What causes gaps between aurora curtains? These unusual gaps can make auroral displays [ http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?aurora ] appear more detailed and intricate. Research [ http://sci.esa.int/content/news/index.cfm?aid=8&cid=31&oid=29100 ] using data from four Cluster spacecraft [ http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=31258 ] orbiting the Earth has likely found the secret: auroral gaps, sometimes knows as black auroras [ http://www.phys.ucalgary.ca/~trondsen/pai/BlackAurora/blackfeatures.html ], are actually anti-auroras. In normal auroras [ http://en.wikipedia.org/wiki/Aurora_%28astronomy%29 ], electrons [ http://www-istp.gsfc.nasa.gov/Education/welect.html ] and/or predominantly negatively charged particles fall toward Earth along surfaces of constant magnetic field [ http://www-istp.gsfc.nasa.gov/Education/wfldline.html ]. They ionize [ http://www-istp.gsfc.nasa.gov/Education/wposion.html ] the Earth's atmosphere [ http://liftoff.msfc.nasa.gov/academy/space/atmosphere.html ] on impact, causing the bright glows. In auroral gaps, however, negatively charged particles may be sucked out from the Earth's ionosphere [ http://www.haarp.alaska.edu/haarp/ion1.html ] along adjoining magnetic field [ http://www-istp.gsfc.nasa.gov/Education/whmfield.html ] lines. These dark anti-auroras [ http://www.gi.alaska.edu/ScienceForum/ASF4/422.html ] can climb to over 20,000 kilometers and last for several minutes. Pictured above [ http://spaceweather.com/aurora/gallery_01mar06.htm ], a series of well-defined auroral gaps is seen dividing green aurora curtains high above Harstad [ http://en.wikipedia.org/wiki/Harstad ], Norway [ http://en.wikipedia.org/wiki/Norway ], earlier this month.
Aurora Alaskan Style
Title
Aurora Alaskan Style
Explanation
Have you checked the space weather report [ http://www.spaceweather.com/ ] lately? With a coronal mass ejection (CME) headed our way and an immense sunspot group [ http://www.sec.noaa.gov/advisories/ 200103281748_bulletin.html ] tracking across the solar photosphere [ http://sohowww.nascom.nasa.gov/data/summary/gif/010329/ smdi_igram_fd_20010329_0136.gif ], skygazers should be on the alert. The interaction of clouds of energetic particles from the active Sun [ http://antwrp.gsfc.nasa.gov/apod/ap010301.html ] with planet Earth's magnetosphere [ http://www-istp.gsfc.nasa.gov/istp/outreach/ geospace.html ] often produces significant geomagnetic storms [ http://spacescience.com/headlines/y2000/ ast07apr_2m.htm ] and auroral displays. In fact, just days ago [ http://www.spaceweather.com/aurora/gallery_20mar01.html ] on March 24, photographer Jan Curtis pointed his camera [ http://climate.gi.alaska.edu/Curtis/curtis.html ] straight up to captured this awesome auroral curtain towering in clear and very cold (-25F) skies over Fairbanks, Alaska, USA. Now, forecasts [ http://www.sec.noaa.gov/forecast.html ] indicate that a recent Earth-directed CME may also trigger moderate geomagnetic storms over the next few days. Night sky aurora [ http://antwrp.gsfc.nasa.gov/apod/ap001108.html ], possibly extending to [ http://antwrp.gsfc.nasa.gov/apod/ap000915.html ] middle latitudes, would be most likely on March 30-31.
