Periodic auroral events at the high-latitude convection reversal in the 16 MLT region

Combined optical and radar observations of two breakup-like auroral events near the polar cap boundary, within 74–76° MLAT and 1210 – 1240 UT (roughly 1540 – 1610 MLT) on 9 Jan. 1989 are reported. A two-component structure of the auroral phenomenon is indicated, with a local intensification of the pre-existing arc as well as a separate, tailward moving discrete auroral event on the poleward side of the background aurora, close to the reversal between well-defined zones of sunward and tailward ion flows. The all-sky TV observations do not indicate a connection between the two components, which also show different optical spectral composition. The 16 MLT background arc is located on sunward convecting field lines, as opposed to the 12–14 MLT auroral emission observed on this day. Although the magnetospheric plasma source (s) of the 16 MLT events are not easily identified from these ground-based data alone, it is suggested that the lower and higher latitude components, may map to the plasma sheet boundary layer and along open field lines to the magnetopause boundary, respectively. The events occur at the time of enhancements of westward ionospheric ion flow and corresponding eastward electrojet current south of 74° MLAT. Thus, they seem to be very significant events, involving periodic (10 min period), tailward moving filaments of field-aligned current/discrete auroral emission at the 16 MLT polar cap boundary

Bruk av farger som støtte i leseopplæringen : Kan bruk av farger i leseopplæringen være med og gi elever med lese- og skrivevansker bedre avkodings- og staveferdigheter?

Sammendrag Dette prosjektet er en effektundersøkelse, der det prøves ut bruk av farger i lese- og skriveopplæringen for elever som gjennom tidligere lese- og skriveopplæring ikke har oppnådd funksjonelle avkodings- og staveferdigheter. Dette gjøres ved å se på effekten ved bruk av farger i leseopplæringen, på avkodings- og staveferdighetene til elevene som er med i undersøkelsen. Bruk av farger i lese- og skriveopplæringen prøves ut på fire elever, to på 5. trinn og to på 7. trinn, som alle strever med lesing og skriving, og som tidligere har blitt undervist i tiltak rettet inn mot styrking av avkodings- og staveferdighetene. Problemstillingen er som følger: Kan bruk av farger i leseopplæringen være med å gi elever med lese- og skrivevansker bedre avkodings- og staveferdigheter? Prosjektet har en kvasi-eksperimentell design, der en liten gruppe elever er gitt en ”eksperimentell” påvirkning/intervensjon, for så å undersøke effekten av påvirkningen. Denne typen design vil kunne redegjøre for eventuelle korttidseffekter intervensjonen fører til, men ut i fra at det er foretatt flere målinger på disse elevene både pre- og post- i forhold til igangsatt intervensjon, skal en også, ved å ta utgangspunkt i en ”base-line”-kurve på førtestene, til en viss grad kunne estimere langtidseffekter (Thorleif Lund i Thorleif Lund, Thor Arnfinn Kleven, Tone Kvernbekken & Knut-Andreas Christophersen, 2002). Lund (2002) referer til denne typen design som ”Avbrutt-tidsserie-design”. For å kunne bruke denne måten å estimere langtidseffekter på er det, i følge Lund, viktig med et tilstrekkelig antall målinger før og etter intervensjonen. Lund oppgir at to målinger før og to etter intervensjonen som et minimum. I mitt prosjekt er det foretatt tre pre-tester og tre post-tester, som vil danne grunnlaget for evaluering av eventuell effekt av intervensjonen. I forhold til å kunne trekke noen generaliserende slutninger, er utvalget i prosjektet så lite, at det ikke vil være mulig. Men en vil kunne få noen indikasjoner på om dette eventuelt er interessant for videre forskning. Resultatet viste at alle elevene hadde en effekt av intervensjonen med hensyn til lesehastighet og lesesikkerhet. De hadde bedret sine avkodingsferdigheter. Effektstørrelsen regnet ut på endringen i gjennomsnittsverdien på tre pre-tester og tre post-tester, ga et resultat på henholdsvis d = 1,04 – 1,67 – 5,3 -5,81 for lesehastighet og d = 1,04 – 1,30 – 1,74 – 4,65 for leseforståelsen hos de fire elevene. Med hensyn til staveferdigheten, var resultatene mer tvetydig. To av elevene hadde en effektstørrelse som tilsa at intervensjonen hadde gitt positivt resultat (d=1,32 og 2,1), mens resultatene til de to andre viste liten eller ingen effekt (d=0,17 og 0,65). I gjennom prosjektet er problemstillingen: Kan bruk av farger i leseopplæringen være med å gi elever med lese- og skrivevansker bedre avkodings- og staveferdigheter? blitt besvart. Resultatene viser at alle elevene har bedret sine avkodingsferdigheter, men ikke alle elevene har i vesentlig grad bedret sine staveferdigheter. Likevel er resultatene såpass interessante, at det burde være grunnlag for å forske videre på ulike aspekter av bruk av farge i leseopplæringen for elever som strever med å tilegne seg funksjonelle avkodings- og staveferdigheter

