Archive for the ‘UV’ Category
This week on SciByte …
We take a look at Solar weather; what it is and how we view it. We also take a look at how all that solar weather affects us here on Earth.
All that and more, on SciByte!
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- Average Star – 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
- About one million Earths could fit inside the sun.
- Diameter : ~865,000 mi / ~1,392,000 km / 109 x Earth
- Mass : 4.38×10^30 lb / 1.99×10^30 kg / 333,000 × Earth
- Consists of 99.86% of mass of Solar System
- Chemically : ~3/4 of the mass is Hydrogen, rest mostly Helium
- Less than 2% consist of heavier elements [Oxygen, Carbon, Neon, Iron, ect]
- DO NOT look directly at the Sun with naked eye,with binoculars or a telescope
- there are Solar scopes, but if your not sure you are gambling with your vision!
- Looking at the sun causes temporary partial blindness
- Delivers ~4miliwatts of sunlight to the retina, slightly heating it and potentially causing damage in eyes that cannot respond properly to the brightness
- Eyes : Cataracts - gradually yellows the lens of the eye over a period of years and is thought to contribute to the formation of cataracts
- Eyes : UV Exposure can actually give you sunburn like lesions on your retina [~90sec]
- Can mutate DNA by causing adjacent bases bond with each other, instead of across the “ladder.” This makes a bulge, and the distorted DNA molecule does not function properly. [PIC]
- Skin : Sunburn - a reaction of the body to the direct DNA damage, which can result from the excitation of DNA by UV-B light. This damage is mainly the formation of a thymine [one of four chemical bases in DNA] dimer. The damage is recognized by the body, which then triggers several defense mechanisms, including DNA repair to revert the damage and increased melanin production to prevent future damage. Melanin transforms UV-photons quickly into harmless amounts of heat without generating free radicals, and is therefore an excellent photoprotectant against direct and indirect DNA damage. [ Video ]
- Skin : Ultraviolet (UV) radiation bears responsibility for 90 percent of non-melanoma skin cancers, which will afflict one out of every five Americans, and 65 percent of melanoma cases, which kill about 8,700 people a year.
- Sunblock – absorbs or reflects some of the sun’s ultraviolet (UV) radiation on the skin exposed to sunlight and thus helps protect against sunburn [made of Organic and inorganic particulates that reflect, scatter, and absorb UV light]
- Sunblock : come off the skin (particularly when exposed to water or toweled off) but their chemical components break down over time. To preserve the efficiency of sunscreens, the products should be stored in a cool, dry place and replaced every year. In addition, they should be reapplied at least every two hours or more frequently if exposed to water or rubbed off.
- FDA Regulation changes : Broad Spectrum : Under the new rules, only products that protect skin from both UVA and UVB sun rays can be marked “broad spectrum,” and sunscreen that does not meet the broad spectrum requirements, or that has a sun protection factor (SPF) of less than 15, must carry a warning that the product does not diminish the risk of skin cancer or prevent premature skin aging.
- FDA Regulation Change : Water resistance : Under the new regulations, water-resistant formulas must say on the label how long the product will protect skin before needing to be reapplied, either 40 or 80 minutes.
- FDA Regulation Change : “Water/sweat Proof” : Manufacturers cannot label sunscreens as “waterproof” or “sweatproof,” or identify their products as “sunblocks,” because these claims overstate their effectiveness.
- FDA Regulation Change : SPF #’s : FDA proposed a rule that would cap advertised SPF at “50 +”, because the evidence that more expensive, higher-SPF products provide more skin protection is lacking. Many who wear high-SPF sunscreen spend more time in the sun and reapply less frequently than those whose sunscreen has a lower SPF.
- Solar magnetic activity cycle, periodic change in the amount of irradiation from the sun that is experienced on Earth. It has a period of about 11 years
- The cycle is observed by counting the frequency and placement of sunspots visible on the Sun.
- Most of the Suns variations are related to the solar magnetic field, which is caused by the moving plasma inside the rotating Sun, which make a dynamo (another name for an electrical generator)
- Occurs when magnetic energy that has built up in the solar atmosphere is suddenly released.
- Radiation is emitted across virtually the entire electromagnetic spectrum, from radio waves at the long wavelength end, through optical emission to x-rays and gamma rays at the short wavelength end.
- The amount of energy released is the equivalent of millions of 100-megaton hydrogen bombs exploding at the same time!
- They occur near sunspots, usually along the dividing line (neutral line) between areas of oppositely directed magnetic fields.
- A large, bright feature extending outward from the Sun’s surface, often in a loop shape [Video] [Video] [Video] [Pic] [Pic]
- Some can sometimes last for many months, during which lengthy observations can be carried out by observatories.
- Some prominences break apart and give rise to coronal mass ejections.
- A massive burst of solar wind, other light isotope plasma, and magnetic fields rising above the solar corona or being released into space
- At solar minimum we observe about one CME a week. Near solar maximum we observe an average of 2 to 3 CMEs per day
- high-energy particles coming from the Sun, consist of protons, electrons and heavy ions. These can endanger life in outer space. [Reach ~80% the speed of light]
- originate from two processes: energetization at a solar flare site or by about 1% of shock waves associated with Coronal Mass Ejection
- They do however provide a good sample of solar material. By studying the isotopic composition of SEPs, scientists can obtain an indirect measurement of the material which formed the solar system, and thus learn about its origins.
