PROBLEMS OF GEOCOSMOS

More documents

Recommendations

Info

Proceedings of the 7th International Conference "Problems of Geocosmos" (St. Petersburg, Russia, 26-30 May 2008) 1 r ( e [ ∇p × ∇V ]) , (3) B j// = z I where еz − r the unit vector directed along the magnetic field. The current flowing from the ionosphere of the northern hemisphere defined to be positive, the gradients are calculated at the ionospheric level. Formula (3) can be rewritten in the other form: 1 B V j// = γ z I r ( e [ ∇pV γ × ∇V ]) We calculate the field-aligned currents neglecting the magnetic flux tubes drift. It is justified if the magnetic γ γ flux tubes drift along the longitudinal direction. In this case solution of the equation (2) is p 1V1 = p2V2 , where the volume of the magnetic flux tube and the plasma pressure at the end of the growth phase and the expansive phase of the substorm are marked by indexes 1,2. We shall assume for convenience that the fieldaligned currents at the end of the growth phase are zero, then the vectors ∇ p1 and ∇ V1 are collinear. In this case the model pressure profile in the plasma is: p V p 1 = (5) V α 0 0 α 1 γ The outer boundary of the plasma layer is stable with respect to the interchange instability if ∇ pV > 0, in our case this condition is fulfilled at α < γ. According to observations in the plasma layer of the magnetosphere tail there are plasma flows before the expansive phase substorm as towards the Earth and in the opposite direction as well, which are accompanied by magnetic impuls. It can mean development of the interchange instability of the plasma layer in this area. γ We shall consider that in this area ∇ pV < 0, and α> γ. The formula for the field-aligned current at the end of expansive phase substorm is: −α −1 p V ( γ − α) r ( e [ ∇V1 × ∇V2 ]) γ B V j// = 0 γ 1 z I 2 Spatial distribution and values of field-aligned currents. Volume of the magnetic flux tubes V1 and V2 for the magnetic potential (1) are calculated numerically in each mesh point with step 1 0 on latitude and 5 0 on longitude, since 16 0 colatitude. Figures 1 and 2 show the values of the volumes V1 and V2 accordingly for the substorm growth phase and expansive phase substorm. The values of volumes are given in terms m 2 RE. It is clearly seen that the isolines of the equal volume during the growth phase and expansive phases substorm do not coincide, there are the currents along magnetic field lines. Figure 3 shows the distribution and values of the currents. The plasma pressure p0 in the plasma layer on distances 8RE at the end of the growth phase was 10 nPa. The power of the plasma pressure decrease assumes equal α=1 down 22 0 and α=2.5 in the interval 16 0 -22 0 . According to calculations the value of currents reaches 0.7 A/km 2 , the maximum of the current flowing from the ionosphere locates close to 20 MLT, the maximum of the current flowing in the ionosphere locates close to 04 MLT. The obtained system of field-aligned currents should be closed in the ionosphere by the western direction current. This current should have the Hall nature, as the current flowing in the plasma layer. Observations of the electric fields in the midnight sector of ionosphere during the expansive phase substorm also show the Hall nature of the western electrojet. According to observations the electric field in this region has the predominately southern direction [4]. Fig.4 shows radial distribution of the plasma pressure in the equatorial cross section of the magnetosphere along the noon-midnight line on the night side of the magnetosphere at the end of growth and expansive phase substorm. The pressure on distances more then 6 RE during the expansive phase substorm decreases to some extent, the decreasing pressure in the magnetosphere tail during the expansive phase substorm is obtained by results of the observations [5]. 295 (4) (6)
