scholarly journals CUTLASS HF radar observations of high-latitude azimuthally propagating vortical currents in the nightside ionosphere during magnetospheric substorms

2000 ◽  
Vol 18 (6) ◽  
pp. 640-652 ◽  
Author(s):  
J. A. Wild ◽  
T. K. Yeoman
Keyword(s):  
Electric Fields ◽  
Time Resolution ◽  
High Latitude ◽  
High Speed ◽  
Radar Data ◽  
Hf Radar ◽  
High Time ◽  
Vortical Flow ◽  
High Time Resolution ◽  
Magnetospheric Substorms

Abstract. High-time resolution CUTLASS observations and ground-based magnetometers have been employed to study the occurrence of vortical flow structures propagating through the high-latitude ionosphere during magnetospheric substorms. Fast-moving flow vortices (~800 m s-1) associated with Hall currents flowing around upward directed field-aligned currents are frequently observed propagating at high speed (~1 km s-1) azimuthally away from the region of the ionosphere associated with the location of the substorm expansion phase onset. Furthermore, a statistical analysis drawn from over 1000 h of high-time resolution, nightside radar data has enabled the characterisation of the bulk properties of these vortical flow systems. Their occurrence with respect to substorm phase has been investigated and a possible generation mechanism has been suggested.Key words: Ionosphere (auroral ionosphere; electric fields and currents) · Magnetospheric physics (storms and substorms)

scholarly journals CUTLASS/IMAGE observations of high-latitude convection features during substorms

1997 ◽  
Vol 15 (6) ◽  
pp. 692-702 ◽  
Author(s):  
T. K. Yeoman ◽  
H. Lühr
Keyword(s):  
Time Resolution ◽  
High Latitude ◽  
Geomagnetic Latitude ◽  
Hf Radar ◽  
High Time ◽  
Spatial Extent ◽  
Line Of Sight ◽  
Return Flow ◽  
High Time Resolution ◽  
Substorm Activity

Abstract. The CUTLASS Finland HF radar has been operational since February 1995. The radar frequently observes backscatter during the midnight sector from a latitude range 70–75° geographic, latitudes often associated with the polar cap. These intervals of backscatter occur during intervals of substorm activity, predominantly in periods of relatively quiet magnetospheric activity, with Kp during the interval under study being 2- and ΣKp for the day being only 8-. During August 1995 the radar ran in a high time resolution mode, allowing measurements of line-of-sight convection velocities along a single beam with a temporal resolution of 14 s, and measurement of a full spatial scan of line-of-sight convection velocities every four minutes. Data from such scans reveal the radar to be measuring return flow convection during the interval of substorm activity. For three intervals during the period under study, a reduction in the spatial extent of radar backscatter occurred. This is a consequence of D region HF absorption and its limited extent in the present study is probably a consequence of the high latitude of the substorm activity, with the electrojet centre lying between 67° and 71° geomagnetic latitude. The high time resolution beam of the radar additionally demonstrates that the convection is highly time dependent. Pulses of equatorward flow exceeding ~600 m s–1 are observed with a duration of ~5 min and a repetition period of ~8 min. Their spatial extent in the CUTLASS field of view was 400–500 km in longitude, and 300–400 km in latitude. Each pulse of enhanced equatorward flow was preceded by an interval of suppressed flow and enhanced ionospheric Hall conductance. The transient features are interpreted as being due to ionospheric current vortices associated with field aligned current pairs. The relationship between these observations and substorm phenomena in the magnetotail is discussed.

scholarly journals Multi-instrument observations of the electric and magnetic field structure of omega bands

2000 ◽  
Vol 18 (1) ◽  
pp. 99-110 ◽  
Author(s):  
J. A. Wild ◽  
T. K. Yeoman ◽  
P. Eglitis ◽  
H. J. Opgenoorth
Keyword(s):  
Electric Fields ◽  
Time Resolution ◽  
Recovery Phase ◽  
High Time ◽  
High Time Resolution ◽  
Band Formation ◽  
Vhf Radar ◽  
E Region ◽  
Ionospheric Electric Field ◽  
Electric Fields And Currents

Abstract. High time resolution data from the CUTLASS Finland radar during the interval 01:30-03:30 UT on 11 May, 1998, are employed to characterise the ionospheric electric field due to a series of omega bands extending ~5° in latitude at a resolution of 45 km in the meridional direction and 50 km in the azimuthal direction. E-region observations from the STARE Norway VHF radar operating at a resolution of 15 km over a comparable region are also incorporated. These data are combined with ground magnetometer observations from several stations. This allows the study of the ionospheric equivalent current signatures and height integrated ionospheric conductances associated with omega bands as they propagate through the field-of-view of the CUTLASS and STARE radars. The high-time resolution and multi-point nature of the observations leads to a refinement of the previous models of omega band structure. The omega bands observed during this interval have scale sizes ~500 km and an eastward propagation velocity ~0.75 km s-1. They occur in the morning sector (~05 MLT), simultaneously with the onset/intensification of a substorm to the west during the recovery phase of a previous substorm in the Scandinavian sector. A possible mechanism for omega band formation and their relationship to the substorm phase is discussed..Key words. Ionosphere (auroral ionosphere; electric fields and currents) · Magnetospheric physics (magnetosphere-ionosphere interactions)

scholarly journals High‐speed MCP anodes for high time resolution low‐energy charged particle spectrometers

