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อภิธานศัพท์: อภิธานศัพท์ฟิสิกส์ (อวกาศ)
E

EMERGING FLUX REGION (EFR)

An area on the sun where new magnetic flux is erupting.

ERUPTIVE

Solar activity levels with at least one radio event(10cm) and several chromospheric events per day (Class C Flares)

ERUPTIVE PROMINENCE ON LIMB (EPL)

A solar PROMINENCE that becomes activa- ted and is seen to ascend from the sun.

EXTREME ULTRAVIOLET (EUV)

A portion of the electromagnetic spectrum from approximately 100 to 1000 angstroms.

EXTREMELY LOW FREQUENCY (ELF)

That portion of the radio frequency spectrum from 30 to 3000 hertz.
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.