Helmet streamers

Helmet Streamers and the Magnetic Structure of the Corona.

During any total solar eclipse, you are guaranteed to see the magnificent solar corona extending far from the obscured solar disk. In general, the corona will not look like a smooth halo of light, but will have structure to it both big and small. The most dramatic large structures are the helmet streamers that look like their namesake and have been recorded in eclipse drawings since the s. During the Eclipse of Sept. The story of Eclipses, G. Chambers He identified an extended, smooth component onto which he superposed large, conical features along with some indication of prominences. This astronomical drawing during the July 28, total solar eclipse was published in Thierry Moreux's 'Les Eclipses' and also shows pronounced conical-shaped features in a remarkably regular pattern.

Helmet streamers

Coronal Features. Click on image for larger version. Helmet Streamers Helmet streamers are large cap-like coronal structures with long pointed peaks that usually overlie sunspots and active regions. We often find a prominence or filament lying at the base of these structures. Helmet streamers are formed by a network of magnetic loops that connect the sunspots in active regions and help suspend the prominence material above the solar surface. The closed magnetic field lines trap the electrically charged coronal gases to form these relatively dense structures. The pointed peaks are formed by the action of the solar wind blowing away from the Sun in the spaces between the streamers. Polar Plumes Polar plumes are long thin streamers that project outward from the Sun's north and south poles. We often find bright areas at the footpoints of these features that are associated with small magnetic regions on the solar surface. These structures are associated with the "open" magnetic field lines at the Sun's poles. The plumes are formed by the action of the solar wind in much the same way as the peaks on the helmet streamers.

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A three-dimensional axisymmetric time-dependent magnetohydrodynamic model has been used to obtain quasi-static helmet-streamer solutions that contain a cavity flux rope in their closed field region. The dynamical equilibrium of the cavity flux rope inside the closed region of the streamer can be described as the partial balance between the outward acting magnetic force and the pressure and gravity forces inside the flux rope, which, in addition, is held down by the helmet dome above. Our solutions indicate that the helmet streamer containing a cavity flux rope has more magnetic energy than the corresponding open field configuration, which means that the state transition from the former to the latter is permitted energetically. These solutions may serve as pre-event coronae for studying the initiation of coronal mass ejections. Subject headings: MHD Sun: corona. Coronal helmet streamers are large-scale, quasi-static structures in the solar corona. The observed streamers vary in size and complexity.

Helmet streamers , also known as coronal streamers , are elongated cusp-like structures in the Sun 's corona which are often visible in white-light coronagraphs and during solar eclipses. They are closed magnetic loops which lie above divisions between regions of opposite magnetic polarity on the Sun's surface. The solar wind elongates these loops to pointed tips which can extend a solar radius or more into the corona. During solar minimum , helmet streamers are found closer to the heliographic equator, whereas during solar maximum they are found more symmetrically distributed around the Sun. Helmet streamers have cusp-like bases that taper radially outward away from the Sun forming long stalks. The base typically extends up to 1. Helmet streamers are structured by closed magnetic fields and lie above boundaries separating opposite magnetic polarity in the Sun's photosphere. Their thin stalks consist of oppositely directed magnetic fields which form current sheets.

Helmet streamers

Coronal Features. Click on image for larger version. Helmet Streamers Helmet streamers are large cap-like coronal structures with long pointed peaks that usually overlie sunspots and active regions. We often find a prominence or filament lying at the base of these structures.

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Coronal Loops Coronal loops are found around sunspots and in active regions. Solar Probe Plus Interstellar Probe. Above the flux rope, the anchored field in the helmet dome also plays an important role in confining the flux rope. Helmet streamers get their shape from two phenomena: The first is that large active regions sunspot groups have magnetic fields that penetrate the chromosphere and can reconnect into large magnetic systems in the corona. The solar wind elongates these loops to pointed tips which can extend a solar radius or more into the corona. Normally, large streamers exhibit a three-part structure, i. Figures 5 and 6 also show the time evolution of the streamer-cavity solutions. Material was copied from this source, which is available under a Creative Commons Attribution 4. David McKenzie david. Subject headings: MHD Sun: corona. For a fully three-dimensional description, the flux rope must have both ends connected to the photosphere. This was a case in which two polarity reversal boundaries contain between them fields with a polarity opposite to that of the global unipolar configuration surrounding them tripolar pseudostreamer. Delete Cancel Save. The first step is to obtain normal helmet-streamer solutions.

During any total solar eclipse, you are guaranteed to see the magnificent solar corona extending far from the obscured solar disk.

Such twin filaments are topologically connected, sharing a neutral point and a separatrix dome. Categories : Sun Solar phenomena. Subjects: Science and technology — Astronomy and Cosmology. Physically, this process could be thought of as the mass draining occurring in the dynamic evolution of a filament. Government and Space Weather. To verify that our open field configuration has energy comparable to their solution, we extended our computation domain to 32 R and recomputed the open state corresponding to case 1. All these procedures are aiming for better numerical accuracy by taking into account the physical and mathematical characteristics of the governing equations. These loops contain denser material than their surroundings. The second phenomena is that the streamers eventually become sculpted by outflowing gas in the expanding corona or the solar wind, which draws them out into linear, radial features at a few million km from the solar surface. The flux rope is still confined by the closed streamer field from above. Bibcode : LRSP The parameters defining the flux rope are a , the flux rope radius; R , the large radius the center of the torus refers to the center of the Sun ; p 0 , thermal pressure at the surface of the torus; 1 , plasma at the central axis of the torus; and 2 , plasma at the surface of the torus.