Magnetic Clouds

A magnetic cloud is a transient ejection in the solar wind defined by relatively strong magnetic fields, a large and smooth rotation of the magnetic field direction over approximately 0.25AU at 1AU, and a low proton temperature [Burlaga et al., 1981]. Magnetic clouds are ideal objects for solar-terrestrial studies because of their simplicity and their extended intervals of southward and northward magnetic fields [Burlaga et al., 1990].

The figure summarizes the following:

A flux rope magnetic cloud model, in which it was assumed that the internal magnetic tension and compression forces were in balance, was successfully applied to the October 1995 WIND event to obtain the size and orientation of a large local volume of the cloud from observations along only a single path through it; see Burlaga et al., 1996.

The model and related analyses confirmed that a cloud had a dominant magnetic field which acted like a huge magnetosphere departing the Sun, stretched out in the ecliptic plane, and having its own 'bow shock' ('driven' shock).

The cloud's front and rear boundaries and the driven shock were locally analyzed and shown to be strongly related geometrically to the estimated cloud-axis.

The internal 'shock' may be due to a stream ramming into the rear of the cloud, but the orientation of the shock is unexpected.
A magnetic storm occurred in the Earth's magnetosphere due to the passage of the strong southward fields in the early part of the magnetic cloud.

Interval #1 of the First Inter Agency Consultative Group Science Campaign was October 18-21, 1995, which foruitously encompasses this October 1995 magnetic cloud and related events observed by WIND. Many space science teams are working on various aspects of this magnetic cloud, its possible solar origin, and its effects on the Earth's magnetosphere, e.g., see Lepping et al., 1997.

Magnetic Cloud Table

MAGNETIC CLOUDS AS DETERMINED BY MFI DATA - PRELIMINARY

The table consists of estimated start and end times, as designated, and physical quantities that were estimated by a magnetic field model [Lepping et al., 1990] that assumes that the field within the magnetic cloud is force free, i.e., so that the electrical current and the magnetic field are parallel and proportional in strength everywhere within its volume. The angles PHI and THETA refer to the estimated direction of the cloud's axis, where PHI is a longitude and THETA is a latitude in GSE coordinates. Dia. is the diameter (in AU) of the magnetic cloud, assumed circular in cross-section, based on model results and the radial speed of the solar wind provided by the WIND SWE instrument (K. W. Ogilvie, PI). B is the model-estimated magnetic field for the axis of the cloud. We point out that the spacecraft rarely encounters the actual axis, but passes above or below at various closest approach (CA) distances that are also estimated by the model (not shown explicitly here - but see CA% below.) |CHI| is actually chi/(3N-5), based on the reduced chi-squared value, which is the usual chi-squared divided by (3N-n), where N is the number of points (usually hour averages) used in the model fitting and n is fixed at 5 which is the number of parameters fitted up to this time; two other parameters are fitted later in the process, making it a 7 parameter model. H represents helical field handedness, right- or left-handed. CA% means the ratio of CA distance of the spacecraft to the cloud's axis to the cloud's radius, expressed in percentage. F is the magnetic flux along the axis of the magnetic cloud estimated by the flux rope model of Lepping et al.(1990), where F = 1.36 BR**2, and where R = Dia/2. Version date: 04/23/03