The Ill-Posed Problem in Growth Empirics

A problem encountered in growth empirics is that the number of explanatory variables is large compared to the number of observations. This makes it impossible to condition on all regressors when determining if a variable is important. We investigate methods used to resolve this problem: Extreme bounds, Sala-i-Martin’s test, BACE, general-to-specific, minimum t-statistics, BIC and AIC. We prove that the problem in general is ill-posed and that the existing methods are inconsistent. We propose a test and apply it to determine if "good policy" increases the effectiveness of foreign aid on growth. The test rejects inference regarding good policy.AIC; BACE; BIC; extreme bounds; general-to-specific; ill-posed inverse problem; robustness

Building stock dynamics and its impacts on materials and energy demand in China

China hosts a large amount of building stocks, which is nearly 50 billion square meters. Moreover, annual new construction is growing fast, representing half of the world's total. The trend is expected to continue through the year 2050. Impressive demand for new residential and commercial construction, relative shorter average building lifetime, and higher material intensities have driven massive domestic production of energy intensive building materials such as cement and steel. This paper developed a bottom-up building stock turnover model to project the growths, retrofits and retirements of China's residential and commercial building floor space from 2010 to 2050. It also applied typical material intensities and energy intensities to estimate building materials demand and energy consumed to produce these building materials. By conducting scenario analyses of building lifetime, it identified significant potentials of building materials and energy demand conservation. This study underscored the importance of addressing building material efficiency, improving building lifetime and quality, and promoting compact urban development to reduce energy and environment consequences in China

Plasma flows, Birkeland currents and auroral forms in relation to the Svalgaard-Mansurov effect

The traditional explanation of the polar cap magnetic deflections, referred to as the Svalgaard-Mansurov effect, is in terms of currents associated with ionospheric flow resulting from the release of magnetic tension on newly open magnetic field lines. In this study, we aim at an updated description of the sources of the Svalgaard-Mansurov effect based on recent observations of configurations of plasma flow channels, Birkeland current systems and aurorae in the magnetosphere-ionosphere system. Central to our description is the distinction between two different flow channels (FC 1 and FC 2) corresponding to two consecutive stages in the evolution of open field lines in Dungey cell convection, with FC 1 on newly open, and FC 2 on old open, field lines. Flow channel FC 1 is the result of ionospheric Pedersen current closure of Birkeland currents flowing along newly open field lines. During intervals of nonzero interplanetary magnetic field <I>B</I>_y component FC 1 is observed on either side of noon and it is accompanied by poleward moving auroral forms (PMAFs/prenoon and PMAFs/postnoon). In such cases the next convection stage, in the form of flow channel FC 2 on the periphery of the polar cap, is particularly important for establishing an IMF <I>B</I>_y-related convection asymmetry along the dawn-dusk meridian, which is a central element causing the Svalgaard-Mansurov effect. FC 2 flows are excited by the ionospheric Pedersen current closure of the northernmost pair of Birkeland currents in the four-sheet current system, which is coupled to the tail magnetopause and flank low-latitude boundary layer. This study is based on a review of recent statistical and event studies of central parameters relating to the magnetosphere-ionosphere current systems mentioned above. Temporal-spatial structure in the current systems is obtained by ground-satellite conjunction studies. On this point we emphasize the important information derived from the continuous ground monitoring of the dynamical behaviour of aurora and plasma convection during intervals of well-organised solar wind plasma and magnetic field conditions in interplanetary coronal mass ejections (ICMEs) during their Earth passage

