scholarly journals Magnetic local time, substorm, and particle precipitation-related variations in the behaviour of SuperDARN Doppler spectral widths

2004 ◽  
Vol 22 (12) ◽  
pp. 4103-4122 ◽  
Author(s):  
M. L. Parkinson ◽  
G. Chisham ◽  
M. Pinnock ◽  
P. L. Dyson ◽  
J. C. Devlin
Keyword(s):  
Spectral Width ◽  
Auroral Oval ◽  
Auroral Zone ◽  
Lower Latitude ◽  
Velocity Spread ◽  
Doppler Velocity ◽  
High Time Resolution ◽  
Particle Precipitation ◽  
Study Interval ◽  
Present Case Study

Abstract. Super Dual Auroral Radar Network (DARN) radars often detect a distinct transition in line-of-sight Doppler velocity spread, or spectral width, from <50ms–1 at lower latitude to >200ms–1 at higher latitude. They also detect a similar boundary, namely the range at which ionospheric scatter with large spectral width suddenly commences (i.e. without preceding scatter with low spectral width). The location and behaviour of the spectral width boundary (SWB) (and scatter boundary) and the open-closed magnetic field line boundary (OCB) are thought to be closely related. The location of the nightside OCB can be inferred from the poleward edge of the auroral oval determined using energy spectra of precipitating particles measured on board Defence Meteorology Satellite Program (DMSP) satellites. Observations made with the Halley SuperDARN radar (75.5° S, 26.6° W, geographic; –62.0°Λ) and the Tasman International Geospace Environment Radar (TIGER) (43.4° S, 147.2° E; –54.5°Λ) are used to compare the location of the SWB with the DMSP-inferred OCB during 08:00 to 22:00 UT on 1 April 2000. This study interval was chosen because it includes several moderate substorms, whilst the Halley radar provided almost continuous high-time resolution measurements of the dayside SWB location and shape, and TIGER provided the same in the nightside ionosphere. The behaviour of the day- and nightside SWB can be understood in terms of the expanding/contracting polar cap model of high-latitude convection change, and the behaviour of the nightside SWB can also be organised according to substorm phase. Previous comparisons with DMSP OCBs have proven that the radar SWB is often a reasonable proxy for the OCB from dusk to just past midnight (Chisham et al., 2004). However, the present case study actually suggests that the nightside SWB is often a better proxy for the poleward edge of Pedersen conductance enhanced by hot particle precipitation in the auroral zone. Simple modeling implies that the large spectral widths must be caused by ~10-km scale velocity fluctuations. Key words. Ionosphere (auroral ionosphere; ionospheremagnetosphere interactions) – Magnetospheric physics (storms and substorms)

scholarly journals On the occurrence and motion of decametre-scale irregularities in the sub-auroral, auroral, and polar cap ionosphere

2003 ◽  
Vol 21 (8) ◽  
pp. 1847-1868 ◽  
Author(s):  
M. L. Parkinson ◽  
J. C. Devlin ◽  
H. Ye ◽  
C. L. Waters ◽  
P. L. Dyson ◽  
...  
Keyword(s):  
Electric Fields ◽  
Spectral Width ◽  
Auroral Oval ◽  
Auroral Zone ◽  
Ionospheric Irregularities ◽  
Lower Latitude ◽  
Doppler Velocity ◽  
Auroral Ionosphere ◽  
Polar Cap ◽  
Sunspot Maximum

