scholarly journals Lower Ionospheric Conductivity Modification Above a Thunderstorm Updraught

2019 ◽  
Vol 124 (8) ◽  
pp. 6938-6949
Author(s):  
K. Koh ◽  
A. Bennett ◽  
S. Ghilain ◽  
Z. Liu ◽  
S. Pedeboy ◽  
...  
Keyword(s):  
Ionospheric Conductivity

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 Global auroral conductance distribution due to electron and proton precipitation from IMAGE-FUV observations

2004 ◽  
Vol 22 (5) ◽  
pp. 1595-1611 ◽  
Author(s):  
V. Coumans ◽  
J.-C. Gérard ◽  
B. Hubert ◽  
M. Meurant ◽  
S. B. Mende
Keyword(s):  
Imaging System ◽  
Potential Drop ◽  
Large Error ◽  
Feedback Mechanism ◽  
Activity Levels ◽  
Auroral Region ◽  
Ionospheric Conductivity ◽  
The North ◽  
Proton Precipitation ◽  
Auroral Particles

Abstract. The Far Ultraviolet (FUV) imaging system on board the IMAGE satellite provides a global view of the north auroral region in three spectral channels, including the SI12 camera sensitive to Doppler shifted Lyman-α emission. FUV images are used to produce instantaneous maps of electron mean energy and energy fluxes for precipitated protons and electrons. We describe a method to calculate ionospheric Hall and Pedersen conductivities induced by auroral proton and electron ionization based on a model of interaction of auroral particles with the atmosphere. Different assumptions on the energy spectral distribution for electrons and protons are compared. Global maps of ionospheric conductances due to instantaneous observation of precipitating protons are calculated. The contribution of auroral protons in the total conductance induced by both types of auroral particles is also evaluated and the importance of proton precipitation is evaluated. This method is well adapted to analyze the time evolution of ionospheric conductances due to precipitating particles over the auroral region or in particular sectors. Results are illustrated with conductance maps of the north polar region obtained during four periods with different activity levels. It is found that the proton contribution to conductance is relatively higher during quiet periods than during substorms. The proton contribution is higher in the period before the onset and strongly decreases during the expansion phase of substorms. During a substorm which occurred on 28 April 2001, a region of strong proton precipitation is observed with SI12 around 14:00MLT at ~75° MLAT. Calculation of conductances in this sector shows that neglecting the protons contribution would produce a large error. We discuss possible effects of the proton precipitation on electron precipitation in auroral arcs. The increase in the ionospheric conductivity, induced by a former proton precipitation can reduce the potential drop along field lines in the upward field-aligned currents by creating an opposite polarization electric field. This feedback mechanism possibly reduces the electron acceleration. Key words. Ionosphere (auroral ionosphere; ionospheremagnetosphere interactions; particle precipitation)

Use of fractal approach to investigate ionospheric conductivity in the auroral zone

2013 ◽  
Vol 118 (7) ◽  
pp. 4108-4118 ◽  
Author(s):  
A. A. Chernyshov ◽  
M. M. Mogilevsky ◽  
B. V. Kozelov
Keyword(s):  
Auroral Zone ◽  
Ionospheric Conductivity ◽  
Fractal Approach
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