----|----START--TIME----|------END--TIME----|-------------------ESTIMATED(MODEL)---------------------------------------------
    |                   |                   |                             |
    |                   |                   |                             |
 YR | MON Day(DOY) HR   | MON Day(DOY) HR   | DT* PHI THETA   V**  Dia    |  B    H  |CHI| asf% [QUAL+] CA%&  F# Figures Ref 
    |                   |                   |    (deg)(deg) (km/s) (AU)   | (nT)    
    |                   |                   |                             |
 95 | Feb  8 (039) 03   | Feb  8 (039) 22   | 20   92    6   410   0.224  | 14.2  L  .0167  25.0   [1]   34   5.5 f1  f2
    |                   |                   |                             |
 95 | Mar  4 (063) 11   | Mar  5 (064) 04   | 18  205  -82   443   0.190  | 14.4  L  .0296  12.2   [2]   52   3.9 f1  f2
    |                   |                   |                             |
 95 | Apr  6 (096) 07   | Apr  6 (096) 18   | 12  147   65   334   0.096  | 14.7  L  .0194  11.7   [2]   76   1.0 f1  f2
    |                   |                   |                             |
 95 | May 13 (133) 10.1 | May 13 (133) 15.8 | 5.7  107  -3   331   0.165  | 20.5  L  .0088   3.2   [3]   98   4.3 f1  f2 
    |                   |                   |                             |
 95 | Aug 22 (234) 22   | Aug 23 (235) 19   | 22  268    4   360   0.233  | 11.8  R  .0137  14.5   [1]   35   4.9 f1  f2
    |                   |                   |                             |
 95 | Oct 18 (291) 19   | Oct 20 (293) 00   | 30  289  -10   404   0.249  | 25.6  R  .0141   3.3   [1]    8  12.7 f1  f2  REF
    |                   |                   |                             |
 95 | Dec 16 (350) 05   | Dec 16 (350) 22   | 18    2  -14   396   0.078  | 17.5  L  .0225  17.8   [3]   81   0.8 f1  f2
-----------------------------------------------------------------------------------------------------------------------------
 96 | May 27 (148) 15   | May 29 (150)  7   | 41  120   33   370   0.353  | 11.9  L  .0154  25.9   [1]   13  11.3 f1  f2
    |                   |                   |                             |
 96 | Jul  1 (183) 17   | Jul  2 (184) 09   | 17   99    5   355   0.164  | 12.5  L  .0228  11.8   [2]   10   2.7 f1  f2
    |                   |                   |                             |
 96 | Aug  7 (220) 13   | Aug  8 (221) 10   | 22  241  -43   344   0.202  |  9.5  R  .0133  16.4   [1]   54   3.0 f1  f2
    |                   |                   |                             |
 96 | Dec 24 (359) 03   | Dec 25 (360) 10   | 32   80   25   355   0.291  | 14.7  R  .0155   3.1   [1]   49   9.6 f1  f2
-----------------------------------------------------------------------------------------------------------------------------
 97 | Jan 10 (010) 05   | Jan 11 (011) 02   | 22  250    3   436   0.193  | 18.0  R  .0130   7.3   [1]   14   5.1 f1  f2  REF
    |                   |                   |                             |
 97 | Feb 10 (041) 03   | Feb 10 (041) 18   |                             |                                       f1  f2
    |                   |                   |                             |
 97 | Apr 21 (111) 15   | Apr 23 (113) 07   | 41  348  -23   360   0.176  | 15.1  R  .0239  15.1   [3]   46   3.5 f1  f2
    |                   |                   |                             |
 97 | May 15 (135) 09   | May 16 (136) 01   | 17  102   -9   450   0.181  | 24.1  L  .0217   4.7   [2]   27   5.9 f1  f2
    |                   |                   |                             |
 97 | May 16 (136) 07   | May 16 (136) 14   | 8.5 299   32   480   0.073  | 10.5  L  .0194  14.7   [3]   34  0.43 f1  f2
    |                   |                   |                             |