Abstract. The statistical occurrence of decametre-scale ionospheric irregularities, average line-of-sight (LOS) Doppler velocity, and Doppler spectral width in the sub-auroral, auroral, and polar cap ionosphere ( - 57°L to - 88°L) has been investigated using echoes recorded with the Tasman International Geospace Environment Radar (TIGER), a SuperDARN radar located on Bruny Island, Tasmania (147.2° E, 43.4° S geographic; - 54.6 °L). Results are shown for routine soundings made on the magnetic meridian beam 4 and the near zonal beam 15 during the sunspot maximum interval December 1999 to November 2000. Most echoes were observed in the nightside ionosphere, typically via 1.5-hop propagation near dusk and then via 0.5-hop propagation during pre-midnight to dawn. Peak occurrence rates on beam 4 were often > 60% near magnetic midnight and ~ - 70 °L. They increased and shifted equatorward and toward pre-midnight with increasing Kp (i.e. Bz southward). The occurrence rates remained very high for Kp > 4, de-spite enhanced D-region absorption due to particle precipitation. Average occurrence rates on beam 4 exhibited a relatively weak seasonal variation, consistent with known longitudinal variations in auroral zone magnetic activity (Basu, 1975). The average echo power was greatest between 23 and 07 MLT. Two populations of echoes were identified on both beams, those with low spectral width and a mode value of ~ 9 ms-1 (bin size of 2 ms-1) concentrated in the auroral and sub-auroral ionosphere (population A), and those with high spectral width and a mode value of ~ 70 ms-1 concentrated in the polar cap ionosphere (population B). The occurrence of population A echoes maximised post-midnight because of TIGER’s lower latitude, but the subset of the population A echoes observed near dusk had characteristics reminiscent of "dusk scatter" (Ruohoniemi et al., 1988). There was a dusk "bite out" of large spectral widths between ~ 15 and 21 MLT and poleward of - 67 °L, and a pre-dawn enhancement of large spectral widths between ~  03 and 07 MLT, centred on ~ - 61 °L. The average LOS Doppler velocities revealed that frequent westward jets of plasma flow occurred equatorward of, but overlapping, the diffuse auroral oval in the pre-midnight sector.Key words. Ionosphere (auroral ionosphere; electric fields and currents, ionospheric irregularities)

scholarly journals Energy–latitude dispersion patterns near the isotropy boundaries of energetic protons

2015 ◽  
Vol 33 (8) ◽  
pp. 1059-1070 ◽  
Author(s):  
V. A. Sergeev ◽  
S. A. Chernyaeva ◽  
S. V. Apatenkov ◽  
N. Y. Ganushkina ◽  
S. V. Dubyagin
Keyword(s):  
Flux Ratio ◽  
Auroral Oval ◽  
Auroral Zone ◽  
Frequent Pattern ◽  
Lower Latitude ◽  
Dispersion Pattern ◽  
Mesoscale Structures ◽  
Angle Scattering ◽  
Dispersion Patterns ◽  
Wave Induced

Abstract. Non-adiabatic motion of plasma sheet protons causes pitch-angle scattering and isotropic precipitation to the ionosphere, which forms the proton auroral oval. This mechanism related to current sheet scattering (CSS) provides a specific energy–latitude dispersion pattern near the equatorward boundary of proton isotropic precipitation (isotropy boundary, IB), with precipitation sharply decreasing at higher (lower) latitude for protons with lower (higher) energy. However, this boundary maps to the inner magnetosphere, where wave-induced scattering may provide different dispersion patterns as recently demonstrated by Liang et al. (2014). Motivated by the potential usage of the IBs for the magnetotail monitoring as well as by the need to better understand the mechanisms forming the proton IB, we investigate statistically the details of particle flux patterns near the proton IB using NOAA-POES polar spacecraft observations made during September 2009. By comparing precipitated-to-trapped flux ratio (J0/J90) at >30 and >80 keV proton energies, we found a relatively small number of simple CSS-type dispersion events (only 31 %). The clear reversed (wave-induced) dispersion patterns were very rare (5 %). The most frequent pattern had nearly coinciding IBs at two energies (63 %). The structured precipitation with multiple IBs was very frequent (60 %), that is, with two or more significant J0/J90 dropouts. The average latitudinal width of multiple IB structures was about 1°. Investigation of dozens of paired auroral zone crossings of POES satellites showed that the IB pattern is stable on a timescale of less than 2 min (a few proton bounce periods) but can evolve on a longer (several minutes) scale, suggesting temporal changes in some mesoscale structures in the equatorial magnetosphere. We discuss the possible role of CSS-related and wave-induced mechanisms and their possible coupling to interpret the emerging complicated patterns of proton isotropy boundaries.

scholarly journals A case study of HF radar spectra and 630.0 nm auroral emission in the pre-midnight sector

2001 ◽  
Vol 19 (3) ◽  
pp. 327-339 ◽  
Author(s):  
M. Lester ◽  
S. E. Milan ◽  
V. Besser ◽  
R. Smith
Keyword(s):  
Magnetic Field ◽  
Special Interest ◽  
Line Emission ◽  
Spectral Width ◽  
Auroral Oval ◽  
Hf Radar ◽  
Polar Cap ◽  
Particle Precipitation ◽  
The Relationship ◽  
Red Line

