scholarly journals Statistics of the field-aligned currents at the high-latitude energetic electron boundaries in the nightside: Cluster observation

2016 ◽  
Vol 121 (3) ◽  
pp. 1979-1989 ◽  
Author(s):  
Jie Ren ◽  
Q. G. Zong ◽  
X. Z. Zhou ◽  
Hui Zhang ◽  
S. Y. Fu ◽  
...  
Keyword(s):  
High Latitude ◽  
Energetic Electron

scholarly journals Magnetic topology of coronal mass ejection events out of the ecliptic: Ulysses/HI-SCALE energetic particle observations

2003 ◽  
Vol 21 (6) ◽  
pp. 1249-1256 ◽  
Author(s):  
O. E. Malandraki ◽  
E. T. Sarris ◽  
G. Tsiropoula
Keyword(s):  
Magnetic Field ◽  
High Latitude ◽  
Energetic Particle ◽  
Large Scale ◽  
Energetic Electron ◽  
Solar Energetic Particle ◽  
Interplanetary Coronal Mass Ejections ◽  
Interplanetary Magnetic Fields ◽  
Interplanetary Physics ◽  
Field Lines

Abstract. Solar energetic particle fluxes (Ee > 38 keV) observed by the ULYSSES/HI-SCALE experiment are utilized as diagnostic tracers of the large-scale structure and topology of the Interplanetary Magnetic Field (IMF) embedded within two well-identified Interplanetary Coronal Mass Ejections (ICMEs) detected at 56° and 62° south heliolatitudes by ULYSSES during the solar maximum southern high-latitude pass. On the basis of the energetic solar particle observations it is concluded that: (A) the high-latitude ICME magnetic structure observed in May 2000 causes a depression in the solar energetic electron intensities which can be accounted for by either a detached or an attached magnetic field topology for the ICME; (B) during the traversal of the out-of-ecliptic ICME event observed in July 2000 energetic electrons injected at the Sun are channeled by the ICME and propagate freely along the ICME magnetic field lines to 62° S heliolatitude.Key words. Interplanetary physics (energetic particles; interplanetary magnetic fields)

scholarly journals Energetic electron precipitation during substorm injection events: High-latitude fluxes and an unexpected midlatitude signature

2008 ◽  
Vol 113 (A10) ◽  
Author(s):  
Mark A. Clilverd ◽  
Craig J. Rodger ◽  
James Brundell ◽  
John Bähr ◽  
Neil Cobbett ◽  
...  
Keyword(s):  
High Latitude ◽  
Energetic Electron ◽  
Electron Precipitation ◽  
Substorm Injection

scholarly journals Sub-ionospheric VLF signal anomaly due to geomagnetic storms: a statistical study

2015 ◽  
Vol 33 (11) ◽  
pp. 1457-1467 ◽  
Author(s):  
K. Tatsuta ◽  
Y. Hobara ◽  
S. Pal ◽  
M. Balikhin
Keyword(s):  
Geomagnetic Storm ◽  
High Latitude ◽  
Geomagnetic Storms ◽  
Energetic Electron ◽  
Low Frequency ◽  
Signal Amplitude ◽  
Occurrence Rate ◽  
Statistical Parameters ◽  
Time Period ◽  
Propagation Paths

Abstract. We investigate quantitatively the effect of geomagnetic storms on the sub-ionospheric VLF/LF (Very Low Frequency/Low Frequency) propagations for different latitudes based on 2-year nighttime data from Japanese VLF/LF observation network. Three statistical parameters such as average signal amplitude, variability of the signal amplitude, and nighttime fluctuation were calculated daily for 2 years for 16–21 independent VLF/LF transmitter–receiver propagation paths consisting of three transmitters and seven receiving stations. These propagation paths are suitable to simultaneously study high-latitude, low-mid-latitude and mid-latitude D/E-region ionospheric properties. We found that these three statistical parameters indicate significant anomalies exceeding at least 2 times of their standard deviation from the mean value during the geomagnetic storm time period in the high-latitude paths with an occurrence rate of anomaly between 40 and 50 % presumably due to the auroral energetic electron precipitation. The mid-latitude and low-mid-latitude paths have a smaller influence from the geomagnetic activity because of a lower occurrence rate of anomalies even during the geomagnetically active time period (from 20 to 30 %). The anomalies except geomagnetic storm periods may be caused by atmospheric and/or lithospheric origins. The statistical occurrence rates of ionospheric anomalies for different latitudinal paths during geomagnetic storm and non-storm time periods are basic and important information not only to identify the space weather effects toward the lower ionosphere depending on the latitudes but also to separate various external physical causes of lower ionospheric disturbances.

scholarly journals Energetic electrons along the high-latitude magnetopause

2012 ◽  
Vol 30 (6) ◽  
pp. 1003-1013 ◽  
Author(s):  
B. M. Walsh ◽  
S. E. Haaland ◽  
P. W. Daly ◽  
E. A. Kronberg ◽  
T. A. Fritz
Keyword(s):  
High Latitude ◽  
Energetic Particle ◽  
Energetic Electron ◽  
High Potential ◽  
Trapping Region ◽  
Particle Layer ◽  
Reconnection Region ◽  
Electron Layer ◽  
Time Periods

