Atmosphere-Ionosphere coupling -manifestations in the low latitude ionosphere
Abstract
As is known, the extent of the impact of the geomagnetic storms on the vertical coupling of the MLTI regions, especially over low latitudes, is not very well understood. To investigate this aspect of the MLTI coupling, a multi-instrument campaign was conducted during March-April 2006, a period when a few moderate geomagnetic storms occurred, in India. During the campaign period, a Multiwavelength dayglow Photometer (MWDPM) was operated along with ionosonde, magnetometer and a meteor radar from Trivandrum (8.5oN, 76.5oE, 0.5oN diplat.), the dip equatorial station in India. The MWDPM provided the optically estimated daytime mesopause temperature while the meteor radar measured the wind and temperature in the lower thermosphere-upper mesosphere region. The MWDPM also provided the near simultaneous measurements on the thermospheric dayglow (O1D 630 nm). GPS satellite based measurements of total electron content (TEC) over a number of locations in India provided the latitudinal distribution of ionization. The new and important observations made during this campaign are the following: (a) The optically measured daytime mesopause temperature shows a prominent decrease in the afternoon hours during the initial and main phases of the geomagnetic storms. This observation, perhaps, is new and unique. (b) Quasi 2 and 5 day oscillations appear to be modulating the mesopause temperature indicating the presence of planetary waves therein. The wind and temperature variability in the lower thermosphere, obtained using the collocated radar further corroborate with these optical measurements and establish the origin of these waves to be in the lower atmosphere. (c) The Equatorial Electrojet (EEJ) induced magnetic field on the ground also exhibit similar variability indicating the presence of these planetary scale oscillations, also in the ionospheric dynamo region. (d) The simultaneously measured thermospheric dayglow (O1D 630 nm) also shows an intensification of a quasi 2-and 5-day wave activity which in turn indicates towards the possible wave modulations in the daytime upward drift over the equator. (e) Interestingly, these modulations in the MTI region are not restricted to the region around equator. The ionization density over a station, almost 25o away in latitude, also exhibits their presence. In this context, these measurements as presented here, are new and will be discussed in context of the vertical coupling of the equatorial MLTI region.
- Publication:
-
38th COSPAR Scientific Assembly
- Pub Date:
- 2010
- Bibcode:
- 2010cosp...38.1257P