Engineering topics

Croskey, C. L.

Publications and source records attributed to Croskey, C. L..

27 records · Page 2

NASA NTRS1984

Electrical structure in the high-latitude middle atmosphere

Large V/m electric fields, both horizontal and vertical, have been observed within bounded regions of the upper stratosphere and lower mesosphere. They seem to occur only in regions where the electrical conductivity is a few times 10 to the -10th S/m or less and appear to be current limited. While low conductivity is necessary, it is not a sufficient condition for occurrence. The observed large horizontal electric fields were found to be anticorrelated with the local neutral wind. Large variations in the conductivity were also observed to occur with fluctuations in magnetic activity, and these were found to be consistent with measured variations in energy deposition during auroral phenomena. Theoretical concepts of mapping of electric fields downward from the thermosphere along equipotential magnetic field lines were shown to hold qualitatively in the D-region at the mV/m level. Perturbations affecting such models were determined to be small.

Maynard, N. C.↗

NASA NTRS1983

Eclipse-related measurements of middle-atmosphere electrical parameters

Measurements of electrical conductivity and its constituent parameters, charge density and ion mobility, are presented for the solar eclipse rocket campaign conducted at Red Lake, Ontario, Canada. Three parachute-borne probes (two Gerdien condensers and a blunt probe) were flown during the eclipse which occurred on 26 February 1979. Additional payloads launched at other times provided important supplemental background measurements. The entire launch series occurred during aurorally active conditions, as indicated by the probe measurements. Specifically, positive conductivity enhancements above 45 km demonstrate the dominance of auroral ionization as a source for positive ions in the region. Such effects evidenced during the eclipse make it difficult to determine the extent to which the decrease in positive conductivity above 60 km is eclipse-related. The negative conductivity component associated with free electrons displays solar dependence both during the eclipse and for the other measurement periods. In spite of the aurorally active conditions, rapid electron loss was observed during totality, thus indicating the importance of non-ionizing solar effects on electrons in the region.

Mitchell, J. D.↗

NASA NTRS1981

Measurement of volt/meter vertical electric fields in the middle atmosphere

A test flight for a series of middle atmosphere electrodynamics rockets was launched from Wallops Island, Virginia, at 7:18 EST on July 31, 1980. The mother-daughter configuration contained a three axis symmetric double probe electric field instrument and a blunt probe on the daughter payload, and a Gerdien condenser and a single axis (vertical) asymmetric double probe electric field instrument on the mother payload. The payloads reached an apogee of 111 km, and data were gathered from all instruments on the downleg. A downward vertical electric field with a maximum amplitude of about 4 V/m was observed in a layer between about 57 and 67 km. The integrated potential across this layer was approximately 20 kV. Conductivity measurements indicated that free electrons were absent from the region of large electric fields; however, the decrease in conductivity was insufficient to maintain vertical current continuity through the layer. These results establish the existence of large mesospheric electric fields, supporting previous results from single axis measurements.

Maynard, N. C.↗

NASA NTRS1981

Measurements of middle-atmosphere electric fields and associated electrical conductivities

A simple antenna for measuring the vertical electric field in the 'middle atmosphere' has been flown on a number of rocket-launched parachute-borne payloads. The data from the first nine such flights, launched under a variety of geophysical conditions, are presented, along with electrical conductivities measured simultaneously. The data include indications of layered peaks of several volts per meter in the mesospheric field at high and low latitudes in situations of relatively low conductivity. During an auroral 'REP' event the electric field reversed direction in the lower stratosphere, accompanied by a substantial enhancement in conductivity. The data generally do not confirm speculations based only on the extension of the thunderstorm circuit from below or the mapping of ionospheric and magnetospheric fields from above, but seem to require, in addition, internal generation processes in the middle atmosphere.

Hale, L. C.↗

NASA NTRS1979

An auroral effect on the fair weather electric field

Evidence is presented for coupling between the upper and lower atmosphere by means of the shorting out of the vertical mesospheric electric field by auroral radiation, which causes a transfer of mesospheric potential to the lower atmosphere. Measurements were made by an electric field antenna which was part of a parachute-borne payload, launched by rocket from near Fairbanks, Alaska. Data obtained from quiet time observations indicate the normal low altitude electric field pattern, with a greater field at high altitudes, while observations at disturbed times show a small field at high altitudes and a greater field at low altitudes. Means for observing this effect at lower latitudes are also suggested. While the data obtained support the proposed mechanism, it is noted that other mechanisms, such as direct modulation by large amounts of solar cosmic rays and aurorally produced charge separation, may also be important.

Hale, L. C.↗

NASA NTRS1978

Electrical conductivity measurements from the STRATCOM 8 experiment

A blunt probe experiment for measuring electrical conductivity was flown with the STRATCOM 8 instrument package. Data were obtained by the instrument throughout the entire measurement period. A preliminary analysis of the data indicates an enhancement in conductivity associated with the krypton discharge ionization lamp, particularly in negative conductivity. The conductivity values and their altitude dependence are consistent with previous balloon and rocket results.

Mitchell, J. D.↗

NASA NTRS1978

Electrical structure and ionizable constituent measurements

In-situ stratospheric ions showed typical characteristics. A Krypton lamp created large numbers of additional ions of remarkably high mobility with a product of number density and ionization cross section of the ionizable constituent(s) greater than 10 cm to the 9th power per cm.

Hale, L. C.↗

NASA NTRS1977

Middle atmosphere ion measurements during January, 1976

Parachute-borne measurements of electrical parameters in the stratosphere and mesosphere are discussed which were made in January 1976 as part of a 'coordinated winter-anomaly program' conducted at Wallops Flight Center, Va. The instruments used included Gerdien condensers, a blunt conductivity probe, and UV lamps for obtaining a measure of atmospheric NO. Measurements of the positive component of electrical conductivity on two 'anomalous' and two 'normal' days are compared, wave-interaction electron densities over the height range from 50 to 90 km are determined for the four days, and the effects of the UV lamps on one 'normal' and one 'anomalous' day are described. The results are shown to support the hypothesis that the enhancements in positive ion conductivity observed on 'anomalous' days are caused by a reduction of the aerosol population that is a 'normal' feature of the stratosphere and mesosphere. A possible scenario for this reduction is considered which involves electric-field transport of aerosol particles out of the upper stratosphere and mesosphere.

Hale, L. C.↗

NASA NTRS1977

Results of ionization measurements in the middle atmosphere

Positive-ion electrical-conductivity measurements, which are now performed with 4-cm diameter meteorological rocket payloads, provide a simple means of monitoring the NO concentration in the mesosphere, as well as the ionization variability. A wavelike dynamical structure is observed at low latitudes. Parachute-borne Gerdien mobility analyzers show, in addition, ion mobility spectra which spread from much greater to much less than that expected for simple gas-phase ions in the mesosphere and also indicate an ion clustering chain in the stratosphere. Large particulate ions apparently form in the daytime and grow very large at night. An instrument combining the mobility analyzer with a flashing source of ionizing radiation could be used as an NO(x) spectrometer.

Croskey, C. L.↗