An Intense Wave/Particle Event in the Auroral Ionosphere

An intense burst of VLF waves, at frequencies just above the local proton gyrofrequency, was observed shortly after each of two intense bursts of field‐aligned suprathermal electrons (E \u3c 250eV) by instruments carried on a sounding rocket flown in diffuse aurora. If the two phenomena are associated with each other, the implication is that the electron acceleration occurred nearby, in a relatively small volume

Modeling the ionospheric E and F1 regions: Using SDO-EVE observations as the solar irradiance driver

Over the altitude range of 90–150 km, in dayside nonauroral regions, ionization is controlled almost entirely by solar ultraviolet irradiance; the response time for ionization during solar exposure is almost instantaneous, and likewise, the time scale for recombination into neutral species is very fast when the photoionizing source is removed. Therefore, if high-resolution solar spectral data are available, along with accurate ionization cross sections as a function of wavelength, it should be possible to model this ionospheric region with greater accuracy. The Extreme Ultraviolet Variability Experiment (EVE) instrument on the National Aeronautics and Space Administration Solar Dynamics Observatory (SDO) satellite, launched in February 2010, is intended to provide just such solar data, at high resolution in both wavelength and time cadence. We use the Utah State University time-dependent ionospheric model to assess the sensitivity in modeling that this solar irradiance data provide, under quiet solar conditions as well as during X-class flares. The sensitivity studies show that the E and F1 regions, as well as the valley region, are strongly dependent upon wavelength in both electron density and ion composition

Promising emission behavior in Pr 3+ /In selenide-chalcogenide-glass small-core step index fiber (SIF)

Selenide-chalcogenide glass, small-core, step-index fiber (SIF), core-doped with Pr3+: 9.51 × 1024 ions m−3 (500 ppmw) is fabricated for the first time with indium to help solubilize Pr3+. Core diameters of 20 or 40 μm are confirmed using scanning electron microscopy and near-field imaging; fibre numerical aperture is ∼0.4. Optical loss is ≥ 4.9 dB m−1 across the 3–9 μm mid-infrared (MIR) spectral range. On pumping at 1.55 μm or 2.013 μm, the SIFs give broad MIR emission across 3.5–6 μm assigned to 3H6 → 3H5 and 3H5 → 3H4. The Pr3+ emission-lifetime at 4.7 μm decreases from bulk-glass (10.1 ± 0.3 ms), to intermediately processed fiber (8.10 ± 0.5 ms) to SIF (7.1 ± 0.5 ms) induced by the processing. On end-pumping SIFs at 2.013 μm, the output pump-power and emission intensity at 4.7 μm became sub-linear and super-linear, respectively, suggesting MIR excited-state saturation is occurring

Resolving Ionospheric E-region Modeling Challenges: The Solar Photon Flux Dependence

The EVE instrument of the NASA Solar Dynamics Observatory (SDO) provides for the first time EUV and XUV measurements of the solar irradiance that adequately define the major source of ionization of the atmosphere. In our study we modeled the E-region of the ionosphere and analyzed how it is affected by the solar irradiance data obtained by EVE and contrast this with the S2000 Solar Irradiance model, used previously. The ionosphere has two major layers, the E-layer at 100 km, and the F-layer at 300 km. The difference in solar irradiances are small except at some wavelength bands, it is these differences that lead to a better understanding of the physical/chemical processes of the E-region. Observations of the ionospheric layers is best achieved using incoherent scatter radars (ISR). We have compared our model with ISR data available from Arecibo Puerto Rico in an effort to understand how specific solar irradiance wavelength bands affect the E-region. This study focuses on two specific wavelength bands 0.1-15 nm and 91-103 nm. Both are responsible for E-region production, but in quite different manners

Multi-year Observations of Mid-latitude Middle Atmospheric Winds, Waves, and Temperature associated with SSW Events over Northern Utah

We investigate the behavior of 14 years of wind, wave, and temperature observations in the middle atmosphere over northeastern Utah, USA during periods of sudden stratospheric warming events. This systematic review of the impacts of sudden stratospheric warming events on the middle atmosphere at a northern mid-latitude site is conducted using ground based measurements from imaging Doppler interferometry and meteor wind radar and Na and Raleigh lidar and space based measurements made by the Sounding of the Atmosphere Using Broadband Emission Radiometry sensor onboard the NASA sponsored Thermosphere Ionosphere mesosphere Energetics Dynamics Mission

Experimental photoluminescence and lifetimes at wavelengths including beyond 7 microns in Sm3+-doped selenide-chalcogenide glass fibers

1000 ppmw Sm3+-doped Ge19.4Sb9.7Se67.9Ga3 atomic % chalcogenide bulk glass and unstructured fiber are prepared. Near- and mid-infrared absorption spectra of the bulk glass reveal Sm3+ electronic absorption bands, and extrinsic vibrational absorption bands, due to host impurities. Fiber photoluminescence, centred at 3.75 μm and 7.25 μm, is measured when pumping at either 1300 or 1470 nm. Pumping at 1470 nm enables the photoluminescent lifetime at 7.3 μm to be measured for the first time which was ~100 μm. This is the longest to date, experimentally observed lifetime in the 6.5-9 μm wavelength-range of a lanthanide-doped chalcogenide glass fiber