Heliospheric current layer

The heliospheric current layer

Side view of the sun with an idealized dipole field at a minimum sunspot :
red the flow of the solar wind, blue the field lines of the solar magnetic field , yellow the heliospheric current layer.

The heliospheric current sheet (engl. Heliospheric current sheet , abbreviated HCS ) is the current sheet in the Heliosphäre in which the polarity of the magnetic field of the sun from north to south substituted.

The sun's magnetic field is constantly changing and is carried far outwards by the solar wind according to its speed of propagation. In combination with the rotation of the sun, the heliospheric current layer therefore takes on the shape of a rotating spiral around the area of ​​the plane of the solar equator. In some publications is the ballerina skirt ( ballerina skirt ) spoken as a normal form of the heliospheric current sheet (see. Figure). In the area of ​​the earth's orbit it is about 10,000 km thick and extends as far outwards as the solar wind that indirectly causes it.

A small electric current flows within the heliospheric current layer .

shape

The Parker Spiral

The heliospheric current layer has idealized the shape of an Archimedean spiral . It is known as the Parker spiral after the American astrophysicist Eugene N. Parker , who predicted the solar wind as plasma of charged particles in the 1950s . Among other things, the solar wind causes the sun's magnetic field, the current shape of which in turn determines the shape of the heliospheric current layer.

The sun's magnetic field can vary from an ordinary dipole field to a field with e.g. B. two northern poles . In addition, the sharply delimited coronal holes , which can appear at any point in the case of maximum sunspots, are only located in the polar regions of the sun at times of minimum sunspot. When the sun formed a second magnetic north pole in 2000, it was predicted that as a result, the current layer would take the form of a billion kilometers large snail shell . Measurements of the ESA - NASA - Ulysses have confirmed this prediction.

Electric current flow

The electric current in the current layer is directed radially inwards and has a maximum magnitude of 10 ⁻¹⁰  A / m² (10 ⁻⁴  A / km²).

In comparison, the Birkeland currents are 1000 times weaker astrophysical currents that can be found in the vicinity of the earth.

history

The heliospheric current layer was discovered in 1965 by John M. Wilcox and Norman F. Ness . In the 1970s, KH Schatten developed the first mathematical model of their shape.

Individual evidence

1. ↑ http://wso.stanford.edu/images/people/wilcox.html (English)
2. ^ John M. Wilcox, Norman F. Ness: Solar source of the interplanetary sector structure (English)
3. ↑ http://lib.bioinfo.pl/auth:Schatten,KH

Web links

• The boundary layer between the solar wind currents and high-energy ions II: Ulysses test of the Pioneer results.
• Mystery of the Sun's Two North Poles by Tony Phillips ( April 20, 2007 memento in the Internet Archive )
• 3 D image from HCS ( Memento from October 17, 2009 in the Internet Archive )
• Messages from the Institute for Geophysics and Meteorology at the University of Cologne Editors: M. Kerschgens, FM Neubauer, M. Pätzold, P. Speth, B. Tezkan, Issue 153, Walter Heibey, Das Weltraumwetter beyond the Earth's orbit, Cologne 2003 , ISSN  0069- 5882 (PDF file)
• University of Osnabrück, sun and interplanetary space (PDF file; 5 MB)