ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Publication Date: 2012-06-07
    Description: We present the results of a statistical study of the absolute and relative locations of the equatorward boundaries of the proton and diffuse electron auroras. The boundaries were analyzed using latitude scans of 630.0 and 486.0 nm (“Hβ”) emissions obtained with the meridian scanning photometers at Gillam and Pinawa, Canada with DMSP overflights. The aurora data were classified into three different steady geomagnetic activity states, one being long-duration quiet intervals and the other two being moderate and active steady magnetospheric convection (SMC) events. Both case and statistical studies show that the quiet times dusk-premidnight proton aurora extends slightly equatorward of the electron aurora. This is reversed on the dawnside. In contrast, the electron aurora during moderate and active SMC intervals lies equatorward of the proton aurora throughout the entire nightside covered in this work (20–03 MLT). There is a dawn-dusk offset in the auroral oval location, with the proton aurora shifting toward premidnight and the electron aurora toward postmidnight. Moreover, with increasing geomagnetic activity, both of the auroras intrude to lower latitude. The penetration of the electron boundary equatorward of the proton precipitation across this MLT range has not been previously identified. We attribute this to the fact that the equatorward part of the diffuse electron aurora is produced by lower energy electrons to which the 630.0 nm emission is more responsive and so marks a more realistic location of the electron equatorward boundary than do the 557.7 nm and UV emissions used in previous intercomparisons of these boundaries.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Publication Date: 2013-12-13
    Description: [1]  Poleward boundary intensifications (PBIs) are auroral intensifications along the poleward boundary of the auroral oval and occur during all levels of geomagnetic activity. However, little is known about the triggering of PBIs. Recent case studies have indicated the existence of longitudinally localized flow channels in the polar cap near, and directed towards, the nightside open-closed field line boundary just before PBIs. Motivated by these studies, we analyze 115 events of coordinated observations by the THEMIS all-sky imager and SuperDARN HF radar at Rankin Inlet to determine if this polar cap flow-PBI relationship is commonly observed. We start with isolated and intense PBIs and examine the probability of them being associated with equatorward-directed polar cap flows. Our results show the association to be frequent (90%), with one-to-one correlations occurring in ~50% of events. Considering the limitations of the radar observations, this result indicates that PBIs are commonly correlated with polar cap flow channels directed towards, and then traversing, the open-closed field line boundary. The flows statistically occur ~1-2 min before the PBI initiations, and the duration and width of the flows are comparable to those of the PBIs. We also perform a reverse study by starting with isolated polar cap flows and obtain similar results. The remarkably high occurrence of association between enhanced polar cap flows and PBIs indicates that enhanced meso-scale flows within the open field line region that traverse the open-closed field line boundary are an important driver of PBI formation.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Publication Date: 2017-06-07
    Description: This study conducted the first extensive and comprehensive investigation of the regional-scale sedimentary polycyclic aromatic hydrocarbons (PAHs) concentration, flux, and budget in the continental shelves of the Eastern China Marginal Seas (ECMSs). Surface sediment samples from multiple sites were collected and assessed, and the latest data from current research was assessed. The spatial distribution pattern of PAHs in the ECMSs was significantly influenced by the regional hydrodynamics, sediment properties (grain-size, total organic carbon (TOC) content, and sedimentation rate), and anthropogenic impacts. Relatively higher PAHs concentrations occurred in areas with fine-grained sediment. Results of source apportionment found that the relative proportions of PAHs showed significant regional variation, mainly influenced by socio-economic differences between north and south China. The PAHs burial flux in the study area ranged from 11.2 to 1308 ng cm −2 y −1 with an average value of 101 ± 104 ng cm −2 y −1 . The area-integrated sedimentary PAHs burial flux across the ECMSs was 494 t y −1 . A mass budget calculation revealed that riverine input and atmospheric deposition were the most significant sources contributing, 28.4% and 71.6%, respectively. The study demonstrated that net PAHs transportation occurs between the Bohai Sea (BS) and Yellow Sea (YS), with a flux of approximately 10.2 t y −1 . PAHs were also transported from YS to the East China Sea (ECS), due to water exchange between the YS and ECS. Additionally, substantial amounts of PAHs in the inner shelf of the ECS were transported out of the shelf area due to cross-shelf plume.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Publication Date: 2019
    Description: Abstract Drifting electron holes (DEHs), manifesting as sudden but mild dropout in electron flux, are a common phenomenon seen in the Earth's magnetosphere. It manifests the change of the state of the magnetosphere. However, previous studies primarily focus on DEHs during geomagnetically active time (e.g. substorm). Not until recently have quiet‐time DEHs been reported. In this paper, we present a systematic study on the quiet‐time DEHs. BeiDa Imaging Electron Spectrometer (BD‐IES) measurements from 2015 to 2017 are investigated. Twenty‐two DEH events are identified. The DEHs cover the whole energy range of BD‐IES (50‐600 keV). Generally, the DEHs are positively dispersive with respect to energy. Time‐of‐flight analysis suggests the dispersion results from electron drift motion, and gives the location where the DEHs originated from. Statistics reveals the DEHs primarily originated from the post‐midnight magnetosphere. In addition, superposed epoch analysis applied to geomagnetic indices and solar wind parameters indicates these DEH events occurred during geomagnetically quiet time. No storm or substorm activity could be identified. However, an investigation of nightside midlatitude ground magnetic records suggests these quiet‐time DEHs were accompanied by Pi2 pulsations. The DEH‐Pi2 connection indicates a possible DEH‐bursty bulk flow (BBF) connection, since nightside midlatitude Pi2 activity is generally attributed to magnetotail BBFs. This connection is also supported by a case study of coordinated magnetotail observations from Magnetospheric Multiscale spacecraft. Therefore, we suggest the quiet‐time DEHs could be caused by the magnetotail BBFs, similar to the substorm‐time DEHs.
    Print ISSN: 2169-9380
    Electronic ISSN: 2169-9402
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Publication Date: 2016-01-01
    Print ISSN: 0002-1962
    Electronic ISSN: 1435-0645
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Publication Date: 2003-07-01
    Print ISSN: 0932-8351
    Electronic ISSN: 1437-0999
    Topics: Architecture, Civil Engineering, Surveying
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Publication Date: 2003-12-01
    Print ISSN: 0932-8351
    Electronic ISSN: 1437-0999
    Topics: Architecture, Civil Engineering, Surveying
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...