2,257 research outputs found
TEC enhancement due to energetic electrons above Taiwan and the West Pacific
The energetic electrons of the inner radiation belt during a geomagnetic
disturbance can penetrate in the forbidden range of drift shells located at the
heights of the topside equatorial ionosphere (<1000 km). A good correlation was
previously revealed between positive ionospheric storms and intense fluxes of
quasi-trapped 30-keV electrons at ~900 km height in the forbidden zone. In the
present work, we use statistics to validate an assumption that the intense
electron fluxes in the topside equatorial ionosphere can be an important source
of the ionization in the low-latitude ionosphere. The data on the energetic
electrons were obtained from polar orbiting satellites over the periods of the
62 strong geomagnetic storms from 1999 to 2006. Ionospheric response to the
selected storms was determined using global ionospheric maps of vertical total
electron content (VTEC). A case-event study of a major storm on 9 November 2004
provided experimental evidence in support to the substantial ionization effect
of energetic electrons during positive ionospheric storms at the low latitudes.
Statistical analysis of nine magnetic storms indicated that the VTEC increases
coincided with and coexisted with intense 30-keV electron fluxes irrespective
of local time and phase of geomagnetic storm. We concluded that extremely
intense fluxes of the 30-keV electrons in the topside low-latitude ionosphere
can contribute ~ 10 - 30 TECU to the localized positive ionospheric storms.Comment: 15 pages, 4 figures, 1 table accepted for publication in Terrestrial,
Atmospheric and Oceanic Sciences (TAO), Dec. 2012 A special issue on
"Connection of solar and heliospheric activities with near-Earth space
weather: Sun-Earth connection
Compressibility of a 2D electron gas under microwave radiation
Microwave irradiation of a two-dimensional electron gas (2DEG) produces a
non-equilibrium distribution of electrons, and leads to oscillations in the
dissipative part of the conductivity. We show that the same non-equilibrium
electron distribution induces strong oscillations in the 2DEG compressibility
measured by local probes. Local measurements of the compressibility are
expected to provide information about the domain structure of the zero
resistance state of a 2DEG under microwave radiation.Comment: v2: analysis of the wave-vector dependence of the compressibility
added; discussion of the Hall conductivity removed (shifted to
cond-mat/0409590 in a revised form
Multiphoton antiresonance
We show that nonlinear response of a quantum oscillator displays antiresonant
dips and resonant peaks with varying frequency of the driving field. The effect
is a consequence of special symmetry and is related to resonant multiphoton
mixing of several pairs of oscillator states at a time. We discuss the
possibility to observe the antiresonance and the associated multiphoton Rabi
oscillations in Josephson junctions.Comment: 4 pages, 3 figures; corrected referenc
Quantum interference in the classically forbidden region: a parametric oscillator
We study tunneling between period two states of a parametrically modulated
oscillator. The tunneling matrix element is shown to oscillate with the varying
frequency of the modulating field. The effect is due to spatial oscillations of
the wave function and the related interference in the classically forbidden
region. The oscillations emerge already in the ground state of the oscillator
Hamiltonian in the rotating frame, which is quartic in the momentum.Comment: Submitted to PR
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