อภิธานศัพท์ฟิสิกส์ (อวกาศ)


อภิธานศัพท์ฟิสิกส์ (อวกาศ)
เลือกดูโดยใช้ดัชนีคำศัพท์

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F

F CORONA

Of the white-light CORONA (that is, the corona seen by the eye at a total solar (ECLIPSE), that portion which is caused by sunlight scattered or reflected by solid particles (dust) in inter- planetary space.

F REGION

The upper layer of the IONOSPHERE, approximately 120 to 1500 km in altitude. The F region is subdivided into the F1 and F2 regions. The F2 region is the most dense and peaks at altitudes between 200 and 600 km. The F1 region is a smaller peak in electron density, which forms at lower altitudes in the daytime.

FACULA

A bright region of the PHOTOSPHERE seen in white light, seldom visible except near the solar LIMB.

FIBRIL

A linear pattern in the H-ALPHA CHROMOSPHERE of the sun, as seen through an H-alpha filter, occurring near strong SUNSPOTS and PLAGE or in FILAMENT channels.

FILAMENT

A mass of gas suspended over the PHOTOSPHERE by magnetic fields and seen as dark lines threaded over the solar DISK. A filament on the LIMB of the sun seen in emission against the dark sky is called a PROMINENCE.

FILAMENT CHANNEL

A broad pattern of FIBRILS in the CHROMOSPHERE, marking where a FILAMENT may soon form or where a filament recently disappeared.

FLARE

A sudden eruption of energy on the solar DISK lasting minutes to hours, from which radiation and particles are emitted.

FLUENCE

Time integrated flux.

FLUX

The rate of flow of a physical quantitiy through a reference surface.

fMIN

The lowest radiowave frequency that can be reflected from the IONOSPHERE.

foEs

The maximum ORDINARY MODE radiowave frequency capable of reflec- tion from the SPORADIC E REGION of the IONOSPHERE.

foF2

The maximum ORDINARY MODE radiowave frequency capable of reflec- tion from the F2 REGION of the IONOSPHERE.

FORBUSH DECREASE

An abrupt decrease, of at least 10%, of the background galactic COSMIC RAY intensity as observed by neutron monitors.