Helmet streamers

A large-scale structure seen in white-light images of the Sun's corona. Streamers are brighter than the surrounding corona because they are of higher density, and are often bottle-shaped, helmet streamers, narrowing away from the Sun.

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.

Helmet streamers

Helmet Streamers and the Magnetic Structure of the Corona. Magnetic field lines from a computer simulation performed in advance of the October 24, solar eclipse , to predict the structure of the solar corona. Field line colors are arbitrary, colors on the Sun's surface show the strength of the magnetic field yellow is largest. Click on image for full size 14K GIF. The gas in the solar corona is at very high temperatures typically million degrees Kelvin in most regions so it is almost completely in a plasma state made up of charged particles, mostly protons and electrons. Strong magnetic fields thread through the corona. Where these magnetic lines of force are closed, the magnetic field is strong enough to trap the solar plasma and keep it from escaping. Plasma accumulates in these regions and forms the beautiful structures called helmet streamers seen during solar eclipses. Prominences are often situated beneath helmet streamers, and active regions occur beneath streamers near the equator sometimes called active regions streamers. In some regions, the coronal magnetic field cannot confine the plasma, and the plasma expands outward, reaching supersonic velocities. Regions on the Sun with these open magnetic field lines which stretch far out into the solar system correspond to coronal holes and are the source of the solar wind, which accelerates outward from the Sun and fills interplanetary space. The electrons in the coronal hole plasma are typically cooler and less dense than streamers, and so they show up as dark regions in both X-rays and white light.

Normally, large streamers exhibit a three-part structure, i.

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.

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.

Helmet streamers

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.

Electrical forces crossword

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. They are a projection of a streamer belt that encircles the Sun. This will cause numerical instability which will make it impossible for the system to relax to a new equilibrium state. After the mass-draining process, the original quasi-equilibrium solution of streamer-flux rope with density enhancement relaxed to a quasi-equilibrium solution of streamer-flux rope with a cavity. These features were discovered when X-ray telescopes were first flown above the earth's atmosphere to reveal the structure of the corona across the solar disc. Bibcode : JGR In the quasi-equilibrium case, we first obtain a self-consistent helmet-streamer solution containing a helical flux rope in its closed field region, as proposed by Low In Figure 7 , we plot the three-dimensional magnetic field of the streamer-flux-rope configuration and the integrated line of sight brightness pB for case 2. These observations reflect the fact that there are complex magnetic configurations in the closed region of the streamer. Facebook LinkedIn Twitter. 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. The details of the streamer-cavity solution will be discussed in the following section. At the lower half, i.

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.

In this section, we shall discuss the physical details of the obtained solutions. PMID Don't have an account? Helmet streamers are structured by closed magnetic fields and lie above boundaries separating opposite magnetic polarity in the Sun's photosphere. Sign in to annotate. ISSN X. Forgot password? Hidden categories: Articles with short description Short description is different from Wikidata All articles lacking reliable references Articles lacking reliable references from July The closed magnetic field lines trap the electrically charged coronal gases to form these relatively dense structures. All rights reserved. This will cause numerical instability which will make it impossible for the system to relax to a new equilibrium state. Coronal helmet streamers are large-scale, quasi-static structures in the solar corona. Search for: 'streamer' in Oxford Reference ». Comparing with the corresponding configuration before mass draining, we see that after mass draining, the whole configuration is still in equilibrium, although the flux rope expands a little.