 5: 502: 500: 492: 491: 481: 480: 477: 476: 464: 461: 458: 457: 415: 408: 380: 365: 364: 362: 359: 358: 357: 350: 347: 342: 341:In solid state 339: 290: 286: 281: 275: 271: 265: 261: 255: 250: 246: 234:speed of sound 217: 213: 208: 202: 198: 192: 188: 182: 177: 173: 146:charge density 114:plasma physics 108: 107: 90:September 2024 58: 56: 49: 43: 40: 36:electric field 30:with opposite 15: 13: 10: 9: 6: 4: 3: 2: 501: 490: 487: 486: 484: 474: 470: 467: 466: 462: 453: 449: 445: 441: 437: 433: 426: 419: 416: 411: 405: 401: 397: 393: 392: 384: 381: 376: 370: 367: 360: 356: 353: 352: 348: 346: 340: 338: 336: 331: 327: 323: 319: 315: 311: 306: 288: 284: 279: 273: 269: 263: 259: 253: 248: 244: 235: 215: 211: 206: 200: 196: 190: 186: 180: 175: 171: 162: 158: 154: 149: 147: 143: 139: 135: 131: 127: 123: 119: 115: 104: 101: 93: 83: 79: 75: 69: 68: 64: 59:This section 57: 53: 48: 47: 41: 39: 37: 33: 29: 25: 21: 435: 431: 418: 390: 383: 369: 344: 310:astrophysics 307: 150: 111: 96: 87: 72:Please help 60: 19: 18: 361:References 314:decoupling 142:divergence 138:convection 120:. In most 254:≈ 181:≈ 134:diffusion 130:electrons 61:does not 42:In plasma 28:particles 24:diffusion 483:Category 452:98142954 349:See also 318:hydrogen 471:at the 326:protons 155:. (See 122:plasmas 82:removed 67:sources 450:  406:  153:vacuum 448:S2CID 428:(PDF) 404:ISBN 335:star 126:ions 65:any 63:cite 440:doi 396:doi 308:In 136:or 112:In 76:by 22:is 485:: 446:. 436:71 434:. 430:. 402:. 337:. 236:, 38:. 454:. 442:: 412:. 398:: 377:. 289:i 285:m 280:/ 274:e 270:T 264:B 260:k 249:s 245:c 216:e 212:m 207:/ 201:e 197:T 191:B 187:k 176:e 172:v 103:) 97:( 92:) 88:( 84:. 70:.

Index

diffusion
particles
electrical charge
electric field

cite
sources
improve this section
adding citations to reliable sources
removed
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plasma physics
quasineutrality
plasmas
ions
electrons
diffusion
convection
divergence
charge density
vacuum
Inertial confinement fusion
thermal velocity
speed of sound
astrophysics
decoupling
hydrogen
gravitational collapse
protons
molecular cloud

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