 97 | Jun 09 (160) 02   | Jun 09 (160) 23   | 22  219  -17   370   0.193  | 15.0  L  .0196   6.4   [2]   53   4.3 f1  f2
    |                   |                   |                             |
 97 | Jun 19 (170) 5.1  | Jun 19 (170) 17.9 |12.8 263  -11   385   0.146  |  9.9  R  .0110  63.6   [3]    0   1.6 f1  f2
    |                   |                   |                             |
 97 | Jul 15 (196) 06   | Jul 16 (197) 01   | 20  112  -29   360   0.141  | 13.2  L  .0233  32.0   [2]   14   2.0 f1  f2
    |                   |                   |                             |
 97 | Aug 03 (215) 14   | Aug 04 (216) 01   | 12   25    6   445   0.063  | 27.5  L  .0210   8.3   [2]   83  0.86 f1  f2
    |                   |       	    |                             |
 97 | Sep 18 (261) 00   | Sep 20 (263) 12   | 61  246   65   320   0.332  | 17.8  R  .0217   2.0   [2]   62  15.0 f1  f2
    |                   |                   |                             |
 97 | Sep 21 (264) 22   | Sep 22 (265) 18   | 21   76   77   425   0.318  | 18.8  L  .0146  13.3   [1]   47  14.6 f1  f2
    |                   |                   |                             |
 97 | Oct 01 (274) 16   | Oct 02 (275) 23   | 32  144   41   450   0.397  | 11.5  L  .0173   3.1   [2]   39  13.8 f1  f2 
    |                   |                   |                             |
 97 | Oct 10 (283) 23   | Oct 12 (285) 00   | 26  273   -5   396   0.227  | 17.0  R  .0116   0.0   [1]   57   6.7 f1  f2
    |                   |                   |                             |
 97 | Nov 07 (311) 5.8  | Nov 08 (312) 4.3  |22.5 228  -20   440   0.220  | 16.9  R  .0087  28.8   [2]   25   6.3 f1  f2
    |                   |                   |                             |
 97 | Nov 08 (312) 4.8  | Nov 08 (312) 14.8 | 10  317   62   395   0.122  | 20.1  R  .0204  14.7   [2]   54   2.3 f1  f2
    |                   |                   |                             |
 97 | Nov 22 (326) 14   | Nov 23 (327) 18   | 29  172  -52   490   0.220  | 21.0  R   .0358  3.4   [3]   17   7.7 f1  f2
---------------------------------------------------------------------------------------------------------------------------
 98 | Jan 07 (007) 03   | Jan 08 (008) 10   | 31   36   47   375   0.210  | 19.5  L  .0115  14.2   [2]    5   6.7 f1  f2
    |                   |                   |                             |
 98 | Jan 08 (008) 14   | Jan 08 (008) 22   | 09  320   -9   355   0.056  | 12.7  R  .0379   0.0   [3]   61  0.31 f1  f2
    |                   |                   |                             |
 98 | Feb 04 (035) 04   | Feb 05 (036) 22   | 43   82    3   320   0.293  | 21.5  L  .0074  11.6   [3]   90  14.1 f1  f2  REF
    |                   |                   |                             |
 98 | Mar 04 (063) 14   | Mar 06 (065) 06   | 41  120   27   360   0.344  | 12.2  L  .0144  11.2   [1]    3  11.1 f1  f2
    |                   |                   |                             |
 98 | May 02 (122) 12   | May 03 (123) 17   | 30    2   55   515   0.435  | 15.6  L  .0139   9.3   [2]   81  22.7 f1  f2
    |                   |                   |                             |
 98 | Jun 02 (153) 10.5 | Jun 02 (153) 15.9 | 5.4  59   28   410   0.065  | 12.7  L  .0067   3.8   [1]   26  0.41 f1  f2
    |                   |                   |                             |
 98 | Jun 24 (175) 16.8 | Jun 25 (176) 21.8 | 29  151   21   460   0.207  | 15.5  L  .0080   24.3  [2]   23   5.1 f1  f2
    |                   |                   |                             |
 98 | Aug 20 (232) 10   | Aug 21 (233) 19   | 34  287   13   315   0.214  | 16.5  R  .0155   1.8   [1]   11   5.8 f1  f2
    |                   |                   |                             |