Abstract. A comparison of HF radar backscatter observed by the CUTLASS Finland radar, meridian scanning photometer data from Longyearbyen, magnetic field variations from IMAGE stations, and particle precipitation measured by the DMSP F12 spacecraft is presented. The interval under discussion occurred in the pre-midnight local time sector, during a period of weakly northward interplanetary magnetic field. A region of HF backscatter, typically 8 degrees wide, occurred in the field of view of the CUTLASS Finland radar. A well defined gradient in the spectral width parameter was present, with mainly low (< 200 m s - 1 ) spectral widths in the lower latitude part of the scatter and predominantly large (> 200 ms - 1 ) spectral widths in the higher latitude part. The relationship between the spectral width and the red line (630.0 nm) emission measured by the meridian scanning photometer is considered. The poleward border of the red line emission, which has, in the past, been proposed as being representative of the polar cap boundary, was co-located to within 1° of magnetic latitude with the gradient in spectral width for part of the interval. Statistically, large spectral widths occurred poleward of the red line emission, while small spectral widths occurred within or equatorward of the red line emission. Near simultaneous DMSP particle observations in the 20 eV to 20 keV range indicate that the poleward border of the red line emission and the gradient in spectral width occurred at the same latitude as the transition from auroral oval to polar rain particle energies. We conclude that the large spectral widths were not caused by particle precipitation associated with the auroral oval. There were two periods of special interest when the relationship between the red line and the spectral width broke down. The first of these happened during enhanced red line and green line (557.7 nm) emission, with a drop out of the radar scatter and an enhanced, narrow westward electrojet. We conclude that this event was a magnetospheric substorm occurring at much higher than usual latitudes. The second period of special interest happened when equatorward moving bands of large spectral width occurred within the region of scatter. Up to 4 of these bands were present during an interval of 100 minutes. Associated with these narrow bands of large spectral width were narrow channels of enhanced westward ion velocities. We conclude that these equatorward moving bands of large spectral width may be related to reconnection processes in the tail. The observations demonstrate that the tail continues to be active even under low solar wind energy input conditions. Furthermore, we conclude that the gradient in the spectral width may be used as a proxy for the polar cap boundary, but only with extreme caution.Key words. Ionosphere (ionosphere-magnetosphere inter-actions; polar ionosphere) – Magnetospheric physics (storms and substorms)

scholarly journals On the lifetime and extent of an auroral westward flow channel (AWFC) observed during a magnetospheric substorm

2003 ◽  
Vol 21 (4) ◽  
pp. 893-913 ◽  
Author(s):  
M. L. Parkinson ◽  
M. Pinnock ◽  
H. Ye ◽  
M. R. Hairston ◽  
J. C. Devlin ◽  
...  
Keyword(s):  
Electric Fields ◽  
Wide Band ◽  
Spectral Width ◽  
Recovery Phase ◽  
Auroral Oval ◽  
Flow Channel ◽  
Doppler Velocity ◽  
Evening Sector ◽  
Phase Interval ◽  
Electric Fields And Currents

Abstract. A -190-nT negative bay in the geomagnetic X component measured at Macquarie Island ( -65° L) showed that an ionospheric substorm occurred during 09:58 to 11:10 UT on 27 February 2000. Signatures of an auroral westward flow channel (AWFC) were observed nearly simultaneously in the backscatter power, LOS Doppler velocity, and Doppler spectral width measured using the Tasman International Geospace Environment Radar (TIGER), a Southern Hemisphere HF SuperDARN radar. Many of the characteristics of the AWFC were similar to those occurring during a polarisation jet (PJ), or subauroral ion drift (SAID) event, and suggest that it may have been a pre-cursor to a fully developed, intense westward flow channel satisfying all of the criteria defining a PJ/SAID. A beam-swinging analysis showed that the westward drifts (poleward electric field) associated with the flow channel were very structured in time and space, but the smoothed velocities grew to ~ 800 ms-1 (47 mVm-1) during the 22-min substorm onset interval 09:56 to 10:18 UT. Maximum west-ward drifts of >1.3 km s-1 (>77 mVm-1) occurred during a ~ 5-min velocity spike, peaking at 10:40 UT during the expansion phase. The drifts decayed rapidly to ~ 300 ms-1 (18 mVm-1) during the 6-min recovery phase interval, 11:04 to 11:10 UT. Overall, the AWFC had a lifetime of 74 min, and was located near -65° L in the evening sector west of the Harang discontinuity. The large westward drifts were confined to a geographic zonal channel of longitudinal ex-tent >20° (>1.3 h magnetic local time), and latitudinal width ~2° L. Using a half-width of ~ 100 km in latitude, the peak electric potential was >7.7 kV. However, a transient velocity of >3.1 km s-1 with potential >18.4 kV was observed further poleward at the end of the recovery phase. Auroral oval boundaries determined using DMSP measurements suggest the main flow channel overlapped the equatorward boundary of the diffuse auroral oval. During the ~ 2-h interval following the flow channel, an ~ 3° L wide band of scatter was observed drifting slowly toward the west, with speeds gradually decaying to ~ 50 ms-1 (3 mVm -1). The scatter was observed extending past the Harang discontinuity, and had Doppler signatures characteristic of the main ionospheric trough, implicating the flow channel in the further depletion of F-region plasma. The character of this scatter was in contrast with the character of the scatter drifting toward the east at higher latitude.Key words. Ionosphere (auroral ionosphere; electric fields and currents; ionosphere-magnetospehere interactions) Magnetospheric physics (storms and substorms)

