Posts Tagged ‘corona’

19 March

Solar Eclipse of March 20, 2015 (The Eclipse starts at 07:41 UTC and Ends at 11:50 UTC or 2:41 A.M.-6:50 A.M. EST)

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Dear Friends, Visitors/Viewers/Readers,

Partial & Annular Solar Eclipse (May 20,2012, CC attribution: Brocken Inaglory)

Partial & Annular Solar Eclipse (May 20,2012, CC attribution: Brocken Inaglory)

(Please click on red links & note magenta)

It’s a Total Solar Eclipse in the Faroe Islands and Svalbard (Norway), and a Partial Solar Eclipse in Europe, northern and eastern Asia and northern and western Africa. The eclipse starts at 07:41 UTC and ends at 11:50 UTC on March 20, 2015. UTC stands for Universal Coordinated Time.

Historical records  have shown that solar eclipses were viewed as omens that brings about death and destructions. Therefore, it is understandable that many ancient civilizations tried to understand and predict this celestial phenomenon. Babylonians and ancient Chinese were able to predict solar eclipses as early as 2500 B.C. The word eclipse comes from ekleipsis, the ancient Greek word for being abandoned. The Chinese legend has it that two astrologers, Hsi and Ho, were executed for failing to predict the solar eclipse of Oct. 22, 2134 B.C.E. (because solar eclipse is associated with the health and success of the Emperor and not predicting one means placing the Emperor in danger). Henceforth, the solar eclipse of Oct. 22, 2134, B.C.E. was the oldest solar eclipse ever recorded in human history.  Babylonians, also believing in the omens associated with solar eclipse, would seat substitute kings during solar eclipses so that these temporary kings would face the anger of the Gods instead of the real king. On the other hand, a solar eclipse in 585 B.C.E stopped the war between the Lydians and Medes, who saw the dark skies as a sign to make peace with each other.

As seen from the Earth, a solar eclipse is a type of eclipse that occurs when the Moon passes between the Sun and Earth, and the Moon fully or partially blocks (“occults“) the Sun. This can happen only at new moon, when the Sun and the Moon are in conjunction as seen from Earth in an alignment referred to as syzygy. In a total eclipse, the disk of the Sun is fully obscured by the Moon. In partial and annular eclipses, only part of the Sun is obscured.

Partial Solar Eclipse of Oct. 23, 2014 (CC -tomruen) Minneapolis 5-36pm_Ruen1

Partial Solar Eclipse of Oct. 23, 2014 (CC -tomruen) Minneapolis 5-36pm_Ruen1

Annular Solar Eclipse (Middlegate,_Nevada, May 20,_2012) (CC-Smrgeog)

Annular Solar Eclipse (Middlegate,_Nevada, May 20,_2012) (CC-Smrgeog)

Solar eclipse 1999 4 NR ( CC-attribution Luc Viatour : www.Lucnix.be)

Total Solar eclipse 1999 4 NR ( CC-attribution Luc Viatour : www.Lucnix.be)

 

 

 

 

 

 

 

 

 

 

 

 

If the Moon were in a perfectly circular orbit, a little closer to the Earth, and in the same orbital plane, there would be total solar eclipses every single month. However, the Moon’s orbit is inclined (tilted) at more than 5 degrees to the Earth’s orbit around the Sun (see ecliptic), so its shadow at new moon usually misses Earth. Earth’s orbit is called the ecliptic plane as the Moon’s orbit must cross this plane in order for an eclipse (both solar as well as lunar) to occur. In addition, the Moon’s actual orbit is elliptical, often taking it far enough away from Earth that its apparent size is not large enough to block the Sun totally. The orbital planes cross each other at a line of nodes resulting in at least two, and up to five, solar eclipses occurring each year; no more than two of which can be total eclipses. However, total solar eclipses are rare at any particular location because totality exists only along a narrow path on the Earth’s surface traced by the Moon’s shadow or umbra.

Since looking directly at the Sun can lead to permanent eye damage or blindness (unless the UV index is between 0 to 1), special eye protection or indirect viewing techniques are used when viewing a solar eclipse. It is technically safe to view only the total phase of a total solar eclipse with the unaided eye and without protection; however, this is a dangerous practice, as most people are not trained to recognize the phases of an eclipse, which can span over two hours while the total phase can only last up to 7.5 minutes for any one location. People referred to as eclipse chasers or umbraphiles will travel to remote locations to observe or witness predicted central solar eclipses.