 98 | Sep 25 (268)  5   | Sep 26 (269) 13   | 33  169   66   710   0.493  | 20.7  L  .0130   6.7   [3]   58  39.1 f1  f2
    |                   |                   |                             |
 98 | Oct 19 (292) 05   | Oct 20 (293) 07   | 27  114  -32   383   0.224  | 21.7  L  .0246   3.7   [2]   39   8.3 f1  f2
    |                   |                   |                             |
 98 | Nov  8 (312) 19   | Nov 10 (314) 01   | 31   40  -65   470   0.235  | 20.3  R  .0155   3.9   [2]   10   8.5 f1  f2
---------------------------------------------------------------------------------------------------------------------------
 99 | Feb 18 (049) 14   | Feb 19 (050) 12   | 23  284    5   590   0.498  | 13.5  L  .0152   4.4   [1]   67  25.6 f1  f2
    |                   |                   |                             |
 99 | Apr 16 (106) 20   | Apr 17 (107) 21   | 26  113  -32   406   0.192  | 25.2  L  .0240   0.0   [2]   40   7.2 f1  f2
    |                   |                   |                             |
 99 | Aug  9 (221) 10.8 | Aug 10 (222) 15.8 | 29  176   76   370   0.284  | 12.6  L  .0104  10.3   [1]   23   7.8 f1  f2
    |                   |                   |                             |
 99 | Sep 21 (264) 21   | Sep 22 (265) 05   |  9   80   10   355   0.088  | 18.5  L  .0194  11.0   [2]   68   1.1 f1  f2
----------------------------------------------------------------------------------------------------------------------------
 00 | Feb 12 (043) 16.9 | Feb 13 (044)  0.6 | 7.8 206  -44   543   0.136  | 16.2  L  .0232  47.4   [3]   70   2.3 f1  f2
    |                   |                   |                             |
 00 | Feb 21 (052) 9.8  | Feb 22 (053) 13.3 |27.5 163   75   380   0.279  | 18.4  R  .0169  13.6   [1]   20  11.0 f1  f2
    |                   |                   |                             |
 00 | Jul 15 (197) 06   | Jul 15 (197) 14   |  9  211  -58   650   0.146  | 15.2  L  .0337  21.1   [3]   74   2.5 f1  f2  REF
    |                   |                   |                             |
 00 | Jul 15 (197) 19   | Jul 16 (198) 09   | 15   46   55   990   0.348  | 46.8  L  .0169  33.3   [1]   16  43.3 f1  f2  REF 
    |                   |                   |                             |
 00 | Jul 28 (210) 21   | Jul 29 (211) 10   | 14  295    8   471   0.185  | 15.9  L  .0267  19.4   [2]   38   4.2 f1  f2
    |                   |                   |                             |
 00 | Aug 01 (214) 00   | Aug 01 (214) 16   | 17  212   15   445   0.228  | 16.8  L  .0150   0.9   [2]   77   6.7 f1  f2
    |                   |                   |                             | 
 00 | Aug 12 (225)  6   | Aug 13 (226)  5   | 24   96   10   567   0.283  | 30.2  L  .0176  17.3   [1]    3  18.5 f1  f2
    |                   |                   |                             |
 00 | Sep 18 (262) 01   | Sep 18 (262) 16   | 16  184  -32   760   0.228  | 46.6  L  .0159   2.5   [3]  100  18.3 f1  f2
    |                   |                   |                             |
 00 | Oct  3 (277) 17.2 | Oct  4 (278) 14.2 | 21   56   32   409   0.186  | 19.3  R  .0097   0.0   [1]   18   5.2 f1  f2
    |                   |                   |                             |
 00 | Oct 13 (287) 18.3 | Oct 14 (288) 16.8 |22.5 140  -24   395   0.214  | 12.6  R  .0105   2.4   [1]   17   4.4 f1  f2
    |                   |                   |                             |
 00 | Oct 28 (302) 23   | Oct 30 (304) 00   | 26   88   27   375   0.502  | 16.0  L  .0104  >100   [3]   17  31.0 f1  f2
    |                   |                   |                             |
 00 | Nov  6 (311) 23   | Nov  7 (312) 18   | 20  112   -9   535   0.280  | 24.3  L  .0085  36.7   [2]   22  14.4 f1  f2
