Sr eV Research Articles

Impact of Space Environment on Geostationary Meteorological Satellite Data Outage

AbstractImpact of space environment changes on geostationary meteorological satellite services, such as data outage, incomplete imagery, or quality degradation were investigated using event logs of Himawari‐8 and Meteosat (MET‐7 and MET‐8) in 2015–2017. The event logs show that such failures were caused by anomalies on spacecraft and in ground system half each. On Himawari‐8, a total of 11 incomplete imagery occurred due to spacecraft anomaly, and among them about 45% (5 anomalies) occurred during energetic electron enhancement and about 9% (1 anomaly) occurred during energetic proton enhancement. In cases of Meteosat, a total of 84 service alerts occurred due to spacecraft anomaly, and among them 35% (29 anomalies) occurred during electron enhancement and 7% (6 anomalies) occurred during both proton and electron enhancement. On the basis of statistical analysis, it is found that the probability of spacecraft anomaly occurrence markedly increases when electron fluence exceeds a threshold. The probability of anomaly is less than 10% when the 1‐MeV electron fluence is less than 104 (/cm2 sr eV), whereas it increases to more than 20% above the fluence. Thresholds are also found for electron fluences at other energies from 200 keV to 1.5 MeV. This study clarifies that changes in the space environment, particularly electron fluence enhancement affect geostationary meteorological satellite services.

Direct Magneto-Optical Compression of an Effusive Atomic Beam for Application in a High-Resolution Focused Ion Beam

An atomic rubidium beam formed in a 70 mm long two-dimensional magneto-optical trap (2D MOT), directly loaded from a collimated Knudsen source, is analyzed using laser-induced fluorescence. The longitudinal velocity distribution, the transverse temperature and the flux of the atomic beam are reported. The equivalent transverse reduced brightness of an ion beam with similar properties as the atomic beam is calculated because the beam is developed to be photoionized and applied in a focused ion beam. In a single two-dimensional magneto-optical trapping step an equivalent transverse reduced brightness of $(1.0\substack{+0.8-0.4})$ $\times 10^6$ A/(m$^2$ sr eV) was achieved with a beam flux equivalent to $(0.6\substack{+0.3-0.2})$ nA. The temperature of the beam is further reduced with an optical molasses after the 2D MOT. This increased the equivalent brightness to $(6\substack{+5-2})$$\times 10^6$ A/(m$^2$ sr eV). For currents below 10 pA, for which disorder-induced heating can be suppressed, this number is also a good estimate of the ion beam brightness that can be expected. Such an ion beam brightness would be a six times improvement over the liquid metal ion source and could improve the resolution in focused ion beam nanofabrication.

Experimental determination of the linewidth of parametric X-ray radiation at electron energies below 10 MeV

The linewidth of parametric X-ray radiation has been determined experimentally applying an absorption technique. Using a copper foil of 27.7 μm thickness and tuning the energy of the PXR peak across the K-absorption edge of copper by tilting a 55 μm thick diamond crystal, the variance of the PXR line at 8.98 keV photon energy was found to be σ = 48 eV. The diamond crystal has been bombarded with electrons of 6.8 MeV kinetic energy delivered by the superconducting linear accelerator S-DALINAC at Darmstadt. The experimental yield of the intensity amounts to N = 0.91 × 10 −5 photons/(electron sr). From the measured variance the spectral density in the peak is deduced to be J = 0.95 × 10 −7 photons/(electron sr eV).

Dynamics Explorer 2 satellite observations and satellite track model calculations in the cusp/cleft region

