ALBERT

Description: [1]  We investigated ionospheric ion upflow during an auroral substorm using simultaneous EISCAT radar and IMAGE satellite data. Approximately 6 minutes after an initial brightening identified with data from the IMAGE WIC instrument, ion upflow was seen and the electron temperature became enhanced, too. The ion upflow, with a velocity of about 150 m/s, and the electron temperature enhancement lasted for about 25 minutes. During the poleward expansion phase surges of large upward ion velocity and flux, and high ion and electron temperatures occurred over Longyearbyen. The upward ion flux reached 2 × 10 14  m -2  s -1 . Naturally enhanced ion-acoustic lines (NEIALs) were seen near the poleward edge of the expanded auroral oval both near the end of expansion phase 17 minutes after onset and also later in the recovery phase. The NEIALs seemed to be accompanied by another type of enhanced echoes, obliquely to the local geomagnetic field. Data from the LENA instrument on the IMAGE satellite show that energetic neutral oxygen reaches the IMAGE satellite about 40 minutes after the initial brightening, and oxygen continues to get detected during the recovery phase. We propose that ion upflow at the poleward edge of the auroral oval during the expansion phase is related to ion/neutral outflow with energy below 18-27 eV, whereas during the recovery phase of a substorm upward ions are accelerated up to about 60 eV and flow out in the entire polar region.

Description: We experimentally observe the location and angular size of the high-frequency (HF) radio window in the bottomside ionosphere, which permits radio wave propagation to the topside ionosphere, with high angular resolution at the European Incoherent Scatter (EISCAT) facility. HF pump-induced ion line enhancements were observed by the EISCAT UHF incoherent scatter radar on the ionospheric bottomside and topside. The radar zenith angle was scanned in small steps in the magnetic meridian. The HF pump duty cycle was deliberately kept low enough to minimize the growth of artificial field-aligned irregularities. The locations of the bottomside radio window and topside enhanced radar echoes are consistent with the expected position determined by ray tracing performed using the observed plasma densities.

Description: We have investigated characteristics of ion upflow and naturally enhanced ion-acoustic lines (NEIALs) based on the European Incoherent Scatter (EISCAT) Svalbard radar (ESR) data continuously obtained between March 2007 and February 2008. For the ion upflow study we have used approximately 78,000 field-aligned profiles obtained with the ESR. For the NEIAL study we have identified approximately 1500 NEIALs in the ESR data at altitudes between 100 and 500 km. The occurrence frequency of ion upflow shows two peaks, at about 0800 and 1300 magnetic local time (MLT), while only one strong peak is seen around 0900 MLT for NEIALs. The upward ion flux also has only one peak around 1100–1300 MLT. The occurrence frequency of ion upflow varies strongly over season. It is higher in winter than in summer, whereas NEIALs are more frequent in summer than in winter. NEIALs frequently occur under high geomagnetic activity and also high solar activity conditions. Approximately 10% of NEIALs in the F region ionosphere were accompanied by NEIALs in the E region (occurred at altitudes below 200 km). About half of the E region enhanced echoes did not have an F region counterpart. Upshifted NEIALs dominate in the E region whereas downshifted NEIALs are usually stronger above an altitude of 300 km. The high occurrence frequency of NEIALs in the prenoon region (0800–1000 MLT) might be associated with acceleration of thermal ions to suprathermal ones. At the same MLT and geomagnetic latitude suprathermal ions and broadband extremely low frequency (BBELF) wave activity have been observed, according to previous studies.

Description: We report on the first mesoscale combined ionospheric and thermospheric observations, partly in the vicinity of an auroral arc, from Svalbard in the polar cap on 2 February 2010. The EISCAT Svalbard radar employed a novel scanning mode in order to obtain F and E region ion flows over an annular region centered on the radar. Simultaneously, a colocated Scanning Doppler Imager observed the E region neutral winds and temperatures around 110 km altitude using the 557.7 nm auroral optical emission. Combining the ion and neutral data permits the E region Joule heating to be estimated with an azimuthal spatial resolution of ∼64 km at a radius of ∼163 km from the radar. The spatial distribution of Joule heating shows significant mesoscale variation. The ion-neutral collision frequency is measured in the E region by combining all the data over the entire field of view with only weak aurora present. The estimated ion-neutral collision frequency at ∼113 km altitude is in good agreement with the MSIS atmospheric model.