A Perseid Aurora
Title
A Perseid Aurora
Explanation
Just after the Moon set [ http://aa.usno.navy.mil/AA/data/docs/RS_OneYear.html ] but before the Sun rose [ http://antwrp.gsfc.nasa.gov/apod/ap991110.html ] in the early morning hours of August 12, meteors [ http://www.amsmeteors.org/showers.html ] pelted the Earth from the direction of the constellation Perseus [ http://www.seds.org/Maps/Stars_en/Fig/perseus.html ], while ions [ http://ParticleAdventure.org/ ] pelted the Earth from the Sun [ http://www.seds.org/nineplanets/nineplanets/sol.html ]. The meteors [ http://www.seds.org/nineplanets/nineplanets/meteorites.html ] were expected as sub-sand grains long left behind by Comet Swift-Tuttle [ http://antwrp.gsfc.nasa.gov/apod/ap960219.html ] annually create the Perseids Meteor Shower [ http://www.science.nasa.gov/newhome/headlines/ast09aug99_1.htm ]. The aurorae [ http://www.geo.mtu.edu/weather/aurora/ ] were unexpected, however, as electrons [ http://www.aip.org/history/electron/ ], protons [ http://hyperphysics.phy-astr.gsu.edu/hbase/particles/proton.html ], and heavier ions [ http://www-spof.gsfc.nasa.gov/Education/Ielect.html ] raced out from a large Coronal Mass Ejection [ http://science.nasa.gov/ssl/pad/solar/cmes.htm ] that had occurred [ http://antwrp.gsfc.nasa.gov/apod/ap000817.html ] just days before on the Sun. In the foreground is Hahn's Peak, an extinct volcano in Colorado [ http://www.state.co.us/ ], USA [ http://www.odci.gov/cia/publications/factbook/us.html ].
Aurora Oklahoma
Title
Aurora Oklahoma
Explanation
Nestled in the central US, the state of Oklahoma is noted for its gorgeous prairie [ http://nature.org/wherewework/northamerica/states/ oklahoma/preserves/tallgrass.html ] skies and wide-open spaces, but not for frequent visitations of the northern lights [ http://www.exploratorium.edu/learning_studio/auroras/ ]. Still, following the intense solar activity [ http://science.nasa.gov/headlines/y2003/ 12nov_haywire.htm ] late last month, aurora did come sweeping down the Oklahoma plains and skywatcher [ http://www.okweatherwatch.com/ ] Dave Ewoldt managed to catch up with this photogenic apparition 40 miles northwest of Oklahoma City at about 3am CST on October 29 [ http://antwrp.gsfc.nasa.gov/apod/ap031030.html ]. Anticipating aurora sightings [ http://science.nasa.gov/spaceweather/aurora/ gallery_01oct03_page8.html ], Ewoldt had spent the evening photographing nighttime [ http://antwrp.gsfc.nasa.gov/apod/ap030424.html ] views of small towns in the area while keeping an eye toward the north. He reports [ http://www.okweatherwatch.com/aurora.html ], "I was just about ready to call it a night when the show started. When it did, it was like someone turned on a lightswitch. I wish it would have lasted longer... [it] seemed like it was completely done in about 25 minutes." Watery reflections of the colorful show highlight the foreground in the stunning image while stars of the Big Dipper and the northern sky shine behind the dazzling Oklahoma auroral [ http://www.cimms.ou.edu/~zaras/aurora.html ] display.