Abstract. A case study is presented to determine the source of the energetic electron layer frequently observed along the high-latitude magnetopause. Measurements by the Cluster spacecraft show bursts of field-aligned electrons occurring during time periods with high potential for dayside reconnection. These properties are compared with the expected signatures from several sources including escape from the exterior cusp, acceleration in a reconnection region, and release from the dayside trapping region through reconnection. The observed properties are most consistent with the electrons being released from the magnetosphere due to reconnection. In this model the electrons would flow along the newly reconnected IMF draped along the magnetopause and propagate along the high-latitude magnetopause. These observations demonstrate an active source for populating the energetic particle layer frequently observed along and just outside the high-latitude magnetopause.

scholarly journals Response of the High-latitude Upper Mesosphere to Energetic Electron Precipitation

2020 ◽  
Vol 893 (1) ◽  
pp. 55
Author(s):  
Zicheng Zou ◽  
Xianghui Xue ◽  
Wen Yi ◽  
Chenglong Shen ◽  
Chengyun Yang ◽  
...  
Keyword(s):  
High Latitude ◽  
Energetic Electron ◽  
Electron Precipitation

scholarly journals Simulation study for ground-based Ku-band microwave observations of ozone and hydroxyl in the polar middle atmosphere

2018 ◽  
Author(s):  
David A. Newnham ◽  
Mark A. Clilverd ◽  
Michael Kosch ◽  
Pekka T. Verronen
Keyword(s):  
High Latitude ◽  
Climate Models ◽  
Middle Atmosphere ◽  
Energetic Electron ◽  
Geomagnetic Latitude ◽  
Global Climate Models ◽  
Frequency Resolution ◽  
Calibration Data ◽  
Model Calculations ◽  
Ku Band

Abstract. The Ku-band microwave frequencies (10.70–14.25 GHz) overlap emissions from ozone (O3) at 11.072 GHz and hydroxyl radical (OH) at 13.441 GHz. These important chemical species in the polar middle atmosphere respond strongly to high latitude geomagnetic activity associated with space weather. Atmospheric model calculations predict that energetic electron precipitation (EEP) driven by magnetospheric sub storms produces large changes in polar mesospheric O3 and OH. The EEP typically peaks at geomagnetic latitudes ~ 65° and evolves rapidly with time longitudinally and over the geomagnetic latitude range 60°–80°. Previous atmospheric modelling studies have shown that during sub storms OH abundance can increase by more than an order of magnitude at 64–84 km and mesospheric O3 losses can exceed 50 %. In this work, an atmospheric simulation and retrieval study has been performed to determine the requirements for passive microwave radiometers capable of measuring diurnal variations in O3 and OH profiles from high latitude northern hemisphere and Antarctic locations to verify model predictions. We show that, for a 11.072 GHz radiometer making 6 h spectral measurements with 10 kHz frequency resolution and root mean square baseline noise of 1 mK, O3 could be profiled over 8 × 10−4–0.22 hPa (~ 98–58 km) with 10–17 km height resolution and ~ 1 ppmv uncertainty. For the equivalent 13.441 GHz measurements with vertical sensor polarisation, OH could be profiled over 3 × 10−3–0.29 hPa (~ 90–56 km) with 10–17 km height resolution and ~ 3 ppbv uncertainty. The proposed observations would be highly applicable to studies of EEP, atmospheric dynamics, planetary scale circulation, chemical transport, and the representation of these processes in polar and global climate models. Such observations would provide a relatively low cost alternative to increasingly sparse satellite measurements of the polar middle atmosphere, extending long-term data records and also providing ground truth calibration data.

scholarly journals Conjugate high-intensity energetic electron precipitation at high latitude

2003 ◽  
Vol 21 (7) ◽  
pp. 1443-1455 ◽  
Author(s):  
T. Christensen ◽  
N. Østgaard ◽  
T. J. Rosenberg ◽  
D. L. Detrick ◽  
G. A. Germany ◽  
...  
Keyword(s):  
High Latitude ◽  
Energetic Electron ◽  
Precipitation Event ◽  
Expansion Phase ◽  
X Ray ◽  
Precipitation Region ◽  
Evening Sector ◽  
Storms And Substorms ◽  
Far Ultraviolet ◽  
Flow Burst

Abstract. On 6 August 1998 an intense precipitation event occurring at high latitude in the evening sector was observed by X-ray and far-ultraviolet imagers on board the Polar satellite and by several ground-based instruments. The precipitation region was centred at approximately 19:00 MLT at 74° MLAT (at an L-shell of about 13). The event started at 22:59 UT and lasted about 10 minutes. It happened during the late expansion phase of a substorm after two hours of strongly southward IMF. Imaging riometers at geomagnetically conjugate sites recorded strong absorption levels which exceeded 7 dB at 38 MHz in a transient and localized intensification occurring within a poleward moving arc-like feature. The temporal and spatial similarities between the recordings from the two conjugate regions are remarkable. The arc-like precipitation region progressed poleward with a velocity of 1.5 km/s. Ground magnetometers co-located with the imaging riometers observed disturbances consistent with poleward moving westward currents. In X-ray and riometer images which are sensitive only to energetic electrons (above 5–10 keV) the event seems isolated, but in UV images the event is seen to occur on the poleward edge of the rapidly poleward expanding evening side aurora. The energy spectrum of precipitating electrons was subject to a temporary hardening which peaked at a mean energy of about 20 keV when the event was at its most intense at 23:02 UT. The event is likely to have been caused by an accelerating mechanism at some height above the ionosphere or by an earthward flow burst in the magnetotail, or possibly both.Key words. Magnetospheric physics (energetic particles, precipitating; storms and substorms; magnetosphere-ionosphere interactions)

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