- Auroras result from emissions of photons in the Earth’s upper atmosphere, above 80 km (50 miles)
- solar wind, a rarefied flow of hot plasma (gas of free electrons and positive ions) emitted by the Sun in all directions
- Usually reaches Earth with a velocity around (250mi/s | 400 km/s) During magnetic storms flows can be several times faster
- Earth’s magnetosphere is formed by the impact of the solar wind on the Earth’s magnetic field. It forms an obstacle to the solar wind, diverting it [Video]
- The magnetosphere is full of trapped plasma as the solar wind passes the Earth.
- The flow of plasma into the magnetosphere increases with increases in solar wind density and speed
- Magnetospheric electrons which are accelerated downward by field-aligned electric fields are responsible for the bright aurora features. The un-accelerated electrons and ions are responsible for the dim glow of the diffuse aurora. [Video] [Pic from ISS]
- The rotation of the Sun skews them (at Earth) by about 45 degrees, so that field lines passing Earth may actually start near the western edge (“limb”) of the visible Sun
- Oxygen Emissions : Green/Brownish-Red
- Nitrogen emissions : Blue or red. Blue if the atom regains an electron after it has been ionized. Red if returning to ground state from an excited state.
- It can take three quarters of a second to emit green light and up to two minutes to emit red. Collisions with other atoms or molecules will absorb the excitation energy and prevent emission. Because the very top of the atmosphere has a higher percentage of oxygen and is sparsely distributed such collisions are rare enough to allow time for oxygen to emit red.
- Green is the most common of all auroras. Behind it is pink, a mixture of light green and red, followed by pure red, yellow (a mixture of red and green), and lastly pure blue.
- Viewing Aurora
- A temporary disturbance of the Earth’s magnetosphere
- Caused by a solar wind shock wave and/or cloud of magnetic field which interacts with the Earth’s magnetic field.
- The increase in the solar wind pressure initially compresses the magnetosphere and the solar wind magnetic field will interact with the Earth’s magnetic field and transfer an increased amount of energy into the magnetosphere.
- Both interactions cause an increase in movement of plasma through the magnetosphere (driven by increased electric fields inside the magnetosphere) and an increase in electric current in the magnetosphere and ionosphere.
- Heats Earth’s upper atmosphere, causing it to expand. The heated air rises, and the density at the orbit of satellites increases significantly. This results in increased drag on satellites in space, causing them to slow and change orbit slightly.
- When magnetic fields move about in the vicinity of a conductor such as a wire, a geomagnetically induced current is produced in the conductor.
- The result of a coronal mass ejection on March 9, 1989.
- The aurora could be seen as far south as Texas
- As this occurred during the Cold War, many worried that a nuclear first-strike might be in progress
- Some satellites in polar orbits lost control for several hours.
- Some weather satellite communications were interrupted causing weather images to be lost.
- A NASA communication satellite recorded over 250 anomalies caused by the increased particles flowing into its sensitive electronics.
- Space Shuttle Discovery : A sensor on one of the tanks supplying hydrogen to a fuel cell was showing unusually high pressure readings on March 13. The problem went away after the solar storm subsided. [Launch Video]
- In Québec, as well as across parts of the northeastern U.S., the electrical supply was cut off to over 6 million people for 9 hours due to a huge geomagnetic storm.
- The variations in the earth’s magnetic field also tripped circuit breakers on Hydro-Québec’s power grid.
- The utility’s very long transmission lines and the fact that most of Quebec sits on a large rock shield prevented current flowing through the earth, finding a less resistant path along the power lines.
- The James Bay network went offline in less than 90 seconds
- The company implemented various mitigation strategies, including raising the trip level, installing series compensation on ultra high voltage lines and upgrading various monitoring and operational procedures. Other utilities in North America, the UK, Northern Europe and elsewhere implemented programs to reduce the risks associated with geomagnetically induced currents
- Produced ground currents as much as ten times stronger than the 1989 Quebec storm
- September 1, English astronomer Richard C. Carrington was sketching a curious group of sunspots—curious on account of the dark areas’ enormous size
- Auroras could be seen overhead from Maine to the tip of Florida
- Cubans saw the auroras directly overhead; ships’ logs near the equator described crimson lights reaching halfway to the zenith
- People could read the newspaper by their crimson and green light. Gold miners in the Rocky Mountains woke up and ate breakfast at 1 a.m., thinking the sun had risen on a cloudy day. Telegraph systems became unusable across Europe and North America.
- Cooler than the other parts of the sun [ ~2000-2500* C / ~3600-4500*F ]
- Occur in banded areas, the latitude changes dependent upon the solar cycle
- Caused by intense magnetic activity, which inhibits convection by an effect comparable to the eddy current brake, forming areas of reduced surface temperature. Like magnets, they also have two poles.
