On radio-star visibility fades and the aurora

Fremouw, E. J.

doi:10.1016/0032-0633(68)90127-x

Cited by 2 publications

(1 citation statement)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Continued investigation of the .scintillation of satellite and radio-star signals traversing the auroral region have been made [Hook, 1963;Fremouw, 1963;Flood, 1963;Basu, Allen, and Aarons, 1964;Aarons, Mullen, and Basu, 1964;Castelli, Aarons, and Silverman, 1965;Aarons and Mullens, 1965]. The majority of these reports indicate the scintillation index of satellite and radio-star signals increases significantly as the geomagnetic latitude of the propagation path approached the auroral zone.…”

Section: Scintillationmentioning

confidence: 99%

U.S.A. National Committee Report, Fifteenth URSI General Assembly, Munich, September 1966: Commission 3, Ionospheric Radio; Progress in Ionospheric Radio

Bowhill¹,

Bibl²,

Calvert³

et al. 1966

Radio Science

View full text Add to dashboard Cite

Auroral absorption measured in the auroral zone with riometers is on the average more pronounced in the winter months for both hemispheres. Also, in winter it has a pronounced diurnal variation with a maximum a few hours before noon. The average absorption in winter is twice that in summer, but sunlight has no influence in its value [Leinbach and Basler, 1963; Basler, 1963]. Individual events at night are characterized by a quiet phase of relatively small absorption, a sharp increase of absorption associated with the breakup phase of the visible aurora, and a fast recovery with irregular fluctuation of absorption. Detailed correlation of areas of absorption and luminosity exists for such events [Ansari, 1964]. The structure is less than 200 km in the north‐south direction and 700 km in the east‐west direction [Parthasarathy and Berkey, 1965]. An event seen only after midnight consists of a relatively slow increase and recovery of extremely high absorption with no de~ailed correlation of light emission and absorption. It is associated with a harder electron spectrum [Ansari, 1964]. A peculiar type of absorption event frequently observed during midmorning usually increases very smoothly, reaches a high value of absorption, and is not accompanied by appreciable magnetic activity [Ansari, 1965]. Absorption associated either with negative bays or with breakup events shows no difference in intensity between day and night [Brown and Barcus, 1963; Brown, 1964]. There is a limited correlation between the high‐energy part of the electron spectrum, as measured by X‐rays in balloons, and the absorption [Barcus, 1965].

show abstract

Section: Scintillationmentioning

confidence: 99%

U.S.A. National Committee Report, Fifteenth URSI General Assembly, Munich, September 1966: Commission 3, Ionospheric Radio; Progress in Ionospheric Radio

Bowhill¹,

Bibl²,

Calvert³

et al. 1966

Radio Science

View full text Add to dashboard Cite

show abstract

Observations and theory of the formation of stable auroral red arcs

Rees¹,

Roble²

1975

Reviews of Geophysics

217

192

View full text Add to dashboard Cite

A population of protons with energy of some tens of keV, called the ring current, is found near the equatorial region of the magnetosphere at several earth radii. During the main phase of geomagnetic storms the ring current shifts toward lower L values into the region of the plasmapause, which is characterized by steep gradients in the plasma density. This interaction together with an anisotropic pitch angle distribution leads to ring current instability and the growth of ion cyclotron wave turbulence. As wave energy is dissipated in the ambient electron gas by Landau damping, the plasmapause electron temperature is raised to a few electron volts, and a substantial temperature gradient is created with respect to the ionosphere. The energy transferred to the ionosphere by pitch angle scattering in the low collision frequency region and by heat conduction in the collision‐dominated regime raises the ionospheric electron temperature to several thousand degrees. Therefore an appreciable number of electrons in the high‐energy tail of the Maxwellian distribution, i.e., electrons with energy greater than 2 eV, exist in the F region of the ionosphere at about 400 km, where atomic oxygen is the dominant neutral gas constituent. Two eV is the threshold for excitation of oxygen atoms to the metastable ¹D level, and these O(¹D) atoms emit 6300‐Å radiation, the signature of stable auroral red (SAR) arcs. Although the energy input rate required to produce electron temperatures sufficient to cause average SAR arcs is less than 0.1 erg cm−2 s−1, the energy radiated in the red line is only about 0.003 erg cm−2 s−1. Thus an SAR arc is an optical manifestation of a slow release of energy from the magnetosphere during a geomagnetic storm. Energetically it is small in comparison with high‐latitude auroral processes.

show abstract

On radio-star visibility fades and the aurora

Cited by 2 publications

References 6 publications

U.S.A. National Committee Report, Fifteenth URSI General Assembly, Munich, September 1966: Commission 3, Ionospheric Radio; Progress in Ionospheric Radio

U.S.A. National Committee Report, Fifteenth URSI General Assembly, Munich, September 1966: Commission 3, Ionospheric Radio; Progress in Ionospheric Radio

Observations and theory of the formation of stable auroral red arcs

Contact Info

Product

Resources

About