GIZAGIZAN DA SUKA FI KOWANNE TSAYI A DUNIYA SUNA SAUKA ƘASA

A daren lokacin bazara, da daɗewa bayan faɗuwar rana, siraran gizagizai na iya haskakawa sosai a sararin samaniya na magariba. An fara bayyana su a 1885, bayan babbar fashewar dutsen wuta na Krakatoa a 1883. Saboda Rana na ci gaba da haskaka su lokacin da ƙasa ke cikin duhu, dole ne suna shawagi sama da kilomita 80 a sama. Idan an yi su ne da ƙanƙarar ruwa, kamar yadda ake zato tun 1912, dole ne iskar wurin ta fi sanyi fiye da kelvin 150. Waɗannan su ne gizagizai masu haske da dare (noctilucent clouds), gizagizai mafi tsayi a Duniya.

Alamar gargaɗi a can saman sama

An daɗe ana zargin cewa suna ɗauke da alamar sauyin yanayi. Ƙaruwar carbon dioxide tana sanyaya stratosphere da mesosphere, matakan sararin sama da ke ƙarƙashin gizagizan. Matakan da suka yi sanyi suna takurewa: saman sararin sama yana “raguwa”, kuma gizagizan, da ke zaune a samansa, ya kamata su riƙa sauka a hankali. Wani samfurin yanayi na wannan yanki, LIMA/MIMAS, yana hasashen hakan daidai — saukar da ke ƙara sauri bayan 1960, sau 6.5 fiye da da, yayin da carbon dioxide ke ƙaruwa da sauri fiye da kowane lokaci.

Gwada wannan yana da wuya. Yawan bayyanar gizagizan ya dogara da yawan masu kallo da yanayin sararin sama; an auna haskensu da kayan aikin da ba a daidaita su ba (uncalibrated). Amma an auna tsayinsu (altitude) tun lokacin da aka gano su. Bita na baya ba su sami wani yanayi bayyananne ba: tsayin yana warwatsuwa a zahiri tsakanin kilomita 79 da 85, fiye da saukar da ake tsammani.

Kwatanta abu da irinsa

Oleg Ugolnikov, na Cibiyar Binciken Sararin Samaniya ta Kwalejin Kimiyya ta Rasha (Space Research Institute of the Russian Academy of Sciences), da abokan aiki a Moscow da Kaliningrad, sun fara kafa ƙa’idoji masu tsauri. Na’urorin lidar na zamani, waɗanda ke binciken sararin sama da hasken laser, suna ganin ƙananan ƙwayoyin ƙanƙara a can saman layin gizagizan, yayin da hotuna ke ganin ƙwayoyi mafi girma a ƙasansa — har zuwa kilomita 2 ƙasa. Don haka dabara ɗaya kawai ake la’akari da ita: triangulation (auna tsayi ta kusurwoyi), wato ɗaukar hoton gajimare ɗaya daga wurare biyu ko fiye da lissafa tsayinsa daga sauyin matsayinsa.

Sun kuma watsar da binciken da ba su da cikakken daidaito. Na farko kwata-kwata, a 1887, ya sami kilomita 79, amma masu kallonsa biyu suna da nisan kilomita 32.4 kawai tsakaninsu kuma an daidaita lokacinsu ne cikin mintuna, abin da ya isa ya haifar da kurakurai sama da kilomita 10. Ƙungiyar tana riƙe wuraren da nisansu ya kai aƙalla kilomita 40 kuma da lokaci daidai kawai: O. Jesse a kewayen Berlin a 1890-1891, C. Störmer kusa da Oslo a 1932-1934, sannan Stockholm, Estonia, Latvia da Scotland, har zuwa tazarar kilomita 200 a 1986.

Sabbin tsayi dubu ashirin

Tun 2020, kusan kyamarori ashirin, yawancinsu a cikin rukunin kyamarori na atomatik mai suna Starvisor, suna kallon sararin sama tsakanin digiri 54 da 61 arewa. Suna aiki a rukunoni masu nisan kilomita 50 zuwa 200 tsakaninsu, suna ɗaukar hotuna har huɗu a minti ɗaya. Wata manhaja (software) tana yanka kowane fili na gizagizai zuwa guntaye, tana haɗa su tsakanin kyamarori, kuma tana lissafa tsayinsu da saurinsu. Sakamakon: kusan tsayi 20,000 daban-daban.

Hanya ta biyu tana tantance su da hotunan guda. Yayin da gajimare ke shiga inuwar Duniya, da farko yakan ƙara zama shuɗi, lokacin da hasken Rana da ke kansa ke ratsa layin ozone, sannan ya ƙara zama ja, yayin da hasken ke ratsa ƙasan sararin sama. Lokacin waɗannan sauye-sauyen launi yana ba da tsayinsa. Bayan gyara saboda hazon ƙananan ƙwayoyi a cikin stratosphere, hanyoyin biyu sun yi daidai a cikin kilomita 0.18.

Warware alamomin

Tsayin waɗannan gizagizai ya dogara kuma da lokacin shekara, lokacin dare, igiyar wata (lunar tides), latitude da ayyukan Rana (solar activity). Ƙungiyar ta daidaita duk waɗannan a lokaci guda, ma’auni bayan ma’auni, daga 1890 zuwa 2026. Tasiri biyu kawai suka fito fili: lokacin shekara, inda gizagizai mafi ƙasa ke kusan 10 ga Yuli, ’yan makonni bayan solstice (ranar da rana ta fi tsawo), da kuma yanayin dogon lokaci.

Ana auna wannan yanayin a matsayin juzu’i K na hasashen samfurin: K = 1 na nufin samfurin daidai ne, K = 0 na nufin babu wani yanayi. Daidaitawar ta ba da K = 0.52 ± 0.18 — saukar da aka gano da tabbaci sama da 99.5%, amma rabin abin da samfurin ke hasashe. A yau, hakan na nufin kusan kilomita 1.2 a kowane ƙarni.

Wani bincike mai sauƙi ya tabbatar da hakan. Kafin 2000, matsakaicin tsayin dukkan ma’aunai ya kasance kilomita 82.52; a shekarun 2020 kilomita 81.83 ne. Gizagizan suna ƙasa da kilomita 0.69, kusan rabin saukar da samfurin ke tsammani tun 1960.

Ƙasa na sauka, sama na tsayawa

Wani ɗan bayani ya fito fili. Gefen sama na kewayon tsayin gizagizan kusan bai motsa ba, ko a tsawon lokacin shekara ko a tsawon shekaru goma-goma. Gefen ƙasa ya sauka kusan ninki biyu na matsakaicin — kusa da saurin da samfurin ke hasashe.

Marubutan suna tsammanin ƙarin triangulation zai ƙara tace matsakaicin tsayin na yau, amma yanayin kansa zai ci gaba da kasancewa da iyaka saboda ƙarancin yawan tsoffin ma’aunai da matsakaicin daidaitonsu. Babban ci gaba na gaske, kamar yadda suka rubuta, zai zo ne idan lidar, taurarin ɗan adam (satellites) da kyamarori sun kalli gizagizan na tsawon lokaci mai isa a ƙarni na 21.