--------------------------------------------------------------------------------------------------------------------------------
 01 | Mar 19 (078) 22   | Mar 22 (081) 10   | 61   80    5   360   0.421  | 16.1  L  .0103  35.7   [1]   13  21.7 f1  f2
    |                   |                   |                             |
 01 | Apr  4 (094) 21.3 | Apr  5 (095)  8.3 | 11  266   21   740   0.378  | 19.3  R  .0143   5.2   [3]   95  21.1 f1  f2
    |                   |                   |                             |
 01 | Apr 11 (101) 21.3 | Apr 12 (102) 17.8 |20.5 257   36   670   0.500  | 24.8  R  .0174  18.3   [3]   52  47.6 f1  f2
    |                   |                   |                             | 
 01 | Apr 22 (112)  0.8 | Apr 23 (113)  1.3 |24.5 283  -73   395   0.246  | 13.1  L  .0079  22.9   [1]    5   6.0 f1  f2
    |                   |                   |                             | 
 01 | Apr 29 (119)  1.8 | Apr 29 (119) 12.8 |11.0 117   42   640   0.244  | 12.3  L  .0109  31.9   [2]  -45   5.7 f1  f2
    |                   |                   |                             |
 01 | May 28 (148) 11.8 | May 29 (149) 10.3 |22.5  49   -7   475   0.246  | 11.6  L  .0109  27.3   [1]   39   5.3 f1  f2
    |                   |                   |                             | 
 01 | Jul 10 (191) 17.3 | Jul 12 (193)  8.8 |39.5 252   15   360   0.258  | 10.9  R  .0122  13.1   [1]   46   5.6 f1  f2
    |                   |                   |                             |
 01 | Oct 31 (304) 21.3 | Nov  2 (306) 10.3 | 37   78    8   340   0.282  | 13.1  L  .0155   3.7   [2]    9   8.0 f1  f2
    |                   |                   |                             |
 01 | Nov 24 (328) 15.8 | Nov 25 (329) 13.3 |21.5 105   27   730   0.594  | 29.9  L  .0143  11.8   [2]   82  80.9 f1  f2
--------------------------------------------------------------------------------------------------------------------------------
 02 | Mar 19 (078) 22.8 | Mar 20 (079) 15.3 |16.5  39   26   370   0.200  | 17.0  R  .0071  19.9   [1]   24   5.3 f1  f2
    |                   |                   |                             |
 02 | Mar 24 (083)  3.8 | Mar 25 (084) 22.8 | 43  295   42   440   0.446  | 18.2  R  .0108   8.7   [1]    1  27.7 f1  f2
    |                   |                   |                             |
 02 | Apr 20 (110) 11.5 | Apr 21 (111) 16.5 | 29  154   37   510   0.337  |  8.7  L  .0154  69.2   [3]   39   7.6 f1  f2
    |                   |                   |                             |
 02 | May 19 (139)  3.8 | May 19 (139) 22.3 |18.5 239   -6   458   0.371  | 20.2  R  .0072   0.1   [1]   82  21.3 f1  f2
    |                   |                   |                             |
 02 | May 23 (143) 23.3 | May 24 (144) 16.8 |17.  283   43   730   0.672  | 23.1  R  .0067   3.3   [3]  100  80.4 f1  f2
    |                   |                   |                             |
 02 | Aug  1 (213) 11.8 | Aug  1 (213) 22.8 |11.0 235   58   454   0.140  | 14.8  R  .0186  72.3   [3]   21   2.2 f1  f2
    |                   |                   |                             |
 02 | Aug  2 (214)  7.3 | Aug  2 (214) 21.3 |14.0 245   13   493   0.265  | 13.3  L  .0081  51.6   [2]   13   7.2 f1  f2
    |                   |                   |                             |
 02 | Sep 30 (273) 22.3 | Oct  1 (274) 11.8 |13.5 110  -10   381   0.118  | 28.2  R  .0086  57.3   [2]   12   3.9 f1  f2
--------------------------------------------------------------------------------------------------------------------------------
 03 | Mar 20 (079) 11.8 | Mar 20 (079) 22.3 |10.5 228  -77   650   0.200  | 16.5  L  .0133   2.0   [1]   67   5.1 f1  f2
--------------------------------------------------------------------------------------------------------------------------------