There are four types of solar eclipses:

  • A total eclipse occurs when the dark silhouette of the Moon completely obscures the intensely bright light of the Sun, allowing the much fainter solar corona to be visible. During any one eclipse, totality occurs at best only in a narrow track on the surface of Earth.
  • An annular eclipse occurs when the Sun and Moon are exactly in line, but the apparent size of the Moon is smaller than that of the Sun. Hence the Sun appears as a very bright ring, or annulus, surrounding the dark disk of the Moon.
  • A hybrid eclipse (also called annular/total eclipse) shifts between a total and annular eclipse. At certain points on the surface of Earth it appears as a total eclipse, whereas at other points it appears as annular. Hybrid eclipses are comparatively rare.
  • A partial eclipse occurs when the Sun and Moon are not exactly in line and the Moon only partially obscures the Sun. This phenomenon can usually be seen from a large part of the Earth outside of the track of an annular or total eclipse. However, some eclipses can only be seen as a partial eclipse, because the umbra passes above the Earth’s polar regions and never intersects the Earth’s surface.Partial eclipses are virtually unnoticeable, as it takes well over 90% coverage to notice any darkening at all. Even at 99% it would be no darker than civil twilight.<http://www.heliodyssey.org/eclipse_facts.html>

The diagrams to the right below shows the alignment of the Sun, Moon and Earth during a solar eclipse.

Geometry of a Total Solar Eclipse

Geometry of a Total Solar Eclipse

The dark gray region between the Moon and Earth is the umbra, where the Sun is completely obscured by the Moon. The small area where the umbra touches Earth’s surface is where a total eclipse can be seen. The larger light gray area is the penumbra, in which a partial eclipse can be seen. An observer in the antumbra, the area of shadow beyond the umbra, will see an annular eclipse.

 

(some parts are taken from wikipedia)

Remember not to look directly at the Sun on Solar Eclipse Day, March 20, 2015 between 07:41 UTC and Ends at 11:50 UTC.

~have a bright and sunny day~

Gathered, written, and posted by sunisthefuture-Susan Sun Nunamaker

Any of your comments or suggestions will be welcomed via sunisthefuture@gmail.com“”.

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21 February

Understanding Our Powerful Sun & Its CME (Coronal Mass Ejection)

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Dear Friends, Visitors/Viewers/Readers,

(Please click on red links below)

As a result of posting The Unexpected Atmospheric Intruder on Feb. 16, 2013, I’ve received multiple  questions/concerns expressed by our viewers toward the space and our Sun.  Therefore, I’ve prepared this particular session on “Understanding Our Powerful Sun & Its CME(coronal mass ejection)” for your viewing pleasure, to further our appreciation of our Sun, and to kindle our curiosity and wonder for exploration into the space.  With the help from NASA Heliophysics (meaning Physics of the Sun),  I’d like to present to you this composite of 2 footage about the Sun, the star at the center of our Solar System, and its CME (coronal mass ejection), the massive burst of solar wind and magnetic fields rising above the solar corona or being released into space.  Be sure to stay long enough to also view the activities of CME.

 

Can you feel the light and intense warmth projected from the screen…from this giant active star ?

Our Sun, with a diamter-1,392,684 km (109 x that of Earth) (NASA)

While the origin and sustenance of life here on Earth are intimately connected to this active star of over 4.6 billion years, our fate in the next 4+ billion years will depend much on our ability to understand and predict Sun’s variability in producing streams of high energy particles and radiation that can help/harm life on Earth or alter its evolution.  Better understanding of the connections between the Sun, solar wind, planetary space environments, and our place in the Galaxy would enable us to uncover the fundamental physical processes occurring throughout the Universe and allow us to predict the impacts of solar variability on humans, our technological systems, and the presence of life here on Earth. Since heliophysics is simply too vast a field to cover in one post, we will be concentrating in some basic understanding of the Sun and its coronal mass ejection (CME) in this one.

