۱۳۹۰ آبان ۲۹, یکشنبه

Dust ریزذره ها ی رقصان در هوا




سپیده ی موشکی در نروژ
The aurora borealis and aurora australisthe northern and southern lights—are visible manifestations of a connection between the Sun and Earth. Blasts of energy and magnetically charged particles from the Sun are constantly flowing out into space and crashing into the magnetic fields of Earth and other planets. At Earth, that energy stirs up the particles and energy trapped in Earth’s space, or magnetosphere, creating the auroras and disturbing the upper reaches of our atmosphere.
Photographers captured these digital photos of a four-stage Black Brant XII sounding rocket and the aurora borealis (inset) on December 12, 2010, during the NASA-funded Rocket Experiment for Neutral Upwelling (RENU). The rocket was launched from Andøya Rocket Range near Andenes, Norway, and carried instruments about 200 miles (320 kilometers) into the atmosphere to observe the aurora and the associated flow of heat, particles, and electromagnetic energy. The photograph of the aurora was taken from the Kjell Henrickson Observatory in Svalbard, which was under the apogee, or peak, of the rocket’s arc through the sky. The rocket landed in the ocean about 900 miles (1450 km) from the launch site.
The goal of RENU was to measure the flow of particles and heat both into and out of Earth’s upper atmosphere near the North Pole during an auroral event. The solar wind stirs up Earth’s magnetic field and creates electrical currents in the ionosphere. Such disturbances can also heat the atoms of the thermosphere and other atmospheric layers, expanding them and creating extra drag on satellites and spacecraft, shortening their lifespan.
Around Earth’s poles, the magnetic field stretches out from the core of the planet into space and tucks back in at the opposite pole. The place where most of those field lines bunch up poke out of the Earth usually aligns in an auroral oval, where particles and energy from space precipitate and smash into the oxygen and nitrogen in the atmosphere to make the reds, greens, and whites of auroras. The funnel-shaped area inside that auroral oval—the polar cusp—is mostly open to space. RENU launched right into that cusp region to observe the flows of particles and energy both inbound and outbound.
1.   Further Reading
2.   Andøya Rocket Range (2010, December 12) Sounding Rocket Campaigns: RENU. Accessed January 3, 2011.
3.   Kjell Henrickson Observatory (2010, December 12). The Waiting Game. Accessed January 3, 2011.
4.   University of New Hampshire (n.d.) Magnetosphere-Ionosphere Research Lab. Accessed January 3, 2011.
5.   University of New Hampshire (2010, December 13) UNH-Led Experiment Hurtled Into Aurora Above Norway By NASA Rocket. Accessed January 3, 2011.
The ground-based photograph of the rocket was taken by Kolbjørn Blix Dahle of Andøya Rocket Range. The inset photo of the aurora was taken by Fred Signeres of The Kjell Henrickson Observatory. Caption by Michael Carlowicz.
Instrument: 
Photograph






Dust over the Gulf of Alaska

Dust blew over the Gulf of Alaska in early November 2011. The Moderate Resolution Imaging Spectroradiometer(MODIS) on NASA’s Terra satellite captured this natural-color image on November 2, 2011.
Blowing toward the south-southwest, the dust plume remains discernible for roughly 100 kilometers (60 miles). The dust emerges from the Copper River Valley, which zigzags through the glacier-rich Chugach Mountains. The slow movement of glaciers over bedrock grinds the rock into glacial flour. This fine sediment is easily lofted into the air by winds blowing through mountain valleys.
This image also shows swirls of iridescent green in the waters along the shore. The bright green probably results from sediment and phytoplankton. Dust can fertilize phytoplankton, prompting big blooms, but the microscopic organisms also thrive in high-latitude seas especially near coastlines, without dust.
1.   References
2.   University Corporation for Atmospheric Research. (2003). Forecasting dust storms. (Registration required). Accessed November 3, 2011.

گرد و خاک بر فراز خلیج آلاسکا

Dust Plumes over the Persian Gulf

One day after multiple dust plumes blew through Iraq, dust hovered over the Persian Gulf. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this natural-color image on July 1, 2011.
As on the previous day, light and dark dust plumes blow in the direction of the Persian Gulf through southeastern Iraq. The dark plume, however, is much thinner than it was the day before.
Dust plumes blow over the Persian Gulf, and dust is especially thick off the coast of the United Arab Emirates. Although much of this dust may have traveled from Iraq, some dust may also have arisen in the Empty Quarter or Rub’ al Khali. This massive sand sea spreads over much of the southern Arabian Peninsula, including parts of Saudi Arabia, Yemen, Oman, and the United Arab Emirates.