The Secret of the Black Auro
…
Title
The Secret of the Black Aurora
Explanation
What causes black aurora? These gaps in normal bright aurora [ http://www.geo.mtu.edu/weather/aurora/ ] are frequently recorded but rarely questioned. Recent research [ http://sci.esa.int/content/news/index.cfm?aid=8&cid=31&oid=29100 ] using data from four Cluster spacecraft [ http://sci.esa.int/content/doc/bb/1979_.htm ] orbiting the Earth has now likely found the secret: black auroras [ http://www.phys.ucalgary.ca/~trondsen/pai/BlackAurora/blackfeatures.html ] are actually anti-auroras. In normal auroras [ http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?aurora ], electrons [ http://www-istp.gsfc.nasa.gov/Education/welect.html ] and/or predominantly negatively charged particles fall toward Earth along surfaces of constant magnetic field [ http://www-istp.gsfc.nasa.gov/Education/wfldline.html ]. They ionize [ http://www-istp.gsfc.nasa.gov/Education/wposion.html ] the Earth's atmosphere [ http://liftoff.msfc.nasa.gov/academy/space/atmosphere.html ] on impact, causing the bright glows. In black anti-auroras, however, negatively charged particles are sucked out from the Earth's ionosphere [ http://server5550.itd.nrl.navy.mil/projects/HAARP/ion1.html ] along adjoining magnetic field [ http://www-istp.gsfc.nasa.gov/Education/whmfield.html ] lines. These dark anti-auroras [ http://www.gi.alaska.edu/ScienceForum/ASF4/422.html ] can climb to over 20,000 kilometers and last for several minutes. Pictured above [ http://www.geo.mtu.edu/weather/aurora/images/aurora/jan.curtis/ ], a black aurora is seen dividing bright auroras over Fairbanks, Alaska [ http://www.state.ak.us/ ], USA [ http://www.cia.gov/cia/publications/factbook/geos/us.html ].
Volcano and Aurora in Icelan
…
Title
Volcano and Aurora in Iceland
Explanation
Sometimes both heaven "and" Earth erupt. In Iceland [ http://www.cia.gov/cia/publications/factbook/geos/ic.html ] in 1991, the volcano Hekla [ http://www.south.is/hekla.html ] erupted at the same time that auroras [ http://www.exploratorium.edu/learning_studio/auroras/ ] were visible [ http://www.iww.is/art/shs/ ] overhead. Hekla [ http://www.norvol.hi.is/hekla.html ], one of the most famous volcanoes [ http://www.crystalinks.com/volcanoesactive.html ] in the world, has erupted [ http://www.volcanolive.com/faq.html ] at least 20 times over the past millennium, sometimes causing great destruction [ http://www.each-mara.net/volcano/santorini.pdf ]. The last eruption [ http://www.norvol.hi.is/heklaeruption.html ] occurred only two years ago but caused only minor damage. The green auroral band [ http://antwrp.gsfc.nasa.gov/apod/ap010402.html ] occurred fortuitously [ http://www.nationalgeographic.com/ngm/100best/wallpaper09.html ] about 100 kilometers above the erupting lava [ http://volcano.und.nodak.edu/vwdocs/frequent_questions/group1_new.html ]. Is Earth [ http://volcano.und.nodak.edu/vw.html ] the Solar System's only planet with both auroras [ http://www.physicsweb.org/article/news/5/1/10 ] and volcanos [ http://www.thursdaysclassroom.com/index_07oct99.html ]?
Aurora's Ring
Title
Aurora's Ring
Explanation
Gusting solar winds [ http://antwrp.gsfc.nasa.gov/apod/ap000318.html ] and blasts [ http://antwrp.gsfc.nasa.gov/apod/ap020516.html ] of charged particles from the Sun made the early days of October rewarding ones for those anticipating auroras [ http://www.exploratorium.edu/learning_studio/ auroras/ ]. While out enjoying the stormy space weather [ http://www.spaceweather.com/ ] from Toemmeraas, Norway, Trygve Lindersen recorded this picturesque apparition [ http://science.nasa.gov/spaceweather/aurora/ gallery_01oct02_c.html ] of the northern lights with a digital camera on October 6. From this perspective, the curtains of green light formed a ring which seemed to hover, wraithlike [ http://www.pantheon.org/articles/a/aurora.html ], just above the foreground trees. But the ring of light was actually 100 kilometers or more above the trees [ http://antwrp.gsfc.nasa.gov/apod/ap010210.html ] and the greenish glow produced by oxygen molecules interacting with energetic electrons and fluorescing near the edge of space. After days of enchanting auroral displays [ http://science.nasa.gov/spaceweather/aurora/ gallery_01oct02.html ] on planet Earth, the solar activity which triggered October's geomagnetic storms [ http://spacescience.com/headlines/y2000/ast07 apr_2m.htm ] seems to have subsided ... for now.
