Helmet streamers

Coronal Features.

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 work done by W. After about 30 hr, helmet streamers, the solution reaches quasi-equilibrium and almost all of the field lines become radial.

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. In the latter case, two streamers are seen on opposite sides of the Sun, close to the equator.

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

For five months in mid , Emily Mason did the same thing every day. Then, in October , she stopped. She realized she had been looking at the wrong thing all along. Computer simulations predicted the coronal rain could be found there. Observations of the solar wind, the gas escaping from the Sun and out into space, hinted that the rain might be happening. In a paper published today in the Astrophysical Journal Letters , Mason and her coauthors describe the first observations of coronal rain in a smaller, previously overlooked kind of magnetic loop on the Sun. After a long, winding search in the wrong direction, the findings forge a new link between the anomalous heating of the corona and the source of the slow solar wind — two of the biggest mysteries facing solar science today. On Earth, rain is just one part of the larger water cycle, an endless tug-of-war between the push of heat and pull of gravity.

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Living Reviews in Solar Physics. Supergranulation Granule Faculae Sunspot Ellerman bomb. The parameters of the magnetic torus used for the two cases are listed in Table 1. We have chosen two solutions for the present study. We have chosen the appropriate parameters of the torus so that after the magnetic torus has moved into the closed region of the streamer, the streamer-flux-rope configuration reaches a quasi-equilibrium state. The observed three-part structure of coronal streamers are believed to reflect the large-scale magnetic field geometry. This discrepancy, we believe, is due to the different integration regions used. For a fully three-dimensional description, the flux rope must have both ends connected to the photosphere. Richard; Wyper, Peter F. In this section, we shall discuss the physical details of the obtained solutions. ISSN X.

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.

We often find bright areas at the footpoints of these features that are associated with small magnetic regions on the solar surface. Cancel Save. On the western edge of the structure, the magnetic morphology above the filaments is that of a side-by-side double streamer, with open field between the two channels. Richard; Wyper, Peter F. However, in order to assure the high accuracy of the solenoidal condition numerically, the divergence-cleaning procedure proposed by Ramshaw is again employed in the present calculation. Part of the thermal pressure in the flux rope is then replaced by magnetic pressure. We find, based on the "magnetic strength" of the flux rope, i. Sign in with your library card Please enter your library card number. In this section, we shall discuss the physical details of the obtained solutions. Magnetic topology of pseudostreamers was described as "contain[ing] twin filaments at its base. However, this tendency is partially balanced by the pressure and gravity inside the flux rope. 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. The mathematical procedure to obtain this solution is first to construct a helical magnetic torus and then to move it into the closed field region of the initial streamer obtained in the first step. This solution describes an equilibrium magnetic torus which satisfies the Grad-Shafranov equation in the approximation of small curvature see Shafranov for details. An axisymmetric magnetic toroid solution given by Shafranov is used in the present simulation.