Electron Density Data Research Articles

Two days in the life of the ionosphere over Arecibo

High resolution incoherent scatter electron density data using Barker‐coded pulses are presented for two separate 24‐hr periods of very different magnetic conditions. The first period in April 1972 was magnetically quiet while the second period spanned parts of two of the five most magnetically disturbed days in July 1972. Solar activity was low with 2800‐MHz indices of 129 and 128 for the April days and indices of 109 and 117 for the July days. Contour plots and selected profiles are presented which show larger sporadic‐E layers and stronger gravity wave effects during the disturbed night than during the quiet night.

Vertical transport of plasma in the night-time ionosphere

A new method is proposed for obtaining the vertical transport velocity of ionisation in the top-side ionosphere at night. The method is applied to electron density data taken at Malvern using pulsed, incoherent scatter radar. Data from seven nights are analysed to determine whether vertical transport of thermal plasma from the exosphere can explain the maintenance of the F-region during the night. On no occasion was the downward flux sufficient and on all but one occasion the downward flux was too small by an order of magnitude. It would appear that the maintenance of the F-region at night cannot be explained solely in terms of downward flux.

Ionospheric temperature and density measurements by means of spherical double probes

Rocket-borne double probes for electric field measurements can be intermittently operated in special, diagnostic modes involving current bias and low-impedance shunts to obtain information on the properties of the ambient ionospheric plasma along the flight path. Several such modes, and the information that they can provide, are analyzed. For example, in a low-impedance mode with asymmetric bias, the attenuation ratio (i.e. signal amplitude in this mode over the signal amplitude in the electric-field measuring mode) is in a simple way related to the electron temperature of the ambient plasma. The special surface coatings (Aquadag or vitreous carbon) normally used for electric field probes provide very homogeneous surface properties, a feature which also contributes to the reliability of the electron temperature measurements. In addition to electron temperature, the modes analyzed can be used to measure electron density and to give some information on ion temperature. The data from four rocket flights from ESRANGE are discussed in the light of these results. Electron temperature was measured in three of these flights. In all cases the temperature profile is in good agreement with theoretically predicted profiles based on the CIRA 1965 reference atmosphere and the solar illumination prevailing during the respective flights (twilight). Electron density profiles obtained by means of the double probe are in good agreement with the density measured by the Langmuir probe in the two flights for which both kinds of data are available. They are also in agreement with the electron density data available from ionosondes. Finally, pulses occurring when one of the probes passed through the rocket's shadow, are used to determine the photoelectron yield of the probe coatings (Aquadag or vitreous carbon). The values obtained, (7 ± 3) × 10 −6 A/m 2 for Aquadag and (4 ± 2) × 10 −6 A/m 2 for vitreous carbon are in good agreement with expectations based on laboratory data and solar Lyman α radiation.

Experimental test of the wind-shear theory. A reply—rocket-borne magnetometers do measure B

The apparent inconsistencies noted by Whitehead (1) in the ionization, electron density, wind and magnetic field data of the rocket flights SL 130 and 131 (Hall et al. (2)) are resolved by the presentation of further experimental detail. Observational accuracy and in particular the heading correction procedure for the magnetic field values are discussed. It is also pointed out that the interaction of the steady EW wind component with the E g ionization profile provides an additional contribution to the E g magnetic field. It is concluded that within the experimental limitations the experiment remains a fair test of the wind-shear theory.

Lightning spectroscopy

The physical characteristics of individual lightning return strokes which have been determined from quantitative analyses of time-resolved lightning spectra are reviewed. Relative line intensities of N II multiplets have been used to estimate channel opacity and temperature. Electron densities have been determined from H α line profiles and N I, O I and N II line intensity ratios. The temperature and electron density data have been used to calculate other channel parameters such as pressure, percent ionization and particle densities.

An evaluation of ionospheric probe performanc—II. The influence of vehicle wake effects on electron density and temperature measurements

The theoretical performance and accuracy of the Sayers type of R.F. capacitance electron density probe are discussed in some detail, and results from two ionospheric flights of this probe are given. After a brief survey of current satellite wake theories, the broad features of a sounding rocket wake are postulated, and its likely extent calculated by a method applicable to almost any rocket and probe configuration. Both electron density and temperature data are shown to correlate well with the rocket attitude and the postulated wake, confirming the existence of a wake and its importance to probe measurements. Evidence for prolonged outgassing from the rocket motors was also found.

Global electron density distributions from the Ariel 3 satellite at mid-latitudes during quiet magnetic periods

Electron density data returned by the Ariel 3 satellite have been separated into seasonal, diurnal, longitudinal and latitudinal groups. ‘Average’ electron density distributions for magnetic L values in the interval (1–11) are presented for each group and large scale features are summarised and discussed.

