Helmet streamers

Coronal Features. Click on image for helmet streamers version. Helmet Streamers Helmet streamers are large cap-like coronal structures with long pointed peaks that usually overlie sunspots and active regions.

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.

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.

Two solutions were obtained based on different parameters of the initial streamer.

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, narrowing away from the Sun. They are also referred to as helmet streamers because of their resemblance to a helmet with a spike on top. The broad base of the streamer is where coronal plasma is trapped along closed magnetic field lines, but at larger distances the magnetic field weakens and the plasma is able to break free from the Sun, producing the narrow spike. Streamers are principally found above active regions and prominences, but also occur at solar minimum when there are few or no active regions.

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.

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. Helmet streamers have cusp-like bases that taper radially outward away from the Sun forming long stalks. The base typically extends up to 1.

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The final step is to obtain helmet-streamer solutions containing a cavity flux rope. The integrated open state energy is 1. It has been known since the lates that the coronal gases are very hot — in fact hotter than 1 million Celsius. Reference entries streamer in A Dictionary of Astronomy 2 rev Length: words. Solar Probe Plus Interstellar Probe. Although photography was routinely in use by this time, Trouvelot insisted that they eye was far better at discerning details than a photograph. For convenience, the prime is dropped in equations A1 A4 which are the final expressions for an axisymmetric magnetic toroid in cylindrical coordinates. The open configuration is deduced numerically from the initial streamer by keeping the magnetic flux distribution at the solar surface constant and adding a radial velocity at the solar surface to blow open the closed field lines of the streamer. Observations show that most prominences, especially those associated with helmet streamers, have magnetic fields with inverse polarity Leroy Advances in Space Research. More parametric studies should be done concerning the stability and energy content of the helmet streamer containing a cavity flux rope. 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. We call this state the corresponding open state. PMC

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

After about 30 hr, the solution reaches quasi-equilibrium and almost all of the field lines become radial. Part of the thermal pressure in the flux rope is then replaced by magnetic pressure. Figures 5 and 6 also show the time evolution of the streamer-cavity solutions. Magnetic field lines from a computer simulation performed in advance of the October 24, solar eclipse , to predict the structure of the solar corona. Figures 5 and 6 show the magnetic field and velocity configurations in the meridional plane after mass draining for the two cases. In Table 2 , we also show the magnetic energy of the corresponding open field configuration. This will cause numerical instability which will make it impossible for the system to relax to a new equilibrium state. Sign in to annotate. In the present model, the flux rope is a wholly detached structure circling the Sun as shown in Figure 7. David H. Subject headings: MHD Sun: corona. For instance, the momentum and the magnetic induction equation are solved by using the Lax-Wendroff finite difference scheme. Your current browser may not support copying via this button. All these procedures are aiming for better numerical accuracy by taking into account the physical and mathematical characteristics of the governing equations.