Description: [1]  A new solid state sodium LIDAR installed at Ramjordmoen, Tromsø (69.6 ∘ N, 19.2 ∘ E) started observations of neutral temperature together with sodium density in the Mesosphere-Lower Thermosphere (MLT) region on 1 October 2010. The new LIDAR provided temperature data with a time resolution of 10 min and with good quality between ∼80 and ∼105 km from October 2010 to March 2011. This paper aims at introducing the new LIDAR with its observational results obtained over the first 6 months of observations. We succeeded in obtaining neutral temperature and sodium density data of ∼255.5 hours in total. We obtained seven nights of data sets with continuous observations lasting for 12 hours or longer, which were analyzed in terms of atmospheric waves in the polar MLT region. In order to evaluate our observations, we compared (1) the sodium density with that published in the literature, (2) average temperature and column sodium density data with those obtained with ALOMAR Weber sodium LIDAR, and (3) the neutral temperature data with those obtained by SABER/TIMED satellite. For the night of 5 October 2010, we succeeded in conducting simultaneous observations of the new LIDAR and the EISCAT UHF radar with the tristatic CP-1 mode. Comparisons of neutral and ion temperatures showed a good agreement at 104 km between 0050 and 0230 UT on 6 October 2010 when the electric field strength was smaller, while significant deviations (up to ∼25 K) are found at 107 km. We evaluated contributions of Joule heating and electron-ion heat exchange, but derived values seem to be underestimated.

Description: We report a sporadic sodium layer (SSL), in particular its fine structure, observed at 92–98 km between 20:00 and 23:30 UT (21:00–24:30 LT) on 11 January 2011 using a sodium lidar, which was installed in the European incoherent scatter (EISCAT) radar site at Tromsø, Norway (69.6°N, 19.2°E) in early 2010. The sodium lidar measurement with 5-sec time-resolution reveals the details of dramatic sodium-density increase as well as short-period wavelike structure in the SSL. The rate of increase of height-integrated sodium density at the beginning of the SSL event was 6.4–9.6 × 1010 m−2 s−1. Dominant oscillation periods in the wavelike structures were 7–11 min at 95–98 km and 3 min at 92–95 km. The calculated power spectral densities are well represented by power laws, implying the presence of the short-period waves and turbulence in the frequency range of 10−4–10−1 Hz.

Description: We investigate the condition for the formation of low-mass second-generation stars in the early Universe. It has been proposed that gas cooling by dust thermal emission can trigger fragmentation of a low-metallicity star-forming gas cloud. In order to determine the critical condition in which dust cooling induces the formation of low-mass stars, we follow the thermal evolution of a collapsing cloud by a one-zone semi-analytic collapse model. Earlier studies assume the dust amount in the local Universe, where all refractory elements are depleted on to grains, and/or assume the constant dust amount during gas collapse. In this paper, we employ the models of dust formation and destruction in early supernovae to derive the realistic dust compositions and size distributions for multiple species as the initial conditions of our collapse calculations. We also follow accretion of heavy elements in the gas phase on to dust grains, i.e. grain growth, during gas contraction. We find that grain growth well alters the fragmentation property of the clouds. The critical conditions can be written by the gas metallicity Z cr and the initial depletion efficiency f dep,0 of gas-phase metal on to grains, or dust-to-metal mass ratio, as ( Z cr /10 –5.5 Z ) = ( f dep,0 /0.18) –0.44 with small scatters in the range of Z cr  = [0.06–3.2] 10 –5 Z . We also show that the initial dust composition and size distribution are important to determine Z cr .

Description: Theoretical models and observations have suggested that the increasing greenhouse gas concentration in the troposphere causes the upper atmosphere to cool and contract. However, our understanding of the long-term trends in the upper atmosphere is still quite incomplete, due to a limited amount of available and well-calibrated data. The European Incoherent Scatter (EISCAT) radar has gathered data in the polar ionosphere above Tromsø for over 33 years. Using this long-term data set we have estimated the first significant trends of ion temperature at altitudes between 200 and 450 km. The estimated trends indicate a cooling of 10-15 K/decade near the F-region peak (220-380 km altitude), whereas above 400 km the trend is nearly zero or even warming. The height profiles of the observed trends are close to those predicted by recent atmospheric General Circulation Models. Our results are the first quantitative confirmation of the simulations and of the qualitative expectations.