گرد غبار بر فراز خلیج فارس

Dust Plumes over the Red Sea

ستون های گرد و غبار بر فراز دریا ی سرخ

Dust plumes blew off the coast of Africa and over the Red Sea through mid-July 2011. Dust was still blowing eastward on July 20, 2011, when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terrasatellite acquired this natural-color image.
The dust blowing off the coast of Sudan is thick enough to completely hide the land and water surface below, but the thickest dust stops short of reaching Saudi Arabia. Farther south, between Eritrea and Yemen, a thin dusty haze hangs over the Red Sea.
Dust storms and drought are the hazards most frequently affecting Sudan, according to the CIA World Factbook. Less than 10 percent of Sudan’s land is arable, and less than 1 percent of the country’s land supports permanent crops.
1.   References
2.   CIA World Factbook. (2011, July 11). Sudan. Accessed July 21, 2011.


Dust Storm in the Sahara

A dust storm blew through parts of Algeria and Mali in early July 2011. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this natural-color image on July 10, 2011.
In places, the airborne dust forms a camel-colored cloud thick enough to completely hide the land surface below, especially near the Algeria-Mali border. The dark land surface northeast of the storm is the relatively high, rocky ground of Tassili n’Ajjer National Park where stone forests stretch skyward.
Source points for the dust storm are not obvious in this image, but a massive sand sea known as Erg Chech covers parts of northeastern Mali and western Algeria. The shifting dunes of this region provide plentiful material for dust storms.


توفان ریزذره ها ی رقصان در هوا در صحرا ی الجزیره و مالی 


فوران کوه آتشفشا ن "نیاموراجیرا " Nyamuragira Volcano Erupts



Africa’s most active volcano, Nyamuragira began to erupt along a new fissure on November 6, 2011. This image, from November 12, shows a river of lava flowing away from the rift. The Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite acquired the image, which combines infrared and visible light. The hot lava glows orange. The cooler clouds are blue, while warm steam is white and orange.
While very fluid, the lava is flowing over flat ground, so it is moving slowly. The lava darkens to black as it cools, and in places it is clear that the surface of the lava has cooled while hot lava flows below. The new fissure is 10-12 kilometers from Nyamiuragira’s summit. A red glow on the peak of the nearby Nyiragongo volcano is a lava lake in the summit crater.
1.   References
2.   Global Volcanism Program. (2011, November 15) Nyamuragira. Accessed November 17, 2011.
3.   Virunga National Park. (2011, November 13). New overnight track to Nyamulagira volcano eruption site! Accessed November 17, 2011.




فوران کوه آتشفشا ن "نیاموراجیرا "
در روز 6 ماه نوامبر 2011، فعال ترین آتشفششان قاره ی آفریقا  ، در راستای شکافی بدرازای 12-10 کیلومتر فوران نمود .
گدازه ها ، تا زمانی که سوزان اند و سیال ، با جنبشی آرام در زمین های هموار جریان دارند .
گدازه ها سیاه رنگ اند و تیره چون زغال ، و در بخش هایی که سطح گدازه سرد شده است در حالی که گدازه های جوشان در زیرش جریان دارند ، روشن تر اند .
دریاچه ای از گدازه در ستیغ " نیاموراجیرا " و در نوک دودکش آتشفشان رخ نمون دارد .

" پلین یاس" و جزیره ی یخی " پین " در قطب جنوب Polynyas and the Pine Island Glacier, Antarctica