We present two detailed case studies of the ionospheric and thermospheric response to soft particle precipitation in the cusp/cleft region using multi‐instrument observations from the Dynamics Explorer 2 (DE 2) satellite during orbits 688 and 748, together with supporting model calculations. The experimental data set is among the most comprehensive reported to date and includes a specification of both the soft particle input to the atmosphere and the detailed local atmospheric response to these inputs. Specifically, observations are presented of precipitating ion and electron fluxes, ion and neutral horizontal and vertical wind speeds, neutral temperatures and densities, and volume emission rates for the OI 630.0‐nm red line, which is often used as a thermospheric signature of soft electron precipitation. The two orbits were chosen to provide representative cases for active (orbit 688; Kp=5; interplanetary magnetic field (IMF) Bz=−0.5 nT) and quiet (orbit 748; Kp=1; IMF Bz=+7.8 nT) geomagnetic conditions. Some of the data were used to provide boundary conditions and inputs to a satellite track code that was used to calculate the ionospheric structure below and along the orbital track. The satellite track code enables us to calculate the Joule‐ and particle‐heating altitude profiles and the ionization rate altitude profile. During each of the two orbits the region of soft electron precipitation associated with the cusp/cleft region was clearly identifiable. The principal findings of this study are as follows: (1) The maxima in the cusp/cleft soft electron (<100 eV) precipitating flux were ∼3 × 10−3 and ∼5×10−4 ergs/(cm2s sr eV) for orbits 688 and 748, respectively, and these fluxes produced oxygen redline volume emission rate maxima of 580 ph/(cm3 s) for the active orbit (688) and ∼80–90 ph/(cm3 s) for the quiet orbit (748). For both orbital passes the red‐line enhancements were evident above the background day glow, peaking at altitudes near 325 km. (2) The calculated ionization rate peaked at an altitude near 265 km, or 60 km lower than the altitude of the enhancement in the 630.0‐nm volume emission rate; the difference is ascribed to low‐altitude quenching of the emission. (3) Large changes in magnitude and direction for both the observed cusp/cleft neutral winds and ion drifts were observed, particularly to the poleward side of the region, with the ion drifts exhibiting more shearlike reversals and the neutral winds undergoing more rotationallike reversals. (4) Despite the negative IMF Bz (−0.5 nT) during orbit 688, the convection characteristic of the ion drifts was consistent with a northward IMF for both orbits. (5) The satellite track code results showed maxima in particle and Joule heating rates at −260 and 120 km altitude, respectively. The Joule heating rate was greater than the particle heating rate at all altitudes below the satellite, and the Joule heating peaked on the poleward side of the cusp/cleft precipitation region. (6) Both ion and relative neutral vertical velocities exhibited perturbations in the upward sense on the poleward side of the cusp/cleft, consistent with intense local heating and up welling.

A system for the intensity calibration of electron spectrometers

A system for the calibration of the intensity/energy response function for electron spectrometers used in Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) is described. The basic physical principles of a complete system are detailed to show how the data are derived and how the calibrations may be made traceable to the SI system. The calibration method gives an accurate energy dependence of the intensity/energy response function which is the functional dependence presently needed for analytical work. For AES this gives a reproducibility demonstrated below 2% and for XPS at 4%. For AES this is also made traceable in an absolute sense, where the response function is given in sr eV units, to an accuracy of 6%. For XPS the units of the response function are also sr eV for focused X-ray monochromators but for diffuse unmonochromated X-ray sources m 2 sr eV units are more appropriate. Accurate traceability for XPS exists for all terms except the X-ray source production efficiency. The full traceability is important for those studying absolute cross sections but is usually unimportant where quantification procedures involve any normalisation procedures.

High-efficiency retarding-potential Mott polarization analyzer

A compact retarding-potential Mott polarimeter is described that employs a thorium target. When operating at an electron accelerating voltage of 25 kV, the instrument provides effective asymmetry (Sherman) functions Seff between −0.15 and −0.25, the exact value being determined by the inelastic energy loss window selected. The corresponding scattering efficiencies I/I0 are in the range ∼6–2×10−3 resulting in optimized efficiencies η (≡S2effI/I0) of ∼1.6×10−4. These efficiencies are much larger than have been obtained previously with similar analyzers. The instrument is simple to construct, is stable in operation, and has a large electron-optical acceptance, estimated to be ∼104 mm2 sr eV. It is fully UHV compatible and is suitable for application in a wide range of spin-dependent studies.

