A new population of terrestrial gamma-ray flashes in the RHESSI data

Terrestrial gamma-ray flashes (TGFs) are the most energetic photon phenomenon occurring naturally on Earth. An outstanding question is as follows: Are these flashes just a rare exotic phenomenon or are they an intrinsic part of lightning discharges and therefore occurring more frequently than previously thought? All measurements of TGFs so far have been limited by the dynamic range and sensitivity of spaceborne instruments. In this paper we show that there is a new population of weak TGFs that has not been identified by search algorithms. We use the World Wide Lightning Location Network (WWLLN) to identify lightning that occurred in 2006 and 2012 within the 800 km field of view of Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). By superposing 740,210 100 ms RHESSI data intervals, centered at the time of the WWLLN detected lightning, we identify at least 141 and probably as many as 191 weak TGFs that were not part of the second RHESSI data catalogue. This supports the suggestion that the global TGF production rate is larger than previously reported

Resilience Engineering and Integrated Operations in the Petroleum Industry

This white paper provides an overview of Resilience Engineering and seeks to answer the following questions: • What is Resilience Engineering? • Why do we need Resilience Engineering in integrated operations? • What is the significance of performance variability? • How does Resilience Engineering work in practice? • How does Resilience Engineering fit with other safety management approaches? • How mature is Resilience Engineering? • What is the added value of Resilience Engineering for integrated operations in petroleum production?publishedVersio

Laser-induced Coulomb explosion of heteronuclear alkali dimers on helium nanodroplets

A sample mixture of alkali homonuclear dimers, Ak$_2$ and Ak$^{\prime}_2$ and heteronuclear dimers, AkAk$^{\prime}$, residing on the surface of helium nanodroplets are Coulomb exploded into pairs of atomic alkali cations, (Ak$^{+}$,Ak$^{+}$), (Ak$^{\prime +}$,Ak$^{\prime +}$), (Ak$^{+}$, Ak$^{\prime +}$), following double ionization induced by an intense 50 fs laser pulse. The measured kinetic energy distribution $P(E_{\text{kin}})$ of both the Ak$^{+}$ and the Ak$^{\prime +}$ fragment ions contains overlapping peaks due to contributions from Coulomb explosion of the homonuclear and the heteronuclear dimers. Using a coincident filtering method based on the momentum division between the two fragment ions in each Coulomb explosion event, we demonstrate that the individual $P(E_{\text{kin}})$ pertaining to the ions from either the heteronuclear or from the homonuclear dimers can be retrieved, for both the Ak$^{+}$ and for the Ak$^{\prime +}$ fragment ions. This filtering method works through the concurrent detection of two-dimensional velocity images of the Ak$^{+}$ and the Ak$^{\prime +}$ ions implemented through the combination of a velocity map imaging spectrometer and a TPX3CAM detector. The key finding is that $P(E_{\text{kin}})$ for heteronuclear alkali dimers can be distinguished despite the simultaneous presence of homonuclear dimers. From $P(E_{\text{kin}})$ we determine the distribution of internuclear distances $P(R)$ via the Coulomb explosion imaging principle. We report results for LiK and for NaK but our method should should also work for other heteronuclear dimers and for differentiating between different isotopologues of homonuclear dimers.Comment: 10 pages, 11 figure