Magnetic cloud

Magnetic cloud

A magnetic cloud is a transient event observed in the solar wind. It was defined in 1981 by Burlaga et al. 1981 as a region of enhanced magnetic field strength, smooth rotation of the magnetic field vector and low proton density and temperature [1]. Magnetic clouds are a possible manifestation of a Coronal Mass Ejection (CME). The association between CMEs and magnetic clouds was made by Burlaga et al. in 1982 when a magnetic cloud was observed by Helios-1 two days after being observed by SMM[2]. However, because observations near Earth are usually done by a single spacecraft, many CMEs are not seen as being associated with magnetic clouds. The typical structure observed for a fast CME by a satellite such as ACE is a fast-mode shock wave followed by a dense (and hot) sheath of plasma (the downstream region of the shock) and a magnetic cloud.

Contents

Other characteristics

Other signatures of magnetic clouds are now used in addition to the one described above: among other, bidirectional superthermal electrons, unusual charge state or abundance of iron, helium, carbon and/or oxygen. The typical time for a magnetic cloud to move past a satellite at the L1 point is 1 day corresponding to a radius of 0.15 AU with a typical speed of 450 km s−1 and magnetic field strength of 20 nT [3]

Other types of ejecta observed at Earth

Magnetic clouds represent about one third of ejecta observed by satellites at Earth. Other types of ejecta are multiple-magnetic cloud events (a single structure with multiple subclouds distinguishable)[4][5] and complex ejecta, which can be the result of the interaction of multiple CMEs.

See also

References

  1. ^ Burlaga, L. F., E. Sittler, F. Mariani, and R. Schwenn, "Magnetic loop behind an interplanetary shock: Voyager, Helios and IMP-8 observations" in "Journal of Geophysical Research", 86, 6673, 1981
  2. ^ Burlaga, L. F. et al., "A magnetic cloud and a coronal mass ejection" in "Geophysical Research Letter"s, 9, 1317-1320, 1982
  3. ^ Lepping, R. P. et al. "Magnetic field structure of interplanetary magnetic clouds at 1 AU" in "Journal of Geophysical Research", 95, 11957-11965, 1990.
  4. ^ Wang, Y. M., et al., Multiple magnetic clouds in interplanetary space, Solar Physics, 211, 333-344, 2002.
  5. ^ Wang, Y. M., et al., Multiple magnetic clouds: Several examples during March - April, 2001, J. Geophys. Res., 108(A10), 1370, 2003.


External links


Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать курсовую

Look at other dictionaries:

  • Cloud Creek crater — is an impact crater in Wyoming, United States.[1] The crater is located in Natrona County, about 48 miles northwest of Casper, near the center of a geological feature known as the Casper Arch.[2]:445 The Cloud Creek structure is circular with a… …   Wikipedia

  • Cloud chamber — with visible tracks from ionizing radiation (short, thick: α particles; long, thin: β particles). See also Animated Version Video of a Cloud chamber in action The cloud chamber, a …   Wikipedia

  • Cloud Cock OO Grand — Studio album by Merzbow Released 1990 Recorded 23 September, 1989 …   Wikipedia

  • Magnetic field — This article is about a scientific description of the magnetic influence of an electric current or magnetic material. For the physics of magnetic materials, see magnetism. For information about objects that create magnetic fields, see magnet. For …   Wikipedia

  • Magnetic braking — The magnetic field lines rotates together with the Sun as a solid object. Ionized material carried along the field lines will at some point rc escape the magnetic field lines and thus take away the Sun s angular momentum Magnetic braking is a… …   Wikipedia

  • Magnetic quantum number — In atomic physics, the magnetic quantum number is the third of a set of quantum numbers (the principal quantum number, the azimuthal quantum number, the magnetic quantum number, and the spin quantum number) which describe the unique quantum state …   Wikipedia

  • Magnetic pistol — …   Wikipedia

  • Magnetic field of the Moon — Total magnetic field strength at the surface of the Moon as derived from the Lunar Prospector electron reflectometer experiment. The external magnetic field of the Moon is very weak in comparison to that of the Earth. Other major differences are… …   Wikipedia

  • Magnetic storm — Storm Storm, n. [AS. storm; akin to D. storm, G. sturm, Icel. stormr; and perhaps to Gr. ? assault, onset, Skr. s? to flow, to hasten, or perhaps to L. sternere to strew, prostrate (cf. {Stratum}). [root]166.] 1. A violent disturbance of the… …   The Collaborative International Dictionary of English

  • Molecular cloud — See also: Solar nebula Within a few million years the light from bright stars will have boiled away this molecular cloud of gas and dust. The cloud has broken off from the Carina Nebula. Newly formed stars are visible nearby, their images… …   Wikipedia

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”