vlastnosti
Vznik [úprava]
Polárna žiara vzniká, keď elektricky nabité častice slnečného vetra, hlavne elektróny ale aj protóny, alfa-častice a niektoré ťažké ióny dopadajú na vrchnú vrstvu zemskej atmosféry. To spôsobuje svetielkovanie molekúl vzduchu. Náraz častice spôsobí u molekuly/atómu nabudenie zodpovedajúce zmenenej elektrónovej konfigurácii. Po krátkom čase a nasledujúcom „uvoľnení“ je vylúčené svetlo (fotón), všeobecne sa tomu hovorí fluorescencia alebo rekombinácia. Aj výbuchy atomových bômb vo vysokých vrstvách atmosféry (400 km) vyvolávajú podobnú reakciu ako napríklad test - Starfish Prime-Test USA 9. júla 1962.
Polárne žiary sa vyskytujú hlavne v polárnych oblastiach, pretože častice slnečného vetra, - elektricky nabitá plazma s priemernou rýchlosťou približne 500-833 km/s (až do 3 000 000 km/h) a s hustotou pribl. 5 × 106 častíc na m3 v blízkosti zeme, sú vychýlené magnetickým poľom Zeme pozdĺž línií magnetického poľa a sú nachýlené k pólom. V oblasti polov smeruje magnetické pole kolmo k povrchu Zeme, a častice môžu vstúpiť do atmosféry. Plazma potrebuje k vniknutiu 2-4 dni pri vzdialenosti Zem- Slnko približ. 150 mil. km.
Polárne žiary sa vyskytujú na Zemi v okolí severného pólu Aurora borealis a v blízkosti južného pólu Aurora australis. V okolí magnetických pólov je výskyt polárnych žiar najvyšší, ale výnimočne sa môžu objaviť aj v našich zemepisných šírkach, dokonca aj na rovníku. Nakoľko slnečný vietor zaplavuje rovnomerne celú guľoplochu s polomerom vzdialenosti Zeme, vyskytujú sa polárne žiary naraz na severnom aj južnom póle. Polárne žiary sa vyskytujú aj na iných planétach slnečnej sústavy, na všetkých, ktoré majú magnetické pole a atmosféru.
Aj ked v mnohých krajinách existujú pranostiky a predpovede polárnej žiary, nemá polárna žiara s počasím nič spoločné. Polárne žiary vznikajú vo výškach od 60 km, ďaleko nad troposférou, vrstva v ktorej sa odohrávajú všetky zmeny počasia siaha len do výšky približne 15km.
Častosť výskytu [úprava]
Výskyt a svetlosť polárnej žiary závisí od sily slnečného vetra, ktorý je zase závislý od aktivity slnka. Pretože slnko má dvanásťročný cyklus aktivity, výskyt polárnych žiar kolíše tiež v tomto cykluse. Obzvlášť v čase maximálnej aktivity, to znamená pri zvlášť silnom slnečnom vetre, sa objavujú polárne žiary v nižších zemepisných šírkach ako napr. stredná Európa. V jeseni 2003 bola preukázateľne pozorovaná polárna žiara v severnom Taliansku.
Mýty a legendy [úprava]
Inuiti pokladali v minulosti polárnu žiaru za pochodne, ktorými ich predkovia osvetľujú úzky most do nebeskej ríše, aby duše mŕtvych našli cestu. V stredovekej Európe boli považované za dych hrdinských bojovníkov. V Nórsku k polárnej žiare prechovávali posvätnú úctu, ale v mnohých krajinách ju považovali, podobne ako kométy, za predzvesť moru, vojny alebo smrti.
Fyzikálne vlastnosti [úprava]
Spektrum polárnej žiary je čiarové. Jej farba zodpovedá časticiam, ktoré ju vyžarujú. Červená farba je vysielaná atómami kyslíka z výšky nad 200 km. V nižších výškach vyžaruje kyslík intenzívnu zelenú farbu. Modrá farba zase pripadá na atómy dusíka vo výške 100 až 200 km. V najnižších vrstvách je žiarenie dusíka karmínové.
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Eskadron -- brand adored by jockeys all around the world
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Eskadron is one of the most valued equestrian brands in the world that focuses primarily on the creation of top quality design clothing and equipment. This German concern was set by Pikeur wanting to meet up with the jockeys' needs, have been searching for professional but also stylish equestrian accessories. Thus, why is Eskadron therefore special and why their collections are so popular with passengers?Eskadron -- why do riders from all around the world love this brand?
Eskadron continues to be tremendously popular among horseriding fans for a dozen or even more years today. This new products are distinguished by their own top quality attention to detail. Eskadron can be appreciated for their unique practicality, elegance, and innovativeness in their own projects, modern design and style, and availability. The new offer has both professional ones and items for recreational riders. So, you'll discover basic equestrian clothing, professional design, and assorted accessories necessary for your appropriate saddling of a horse. Eskadron offers saddle fabrics, halters, rugs, bell boots for horses, boots, fly vases, bandages, however in addition hoodies, tshirts, breeches, also reveal jackets. All products come from the European Union, which additionally verifies their quality.Eskadron's collections
Eskadron has many collections. Some are seasonal, others are constantly available in their own offer. The very popular collections of the brand are:
Vintage Sports - launched twice a year, this line consists only of horse equipment. Products using this collection are extremely easy, in conventional soft colours but at the same time quite tasteful.
Platinum - launches once a year for people who prefer conventional solutions. You will mostly find black and gray colors combined with delicate picture motifs.
Young Star - lineup for kids that begin their adventure with horse riding. It's basic horse riding accessories in bright colors and exceptional designs.
Equestrian Fanatics - clothing line created for riders that like to stick outside. Available jackets, hoodies, and backpacks successfully unite casual clothing with equestrianism.
Classic offer - Their constant offer of clothing, equipment, and accessories. It is possible to find services and products useful for training and regular rides but also elegant show clothing.
Eskadron can be a fresh used by riders from all over the world. For the comfort of riding and safety both yours and your horse, it is well worth buying highquality articles, which may permit one to fully appreciate this sport that is exceptional.
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