This work investigates solar events occurred in September 2017 characterized by a series of Forbush decreases and a ground level enhancement (GLE). Forbush decreases is a rapid decrease in the ...observed https://en.wikipedia.org/wiki/Galactic_cosmic_ray intensity following a coronal mass ejection while GLE is induced by a strong solar event for which the flux of high‐energy solar particles is sufficient to enhance the radiation level on the ground. These investigations were performed using data recorded by a neutron spectrometer network composed of a Bonner sphere system. Two instruments located at Pic‐du‐Midi Observatory (+2,885 m above sea level) and at Concordia station (Antarctica, +3,233 m) record simultaneously and continuously the neutron spectra, allowing to consider short‐term variations during solar events. The main objective is to analyze neutron spectral properties including their energy distributions and dynamics. This paper presents cosmic ray‐induced neutron spectra during active solar event leading to changes in the local cosmic ray spectrum (Forbush decreases and a GLE). Concerning the GLE, analyses show that neutrons in the evaporation domain are particularly amplified during the GLE, while other energetic domains increase uniformly.
Key Points
This paper presents an analysis of neutron spectrum variations during solar event of September 2017
Investigations are based on data recorded by a neutron spectrometer network (midlatitude and Antarctica stations)
The peak of evaporation is particularly amplified during the GLE
Emission of light by a single electron moving on a curved trajectory (synchrotron radiation) is one of the most well-known fundamental radiation phenomena. However experimental situations are more ...complex as they involve many electrons, each being exposed to the radiation of its neighbors. This interaction has dramatic consequences, one of the most spectacular being the spontaneous formation of spatial structures inside electrons bunches. This fundamental effect is actively studied as it represents one of the most fundamental limitations in electron accelerators, and at the same time a source of intense terahertz radiation (Coherent Synchrotron Radiation, or CSR). Here we demonstrate the possibility to directly observe the electron bunch microstructures with subpicosecond resolution, in a storage ring accelerator. The principle is to monitor the terahertz pulses emitted by the structures, using a strategy from photonics, time-stretch, consisting in slowing-down the phenomena before recording. This opens the way to unpreceeded possibilities for analyzing and mastering new generation high power coherent synchrotron sources.
Synchrotron radiation time structure is becoming a common tool for studying dynamic properties of materials. The main limitation is often the wide time domain the user would like to access with ...pump–probe experiments. In order to perform photoelectron spectroscopy experiments over time scales from milliseconds to picoseconds it is mandatory to measure the time at which each measured photoelectron was created. For this reason the usual CCD camera‐based two‐dimensional detection of electron energy analyzers has been replaced by a new delay‐line detector adapted to the time structure of the SOLEIL synchrotron radiation source. The new two‐dimensional delay‐line detector has a time resolution of 5 ns and was installed on a Scienta SES 2002 electron energy analyzer. The first application has been to characterize the time of flight of the photoemitted electrons as a function of their kinetic energy and the selected pass energy. By repeating the experiment as a function of the available pass energy and of the kinetic energy, a complete characterization of the analyzer behaviour in the time domain has been obtained. Even for kinetic energies as low as 10 eV at 2 eV pass energy, the time spread of the detected electrons is lower than 140 ns. These results and the time structure of the SOLEIL filling modes assure the possibility of performing pump–probe photoelectron spectroscopy experiments with the time resolution given by the SOLEIL pulse width, the best performance of the beamline and of the experimental station.
The Microwave Limb Sounder on Aura has produced an extensive set of measurements of CO in the middle atmosphere. The measurements are usable for scientific studies from the upper troposphere up to 90 ...km altitude. We describe these measurements and validate them by demonstrating their internal consistency and by comparing them to other remotely sounded measurements and to 2‐D model simulations. Comparisons with other measurements suggest that MLS has a positive bias of 25–50% in the mesosphere and a negative bias of up to 70% in the (almost CO‐free) lower stratosphere. The geophysical features observed in the MLS CO field show excellent qualitative agreement with other measurements.
► Coupling of an atmospheric pressure photoionization source with a vacuum ultra-violet (VUV) beamline. ► The set up allows photoionization up to 20eV. ► Compared to classical atmospheric pressure ...photoionization (APPI), our set up offers spectral purity and tunability. ► Allows photoionization mass spectrometry on fragile and hard to vaporize molecules.
We report here the first coupling of an atmospheric pressure photoionization (APPI) source with a synchrotron radiation beamline in the vacuum ultra-violet (VUV). A commercial APPI source of a QStar Pulsar i from AB Sciex was modified to receive photons from the DISCO beamline at the SOLEIL synchrotron radiation facility. Photons are delivered at atmospheric pressure in the 4–20eV range. The advantages of this new set up, termed SR-APPI, over classical APPI are spectral purity and continuous tunability. The technique may also be used to perform tunable photoionization mass spectrometry on fragile compounds difficult to vaporize by classical methods.
PDF