scholarly journals Relationship between large-scale ionospheric field-aligned currents and electron/ion precipitations: DMSP observations

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Chao Xiong ◽  
Claudia Stolle ◽  
Patrick Alken ◽  
Jan Rauberg
Keyword(s):  
Time Distribution ◽  
Large Scale ◽  
Particle Flux ◽  
Particle Energy ◽  
Lower Latitude ◽  
Particle Precipitation ◽  
Data Set ◽  
The Mean ◽  
Two Parameters ◽  
Meteorological Satellite

Abstract In this study, we have derived field-aligned currents (FACs) from magnetometers onboard the Defense Meteorological Satellite Project (DMSP) satellites. The magnetic latitude versus local time distribution of FACs from DMSP shows comparable dependences with previous findings on the intensity and orientation of interplanetary magnetic field (IMF) By and Bz components, which confirms the reliability of DMSP FAC data set. With simultaneous measurements of precipitating particles from DMSP, we further investigate the relation between large-scale FACs and precipitating particles. Our result shows that precipitation electron and ion fluxes both increase in magnitude and extend to lower latitude for enhanced southward IMF Bz, which is similar to the behavior of FACs. Under weak northward and southward Bz conditions, the locations of the R2 current maxima, at both dusk and dawn sides and in both hemispheres, are found to be close to the maxima of the particle energy fluxes; while for the same IMF conditions, R1 currents are displaced further to the respective particle flux peaks. Largest displacement (about 3.5°) is found between the downward R1 current and ion flux peak at the dawn side. Our results suggest that there exists systematic differences in locations of electron/ion precipitation and large-scale upward/downward FACs. As outlined by the statistical mean of these two parameters, the FAC peaks enclose the particle energy flux peaks in an auroral band at both dusk and dawn sides. Our comparisons also found that particle precipitation at dawn and dusk and in both hemispheres maximizes near the mean R2 current peaks. The particle precipitation flux maxima closer to the R1 current peaks are lower in magnitude. This is opposite to the known feature that R1 currents are on average stronger than R2 currents.

scholarly journals A Statistical study of the Doppler spectral width of high-latitude ionospheric F-region echoes recorded with SuperDARN coherent HF radars

2002 ◽  
Vol 20 (11) ◽  
pp. 1769-1781 ◽  
Author(s):  
J.-P. Villain ◽  
R. André ◽  
M. Pinnock ◽  
R. A. Greenwald ◽  
C. Hanuise
Keyword(s):  
High Latitude ◽  
Statistical Study ◽  
Spectral Width ◽  
Auroral Oval ◽  
F Region ◽  
Radar Network ◽  
Period 2 ◽  
Time Period ◽  
High Latitude Ionosphere ◽  
Data Points