Some topside electron density measurements from Ariel III satellite during the geomagnetic storm of 25–27 May 1967

The Ariel III electron density data obtained during the magnetic storm of May 25–27 1967, have been studied and show that the storm day profile (electron density along the satellite orbit) was almost symmetric around the invariant magnetic equator. Since the satellite orbit was not perfectly circular, storm time electron densities encountered in the Southern Hemisphere were, on average, greater than the quiet day electron densities; whereas the opposite was the case in the north. Observations of visual aurora and the occurrence of the trough seem to be correlated on the storm day.

Calculated and observed features of stable auroral red arcs during three geomagnetic storms

Satellite electron temperature and density data are used to calculate the structure of several stable auroral red arcs (SAR arcs) according to the thermal conduction model of the arc. The calculated lambda 6300 emission rates are compared with ground-based photometric observations taken at the same time and in the vicinity of the satellite crossings of the arcs. The SAR arcs analyzed include a range of lambda 6300 intensities, geographical locations, and times during the associated geomagnetic storm. In addition, satellite data were obtained at different altitudes over and within the SAR-arc region. Enhanced electron temperatures within or on the equatorward edge of an electron-density depression are common features of all the SAR arcs examined. There is general agreement between the calculated and observed lambda 6300 emission features for SAR arcs observed during the geomagnetic storm periods of Oct. 29 to Nov. 2, 1968, May 14-15, 1969, and Mar. 8-9, 1970. For these SAR arcs, thermal conduction from the magnetosphere alone is sufficient to excite the lambda 6300 emission to its observed intensity.

Characteristics of the mid-latitude trough as determined by the electron density experiment on Ariel III

Criteria are established to identify mid-latitude troughs by computer analysis of Ariel III electron density data and are used to study the variations of such troughs with time of day, season and magnetic activity. The statistics presented are based on over 1000 troughs and the features found are compared with previous work.

Differential Phase Shift of Partially Reflected Radio Waves

The addition of phase difference measurements to differential absorption experiments is shown to be both feasible and desirable. The phase information can provide a more sensitive measurement of electron density above about 75 km. The differential phase shift is only weakly dependent on collision frequency in this range, and so an accurate collision frequency profile is not a prerequisite. The differential phase shift and differential absorption measurements taken together can provide both electron density and collision frequency data from about 70 to 90 km.

Changes in the ionospheric F2-layer at a place near the Sq-current focus during geomagnetic storms

In this paper hourly data of maximum electron density and total electron content in a unit column up to the level of peak electron density of the F2-layer at Puerto Rico (magnetic dip 52.5°N) in the American sector are studied to find their DS and D st variations and to compare them with those of the horizontal component of the Earth's magnetic field for 93 SC type geomagnetic storms which occurred during the period September 1957–March 1962. These variations are obtained separately for positive and negative F2-storms and then averaged for all the types. It is found that the positive F2-storms are in a way connected with the equatorial type of DS variation of the H-field and the negative F2-storms with the high-latitude type DS variation of the H-field. The D st variation of the H-field is practically of the same character for both positive and negative F2-storms. These findings combined with those of others indicate that it is the DS current in the ionosphere that cause the observed changes in the F2-layer through electromagnetic movements; diffusion along the field lines and changes in the loss-rates of electrons may also contribute to the nett effects. A statistical survey shows that while there are equal chances for positive F2-storms in Summer and Winter at Puerto Rico, there is a much larger number of negative F2-storms in Summer than in Winter. At a southern conjugate place, there is a much larger number of positive F2-storms in Winter, but equal number of negative F2-storms in Summer and Winter. More than half the total number of the F2-storms are found to be similar types (33 per cent positive, 23 per cent negative) from the consideration of the F2-changes during individual magnetic storms at the conjugate places. These are discussed in the concluding section of the paper.

Electron density and temperature in the vicinity of the 29 september 1967 middle latitude red arc

Electron temperature and density data were obtained as the Alouette satellites passed over the middle latitude red arc that was observed by the Fritz peak and Richland airglow observatories on September 29,1967. These data indicate that the electron temperature is enhanced and that the electron density is depressed along the magnetic field lines that intersect the red arc. The temperature at about 2000 km increased from approximately 2000°K equatorward of the arc to a peak value of nearly 6000°K on the field line intersecting the arc. The density was depressed by more than an order of magnitude at some altitudes. Visual aurora was observed poleward of the arc; the arc and aurora were separated by several degrees of latitude. Both the electron temperature and density were enhanced over the aurora.

