The upper‐frequency cutoffs of magnetospherically reflected (MR) whistlers observed by the Ogo 1 and 3 satellites are explained in terms of trapping of the upper‐frequency components above the cutoff by sharp density gradients across L shells. The lower‐frequency cutoffs are interpreted in terms of wave guide attenuation and D region absorption of the atmospheric source energy and defocusing of the MR whistler energy in the magnetosphere.

Global lightning distributions for the period August 1977 to June 1978 have been obtained from lightning sensors on Defense Meteorological Satellite Program (DMSP) flights 2 and 3. Seasonally averaged trigger rates are calculated for 10°×10° cells on the earth, an area roughly equal to the resolution limit of the sensors. These data indicate that 37% of global lightning activity originates over the oceans at dawn, and this fraction drops to 15% at dusk. The seasonally averaged mean global lightning flash rate varies by about 10% through the year, with an absolute value within the range of 40–120 flashes per second.

The precipitation of energetic electrons which are commonly observed in the drift loss cone east of 60° east longitude between L ∼1.6 and L ∼1.8 can be accounted for by a Doppler‐shifted cyclotron resonance between the electrons and nonducted whistler mode waves from high‐power, ground‐based VLF transmitters. A ray‐tracing analysis using a diffusive‐equilibrium model shows that 17.1‐kHz waves starting with vertical wave normals between 23° and 31° magnetic latitude cross the magnetic equator between L ∼1.6 and f L ∼1.8 with wave normals of approximately 63°. A relativistic cyclotron‐resonance analysis for the same model plasmasphere using the ray‐tracing results gives an energy versus L shell dependence for the precipitated electrons which is in excellent agreement with the observed dependence. The primary VLF transmitter is most probably the UMS transmitter located near Gorki, USSR. It transmits on 17.1 kHz. VLF records covering this frequency band were available for only three of the time periods when electrons were observed. In two cases UMS was transmitting at the time required to account for the observations. In the third case a higher frequency is required to fit the data. At the time, the NWC transmitter at North West Cape, Australia was operating at 22.3 kHz. These data are consistent with a model in which weak pitch angle scattering by whistler mode waves from NWC does not completely fill the drift loss cone at the longitude of NWC.

This paper describes a coordinated rocket and ground-based study to investigate equatorial spread F irregularities. Measurements by the Jicamarca backscatter radar, ionosondes, and airglow instrumentation and of radio scintillations were correlated with high spatial resolution measurements of electron densities, particle fluxes, and VLF-ELF fields from a rocket probe. Experimentally, we find that (l) very high positive and negative electron density gradients are responsible for the enhanced radar echoes, (2) energetic particles are not part of the spread F phenomena, (3) wave measurements are strongly correlated with the Doppler character of the radar signals, and (4) there is a one-to-one correspondence of the largescale irregularities responsible for scintillations of satellite radio transmissions and ionosonde spread echoes with the small-scale irregularities responsible for the backscatter of VHF radar signals. We present and discuss the implications of the data. A general description of the phenomena and theories attempting to explain spread F, circa 1970, has been given by Farley et al. [1970]. The irregularities which cause the spread ionograms and radio scintillations occur at all heights in the F region and can be observed with the Jicamarca incoherent backscatter radar at all altitudes up to 1200 km. Recently, a number of new and possibly related phenomena have been observed, including intense soft particle fluxes [Heikkila, 1971], strong VLF emissions [Laaspere and Semprebon, 1974], enhanced optical emissions [Leoasseur and Blamont, 1973; Meier and Weller, 1975], and abnormal ion composition and flow [Hanson and Sanatani , 1971]. These observations led to a desire to simultaneously measure the vertical profile well into the topside ionosphere of energetic particles, ion composition, the electric and magnetic field components, atmospheric emissions, and the critically important electron density fluctuations. A crucial part of this experiment was to couple these in situ measurements with simultaneous ground-based measurements of scintillations, Jicamarca radar backscattered power and spectra, ionosonde reflections, and optical emissions.Coupling of these techniques provides the data necessary to determine whether the 3-m irregularities detected by the radar are related to the large-scale irregularities observed with ionosondes and scintillations. From these data we also anticipated being able to determine the interrelationships, if any, betweenThe ground-based data reported in this paper were obtained from several installations which together with the equipment utilized are shown in Table 1. The locations of these sites are shown in Figure 1. The launch site permits rockets to be launched along the magnetic field lines or equatorial electrojet. The Anc6n, Huancayo, and Jicamarca observatories were operated by personnel of the Instituto Geofisico del Peru. The range was operated under the authority of the Peruvian government by the instituto and experimental personnel. A nc6n Obseroatory The Anc6n Observa...

Motivated by proton auroral studies, we extend the microscopic approach developed for electrons, which is based on detailed collisional cross sections, to deal with the problem of proton energy deposition in N2. Our calculated excitation efficiencies, which include the contributions from charge exchange processes and secondary electrons, remain fairly constant from 1 kev to 10 Mev for the ionization states but vary considerably below 10 kev for excitation states and dissociation processes due to charge exchange effects. The estimates of the Lyman α and Hα photon production are found to be very sensitive to the low‐energy hydrogen impact cross section. The Lyman α and Hα photon production tends to be higher than previous estimates of Eather. Good agreement with the results of Chubb and Hicks is obtained for the Lyman α/Lyman‐Birge‐Hopfield intensity ratio. Total intensities for a typical proton auroral energy of 4 kev and a polar glow aurora of 1 Mev are presented.