The almost perfectly spherical Sun consists of hot plasma

Sun’s plasma  trapped by magnetic fields shows up as thin lines in extreme UV light (NASA)

interwoven with magnetic fields,

with a diameter of about 1,392,684 km (about 109 x that of earth) and a mass about 2 x 10^30 kilograms (about 330,000 x that of earth). It accounts for almost 99.86% of the total mass of the Solar System.  Chemically, about three quarters of the Sun’s mass consists of hydrogen while the rest is mostly helium…and the remainder (about 1.69%) consists of heavier elements such as oxygencarbonneoniron, etc.  The Sun formed from the gravitational collapse of a region within a large molecular cloud. Most of the matter gathered in the center, while the rest flattened into an orbiting disk that would become the Solar System. The central mass became increasingly hot and dense, eventually initiating thermonuclear fusion in its core. It is thought that almost all other stars form by this process. The Sun’s stellar classification, based on spectral class, is G2V, and is informally designated as a yellow dwarf, because its visible radiation is most intense in the yellow-green portion of the spectrum and although its color is white, from the surface of the Earth it may appear yellow because of atmospheric scattering of blue light. In the spectral class label, G2 indicates its surface temperature of approximately 5778 K (5505 °C), and V indicates that the Sun, like most stars, is a main-sequence star, and thus generates its energy by nuclear fusion of hydrogen nuclei into helium. In its core, the Sun fuses 620 million metric tons of hydrogen each second.  The Sun (the star closest to Earth, approximately 149.6 million kilometers away or the distance that light travels in 8 minutes and 19 seconds) is brighter than about 85% of the stars in the Milky Way galaxy.

The Milky Way

Star Formatioin

Its hot corona continuously expands in space, creating the solar wind,  a stream of charged particles that extends to the heliopause at roughly 100 astronomical units. (Source: wikipedia)

Coronal mass ejections (CMEs) release huge quantities of matter and  electromagnetic radiation into space above the sun’s surface, either near the corona (sometimes called a solar prominence), or farther into the planet system, or beyond (interplanetary CME).

Sun’s CME (interplanetary)

The ejected material is a plasma consisting primarily of electrons and protons, but may contain small quantities of heavier elements such as helium, oxygen, and even iron. The theory of heavier element emissions during a CME is speculative information and requires further verification. It is highly unlikely that a CME contains any substantial amount of heavier elements, especially considering that the sun has not yet arrived at the point of helium flash and thus cannot begin to fuse elements heavier than helium. Coronal mass ejections are associated with enormous changes and disturbances in the coronal magnetic field. They are usually observed with a white-light coronagraph. Recent scientific research has shown that the phenomenon of magnetic reconnection is responsible for CME and solar flares. Magnetic reconnection is the name given to the rearrangement of magnetic field lines when two oppositely directed magnetic fields are brought together. This rearrangement is accompanied with a sudden release of energy stored in the original oppositely directed fields. Most ejections originate from active regions on the Sun’s surface, such as groupings of sunspots associated with frequent flares. Near solar maxima the Sun produces about three CMEs every day, whereas near solar minima there is about one CME every five days.

As magnetic fields of the sun rearrange and realign, sunspots can appear on its surface. From Feb.19-20, 2013, scientists watched a giant sunspot form in under 48 hours. The sunspot shown in this image from the SDO (Solar Dynamics Observatory) has grown to over six Earth diameters across, but its full extent is hard to judge since the spot lies on a sphere not a flat disk. (NASA)

NASA-Another CME from Sunspot, via coronograph spectrometers

 

 

 

 

 

 

 

 

On the sun, magnetic reconnection may happen on solar arcades—a series of closely occurring ropes of magnetic lines of force. These lines of force quickly reconnect into a low arcade of ropes,

Sun’s CME flux ropes

Sun’s CME flux ropes in figure 8

leaving a helix of magnetic field unconnected to the rest of the arcade. The sudden release of energy in this reconnection causes the solar flare. The unconnected magnetic helical field and the material that it contains may violently expand outwards forming a CME.This also explains why CMEs and solar flares typically erupt from what are known as the active regions on the sun where magnetic fields are much stronger on average.

Sun’s CME flux ropes seen from different angles

NASA SDO (Solar Dynamics Observatory) telescope (NASA)

 

 

 

 

 

 

 

 

I hope you enjoyed viewing/reading this piece as much as I had in researching and composing this piece.

~have a bright and sunny day~

Gathered, written, and posted by sunisthefuture-Susan Sun Nunamaker

Any of your comments/suggestions/questions are welcomed at sunisthefuture@gmail.com

Homepage:  http://www.sunisthefuture.net


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