Acceleration of particles in the upper ionosphere and the magnetosphere due to decay interactions of whistlers, part 1

A numerical analysis of the three-wave decay interaction of oblique whistler mode waves with different types of ion waves is presented. It is shown that at altitudes h < 2000 km the most effective mechanism is the decay interaction of whistlers with quasielectrostatic ion-cyclotron waves (the increment is Γ ~ 25s−1 for an initial whistler pump wave amplitude of ℰ10 = 10 mVm-1) as well as with Alfvén waves and ion-ion hybrid waves (Γ ~ 10s−1 for the same pump amplitude ℰ10). When taking into account the media inhomogeneity and the decay wave stabilization due to pump wave amplitude depletion, the magnitudes of excited ion waves are found to be E3 ~ 50-120μV/(mHz½) for ℰ10 = 10 mVm-1. At such amplitudes parametrically excited ion waves can provide transverse ion acceleration with a rate of 0.5eVs−1 and longitudinal electron acceleration up to 5eV at a distance of the order of 2000 km, the flux reaching 3 × 107 el/(cm2s sr eV).

Low-energy diffuse scattering electron-spin polarization analyzer

A new, compact (approximately fist sized), efficient electron-spin analyzer is described. It is based on low-energy (150 eV) diffuse scattering from a high-Z target, for example, an evaporated polycrystalline Au film opaque to the incident electron beam. By collecting a large solid angle of scattered electrons, a figure of merit S2I/I0=10−4 is achieved with an analyzing power S=0.11. The figure of merit degrades only marginally (&amp;lt;10%) for beams with an energy width of 40 eV or after one month of operation at 10−8 Torr. The electron optical acceptance is of order 100 mm2 sr eV. The details of the design and construction are discussed and its performance is compared to six other spin analyzers. Illustrative results are presented from an application to scanning electron microscopy with polarization analysis (SEMPA) to image magnetic microstructure.

Relations between morning sector Pi 1 pulsation activity and particle and field characteristics observed by the De 2 satellite

Impulsive short‐period magnetic field fluctuations (Pi 1) observed by ground instrumentation in the morning sector auroral zone have in recent years been convincingly tied to the presence overhead of pulsating aurora. We here present simultaneous records from ground‐based magnetometer, photometer, and riometer instrumentation at Siple, Antarctica, and its conjugate point, Roberval, Quebec, and low‐altitude particle and magnetic and electric field data from the DE‐2 spacecraft. Satellite magnetometer observations support earlier findings of a link between morning sector Pi 1 and the presence of a region 2 Birkeland current sheet. The addition of energetic electron and electric field observations provides a more complete characterization of the environment of Pi 1 pulsation events. Intense fluxes of energetic electrons (from 10 keV to over 35 keV) are observed simultaneously with Pi 1 pulsations and region 2 Birkeland currents. When intense (&gt;10−5 ergs/cm² s sr eV) fluxes of lower energy electrons (E &lt; 1 keV) are also present, we observe strong region 2 Birkeland currents and strong Pi 1 pulsations; when lower energy electrons are less abundant, region 2 Birkeland currents and Pi 1 pulsations are considerably weaker. No Pi 1 pulsations have been found in regions without intense fluxes of energetic electrons. Simultaneous observations of magnetic and electric fields in space indicate complex localized current and field structures, which are likely to be the source of the magnetic pulses observed on the ground.

Monoenergetic Cs+ source with increased brightness

Sequential absorption of two laser photons converts a Cs atomic beam into a ’’cold’’ Cs+ ion beam, i.e., a beam with minimal random kinetic energy [Appl. Phys. Lett. 36, 495 (1980)]. Improvements have now increased the spectral brightness by 2.7×104 times, i.e., to 2.7 A/cm2 sr eV, and have thereby made this source practical for ion microscopy and similar experiments requiring high-brightness beams with minimal energy spread.

Cw monoenergetic Cs+ ion source by photoionization

Sequential absorption of two photons converts a Cs atomic beam into an ion beam with minimal change in the original thermal energy of the atoms. The random ion energy is measured to be &amp;lt;0.15 eV; consequently this ion beam is one of the ’’coldest’’ ion sources to date. Currently, the source brightness is 10−4 A/cm2 sr eV and appears extendible to ∼5 A/cm2 sr eV.