Incoherent scatter observations of the ionosphere over Chatanika, Alaska

478

433

An enigma of equatorial research has been the observed seasonal and longitudinal occurrence patterns of equatorial scintillations (and range‐type spread F). We resolve this problem by showing that the seasonal maxima in scintillation activity coincide with the times of year when the solar terminator is most nearly aligned with the geomagnetic flux tubes. That is, occurrence of plasma density irregularities responsible for scintillations is most likely when the integrated E‐region Pedersen conductivity is changing most rapidly. Hence the hitherto puzzling seasonal pattern of scintillation activity, at a given longitude, becomes a simple deterministic function of the magnetic declination and geographic latitude of the magnetic dip equator. This demonstrated relationship is consistent with equatorial irregularity generation by the collisional Rayleigh‐Taylor instability and irregularity growth enhancement by the current convective and (wind‐driven) gradient drift instabilities. Some discrepancies in this relationship, however, have been found in scintillation data obtained at lower radio frequencies (below, say, 300 MHz) that suggest the presence of other irregularity‐influencing processes. The role of field‐aligned currents, associated with the longitudinal gradient in integrated E‐region Pedersen conductivity produced at the solar terminator, in equatorial irregularity generation via the current convective instability has not been discussed previously.

Section: Scintillation Activity and E Region Sunsetmentioning

confidence: 99%

Control of the seasonal and longitudinal occurrence of equatorial scintillations by the longitudinal gradient in integrated E region Pedersen conductivity

Tsunoda¹

1985

478

433

“…These uncertainties in the measured velocity then have to be used, considering the geometry of the system, to determine the propagated error in electric fields. Watt [1973] for August 9-10, 1971, at Chatanika, Alaska. night sector (corresponding to a northward electric field) and an eastward velocity in the prenoon sector (corresponding to a southward electric field) as described in Figure lb.…”

Section: A V = [V/(2n)x/•'](pn/ps) M/s Where V• Is Ion Thermal Velocmentioning

confidence: 99%

Comparison of high-latitude and mid-latitude ionospheric electric fields

Carpenter¹,

Kirchhoff²

1975

Simultaneous measurements of the F region electric field by the incoherent scatter technique have been made at Chatanika, Alaska (65.1°N, 147.5°W), and Millstone Hill, Massachusetts (42.6°N, 71.5°W), on July 18–19 and August 7–8, 1973. Good correlation was observed in the time variation of the perpendicular electric field at the two stations. Magnetic conditions for these days were relatively quiet with some variations evident from the high‐latitude magnetograms and the Chatanika radar, but no distinct effect appeared on the mid‐latitude magnetograms. Since magnetospheric electric fields are thought to be the source of high‐latitude electric fields such as those observed at Chatanika, the good correlation in the perpendicular electric field for the two stations indicates that the magnetospheric originated electric fields have an appreciable effect down to at least L = 3.2.

“…The Chatanika facility is an L band (1290 MHz) fully steerable incoherent scatter radar system located at 65.1øN, 147.45øW (L = 5.7) near Fairbanks, Alaska. The system has been described in considerable detail [Leadabrand et al, 1972;Baron, 1972;Watt, 1973] and will not be described further here.…”

mentioning

confidence: 99%

Joint radar-satellite determination of the effective recombination coefficient in the auroralEregion

Watt¹,

Newkirk²,

Shelley³

1974

This paper reports on the experimental determination of the effective recombination coefficient α in the auroral E region. The technique consists of obtaining measurements, time coincident and nearly space coincident, of electron density from the Chatanika incoherent scatter radar and of electron production rate from the 1971‐089A satellite. Electron density profiles are determined along the radar beam, and electron production profiles are field aligned. The horizontal separation caused by these and other factors can give rise to uncertainties in the presence of horizontal gradients in electron density or production. Values of a obtained by this technique are nevertheless in reasonable agreement with the results of others. Since the technique offers the possibility of frequent and routine determinations of α profiles (typically, four per day), it clearly represents a powerful means for providing synoptic studies of this ionospheric parameter.