Can magnetotail reconnection produce the auroral intensities observed in the conjugate ionosphere?

[1] In a recent case study, Borg et al. (2007) reported that an inverted V structure, caused by a field-aligned potential drop of 30 kV producing very strong X-ray aurora, was found in connection with tail reconnection. However, the in situ particle measurements indicated clearly that the particles responsible for the X-ray aurora were not accelerated by the reconnection process. In this article, we report the predicted auroral intensities of thirteen reconnection events where Cluster passed through the reconnection region. For six of the events, global auroral imaging data were available and the predicted auroral intensities could be compared with the observed intensities. Our main findings are as follows: (1) Acceleration in the reconnection region is generally not sufficient to account for the observed auroral intensities. (2) Additional acceleration between the reconnection region and the ionosphere is needed to explain the auroral intensities. Although we see signatures that point toward potential drops at the flanks of bursty bulk flows (BBFs), we also find signatures of Alfvén wave accelerated electrons at 700 km and we are not able to determine the most likely acceleration mechanism. (3) The reconnection events are observed 2–14 min after substorm onset and indicate that reconnection is an expanding process observed along the poleward boundary of the aurora.publishedVersio

Timescales of Dayside and Nightside Field-Aligned Current Response to Changes in Solar Wind-Magnetosphere Coupling

Principal component analysis is performed on Birkeland or field-aligned current (FAC) measurements from the Active Magnetosphere and Planetary Electrodynamics Response Experiment, to determine the response of dayside and nightside FACs to reversals in the orientation of the interplanetary magnetic field (IMF) and the occurrence of substorms. Dayside FACs respond promptly to changes in IMF BY, but the nightside response is delayed by up to an hour and can take up to 4 hr to develop fully, especially during northward IMF. Nightside FAC asymmetries grow during substorm growth phase when the IMF has a significant BY component, and also promptly at substorm onset. Our findings suggest that magnetotail twisting and/or BY penetration into the magnetotail, due to subsolar reconnection with east-west orientated IMF, are the main cause of these nightside FAC asymmetries and that asymmetries also arise due to magnetotail reconnection of these twisted field lines

Kartlegging av kardiovaskulær risiko i en akutt psykoseenhet og videreføring av informasjon til DPS

Kunnskapsgrunnlaget: Pasienter som er under behandling for psykose er i en høyrisikogruppe for utvikling av metabolsk syndrom og kardiovaskulær sykdom med betydelig reduserte livsutsikter. I henhold til de norske nasjonale retningslinjer anbefales måling av vekt, KMI og blodlipider før oppstart av behandling. Videre anbefales jevnlig oppfølging av disse parameterne for raskt å kunne intervenere ved tegn til utvikling av metabolsk syndrom. Dagens praksis: Dagens Praksis ved Psykose 4 ved Ullevål Sykehus bekrefter antagelsen om at psykosepasienter ikke blir tilstrekkelig fulgt opp med tanke på hjerte-kar sykdommer. Selv om avdelingen gjør mye bra og har et bevisst forhold til kosthold og aktivitet, vil innføring av ytterligere tiltak kunne gi bedre somatisk oppfølgning av disse pasientene. For eksempel brukes det ikke systematiske screeningsverktøy for kardiovaskulær-risikoberegning. Dette vil gi et godt utgangspunkt for de instanser som skal behandle pasienten videre. Per i dag fungerer ikke overlevering av slik informasjon (epikrise) optimalt. Tiltak: Hovedmålet er å systematisere screeningen for hjerte- og karsykdom, slik at den videre oppfølgingen blir optimalisert. Vi foreslår å ta i bruk NORRISK kalkulatoren til å beregne totalrisiko for utvikling av hjerte- og karsykdom (tiltak 1) og iverksette adekvate behandlingstiltak deretter. I noen tilfeller vil være naturlig at den videre oppfølgingen og oppstart av medikamentell behandling, foretas av andre helseinstitusjoner, som fastlege, DPS og annet. Vi foreslår derfor å innføre en revidert standardisert epikrisemal (tiltak 2) for å bedre informasjonsflyten. Til sist, vil det være nødvendig å avholde et informasjonsmøte (tiltak 3) før noen av tiltakene kan settes ut i praksis. Indikatorer: Vi har valgt struktur- og prosessindikatorer og foreslår implementering av NORRISK dokumentering i pasientjournal og i epikrisen. Ledelse og gjennomføring: For å sikre god implementering av nye tiltak i avdelingen er det viktig med tydelig ledelse og god informasjon til de ansatte. Avdelingsoverlege bør gjennom endring i epikrisemal og informasjon til legene sørge for at det blir gitt tydelig dokumentasjon av pasientens kardiovaskulære risiko videre til fastlege og DPS. Avdelingssykepleier bør ta ansvar for informasjon av ansatte som fungerer som pasientkontakter, samt tilgjengelig dokumentasjon i kartleggingsskjema. Tidligere spørreskjema har vist diskrepans mellom holdninger og praksis angående forebygging av kardiovaskulær sykdom, noe som trolig vil lette innføring av tiltakene. Kvalitetssikring gjøres ved å kontrollere at tiltakene er gjennomført for hver utskrevne pasient, samt eventuelt gjennomføre ny spørreundersøkelse og PDSA-sirkler. Diskusjon og konklusjon: Til tross for mangel på gode studier som viser at screening for metabolsk syndrom og kardiovaskulære risikofaktorer fører til mindre kardiovaskulær sykdom og død hos psykosepasienter, er det enighet i norske og internasjonale retningslinjer om at det skal gjennomføres. Vi anser tiltakene våre som fullt ut gjennomførbare på akuttpsykiatrisk psykoseenhet på Ullevål sykehus og at disse vil bedre forebygging av hjerte- karsykdom hos psykosepasienter