Abstract. The HF radars of the Super Dual Auroral Radar Network (SuperDARN) provide measurements of the E × B drift of ionospheric plasma over extended regions of the high-latitude ionosphere. We have conducted a statistical study of the associated Doppler spectral width of ionospheric F-region echoes. The study has been conducted with all available radars from the Northern Hemisphere for 2 specific periods of time. Period 1 corresponds to the winter months of 1994, while period 2 covers October 1996 to March 1997. The distributions of data points and average spectral width are presented as a function of Magnetic Latitude and Magnetic Local Time. The databases are very consistent and exhibit the same features. The most stringent features are: a region of very high spectral width, collocated with the ionospheric LLBL/cusp/mantle region; an oval shaped region of high spectral width, whose equator-ward boundary matches the poleward limit of the Holzworth and Meng auroral oval. A simulation has been conducted to evaluate the geometrical and instrumental effects on the spectral width. It shows that these effects cannot account for the observed spectral features. It is then concluded that these specific spectral width characteristics are the signature of ionospheric/magnetospheric coupling phenomena.Key words. Ionosphere (auroral ionosphere; ionosphere-magnetosphere interactions; ionospheric irregularities)

scholarly journals Evaluation of the geometry of ionospheric current systems related to rapid geomagnetic variations

2004 ◽  
Vol 22 (1) ◽  
pp. 63-72 ◽  
Author(s):  
S. V. Apatenkov ◽  
V. A. Sergeev ◽  
R. Pirjola ◽  
A. Viljanen
Keyword(s):  
Dynamic Pressure ◽  
Auroral Oval ◽  
Auroral Zone ◽  
Middle Part ◽  
Magnetic Storms ◽  
Geomagnetically Induced Currents ◽  
Geomagnetic Variations ◽  
Ionospheric Current ◽  
Solar Wind Parameters ◽  
Current Systems

Abstract. To learn about the geometry and sources of the ionospheric current systems which generate strong geomagnetically induced currents, we categorize differential equivalent current systems (DEC) for events with strong dB/dt by decomposing them into the contributions of electrojet-type and vortex-type elementary systems. By solving the inverse problem we obtain amplitudes and locations of these elementary current systems. One-minute differences of the geomagnetic field values at the IMAGE magnetometer network in 1996–2000 are analysed to study the spatial distributions of large dB/dt events. The relative contributions of the two components are evaluated. In particular, we found that the majority of the strongest dB/dt events (100–1000nT/min) appear to be produced by the vortex-type current structures and most of them occur in the morning LT hours, probably caused by the Ps6 pulsation events associated with auroral omega structures. For strong dB/dt events the solar wind parameters are shifted toward strong (tens nT) southward IMF, enhanced velocity and dynamic pressure, in order for the main phase of the magnetic storms to occur. Although these events appear mostly during magnetic storms when the auroral oval greatly expands, the area of large dB/dt stays in the middle part of the auroral zone; therefore, it is connected to the processes taking part in the middle of the magnetosphere rather than in its innermost region populated by the ring current. Key words. Geomagnetism and paleomagnetism (rapid time variations) – Ionosphere (auroral ionosphere; ionospheric disturbances)

scholarly journals A statistical comparison of SuperDARN spectral width boundaries and DMSP particle precipitation boundaries in the morning sector ionosphere

2005 ◽  
Vol 23 (3) ◽  
pp. 733-743 ◽  
Author(s):  
G. Chisham ◽  
M. P. Freeman ◽  
T. Sotirelis ◽  
R. A. Greenwald ◽  
M. Lester ◽  
...  
Keyword(s):  
Energy Flux ◽  
Spectral Width ◽  
Incident Electron Energy ◽  
Small Scale ◽  
Closed Field ◽  
Particle Precipitation ◽  
Ionospheric Conductivity ◽  
Morning Sector ◽  
Latitudinal Difference ◽  
Good Proxy

Abstract. Determining reliable proxies for the ionospheric signature of the open-closed field line boundary (OCB) is crucial for making accurate ionospheric measurements of many magnetospheric processes (e.g. magnetic reconnection). This study compares the latitudes of Spectral Width Boundaries (SWBs), identified in the morning sector ionosphere using the Super Dual Auroral Radar Network (SuperDARN), with Particle Precipitation Boundaries (PPBs) determined using the low-altitude Defense Meteorological Satellite Program (DMSP) spacecraft, in order to determine whether the SWB represents a good proxy for the ionospheric projection of the OCB. The latitudes of SWBs and PPBs were identified using automated algorithms applied to 5 years (1997-2001) of data measured in the 00:00-12:00 Magnetic Local Time (MLT) range. A latitudinal difference was measured between each PPB and the nearest SWB within a ±10min Universal Time (UT) window and within a ±1h MLT window. The results show that the SWB represents a good proxy for the OCB close to midnight (~00:00-02:00 MLT) and noon (~08:00-12:00 MLT), but is located some distance (~2°-4°) equatorward of the OCB across much of the morning sector ionosphere (~02:00-08:00 MLT). On the basis of this and other studies we deduce that the SWB is correlated with the poleward boundary of auroral emissions in the Lyman-Birge-Hopfield ``Long" (LBHL) UV emission range and hence, that spectral width is inversely correlated with the energy flux of precipitating electrons. We further conclude that the combination of two factors may explain the spatial distribution of spectral width values in the polar ionospheres. The small-scale structure of the convection electric field leads to an enhancement in spectral width in regions close to the OCB, whereas increases in ionospheric conductivity (relating to the level of incident electron energy flux) lead to a reduction in spectral width in regions just equatorward of the OCB.