Changes in electron density and collision frequency at University Park, Pennsylvania during the stratospheric warming of 1967/68

The electron density and collision frequency profiles obtained from the high power wave interaction observations at The Pennsylvania State University were examined for possible changes during the stratospheric warming of December 1967 to January 1968. The electron density increased quite sharply above 70 kilometers with maximum enhancement (about a factor of 10) at about 75 to 80 km. No change was observed in the collision frequency at heights between 50 and 90 km, and there was no significant change in the electron density below 70 km. From examination of the electron density and absorption data it appears that the effect began early December, 1967, reached a maximum between December 25 and January 1, and ended about January 20, 1968. There is some indication that the diurnal variation in electron density at 80 km became slower during the warming than during normal days, possibly indicating increasing control of ionization production through L α .

Geomagnetic and solar control of ionization at 1000 km

The electron density data obtained from Alouette I is examined for the individual passes to determine the geomagnetic and solar control of ionization at 1000 km. The solar zenith angle χ is chosen as a convenient solar parameter since it implicitly includes the effect of diurnal, seasonal and latitudinal variations. The magnetic effects are studied in terms of dip angle I. It is found that plasma frequency at 1000 km varies as cos 2 I cos 2 χ/2 in a linear way.

F-Region nightglow emissions of atomic oxygen: 2. Analysis of 6300 A and electron density data

F-layer nightglow 6300 angstrom emission intensity and electron density data, noting variations in emissions

Rocket measurements ofSqcurrents at midlatitude

Rubidium-vapor magnetometers were flown to altitudes near 150 km over Wallops Island, Virginia, in four Nike-Apache rockets. Two flights were made at times when no ionospheric current was expected, and none was encountered. The other two flights measured a current sheet with lower edge at 105 km and upper edge at 123 km, the total current being in agreement with that expected from the ground observations. One of the flights not encountering measurable ionospheric current was flown in conjunction with another rocket in order to obtain nearly simultaneous measurements of magnetic field, electron density, and winds. The ionospheric current calculated using the electron density and wind data was too small to have been observed by the rocket magnetometer.

Electron and molecular nitrogen temperature and density in the thermosphere

Four rocket-borne ejectable instruments, called ‘thermosphere probes,’ launched into the thermosphere above Wallops Island, Virginia, have measured the concentration and temperature of molecular nitrogen and electrons under various atmospheric conditions during the period approaching solar minimum. A fixed-tuned omegatron mass spectrometer mounted within an orificed chamber was employed for the N2 concentration measurements. The gas temperature was derived from the N2 scale height, and in some cases was measured directly by a velocity scan technique. Cylindrical and hemispherical Langmuir probes were employed for the electron temperature and density measurements. The four launchings were carried out in the afternoon, at sunset, at night, and during the July 20, 1963, solar eclipse. Calculations of energy deposition confirm earlier experimental and theoretical results which show that solar extreme ultraviolet is the major source of electron heating in the daytime F region. This is also clear from the factor of 2 reduction of F-region electron temperature during the eclipse. The heating observed in the E region can be explained only in part by solar X rays and appears to require an additional source such as an electric field. The gas temperatures agree well with theoretical model temperatures, but the model values of N2 concentration appear to be high by about a factor of 2. The flights reveal a temporal variation in N2 concentration in the lower thermosphere which may be either diurnal or seasonal. These variations suggest either large temperature variations below the diffusion level or mass motion phenomena such as winds or tides. Comparison of electron temperature and density data with simultaneous data from Explorer 17 obtained during a flight launched over the satellite shows the measurements to agree among themselves and to be consistent with ionosonde electron density results.

Field Aligned Strata in the Ionization above the Ionospheric F2 Layer

Electron density data collected by the satellite Ariel I during 60 orbits from April 30 to July 1, 1962, over a wide range of latitude and longitude were analyzed. There are strong indications that ledges observed on oblique electron density profiles were due to magnetic field aligned ionization strata in the region above the ionospheric F2 layer. Evidence for magnetic enhancement of the ionization, diurnal variation of the altitude of ledges, the effects of geographic and magnetic latitude and longitude, and stratification of ionization within magnetic shells are discussed. (C.H.)

Some numerical solutions of the continuity equation for electrons in the nighttime F region of the ionosphere

A simple digital computer program has been designed by means of which the magnitudes of the terms in the continuity equation for electrons in the F region of the ionosphere can be calculated from observed electron density data for different assumed atmospheric models. These models are based on rocket, satellite, and other experimental data on the characteristics of the upper atmosphere at ionospheric levels. It is possible to assess the significance of such experimental data for the physics of the F region. In general it is found that to satisfy the continuity equation it is necessary to assume a drift of electrons (and ions) due to electromagnetic forces in addition to that arising from the diffusion of charged particles in the earth's gravitational field. The magnitude of the vertical component of the electromagnetic drift velocity in the F region at night is calculated for these models by means of electron density-height profiles observed under both magnetically quiet and disturbed conditions. Average values throughout the night for quiet conditions at several stations show a strong latitudinal dependence. The velocities calculated for a night of high magnetic activity at Puerto Rico were found to be considerably greater than those for a number of quiet nights in the same period.