North-south asymmetries in cold plasma density in the magnetotail lobes: Cluster observations

In this paper, we present observations of cold (0–70 eV) plasma density in the magnetotail lobes. The observations and results are based on 16 years of Cluster observation of spacecraft potential measurements converted into local plasma densities. Measurements from all four Cluster spacecraft have been used, and the survey indicates a persistent asymmetry in lobe density, with consistently higher cold plasma densities in the northern lobe. External influences, such as daily and seasonal variations in the Earth's tilt angle, can introduce temporary north‐south asymmetries through asymmetric ionization of the two hemispheres. Likewise, external drivers, such as the orientation of the interplanetary magnetic field can set up additional spatial asymmetries in outflow and lobe filling. The persistent asymmetry reported in this paper is also influenced by these external factors but is mainly caused by differences in magnetic field configuration in the Northern and Southern Hemisphere ionospheres

The asymmetric geospace as displayed during the geomagnetic storm on 17 August 2001

Previous studies have shown that conjugate auroral features are displaced in the two hemispheres when the interplanetary magnetic field (IMF) has a transverse (Y) component. It has also been shown that a BY component is induced in the closed magnetosphere due to the asymmetric loading of magnetic flux in the lobes following asymmetric dayside reconnection when the IMF has a Y component. The magnetic field lines with azimuthally displaced footpoints map into a “banana”-shaped convection cell in one hemisphere and an “orange”-shaped cell in the other. Due to the Parker spiral our system is most often exposed to a BY-dominated IMF. The dipole tilt angle, varying between ±34∘, leads to warping of the plasma sheet and oppositely directed BY components in dawn and dusk in the closed magnetosphere. As a result of the Parker spiral and dipole tilt, geospace is asymmetric most of the time. The magnetic storm on 17 August 2001 offers a unique opportunity to study the dynamics of the asymmetric geospace. IMF BY was 20–30 nT and tilt angle was 23∘. Auroral imaging revealed conjugate features displaced by 3–4 h magnetic local time. The latitudinal width of the dawnside aurora was quite different (up to 6∘) in the two hemispheres. The auroral observations together with convection patterns derived entirely from measurements indicate dayside, lobe and tail reconnection in the north, but most likely only dayside and tail reconnection in the Southern Hemisphere. Increased tail reconnection during the substorm expansion phase reduces the asymmetry

Timescales of dayside and nightside field-aligned current response to changes in solar wind-magnetosphere coupling

Principal component analysis is performed on Birkeland or field-aligned current (FAC) measurements from the Active Magnetosphere and Planetary Electrodynamics Response Experiment, to determine the response of dayside and nightside FACs to reversals in the orientation of the interplanetary magnetic field (IMF) and the occurrence of substorms. Dayside FACs respond promptly to changes in IMF BY, but the nightside response is delayed by up to an hour and can take up to 4 hr to develop fully, especially during northward IMF. Nightside FAC asymmetries grow during substorm growth phase when the IMF has a significant BY component, and also promptly at substorm onset. Our findings suggest that magnetotail twisting and/or BY penetration into the magnetotail, due to subsolar reconnection with east-west orientated IMF, are the main cause of these nightside FAC asymmetries and that asymmetries also arise due to magnetotail reconnection of these twisted field lines.</p