Preliminary results from Project Waterhole — an auroral modification experiment

1981 ◽  
Vol 59 (8) ◽  
pp. 1175-1182 ◽  
Author(s):  
B. A. Whalen ◽  
A. W. Yau ◽  
F. Creutzberg ◽  
R. L. Gattinger ◽  
F. R. Harris ◽  
...  
Keyword(s):  
Energetic Electron ◽  
Electron Precipitation ◽  
Sounding Rocket ◽  
Plasma Diagnostic ◽  
E Region ◽  
Field Aligned Current ◽  
Field Lines ◽  
Plasma Depletion ◽  
Current Systems ◽  
By Products

A sounding rocket carrying 100 kg of high explosives and plasma diagnostic instrumentation was launched from Churchill Research Range on 6 April 1980 over a premidnight auroral arc. The object of the experiment was to produce an ionospheric hole or plasma density depletion near 300 km altitude on field lines connected to an auroral arc. The plasma depletion is produced when the explosive by-products (mostly water) charge-exchange with the ambient O+ ions and then rapidly recombine. It was speculated that the presence of the "hole" would interfere with the field aligned current systems associated with the arc and would in turn perturb the auroral source mechanism. The release occurred about 10 km poleward of the auroral arc fieldlines. As expected, a large ionospheric hole was detected by the rocket-borne plasma sensors. Within a few seconds following the release (a) the energetic electron precipitation observed in the hole dropped to background levels, (b) the luminosity of the auroral arc observed by a ground-based auroral scanning photometer decreased by a factor of two, and (c) the ionospheric E region density below the hole decayed at a rate consistent with a sudden reduction in particle precipitation. The simultaneous onset of these gross changes in electron precipitation coincident with the release strongly suggests a cause and effect relationship and demonstrates the intimate relationship that exists between the state of the ionospheric plasma and the auroral acceleration mechanism.

scholarly journals Remote sensing and modeling of energetic electron precipitation into the lower ionosphere using VLF/LF radio waves and field aligned current data

2015 ◽  
Vol 13 ◽  
pp. 233-242
Author(s):  
E. D. Schmitter
Keyword(s):  
Distribution Function ◽  
Energetic Electron ◽  
Lower Ionosphere ◽  
Signal Amplitude ◽  
Reaction Rates ◽  
Current Data ◽  
Electron Precipitation ◽  
Propagation Path ◽  
Satellite Mission ◽  
Field Aligned Current

Abstract. A model for the development of electron density height profiles based on space time distributed ionization sources and reaction rates in the lower ionosphere is described. Special attention is payed to the definition of an auroral oval distribution function for energetic electron energy input into the lower ionosphere based on a Maxwellian energy spectrum. The distribution function is controlled by an activity parameter which is defined proportional to radio signal amplitude disturbances of a VLF/LF transmitter. Adjusting the proportionality constant allows to model precipitation caused VLF/LF signal disturbances using radio wave propagation calculations and to scale the distribution function. Field aligned current (FAC) data from the new Swarm satellite mission are used to constrain the spatial extent of the distribution function. As an example electron precipitation bursts during a moderate substorm on the 12 April 2014 (midnight–dawn) are modeled along the subauroral propagation path from the NFR/TFK transmitter (37.5 kHz, Iceland) to a midlatitude site.

The role of energetic electron precipitation and background dynamics on the seasonal NO variability in the MLT region

2021 ◽  
Author(s):  
Christine Smith-Johnsen ◽  
Hilde Nesse Tyssøy ◽  
Daniel Robert Marsh ◽  
Anne Smith ◽  
Ville Maliniemi
Keyword(s):  
Climate Model ◽  
Lower Thermosphere ◽  
Energetic Electron ◽  
Sensitivity Study ◽  
Electron Precipitation ◽  
Ion Chemistry ◽  
Wave Forcing ◽  
D Region ◽  
E Region ◽  
Cluster Ion

<p><span>Energetic electron precipitation (EEP) ionizes the Earth's atmosphere and leads to production of nitric oxide (NO) throughout the polar Mesosphere and Lower Thermosphere (MLT). In this study we investigate the direct and indirect NO response to the EEP using the Whole Atmosphere Community Climate Model (WACCM) version 6. In comparison to observations from SOFIE / AIM (Solar Occultation For Ice Experiment / Aeronomy of Ice in the Mesosphere), we find that EEP production of NO in the D-region is well simulated when both medium energy electron precipitation and negative and cluster ion chemistry are included in the model. However, the main EEP production of NO occurs in the E-region, and there the observed and modeled production differ. This discrepancy impacts also the D-region due to downward transport of long lived NO. The transport across the mesopause is seasonally dependent, and WACCM’s underestimate of D-region NO is highest during winter when downwelling from above is strong. The drivers of this transport are further investigated by a sensitivity study of WACCM’s gravity wave forcing.</span></p>

