Heliospheric current sheet

Heliospheric current sheet

The heliospheric current sheet (HCS) is the surface within the Solar System where the polarity of the Sun's magnetic field changes from north to south. This field extends throughout the Sun's equatorial plane in the heliosphere. [ [http://science.nasa.gov/headlines/y2003/22apr_currentsheet.htm A Star with two North Poles] , April 22, 2003, Science @ NASA] [Riley, Pete; Linker, J. A.; Mikić, Z., " [http://adsabs.harvard.edu/abs/2002JGRA.107g.SSH8R Modeling the heliospheric current sheet: Solar cycle variations] ", (2002) "Journal of Geophysical Research" (Space Physics), Volume 107, Issue A7, pp. SSH 8-1, CiteID 1136, DOI 10.1029/2001JA000299. ( [http://ulysses.jpl.nasa.gov/science/monthly_highlights/2002-July-2001JA000299.pdf Full text] )] The shape of the current sheet results from the influence of the Sun's rotating magnetic field on the plasma in the interplanetary medium (Solar Wind). [ [http://quake.stanford.edu/~wso/gifs/HCS.html] Dead link|date=March 2008] A small electrical current flows within the sheet, about 10−10 A/m². The thickness of the current sheet is about 10,000 km.

The underlying magnetic field is called the interplanetary magnetic field, and the resulting electric current forms part of the heliospheric current circuit.Israelevich, P. L., "et al", " [http://aanda.u-strasbg.fr/papers/aa/full/2001/34/aah2814/aah2814.html MHD simulation of the three-dimensional structure of the heliospheric current sheet] " (2001) "Astronomy and Astrophysics", v.376, p.288-291] The Heliospheric current sheet is also sometimes called the "Interplanetary Current Sheet".

Characteristics

Ballerina's skirt shape

As the Sun rotates, its magnetic field twists into a Parker spiral,Parker, E. N., " [http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?1958ApJ...128..664P Dynamics of the Interplanetary Gas and Magnetic Fields] ", (1958) "Astrophysical Journal", vol. 128, p.664] a form of an Archimedean spiral, named after its discovery by Eugene Parker. Parker's spiral magnetic field was divided in two by a current sheet [ " [http://www.nature.com/nature/journal/v264/n5588/abs/264730a0.html;jsessionid=55DC5F768647B390C384E7AF83122081 Current Sheet Magnetic Model for the Solar Corona] ", K. H. Schatten, Cosmic Electrodynamics, 2, 232-245, 1971.] , a mathematical model first developed in the early '70's by Schatten. As the spiraling magnetic sheet changes polarity, it warps into a wavy spiral shape that has been likened to a ballerina's skirt.Rosenberg, R. L. and P. J. Coleman, Jr., Heliographic latitude dependence of the dominant polarity of the interplanetary magnetic field, "J. Geophys. Res.", 74 (24), 5611-5622, 1969.] Wilcox, J. M.; Scherrer, P. H.; Hoeksema, J. T., " [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1980STIN...8133113W&db_key=AST&data_type=HTML&format=&high=42ca922c9c12139 The origin of the warped heliospheric current sheet] " (1980)] Further dynamics have suggested that "The Sun with the heliosheet is like a bashful ballerina who is repeatedly trying to push her excessively high flaring skirt downward".Mursula, K.; Hiltula, T., " [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003GeoRL..30vSSC2M&db_key=AST&data_type=HTML&format=&high=42ca922c9c03266 Bashful ballerina: Southward shifted heliospheric current sheet] " (2003), Geophysical Research Letters, Volume 30, Issue 22, pp. SSC 2-1]

The cause of the ballerina spiral shape has sometimes been called the "garden sprinkler effect" or "garden hose effect" [Louise K. Harra, Keith O. Mason, "Space Science" 2004, Imperial College Press, ISBN 1860943616] [Smith, E., " [http://trs-new.jpl.nasa.gov/dspace/handle/2014/18860?mode=simple The Sun, Solar Wind, and Magnetic Field] ", Jul 1999, Proceedings of the International School of Physics Enrico FERMI Varenna, Italy] , and likening to holding a lawn sprinkler, and moving it in your hand vertically up and down, while your body rotates. The stream of water represents the Solar Wind, and moves radially outwards at all times.

Magnetic field

The heliospheric current sheet rotates along with the Sun once every 27 days, during which time the peaks and troughs of the skirt pass through the Earth's magnetosphere, interacting with it. Near the surface of the Sun, the magnetic field produced by the radial electric current in the sheet is of the order of 5×10−6 T.

The magnetic field at the surface of the Sun is about 10-4 tesla. If the form of the field were a magnetic dipole, the strength would decrease with the cube of the distance, resulting in about 10-11 tesla at the Earth's orbit. The heliospheric current sheet results in higher order multipole components so that the actual magnetic field at the Earth due to the Sun is 100 times greater.

Electric current

The electric current in the heliospheric current sheet is directed radially inward, the circuit being closed by outward currents aligned with the Sun's magnetic field in the solar polar regions. The total current in the circuit is on the order of 3×109 amperes. As a comparison with other astrophysical electric currents, the Birkeland currents that supply the Earth's aurora are about a thousand times weaker at a million amperes. The maximum current density in the sheet is on the order of 10-10 A/m² (10-4 A/km²).