2017 ◽  
Vol 122 (2) ◽  
pp. 1816-1830 ◽  
Author(s):  
Yoshifumi Saito ◽  
Shoichiro Yokota ◽  
Kazushi Asamura ◽  
Amanda Krieger
Keyword(s):  
Charged Particle ◽  
Time Resolution ◽  
High Speed ◽  
Low Energy ◽  
High Time ◽  
High Time Resolution

scholarly journals Substorm dynamics revealed by ground observations of two-dimensional auroral structures on 9 October 2000

2005 ◽  
Vol 23 (12) ◽  
pp. 3599-3613 ◽  
Author(s):  
J. Liang ◽  
E. F. Donovan ◽  
G. J. Sofko ◽  
T. Trondsen
Keyword(s):  
Electric Fields ◽  
Time Resolution ◽  
Plasma Sheet ◽  
Wave Activity ◽  
High Time ◽  
Geosynchronous Orbit ◽  
High Time Resolution ◽  
Two Dimensional ◽  
Mode Instability ◽  
The Third

Abstract. Multi-instrument observations of a small substorm event on 9 October 2000 provide, with high time resolution, two-dimensional information about substorm dynamics. A sequence of three optical intensifications, each associated with a Pi2 burst, were found, in which the third auroral intensification marked the onset of a small substorm. All three intensifications originated close to midnight, but evolved progressively eastward. Within each of the three optical intensifications, a few azimuthally-spaced patches appeared, the first one near midnight and the subsequent patches successively eastward in the postmidnight sector, providing evidence for drift wave activity in the near-geosynchronous-orbit plasma sheet (NGOPS). The SuperDARN measurements reveal the development of eastward electric fields at NGOPS latitude within each Pi2 burst interval. These observations can be interpreted as supporting the drift-Alfvén-ballooning (DAB) mode instability and its role in substorm expansion at NGOPS.

High-Time-Resolution Astrophysics using the Thai 2.4-m Telescope with Ultraspec

2017 ◽  
Vol 14 (S339) ◽  
pp. 185-188
Author(s):  
P. Irawati
Keyword(s):  
Time Resolution ◽  
High Speed ◽  
Period Change ◽  
Low Noise ◽  
High Time ◽  
High Time Resolution ◽  
Third Body ◽  
Data Set ◽  
High Speed Photometry

AbstractThe Thai National Observatory (TNO) is equipped with a 2.4-m Ritchey-Chretien telescope and the high-speed versatile Ultraspec camera. The instrument employs a low-noise frame-transfer EMCCD, suitable for the observation of faint objects and for high-time-resolution astrophysics. We present some of the results obtained in the first four years of operation, focusing particularly on fast photometry of lunar and stellar occultations, and follow-up efforts on a few white-dwarf binaries. Among the latter is the polar cataclysmic variable UZ For. This system displays period changes and is suspected of hosting circumbinary planets. Our high-speed photometry data show a decreasing trend in the O–C diagram of UZ For. Using our new data set, we will investigate whether the period change in this binary is due to a possible third body, or to other mechanism(s).

scholarly journals Investigations of Protein and Biomolecules using a 280 nm or 295 nm Picosecond Laser for High Speed Measurements and High Time Resolution

2020 ◽  
Vol 118 (3) ◽  
pp. 472a
Author(s):  
Christian Oelsner ◽  
Eugeny Ermilov ◽  
Thomas Schönau ◽  
Dietmar Klemme ◽  
Guillaume Delpont ◽  
...  
Keyword(s):  
Time Resolution ◽  
High Speed ◽  
Picosecond Laser ◽  
High Time ◽  
High Time Resolution

Solar Corona Investigation by the Coronal Line Photometer at Lomnický Peak

1994 ◽  
Vol 144 ◽  
pp. 431-434
Author(s):  
M. Minarovjech ◽  
M. Rybanský
Keyword(s):  
Solar Corona ◽  
Time Resolution ◽  
Active Regions ◽  
High Time ◽  
High Time Resolution ◽  
List Type ◽  
Type Number ◽  
Coronal Line ◽  
Global Cycle

AbstractThis paper deals with a possibility to use the ground-based method of observation in order to solve basic problems connected with the solar corona research. Namely:1.heating of the solar corona2.course of the global cycle in the corona3.rotation of the solar corona and development of active regions.There is stressed a possibility of high-time resolution of the coronal line photometer at Lomnický Peak coronal station, and use of the latter to obtain crucial observations.

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