The role of EEP forcing and background dynamics on the seasonal NO variability in the MLT region

2020 ◽  
Author(s):  
Christine Smith-Johnsen ◽  
Hilde Nesse Tyssøy ◽  
Daniel Marsh ◽  
Anne Smith
Keyword(s):  
Climate Model ◽  
Energetic Electron ◽  
Eddy Diffusion ◽  
Electron Precipitation ◽  
Ion Chemistry ◽  
D Region ◽  
E Region ◽  
Cluster Ion ◽  
Mlt Region

<p><a name="docs-internal-guid-803d1a38-7fff-fefe-52f7-d0a055a4547b"></a><a name="docs-internal-guid-b8d76d48-7fff-149a-6440-413c0de833ae"></a> <span>Energetic electron precipitation (EEP) ionizes the Earth's atmosphere and leads to production of nitric oxide (NO) from 50 to 150 km altitude. In this study we investigate the direct and indirect NO response to EEP using the Whole Atmosphere Community Climate Model (WACCM). In comparison to observations from SOFIE / AIM (Solar Occultation For Ice Experiment / Aeronomy of Ice in the Mesosphere), we find that EEP production of NO in the D-region is well simulated when both medium energy electron precipitation and negative and cluster ion chemistry is included in the model. However, the main EEP production of NO occurs in the E-region, and there the observed and modeled production differ. This discrepancy impacts also the D-region, and is seasonally dependent with the highest underestimate of D-region NO occuring during winter. The modeled transport across the mesopause during winter is generally weak, but strengthens with increased gravity wave activity. Increased eddy diffusion, increases NO at all altitudes through the polar MLT region</span></p>

scholarly journals The UV aurora and ionospheric flows during flux transfer events

2001 ◽  
Vol 19 (2) ◽  
pp. 179-188 ◽  
Author(s):  
D. A. Neudegg ◽  
S. W. H. Cowley ◽  
K. A. McWilliams ◽  
M. Lester ◽  
T. K. Yeoman ◽  
...  
Keyword(s):  
Ultra Violet ◽  
Spectral Width ◽  
Hf Radar ◽  
Electron Precipitation ◽  
Flux Transfer Events ◽  
Optical Feature ◽  
Geomagnetic Fields ◽  
Field Aligned Current ◽  
Flux Transfer ◽  
Current Systems

Abstract. Far Ultra Violet (FUV) signatures in the polar ionosphere during a period of magnetopause reconnection are compared with ionospheric flows measured in the cusp ‘throat’ and dusk cell by the CUTLASS Hankasalmi HF radar. Regions of peak FUV emission in the 130.4 nm and 135.6 nm range, observed by the Polar spacecraft’s VIS Earth Camera, consistently lie at the turning point of the flows from the dusk cell, poleward into the throat, and at the equatorward edge of the region of high and varied radar spectral-width associated with the cusp. The Equator-S spacecraft was near the magnetopause at the time of the ionospheric observations and geomagnetically conjugate with the region of ionosphere observed by the radar. Flux transfer events (FTEs), suggestive of bursty reconnection between the IMF and geomagnetic fields, were observed by Equator-S prior to and during the periods of high FUV emission. Enhanced poleward ionospheric flow velocities in the polar cusp region, previously shown to be associated with bursty reconnection, consistently lie poleward of the enhanced FUV optical feature. The enhanced optical feature is consistent with the expected position of the largest upward region 1 field-aligned current, associated with electron precipitation, on the dusk edge of the merging gap. The optical feature moves duskward and equatorward during the course of the reconnection sequence, consistent with expansion of the merging line and the polar cap with newly added open magnetic flux by the FTEs. The DMSP F14 spacecraft passed through the enhanced FUV region and measured strong, structured electron precipitation far greater than in the adjacent regions.Key words. Magnetospheric physics (current systems; magnetopause, cusp and boundary layers; magnetosphere-ionosphere interactions)

scholarly journals Strong localized variations of the low-altitude energetic electron fluxes in the evening sector near the plasmapause

