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Connexions between geomagnetic and auroral activity and trapped ions

1963; Elsevier BV; Volume: 11; Issue: 5 Linguagem: Inglês

10.1016/0032-0633(63)90070-9

1873-5088

J. H. Piddington,

Geomagnetism and Paleomagnetism Studies

‘Primary ions’ (energy 0.1 – 10 keV) and ‘secondary ions’ (energy 25 – 500 keV) are separated on the basis of: (a) energy spectrum in interplanetary space, (b) energy acquired while entering the geomagnetic field, (c) storage of primary ions in a ‘third’ trapping zone, (d) acceleration of a few primary ions and transfer to the second zone, (e) precipitation mechanisms and (f) auroral and other atmospheric effects. A mechanism is suggested for introducing primary ions in the geomagnetic cavity and storing them in a zone between geocentric distances ∼7–12 Earth radii. Many will be lost directly into the ionosphere above the poles, others will be lost after an hour or so at high latitudes near local midnight. The flux in the third zone might reach 1010 electrons cm−2 sec−1, mostly of energy ⋟ 100 eV. Magnetospheric motions caused by the solar ion stream give rise to electric fields which may accelerate some primary ions and store them in a ‘second’ (outer) trapping zone. The same ‘dynamo’ motions, through hydromagnetic instability, give rise to small-scale vortex cells mainly in and near the auroral zones. The instability cells have small dimensions (⋞20 km in the ionosphere) across the field but are very elongated (∼105 km). They rotate about their axes and develop helical twists; being in a region of shear they are torn apart so that ‘strands’ of magnetic force become threaded transversely across the main field. These narrow strands tend to short circuit the electric potential fields, causing currents to discharge into the auroral zones. This electrical mechanism may explain the dumping, sometimes accompanied by acceleration, of primary ions. The same magnetic field distortion may also explain the dumping of higher energy ions by changing their magnetic moments. The two dumping mechanisms are thus closely connected but may operate independently. Paэдeляйt ⪢пepвичныe иoны⪡ (cэнepгияmи 0,1–10 кэв) и ⪢вtopичняe иoны⪡ (c энepгияmи 25–500 кэв) нa ocнoвaнии: (a) энepгetичecкoгo cпeкtpa в meжплaнetнom пpoctpaнctвe; (б) энepгии пpиoбpeteннoй вo вpemя вчoдa в гeomaгниtнoe пoлe; (в) нaкoплeния пepвичныч иoнoв в ⪢tpetьeй⪡ зoнe-лoвyщкe ; (г) ycкopeния нecкoлькич пepвичныч иoнoв и пepeнoca вo вtopyю зoнy; (д) ocaдoчныч meчaнизmoв; (e) пoляpныч cияний и дpyгич atmocфepныч эффeкtoв. Пpeдлaгaetcя metoд для ввoдa пepвичныч иoнoв в гeomaгниtнyю пoлoctь и иaкoплeния ич в зoнe нa гeoцeнtpичecкom pacctoянии meждy 7 и 12 paдиycamи зemли. mнoгиe tepяюtcя пpяmo в иoнocфepy нaд пoлюcamи, a дpyгиe чepeз чac или oкoлo эtoгo tepяtcя нa выcoкич шиpotaч oкoлo mectнoй пoлyнoчи. Пotoк в tpetьeй зoнe moжet дoctигatь 1010 qeлeкtpoнoв · CM−2 ceкt-1 (бoльшeй чactью c энepгиeй 100 эв). maгниtocфepныe движeния, вызвaнныe coляpныmи иoнныmи пotoкamи, пopoждaюt элeкtpичecкиe пoля, кotopыe moгyt ycкopиtь нeкotopыe пepвичныe иoны и нaкoпляtь ич вo ⪢вtopoй⪡ (внeшнeй) зoнe-лoвyшкe. taкиe жe ⪢динamo⪡ движeния, из-зa гидpomaгниtнoй нeyctoйчивoctи, oбpaзyюt meлкomacшtaбныe вичpeвыe ячeйки, глaвныm oбpaзom в зoнaч пoляpныч cияний и близкo ot нич. Ячeйки нeyctoйчивoctи иmeюt maлыe paзmepы (20 кm в иoнocфepe) пoпepeк пoля, нo oни oчeнь yдлинeнныe (105кm) . oни вpaщaюtcя oкoлo cвoич oceй и paзвивaюt винtoвыe cкpytки. нaчoдяcь в oблactи cpeзa, oни paзpывaюtcя taк, чto ⪢пpяди⪡ maгниtнoй cилы пpoбиpaюtcя пoпepeк глaвнoгo пoля. Эtи пpяди иmeюt teндeнцию кopotкo эamыкatь злeкtpичecкиe пoteнциaльныe пoля, вызывaя paзpяд toкoв в зoны пoляpныч cияний. Эtot элeкtpичecкий meчaнизm moжet oбъяcниtь cбpoc, инoгдa coпpoвoждaemый ycкopeниem, пepвичныч иoнoв. taкoe-жe иcкpивлeниe maгниtнoгo пoля moжet taкжe oбъяcниtь cбpoc иoнoв выcшeй энepгии пepemeнoй ич maгниtнoгo momeнta. taкиm oбpaзom oбa meчaнизma cбpoca tecнo cвязaны, нo, moжet быtь, paбotaюt нeзaвиcиmo.