Description: The making and breaking of atomic bonds are essential processes in chemical reactions. Although the ultrafast dynamics of bond breaking have been studied intensively using time-resolved techniques, it is very difficult to study the structural dynamics of bond making, mainly because of its bimolecular nature. It is especially difficult to initiate and follow diffusion-limited bond formation in solution with ultrahigh time resolution. Here we use femtosecond time-resolved X-ray solution scattering to visualize the formation of a gold trimer complex, [Au(CN)2(-)]3 in real time without the limitation imposed by slow diffusion. This photoexcited gold trimer, which has weakly bound gold atoms in the ground state, undergoes a sequence of structural changes, and our experiments probe the dynamics of individual reaction steps, including covalent bond formation, the bent-to-linear transition, bond contraction and tetramer formation with a time resolution of approximately 500 femtoseconds. We also determined the three-dimensional structures of reaction intermediates with sub-angstrom spatial resolution. This work demonstrates that it is possible to track in detail and in real time the structural changes that occur during a chemical reaction in solution using X-ray free-electron lasers and advanced analysis of time-resolved solution scattering data.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kim, Kyung Hwan -- Kim, Jong Goo -- Nozawa, Shunsuke -- Sato, Tokushi -- Oang, Key Young -- Kim, Tae Wu -- Ki, Hosung -- Jo, Junbeom -- Park, Sungjun -- Song, Changyong -- Sato, Takahiro -- Ogawa, Kanade -- Togashi, Tadashi -- Tono, Kensuke -- Yabashi, Makina -- Ishikawa, Tetsuya -- Kim, Joonghan -- Ryoo, Ryong -- Kim, Jeongho -- Ihee, Hyotcherl -- Adachi, Shin-ichi -- England -- Nature. 2015 Feb 19;518(7539):385-9. doi: 10.1038/nature14163.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701, South Korea [2] Department of Chemistry, KAIST, Daejeon 305-701, South Korea. ; Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan. ; RIKEN SPring-8 Center, Kouto 1-1-1, Sayo, Hyogo 679-5148, Japan. ; Japan Synchrotron Radiation Research Institute, Kouto 1-1-1, Sayo, Hyogo 679-5198, Japan. ; Department of Chemistry, The Catholic University of Korea, Bucheon 420-743, South Korea. ; Department of Chemistry, Inha University, Incheon 402-751, South Korea. ; 1] Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan [2] Department of Materials Structure Science, School of High Energy Accelerator Science, The Graduate University for Advanced Studies, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25693570" target="_blank"〉PubMed〈/a〉

Description: The central few hundred parsecs of the Milky Way host a massive black hole and exhibit very violent gas motion and high temperatures in molecular gas. The origin of these properties has been a mystery for the past four decades. Wide-field imaging of the (12)CO (rotational quantum number J = 1 to 0) 2.6-millimeter spectrum has revealed huge loops of dense molecular gas with strong velocity dispersions in the galactic center. We present a magnetic flotation model to explain that the formation of the loops is due to magnetic buoyancy caused by the Parker instability. The model has the potential to offer a coherent explanation for the origin of the violent motion and extensive heating of the molecular gas in the galactic center.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fukui, Yasuo -- Yamamoto, Hiroaki -- Fujishita, Motosuji -- Kudo, Natsuko -- Torii, Kazufumi -- Nozawa, Satoshi -- Takahashi, Kunio -- Matsumoto, Ryoji -- Machida, Mami -- Kawamura, Akiko -- Yonekura, Yoshinori -- Mizuno, Norikazu -- Onishi, Toshikazu -- Mizuno, Akira -- New York, N.Y. -- Science. 2006 Oct 6;314(5796):106-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Astrophysics, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan. fukui@a.phys.nagoya-u.ac.jp〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17023654" target="_blank"〉PubMed〈/a〉