- Although they are at temperatures of roughly 3000–4500 K (2727–4227 °C/ 4940-7640 *F), the contrast with the surrounding material at about 5,780 K (5506*C/9944*F) leaves them clearly visible as dark spots, as the intensity is a function of temperature to the fourth power.
- If the sunspot were isolated from the surrounding photosphere it would be brighter than an electric arc.
- Possible Similar Phenomenon have been observed (Starspots) on other stars as cooler and warmer spots on stars [ HD12545 ]
- Solar tsunamis were discovered in 1997 by the Solar and Heliospheric Observatory
- When first witnessed, solar physicists doubted what they were seeing
- Rise higher than the Earth, and ripple out from a central point in a circular pattern millions of kilometers in circumference
- Video of Solar Tsunami from the Solar and Heliospheric Observatory (SOHO)
Satellites / Instruments
- There are a number missions involved with studying the Sun
- Spoke about this in J@N “Spotlight on NASA | J@N [ 2.28.11 ]”
- Two Year Mission to employ two nearly identical space-based observatories – one ahead of Earth in its orbit, the other trailing behind – to provide the first-ever stereoscopic measurements to study the Sun and the nature of its coronal mass ejections, or CMEs.
- Launched on Oct. 25, 2006; the two systems started to give three-dimensional images of our Sun in April 2007.
- Has four instrument packages are mounted on each of the two STEREO spacecraft: details below
- Mass: 1,364 pounds (620 kilograms)
- Dimensions: 3.75ft x 4.00ft x
- 3.75 feet (1.14 meters)
- 4.00 feet (1.22 meters) wide (launch configuration)
- 21.24 feet (6.47 meters) wide (solar arrays deployed)
- 6.67 feet (2.03 meters) deep
- Power consumption: 475 watts
- Data downlink: 720 kilobits per second
- Memory: 1 gigabyte
- Comprised of four instruments:
- These instruments study the 3-D evolution of CME’s from birth at the Sun’s surface through the corona and interplanetary medium to its eventual impact at Earth.
- Takes remote images of the CME as it erupts from the Sun and travels into space
- By studying the evolution of CME’s, we can better predict when they will occur and which ones will likely impact the Earth, and how they will affect the Earths magnetosphere. Earlier detection and warning could give us time to shut down power grids (ect.) or to take precautions that might protect what technology we can. It also gives us time for any astronauts in orbit to get to the safest place they can.
- SWAVES is an interplanetary radio burst tracker that traces the generation and evolution of traveling radio disturbances from the Sun to the orbit of Earth.
- Detects the traveling shock ahead of the CME through radio bursts
- Remember : Radio waves are part of the electromagnetic radiation, and therefore travel at the speed of light
- This instrument allows us to detect the coronal and interplanetary (IP) shock of the most powerful CMEs, providing a radial profile through spectral imaging, determining the radial velocity
- Also allows us to detect and measure the density and interplanetary magnetic field (IMF) Learning how they interact with the Suns magnetic field lines and the Inter-planatery Magnetics will allow us to better understand and predict how they travel through the inter-planetary medium.
- Samples the 3-D distribution and provide plasma characteristics of solar energetic particles and the local vector magnetic field.
- measures its electrons, embedded magnetic fields, and more energetic particles of the solar wind
- We know Solar Energetic Particles (SEPs) are dangerous so modeling where they originate will give us a better ability to predict them.
- Provides plasma characteristics of protons, alpha particles and heavy ions. This experiment will provide key diagnostic measurements of the form of mass and charge state composition of heavy ions and characterize the CME plasma from ambient coronal plasma.
- measures the density, speed, flow, and material of the solar wind
- samples the solar wind and suprathermal particles, providing measurements of kinetic properties and composition
- Solar cycle
- NASA : Having a Solar Blast – UPDATE
- NASA : Mystery of the Solar Tsunami—Solved
- Space.com : Huge Sun Eruption of June 7, 2011
- Space.com : Powerful Solar Flare May Charge Up Northern Lights Thursday
- Space.com : Amazing New Sun Photos from Space
- Discovery : Epic Solar Flare Pops Sun’s Magnetic Cork
- Universe Today : More Eye-Popping Video from the June 7 Solar Explosion
- Universe Today : Monster Prominence Erupts from Sun
- Live Science : Sun Unleashes ‘Spectacular’ & Powerful Eruption
- National Geographic : Solar Flare Sparks Biggest Eruption Ever Seen on Sun
- Scientific American : Bracing the Satellite Infrastructure for a Solar Superstorm
- Scientific American : Full Exposure: How Will the FDA’s Sunscreen Regulations Help Prevent Skin Cancer?
- FDA announces new requirements for over-the-counter (OTC) sunscreen products marketed in the U.S.
- Press Release : Smallest KPNO Telescope Discovers Biggest Starspots
- News Articles on Google Search for June 7 Coronal MAss Ejection
- WIKI : The Sun
- WIKI : Coronal Mass Ejections
- WIKI : Solar Cycle
- WIKI : Geomagnetic Storms
- WIKI : Solar Prominence
- WIKI : March 1989 geomagnetic storm
- WIKI : Corona
- WIKI : Sun Observation and effects