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Lightning can cause ionospheric perturbations in the D-region in one of two ways. The first is through VLF (very low frequency) radio waves launched into the magnetosphere. These so-called "whistler" mode waves can interact with radiation belt particles and cause them to precipitate onto the ionosphere, adding ionization to the D-region.
This is called a short wave fadeout (SWF). These fadeouts last for a few minutes to a few hours and are most severe in the equatorial regions where the Sun is most directly overhead. Although High Frequency signals suffer a fadeout because of the enhanced D-layer, the Sudden Ionospheric Disturbance enhances long wave radio
The anterior segment or anterior cavity [1] is the front third of the eye that includes the structures in front of the vitreous humour: the cornea, iris, ciliary body, and lens. [2] [3] Within the anterior segment are two fluid-filled spaces: the anterior chamber between the posterior surface of the cornea (i.e. the corneal endothelium) and the ...
The eyes sit in bony cavities called the orbits, in the skull. There are six extraocular muscles that control eye movements. The front visible part of the eye is made up of the whitish sclera, a coloured iris, and the pupil. A thin layer called the conjunctiva sits on top of this. The front part is also called the anterior segment of the eye.
The anterior chamber is the aqueous humor-filled space inside the eye between the iris and the cornea's innermost surface, the endothelium. [1] Hyphema, anterior uveitis and glaucoma are three main pathologies in this area. In hyphema, blood fills the anterior chamber as a result of a hemorrhage, most commonly after a blunt eye injury.
The globe of the eye, or bulbus oculi, is the frontmost sensory organ of the human ocular system, going from the cornea at the front, to the anterior part of the optic nerve at the back. More simply, the eyeball itself, as well as the ganglion cells in the retina that eventually transmit visual signals through the optic nerve.
The posterior chamber consists of small space directly posterior to the iris but anterior to the lens. The posterior chamber is part of the anterior segment [1] and should not be confused with the vitreous chamber (in the posterior segment). Posterior chamber is an important structure involved in production and circulation of aqueous humor ...
The choroid, also known as the choroidea or choroid coat, is a part of the uvea, the vascular layer of the eye. It contains connective tissues , and lies between the retina and the sclera . The human choroid is thickest at the far extreme rear of the eye (at 0.2 mm), while in the outlying areas it narrows to 0.1 mm. [ 1 ] The choroid provides ...