Polar observations of ion/electron bursts at the pre-dawn polar cap boundary: evidence for internal reconnection of overdraped lobe flux

Observations made by Polar of ion-electron bursts on the dawn side of the polar cap are presented. They occurred when conditions external to the magnetosphere corresponded to that of the sheath region of a magnetic cloud, which was characterized by very high densities/dynamic pressure and a magnetic field which was strong in all components and which was tilted antisunward (Bx\u3c0) and northward (Bz\u3e0) with its clock angle lying between 20 and 90° (By: 8–15 nT). A clear temporal development in the energy range spanned by the individual ion bursts (from 0.2–2 keV to 1–10 keV) was present. We relate this to a corresponding temporal evolution in the cloud sheath field and plasma. We analyze the solar wind-magnetosphere aspects of the observations using the concepts of (i) (i) overdraped lobe flux, (ii) Bx- and By-regulated sequential reconnections in opposite hemispheres (magnetopause and internal modes), and (iii) newly-closed magnetic flux. In particular, we find that the most energetic ion bursts (accompanied by bi-directionally streaming electrons at 1–10 keV and intense magnetosheath-origin fluxes) are located on newly closed field lines generated by internal reconnection occurring between overdraped lobe field lines and the closed geomagnetic field. This result corroborates a topology of lobe reconnection under conditions of dipole tilt and/or nonzero IMF Bx component advanced by Watanabe et al. (2006), which in our case is adapted to nonzero IMF By conditions

Monitoring magnetosheath-magnetosphere interconnection topology from the aurora

International audienceA strong southward rotation of the IMF (BZ from 5 to -6 nT in ~ 20 s) on 4 January 1995 caused an abrupt reconfiguration of midday aurorae and plasma convection consisting of the following: (1) the red-line aurora associated with magnetosheath plasma transfer at the low-latitude magnetopause appeared at the same time that (2) the green-line aurora from precipitating energetic plasma sheet particles equatorward of the cusp (near the open-closed field line boundary) weakened visibly and shifted equatorward, (3) the high-latitude aurora during the previous northward IMF, which is associated with lobe reconnection, persisted briefly (3 min) and brightened, before it disappeared from the field-of-view, (4) the activation of a strong convection bay (DPY current) at cusp and sub-cusp latitudes when the field turned strongly south, (5) a distinct wave motion of the plasma sheet outer boundary, as inferred from the aurora, which correlates closely with Pc 5 magnetic pulsations. Our interpretation of the dramatic reconfiguration is that reconnection poleward of the cusp coexisted briefly with reconnection at sub-cusp latitudes. The latter provided a magnetic field connection which enabled, on the one hand, magnetosheath particles to enter and cause the red-line cusp aurora, and on the other hand, allowed for magnetospheric energetic particles to escape and weaken the outer plasma sheet source of the green-line emission. The coexistence of the two cusp auroras reflects the time required for one field line topology to replace another, which, under the prevailing high speed wind ( ~ 650 km/s), lasts ~ 3?4 min. The motion of open flux tubes propagating from equator to pole during this transition is traced in the aurora by a poleward moving form. The waves on the outer boundary of the plasma sheet are most likely due to the Kelvin-Helmholtz instability. The study illustrates the ability of local auroral observations to monitor even a global change in magnetospheric magnetic topology