scholarly journals Imaging radar observations of Farley Buneman waves during the JOULE II experiment

2008 ◽  
Vol 26 (7) ◽  
pp. 1837-1850 ◽  
Author(s):  
D. L. Hysell ◽  
G. Michhue ◽  
M. F. Larsen ◽  
R. Pfaff ◽  
M. Nicolls ◽  
...  
Keyword(s):  
Electric Fields ◽  
Spectral Width ◽  
Auroral Zone ◽  
Convection Flow ◽  
Coherent Scatter ◽  
Flow Angle ◽  
Doppler Shifts ◽  
Ion Acoustic ◽  
The Waves ◽  
Acoustic Speed

Abstract. Vector electric fields and associated E×B drifts measured by a sounding rocket in the auroral zone during the NASA JOULE II experiment in January 2007, are compared with coherent scatter spectra measured by a 30 MHz radar imager in a common volume. Radar imaging permits precise collocation of the spectra with the background electric field. The Doppler shifts and spectral widths appear to be governed by the cosine and sine of the convection flow angle, respectively, and also proportional to the presumptive ion acoustic speed. The neutral wind also contributes to the Doppler shifts. These findings are consistent with those from the JOULE I experiment and also with recent numerical simulations of Farley Buneman waves and instabilities carried out by Oppenheim et al. (2008). Simple linear analysis of the waves offers some insights into the spectral moments. A formula relating the spectral width to the flow angle, ion acoustic speed, and other ionospheric parameters is derived.

scholarly journals High time resolution measurements of the thermosphere from Fabry-Perot Interferometer measurements of atomic oxygen

2007 ◽  
Vol 25 (6) ◽  
pp. 1269-1278 ◽  
Author(s):  
E. A. K. Ford ◽  
A. L. Aruliah ◽  
E. M. Griffin ◽  
I. McWhirter
Keyword(s):  
Gravity Waves ◽  
Time Resolution ◽  
Lower Thermosphere ◽  
Line Emission ◽  
Auroral Oval ◽  
High Time ◽  
High Time Resolution ◽  
Short Period ◽  
Fabry Perot ◽  
Thermospheric Winds

Abstract. Recent advances in the performance of CCD detectors have enabled a high time resolution study of the high latitude upper thermosphere with Fabry-Perot Interferometers (FPIs) to be performed. 10-s integration times were used during a campaign in April 2004 on an FPI located in northern Sweden in the auroral oval. The FPI is used to study the thermosphere by measuring the oxygen red line emission at 630.0 nm, which emits at an altitude of approximately 240 km. Previous time resolutions have been 4 min at best, due to the cycle of look directions normally observed. By using 10 s rather than 40 s integration times, and by limiting the number of full cycles in a night, high resolution measurements down to 15 s were achievable. This has allowed the maximum variability of the thermospheric winds and temperatures, and 630.0 nm emission intensities, at approximately 240 km, to be determined as a few minutes. This is a significantly greater variability than the often assumed value of 1 h or more. A Lomb-Scargle analysis of this data has shown evidence of gravity wave activity with waves with short periods. Gravity waves are an important feature of mesosphere-lower thermosphere (MLT) dynamics, observed using many techniques and providing an important mechanism for energy transfer between atmospheric regions. At high latitudes gravity waves may be generated in-situ by localised auroral activity. Short period waves were detected in all four clear nights when this experiment was performed, in 630.0 nm intensities and thermospheric winds and temperatures. Waves with many periodicities were observed, from periods of several hours, down to 14 min. These waves were seen in all parameters over several nights, implying that this variability is a typical property of the thermosphere.

Sign in / Sign up

Export Citation Format

Share Document