Ionosphere at low frequencies

Olga Alexandrova — 2018-03-20T16:28:33Z

The Earth atmosphere is described in several layers following the height evolution of the neutral density and temperature. From about 70km another layer appears composed of ionized particles : the ionosphere. This layer is of particular interest for its role in the global electrical currents of the Earth magnetosphere but also in long distance radio transmission (still used on disaster regions for example). The Earth and ionosphere serve then as waveguide to transmit the information.

Quite surprisingly, the lowest parts of the ionosphere (70-100km) are almost unknown. Indeed, they are too low to be explored by spacecraft but too high for balloons sounding.Taking advantage of the reflection of the VLF-waves on the ionosphere, the time evolution of the electric conductivity (and thus the electron density) can be inferred on localized area of the ionosphere.

The variation of the electron density is particularly important during solar flares. Thus, electron density disturbances can propagate in the ionosphere, generating perturbations of waves transmission. This may be critical for some industrial activities (like radio broadcast or civil aviation).

Multiplying the receiver stations around Europe can enable to draw maps of the conductivity, in almost real time. The aim of the meeting is to gather people interested in participating to this network of low frequency receivers, for mid-latitude regions, in particular Europe.

Voir le site de l'atelier : http://esters.obspm.fr/spip.php?article84

Programme scientifique préliminaire

09 :30 – 10 :00 « Ionosphere at low frequency » M. Clilverd
10 :00 – 10 :20 « GNSS as a global observing system for ionospheric monitoring and research » Cherniak I.
10 :20 – 10 :40 « Global Ionospheric and Thermospheric Effects of the June 2015 Geomagnetic Disturbances : Multi-Instrumental Observations and Modeling » TBC
10:40 - 11:00 « Synchronized Pulsations in the Earths Lower Ionosphere and Solar Flare Emission » L. Hayes

11 :00 – 11 :20 Coffee Break

11 :20 – 11 :35 « September 2017 solar flares as seen by the Meudon Observatory VLF-receiver » C. Briand
11 :35 – 11 :50 « The UAH VLF monitoring station » C. Cid
11 :50 – 12 :10 « Ionosondes network » E. Blanch
12 :10 – 12 :30 « Ionospheric Research at INGV » L. Alfonsi

Lunch and visit of the VLF monitor

14 :00-14 :30 « The AARDDVARK network » M. Clilverd
14 :30 – 15 :00 « LATNET and SAVNET » J.P. Raulin
15 :30 – 16 :00 « GIFDS » N. Jakowski
16 :00 – 16 :20 – Coffee Break

16 :20 – 17 :00 Discussion

Publications

Thomson, N. R., Clilverd, M. A. and Rodger, C. J., "Midlatitude ionospheric D region : Height, sharpness, and solar zenith angle", Journal of Geophysical Research (Space Physics, 2017, 122, 8933-8946
Haynes, S. Gallagher, P.T. et al., "Pulsations in the Earth's lower ionosphere synchro- nized with solar ﬂare emission", Journal of Geophysical Research : Space Physics, 2017, 122,9841–9847
Borgazzi, A. Lara, A. Paz, G. and Raulin, J. P., "The ionosphere and the Latin America VLF Network Mexico (LAVNet-Mex) station", Advances in Space Research, 2014, 54, 536-545
Wenzel, D. Jakowski, N. , Berdermann, J. et al., "Global ionospheric flare detection system (GIFDS)", Journal of Atmospheric and Solar-Terrestrial Physics, 2016, 138, 233-242

Centre de Conférences Jules Janssen

Ionosphere at low frequencies

Programme scientifique préliminaire

Publications