Though far distant from any permanent settlement, Antarctica is poised to impact human life around the globe. Sea levels are rising in part because land-based ice is melting. Rising sea levels increase coastal erosion and flooding. And one of the largest single contributors to sea level rise in recent years is Antarctica’s Pine Island Glacier. Shrinking at a rate of 100 meters (300 feet) per year, the Pine Island Glacier is responsible for seven percent of the world’s recent sea level rise. Why is the Pine Island Glacier melting so quickly?
The Pine Island Glacier flows out of Antarctica’s Hudson Mountains and floats over the ocean. Scientists think that the glacier is shrinking because the ocean water that flows under the glacier is warming, increasing melt at the base. Some of the evidence for this idea comes from satellite images like this one. The Landsat satellite acquired the image on January 13, 2001.
Sea ice abuts the floating glacier tongue except in three places along the front of the glacier. These ice-free areas are called polynyas. Polynyas are routinely present in these three locations when sea ice is present. The polynyas most likely form where warm ocean currents rise toward the ocean surface.
Ocean water in this part of the Antarctic has three layers. The deepest water is very cold and very dense, and the top layer is also cold. The middle layer, between 600 and 1,200 meters (2,000 and 4,000 feet) deep, is warmer. The continental shelf here is about 600 meters (2,000 feet) deep, and as the warm water from the open ocean meets the shelf, it continues to flow toward land and rises beneath the floating glacier. The polynyas suggest that the warm water exits the cavity beneath the glacier in three locations where the sea ice has melted. It is likely that the warm water consistently exits at these locations, but in years that are free of sea ice (like 2011), the polynyas aren’t visible and so this cannot be confirmed from images.
While scientists suspect warm ocean water is causing the rapid melt of the Pine Island Glacier, they don’t know exactly how the water is moving through the cavity beneath the glacier or how the melt is happening. To answer these questions, scientists need to know the shape of the ocean cavity and how the water moves through it. NASA scientists are on two separate field campaigns in Antarctica to answer these questions. Both groups are taking measurements to understand what is happening beneath the glacier.
Starting in mid-December 2011, Robert Bindschadler, a glaciologist at NASA Goddard Space Flight Center, will be leading a long-anticipated six-week expedition to the glacier. He and other team members will drill through the ice to measure the underside of the ice and the ocean and currents beneath it. Bindschadler scouted locations for the expedition in 2008, when he became the first person to set foot on the crevasse-riddled Pine Island Glacier tongue.
The second Antarctic expedition, IceBridge, is in its final weeks. IceBridge flies airplanes over the ice carrying radar and lidar equipment to measure its thickness. In 2009, the IceBridge team used a gravimeter to map out the shape of the ocean floor beneath the Pine Island Glacier. Their measurements revealed a deep channel under the glacier tongue through which warm water could flow.
The team is taking additional measurements in 2011 to get a clearer picture of the ground beneath the glacier and the ocean. The new measurements will also help scientists track how much the glacier is melting from year to year. In their first flight over the glacier in 2011, the IceBridge team discovered a crack. Eventually the ice will break off at the crack forming a new iceberg. Such events are natural, and in fact, a similar crack is visible in the 2001 image, the last time the Pine Island Glacier calved a large iceberg. The crack will not impact Bindschadler’s expedition and may offer a unique opportunity for the team to measure what happens on a glacier tongue during a calving event.
1.   References
2.   Bindschadler, R., Vaughan, R., and Vornberger, P. (2011, September). Variability of basal melt beneath the Pine Island Glacier ice shelf, West Antarctica. Journal of Glaciology, 57 (204), 581-595. Accessed November 16, 2011.
3.   Riebeek, H. (2011, November 2). IceBridge: Building a record of Earth’s changing ice, one flight at a time. NASA Earth Observatory. Accessed November 16, 2011.
4.   Vinas, M. (2011, November 9). International team to drill beneath massive Antarctic ice shelf. NASA. Accessed November 16, 2011

" پلین یاس" و جزیره ی یخی " پین " در قطب جنوب



در بخش هایی از قطب جنوب ، رویه ی دریا در حال با لا آمدن است ؛ سبب این پدیده آن است که بخش زیرین ِ  پهنه های یخچالی ، در حال ذوب شدن است . . این بلند شدن و برخاستن ، سبب فرسایش کناری و جریان سیلاب های بزرگ  می گردد . بارزترین این پدیده در سال های اخیر، در جزیره ی " پین "  است که سبب کوچک شدن آن در حدود 100 مترمربع در سال  می شود؛ 7% بالا آمدن رویه ی دریا ها در روی پوسته ی زمین را این رخداد  باعث  می گردد .
پرسمان این است "
چرا  جزیره ی یخچالی " پین " در حال ذوب شدن است ؟
جزیره ی یخی " پین " در بیرون کوههای " هادستون " قطب جنوب، بر رویه ی اقیانوس شناور است . دانشمندان بر این باورند که این پدیده بسبب گرم شدن آب اقیانوس در زیر جزیره ی یخی است . عکس های ماهواره ای که تصویر بالا نمونه ای از آن است، این نظریه را تائید می کند . - تصویر بالا در روز 13 ماه ژانویه سال 2001 از جزیره ی یخی برداشته شده است . –
" " پولین یاس " ها به مناطقی در این جزایر یخچالی گفته می شود که پوشش یخی ندارند . - شبیه به هنگامی که جریان های آبگرم اقیانوسی به رویه ی اقیانوس می رسند.-
        آب اقیانوس در این بخش از قطب جنوب از سه لایه ی متمایز از هم شکل گرفته است :
_بخش زیرین : آب بسیار سرد است و متراکم دارد .
_ بخش بالایی : آب سرد  جریان دارد .
_ بخش میانی : آب گرم است . این لایه در عمق 1200 -600 متری از رویه ی اقیانوس جریان دارد .
        شیب قاره ای در این بخش از پوسته ی زمین ، عمقی برابر600 متر دارد ؛ هنگامی که آب گرم ازاقیانوس آزاد، به شیب قاره ای می رسد به سوی بالا حرکت می کند . این مهم سبب بلند شدن یخ های جزیره ی یخچالی شناور  می گردد.
       دانشمندان چگونگی جریان آب از درون گودال ها و شیوه ی ذوب شدن یخچال ها در زیر  آنها  را بدرستی نمی دانند . برای دریافت این مهم ، دانشمندان ِ مرکز فضایی ناسا ، در دو گروه به بررسی این پدیده پرداخته اند.