Aurora Over Clouds
Title
Aurora Over Clouds
Explanation
Aurorae usually occur high above the clouds. The auroral glow [ http://www.geo.mtu.edu/weather/aurora/ ] is created when fast-moving charged particles from the Earth's magnetosphere [ http://csep10.phys.utk.edu/astr161/lect/earth/ magnetic.html ] impact air molecules high in the Earth's atmosphere [ http://csep10.phys.utk.edu/astr161/lect/earth/atmosphere.html ]. An oxygen molecule [ http://pearl1.lanl.gov/periodic/elements/8.html ], for example, will emit a green light when reacquiring an electron [ http://www.aip.org/history/electron/ ] lost during a collision. The lowest part of an aurora [ http://www.pfrr.alaska.edu/~pfrr/AURORA/INDEX.HTM ] will typically occur at 100 kilometers and up, while most clouds [ http://seaborg.nmu.edu/Clouds/types.html ] usually exist only below about 10 kilometers. The relative heights of cloud [ http://antwrp.gsfc.nasa.gov/apod/ap030430.html ]s and auroras [ http://antwrp.gsfc.nasa.gov/apod/ap011223.html ] are shown clearly in the above picture [ http://www.spacew.com/gallery/image001510.html ] taken last month from near Quebec City, Canada [ http://www.cia.gov/cia/publications/factbook/geos/ca.html ]. The most likely time to see an aurora [ http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?aurora ] is around midnight.
Aurora: Curtains in the Sky
Title
Aurora: Curtains in the Sky
Explanation
Looking out over Lake Superior [ http://www.cciw.ca/glimr/geographic-search/superior/intro.html ] at dusk you see Venus [ http://antwrp.gsfc.nasa.gov/apod/ap950815.html ] (lower left) and ... curtains? Like an ant [ http://www.orkin.com/orkin/page6.html ] looking up at window curtains [ http://homeandfamily.com/features/deco/deco_curtains.html ], aurora [ http://dac3.pfrr.alaska.edu/~ddr/ASGP/STRSCOOP/AURORA/ ] frequently appear as huge flowing light displays. These colorful, often spectacular phenomena [ http://beatles.imv.uit.no/publikas/waynorth/contents.htm ] are most frequently visible from locations near the Earth's poles. Aurora [ http://dac3.pfrr.alaska.edu/~ddr/ASGP/STRSCOOP/AURORA/SUMMARY.HTM ] are caused by electrons [ http://pdg.lbl.gov/cpep/adventure.html ] from the solar wind funneling to Earth along magnetic field lines [ http://www-spof.gsfc.nasa.gov/Education/Intro.html ], and striking atoms and molecules in our atmosphere. Auroral [ http://www.geo.mtu.edu/weather/aurora/ ] color is determined by which atmospheric ions are struck and recombine to form neutral atoms. Hourly updates of auroral sightings [ http://www.geo.mtu.edu/weather/aurora/sightings.html ] are posted to the WWW. It is still controversial whether aurora make any sound audible from the ground. If you think you have "heard an aurora," please report it [ http://www.tp.umu.se/Space/AuroralSounds.html ]!
Explorer 1 Preparations
title
Explorer 1 Preparations
date
01.20.1958
description
Technicians lower Explorer 1, the first American satellite, onto the launch vehicle's fourth stage motor. This photo was taken in the gantry at Launch Complex 26 at Patrick Air Force Base in Florida. *Image Credit*: Jet Propulsion Laboratory
Explanatory Image of the Fir
…
Title
Explanatory Image of the First Explorer VI Picture of Earth
Full Description
The lined areas at the left represent a cloud-cover map, prepared from meteorology charts, which have been superimposed on a glove to show how the lighted area which the Explorer VI television scanner saw on August 14, 1959.
Date
08/14/1959
NASA Center
Headquarters
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