Proceedings of the 7th International Conference "Problems of Geocosmos" (St. Petersburg, Russia, 26-30 May 2008) Fig.1 The distributions magnetic flux tubes for the substorm growth phase. Fig.2 The distributions magnetic flux tubes for the substorm expansive phase. Summary. According to the obtained results the intensification of the western electrojet and dipolarisation of the Earth magnetic field lines during an expansive phase substorm are interdependent phenomena. At depolarization of the Earth magnetic field lines the system of field-aligned currents are formed, the currents flowing from the ionosphere in premidnight hours and flowing in the ionosphere after midnight. The intensity of field-aligned currents of this system is sufficient to increase the transverse ionospheric current of the western direction. This current will have the Hall nature, as well as currents flowing in the plasma layer. The appearance of the current wedge of the substorm can be caused by the decrease pressure near midnight γ in the plasma sheet as a result of the dipolarization magnetic field lines with the assumption ∇ pV
Page 1 and 2:
Saint-Petersburg State University P
Page 3 and 4:
Proc. of the 7th Intern. Conf. "Pro
Page 5 and 6:
Page 7 and 8:
Page 9 and 10:
Page 11 and 12:
Î�ÒÙ×�ØØ��Ñ��Ò
Page 13 and 14:
Proceedings of the 7th Internationa
Page 15 and 16:
��ÒÓÛÐ��Ñ�ÒØ
Page 17 and 18:
Page 19 and 20:
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
(the first number), two three-lette
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
vertical fields. The vertical field
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Page 69 and 70:
Page 71 and 72:
Page 73 and 74:
Page 75 and 76:
Page 77 and 78:
Page 79 and 80:
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
Page 161 and 162:
Page 163 and 164:
Page 165 and 166:
Page 167 and 168:
Page 169 and 170:
Page 171 and 172:
90 60 30 0 -30 -60 Proceedings of t
Page 173 and 174:
Page 175 and 176:
Page 177 and 178:
Page 179 and 180:
Page 181 and 182:
Page 183 and 184:
Page 185 and 186:
Page 187 and 188:
Page 189 and 190:
Page 191 and 192:
Page 193 and 194:
Page 195 and 196:
Page 197 and 198:
Page 199 and 200:
Page 201 and 202:
Page 203 and 204:
Page 205 and 206:
Page 207 and 208:
Page 209 and 210:
Page 211 and 212:
Page 213 and 214:
Page 215 and 216:
Page 217 and 218:
Page 219 and 220:
Page 221 and 222:
Page 223 and 224:
Page 225 and 226:
Page 227 and 228:
Page 229 and 230:
Page 231 and 232:
Page 233 and 234:
Page 235 and 236:
Page 237 and 238:
Page 239 and 240:
Page 241 and 242:
a Proceedings of the 7th Internatio
Page 243 and 244:
Page 245 and 246:
Page 247 and 248:
Page 249 and 250:
Page 251 and 252:
Page 253 and 254: Proceedings of the 7th Internationa
Page 275 and 276: Introduction ON THE NATURE OF PLASM
Page 303: Proceedings of the 7th Internationa
Page 309 and 310: Vy Here index j =1,2 characterizes,
Page 311 and 312: Jy Proceedings of the 7th Internati
Page 337 and 338: Fig. 3. Dependence of 1D interpreta
Page 355 and 356:
Page 357 and 358:
Page 359 and 360:
Page 361 and 362:
Page 363 and 364:
Page 365 and 366:
Page 367 and 368:
Page 369 and 370:
Page 371 and 372:
Page 373 and 374:
Page 375 and 376:
Page 377 and 378:
Page 379 and 380:
Page 381 and 382:
Page 383 and 384:
Page 385 and 386:
Page 387 and 388:
Page 389 and 390:
Page 391 and 392:
Page 393 and 394:
Page 395 and 396:
Page 397 and 398:
Page 399 and 400:
Page 401 and 402:
Page 403 and 404:
Page 405 and 406:
Page 407 and 408:
Page 409 and 410:
Page 411 and 412:
Page 413 and 414:
Page 415 and 416:
Page 417 and 418:
Page 419 and 420:
Page 421 and 422:
Page 423 and 424:
Page 425 and 426:
Page 427 and 428:
Page 429 and 430:
Page 431 and 432:
Page 433 and 434:
Page 435 and 436:
Page 437 and 438:
Page 439 and 440:
Page 441 and 442:
Page 443 and 444:
Page 445 and 446:
Page 447 and 448:
Page 449 and 450:
Page 451 and 452:
Page 453 and 454:
Page 455 and 456:
Page 457 and 458:
Page 459 and 460:
Page 461 and 462:
Page 463 and 464:
Page 465 and 466:
Page 467 and 468:
Page 469:
Page 476 and 477:
Page 478 and 479:
Page 480 and 481:
Page 482 and 483:
Page 484 and 485:
Page 486 and 487:
Page 488 and 489:
Page 490 and 491:
Page 492 and 493:
Page 494 and 495:
2. Burlaga & Klein method. The main
Page 496 and 497:
Page 498 and 499:
Page 500 and 501:
Page 502 and 503:
Page 504 and 505:
show all

PROBLEMS OF GEOCOSMOS

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?