* DT, Duration of event.

** Average solar wind speed courtesy of WIND/SWE: Dr. K. Ogilvie, PI.

asf% (< 100), the asymmetery factor, is the percent difference between the quantity DT/2, the mid-point of the observed event, and the estimated closest approach time, according to the model. asf% is always positive. When asf% is 0 % the cloud field structure is ideally perfectly symmetric.

+ QUALITY, measured subjectively: 1 = EXCELLENT, 2 = GOOD, 3 = POOR, CL = CLOUD-LIKE
When the designation is CL helical flux rope fitting is not likely to be successful for any reasonable model.

& CA% means the ratio of Closest Approach distance to the radius, expressed in %; 0 % then means that the spacecraft encountered the axis of the cloud and 100 % means that the spacecraft just skimmed the outer boundary.

# Magnetic flux along the magnetic cloud axis, in units of 10**10 G-km**2, estimated by the flux rope cloud model of Lepping et al.(1990), where F = 1.36 BR**2, and where R = Dia/2.

-------------------------------------------------------------------------------

References:

Burlaga, L. F., E. Sittler, F. Mariani, and R. Schwenn, Magnetic loop behind an interplanetary shock: Voyager, Helios and IMP-8 observations, J. Geophys. Res., 86, 6673, 1981.

Burlaga, L. F., R. Lepping, and J. Jones, Global configurations of magnetic cloud, in Physics of Flux Ropes, p.373, edited by C. T. Russell, E. R. Priest and L. C. Lee, AGU Geophysical Monograph 58, American Geophysical Union, Washington D. C., 1990.

Burlaga, L. F., R. P. Lepping, W. H. Mish, K. W. Olgilvie, A. Szabo, and A. J. Lazarus, J. T. Steinberg, A magnetic cloud observed by WIND on October 18-20, 1995, NASA/GSFC Laboratory for Extraterrestrial Physics Internal Document, February 1996.

Burlaga, L. F., R. J. Fitzenreiter, R. P. Lepping, K. W. Ogilvie, A. Szabo, A. J. Lazarus, J. T. Steinberg, G. Gloeckler, R. A. Howard, D. J. Michels, C. J. Farrugia, R. P. Lin, and D. E. Larson, A magnetic cloud containing prominence material: January 1997, J. Geophys. Res., 103, 277-285, 1998.

Lepping, R. P., J. A. Jones, and L. F. Burlaga, Magnetic field structure of interplanetary magnetic clouds at 1 AU, J. Geophys. Res., 95, 11,957, 1990.

Lepping, R. P., L. F. Burlaga, A. Szabo, K. W. Ogilvie, W. Mish, D. Vassiliadis, A. J. Lazarus, J. T. Steinberg, C. J. Farrugia, J. Janoo, and F. Mariani, The WIND magnetic cloud and events of October 18-20, 1995: Interplanetary properties and as triggers for geomagnetic activity, J. Geophys. Res., 102, 14,049, 1997.

Lepping, R.P. and D. Berdichevsky, Interplanetary magnetic cloud: Sources, properties, modeling, and geomagnetic relationship, Recent Res. Devel. Geophysics, 3, Research Signpost, Trivandrum-8, India, 77-96, 2000.

Lepping, R.P., D. Berdichevsky, Magnetic clouds as intermediary agents between their solar sources and the magnetosphere, Eos, Transactions, American Geophysical Union, vol, 82, No.20, May 15, 2001a.

Lepping, R.P., D.B. Berdichevsky, L.F. Burlaga, A.J. Lazarus, J. Kasper, M.D. Desch, C.-C. Wu, D.V. Reames, H.J. Singer, C.W. Smith and K. Ackerson, The Bastille day magnetic clouds and upstream shocks: near earth interplanetary observations, Solar Phys., in press, 2001b.

Lepping, R.P., D. Berdichevsky, A. Szabo, C. Arqueros, and A.J. Lazarus, Profile of a generic magnetic cloud at 1 AU for the Quiet Solar Phase: WIND Observations, Solar Phys., submitted, 2001c.

For more references see the WIND MFI Bibliography page.

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