1998 ◽  
Vol 16 (1) ◽  
pp. 25-33 ◽  
Author(s):  
E. E. Titova ◽  
T. A. Yahnina ◽  
A. G. Yahnin ◽  
B. B. Gvozdevsky ◽  
A. A. Lyubchich ◽  
...  
Keyword(s):  
Sharp Increase ◽  
Electron Flux ◽  
Particle Interaction ◽  
Energetic Electron ◽  
Recovery Phase ◽  
Electron Precipitation ◽  
Statistical Characteristics ◽  
Evening Sector ◽  
Proton Precipitation ◽  
Low Altitude

Abstract. Specific type of energetic electron precipitation accompanied by a sharp increase in trapped energetic electron flux are found in the data obtained from low-altitude NOAA satellites. These strongly localized variations of the trapped and precipitated energetic electron flux have been observed in the evening sector near the plasmapause during recovery phase of magnetic storms. Statistical characteristics of these structures as well as the results of comparison with proton precipitation are described. We demonstrate the spatial coincidence of localized electron precipitation with cold plasma gradient and whistler wave intensification measured on board the DE-1 and Aureol-3 satellites. A simultaneous localized sharp increase in both trapped and precipitating electron flux could be a result of significant pitch-angle isotropization of drifting electrons due to their interaction via cyclotron instability with the region of sharp increase in background plasma density.Key words. Ionosphere (particle precipitation; wave-particle interaction) Magnetospheric Physics (plasmasphere)

scholarly journals ULF modulation of energetic electron precipitation observed by VLF/LF radio propagation

2020 ◽  
Vol 2020 (372) ◽  
pp. 29-40
Author(s):  
Takuya Miyashita ◽  
Hiroyo Ohya ◽  
Fuminori Tsuchiya ◽  
Asuka Hirai ◽  
Mitsunori Ozaki ◽  
...  
Keyword(s):  
Energetic Electron ◽  
Electron Precipitation ◽  
Radio Propagation

scholarly journals The effect of energetic electron precipitation on middle mesospheric night-time ozone during and after a moderate geomagnetic storm

2012 ◽  
Vol 39 (21) ◽  
pp. n/a-n/a ◽  
Author(s):  
M. Daae ◽  
P. Espy ◽  
H. Nesse Tyssøy ◽  
D. Newnham ◽  
J. Stadsnes ◽  
...  
Keyword(s):  
Geomagnetic Storm ◽  
Energetic Electron ◽  
Electron Precipitation ◽  
Night Time

scholarly journals Effects of solar eclipse on the electrodynamical processes of the equatorial ionosphere: a case study during 11 August 1999 dusk time total solar eclipse over India

2002 ◽  
Vol 20 (12) ◽  
pp. 1977-1985 ◽  
Author(s):  
R. Sridharan ◽  
C. V. Devasia ◽  
N. Jyoti ◽  
Diwakar Tiwari ◽  
K. S. Viswanathan ◽  
...  
Keyword(s):  
Electric Fields ◽  
Solar Eclipse ◽  
Equatorial Ionosphere ◽  
Hf Radar ◽  
F Region ◽  
Large Enhancement ◽  
Temporal Structures ◽  
E Region ◽  
Field Lines ◽  
Electric Fields And Currents

Abstract. The effects on the electrodynamics of the equatorial E- and F-regions of the ionosphere, due to the occurrence of the solar eclipse during sunset hours on 11 August 1999, were investigated in a unique observational campaign involving ground based ionosondes, VHF and HF radars from the equatorial location of Trivandrum (8.5° N; 77° E; dip lat. 0.5° N), India. The study revealed the nature of changes brought about by the eclipse in the evening time E- and F-regions in terms of (i) the sudden intensification of a weak blanketing ES-layer and the associated large enhancement of the VHF backscattered returns, (ii) significant increase in h' F immediately following the eclipse and (iii) distinctly different spatial and temporal structures in the spread-F irregularity drift velocities as observed by the HF radar. The significantly large enhancement of the backscattered returns from the E-region coincident with the onset of the eclipse is attributed to the generation of steep electron density gradients associated with the blanketing ES , possibly triggered by the eclipse phenomena. The increase in F-region base height immediately after the eclipse is explained as due to the reduction in the conductivity of the conjugate E-region in the path of totality connected to the F-region over the equator along the magnetic field lines, and this, with the peculiar local and regional conditions, seems to have reduced the E-region loading of the F-region dynamo, resulting in a larger post sunset F-region height (h' F) rise. These aspects of E-and F-region behaviour on the eclipse day are discussed in relation to those observed on the control day.Key words. Ionosphere (electric fields and currents; equatorial ionosphere; ionospheric irregularities)

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