Active experimentation with the ionospheric plasma

Abstract

Considerable effort in recent years has been directed towards experiments that actively perturb the ionospheric plasma, producing a measure of control over its properties (locally and ephemerally) and also exciting a variety of plasma instabilities. Space vehicles have been used for the release in the ionosphere of exotic chemicals and for the operation in the ionosphere of charged particle accelerators. Ground based radio transmitters at VHF perturb the magnetosphere, while transmitters at HF and higher frequencies perturb the ionosphere. This paper discusses the last technique, often called ionospheric heating, which uses powerful transmitters to change electron densities and temperatures and to excite a variety of parametric instabilities in the ionospheric plasma. Recent work in this area is cited and a qualitative description is given of the physical mechanisms that underlie many of the observed phenomena. Bibliographies of recent work are included for the other three techniques of active experimentation.

Fe L-Edge X-ray Absorption Spectroscopy of Low-Spin Heme Relative to Non-heme Fe Complexes: Delocalization of Fe d-Electrons into the Porphyrin Ligand

“…In such a case the system will be unstable to a symmetry-breaking distortion of the heme plane. These effects of axial ligand orientation have been discussed elsewhere, in terms of NMR experiments, 29,30,41,42,106 crystallography 107 and DFT calculations. [108][109][110][111][112][113] Extension of these axial ligand effects on the LUMO to heme sites in proteins provides some insights into super-exchange contributions to electron transfer.…”

“…Rotating the ImH planes out of the xz plane and staggering these orientations changes the coefficients of mixing with the two porphyrin 3e g (D 4h ) orbitals (vide infra). 30,41 The degree of π back-bonding from Fe(III) to the porphyrin can be assessed from the coefficients of the occupied metal orbital 72, (d xz ) and their relation to the unoccupied porphyrin 4e g (D 4h ) orbitals (since orbital 73 d yz is unoccupied, its interaction with the porphyrin 4e g orbital does not contribute to back-bonding). From Table 2 Metal L-edge energy shifts are a consequence of three factors: the charge on the absorbing metal in the molecule, (Z eff ), ligand field splittings, and any difference in the nature of the transitions contributing to the spectra.…”

“…The NMR spectra of low-spin Fe(III) provide evidence for significant π donation from the porphyrin ring to the Fe, and evidence for little back-bonding. 29,30,41,42 No spectroscopic approach has simultaneously provided substantial information about the bonding and back-bonding in low spin Fe(II) porphyrins. These interactions in both redox states are of key importance in identifying ET pathways in the cytochromes, and contribute directly to O 2 activation in a number of heme enzymes.…”

Persistent enhancement of the HF pump‐induced plasma line measured with a UHF diagnostic radar at HAARP

“…The ion‐acoustic frequency is dependent on the plasma temperature [ Isham and Hagfors , 1993, equation (1)]. The former peak is known as the purely growing mode, which is due to the OTSI [ Kantor , 1974; Carlson and Duncan , 1977; Walker , 1979; Nicholson et al , 1984; Sprague and Fejer , 1995; Stubbe , 1996a]. The latter peaks with the frequency offset of f ia and nf ia are known as the decay and the cascade lines, respectively.…”

Going with the Electron Flow: Heme Electronic Structure and Electron Transfer in Cytochrome c

“…NMR spectroscopy applied to paramagnetic ( S = ) Fe(III)cyt c variants has been a valuable tool for relating heme active site structure to electronic structure . The heme chemical shifts reflect the distribution of unpaired electron spin density, which is a good approximation of the singly occupied molecular orbital (SOMO) .…”