History

The heliospheric current sheet was discovered by John M. Wilcox and Norman F. Ness, who published their finding in a 1965.John M. Wilcox and Norman F. Ness, "Quasi-Stationary Corotating Structure in the Interplanetary Medium" (1965) "Journal of Geophysical Research", 70, 5793.] Hannes Alfvén and Per Carlqvist speculate on the existence of a galactic current sheet, a counterpart of the heliospheric current sheet, with an estimated galactic current of 1017 to 1019 amperes, that might flow in the plane of symmetry of the galaxy.Hannes Alfvén and Per Carlqvist, " [http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1978Ap%26SS..55..487A Interstellar clouds and the formation of stars] " (1978) in "Astrophysics and Space Science", vol. 55, no. 2, May 1978, p. 487-509.]

References

ee also

* Interplanetary Magnetic Field

External links

* [http://www.izmiran.rssi.ru/magnetism/SSIMF/SB/mfi/hcs.html The Heliospheric Current Sheet]
* [http://www.firstscience.com/site/articles/north.asp A Star With Two North Poles] (features animation)
* [http://pluto.space.swri.edu/IMAGE/glossary/IMF.html The interplanetary magnetic field]
* [http://gse.gi.alaska.edu/recent/3DHCS.html 3-Dimensional View of the Heliospheric Current Sheet]
* [http://adsabs.harvard.edu/cgi-bin/nph-abs_connect?db_key=AST&sim_query=YES&aut_xct=NO&aut_logic=OR&obj_logic=OR&author=&object=&start_mon=&start_year=&end_mon=&end_year=&ttl_logic=OR&title=%22Heliospheric+Current+Sheet%22&txt_logic=OR&text=&nr_to_return=100&start_nr=1&jou_pick=ALL&ref_stems=&data_and=ALL&group_and=ALL&start_entry_day=&start_entry_mon=&start_entry_year=&end_entry_day=&end_entry_mon=&end_entry_year=&min_score=&sort=SCORE&data_type=SHORT&aut_syn=YES&ttl_syn=YES&txt_syn=YES&aut_wt=1.0&obj_wt=1.0&ttl_wt=0.3&txt_wt=3.0&aut_wgt=YES&obj_wgt=YES&ttl_wgt=YES&txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1 NASA Astrophysics Data System article references] ( [http://adsabs.harvard.edu/cgi-bin/nph-abs_connect?db_key=AST&sim_query=YES&aut_xct=NO&aut_logic=OR&obj_logic=OR&author=&object=&start_mon=&start_year=&end_mon=&end_year=&ttl_logic=OR&title=%22Heliospheric+Current+Sheet%22&txt_logic=OR&text=&nr_to_return=100&start_nr=1&jou_pick=ALL&ref_stems=&data_and=YES&gif_link=YES&group_and=ALL&start_entry_day=&start_entry_mon=&start_entry_year=&end_entry_day=&end_entry_mon=&end_entry_year=&min_score=&sort=SCORE&data_type=SHORT&aut_syn=YES&ttl_syn=YES&txt_syn=YES&aut_wt=1.0&obj_wt=1.0&ttl_wt=0.3&txt_wt=3.0&aut_wgt=YES&obj_wgt=YES&ttl_wgt=YES&txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1 Online full text articles] )


Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать курсовую

Look at other dictionaries:

  • Heliospheric current sheet — The Parker Spiral Die Sonne hat ein Magnetfeld, das nur entfernt als Dipolfeld angesehen werden kann. An den Polregionen befinden sich die scharf begrenzten koronalen Löcher. In der Äquatorregion befinden sich aktivere Gebiete, die sich durch… …   Deutsch Wikipedia

  • Current sheet — The heliospheric current sheet results from the influence of the Sun s rotating magnetic field on the plasma in the interplanetary medium[1] A current sheet is an electric current that is confined to a surface, rather than …   Wikipedia

  • Birkeland current — Schmatic of the Birkeland or Field Aligned Currents and the ionospheric current systems they connect to.[1] A Birkeland current is a set of currents which flow along geomagnetic field line connecting the Earth’s magnetosphere to the Earth s hi …   Wikipedia

  • Interplanetary medium — [ heliospheric current sheet results from the influence of the Sun s rotating magnetic field on the plasma in the interplanetary medium. [http://quake.stanford.edu/ wso/gifs/HCS.html] ] The interplanetary medium is the material which fills the… …   Wikipedia

  • Parker spiral — [ heliospheric current sheet is a three dimensional form of the Parker spiral that results from the influence of the Sun s rotating magnetic field on the plasma in the interplanetary medium. [http://wso.stanford.edu/gifs/helio.gif] ] The Parker… …   Wikipedia

  • Sun — This article is about the star. For other uses, see Sun (disambiguation). The Sun …   Wikipedia

  • Heliosphere — The heliosphere is a bubble in space blown into the interstellar medium (the hydrogen and helium gas that permeates the galaxy) by the solar wind. Although electrically neutral atoms from interstellar space can penetrate this bubble, virtually… …   Wikipedia

  • Solar System — This article is about the Sun and its planetary system. For other systems, see planetary system and star system. For a list of physical and orbital statistics for the Solar System s largest bodies, see List of gravitationally rounded objects of… …   Wikipedia

  • Cluster (spacecraft) — Cluster Operator European Space Agency in international collaboration with NASA Major contractors Dornier GmbH (now part of EADS) Mission type Orbiter Satellite of Earth …   Wikipedia

  • Magnetosphere of Jupiter — Discovery[1] Discovered by …   Wikipedia

Share the article and excerpts

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