Long term ionospheric trends over Ahmedabad

Abstract

There is a decrease in hpF2 (16 km for midday and 10 km for midnight). The lowering of F2 layer peak will affect radio propagation.

A revised approach to the ƒ<i>o</i>F2 long-term trends analysis

“…We analyze (for each LT moment) relative rather than absolute δfoF2 deviations considered in the foF2 and hmF2 trend analyzes by Bremer (1998); Ulich and Turunen (1997); Jarvis et al (1998); Upadhyay and Mahajan (1998);Sharma et al (1999);Foppiano et al (1999). As far as we know relative deviations were considered only by Deminov et al (2000) in their foF2 long-term trend analysis.…”

“…Due to an increasing interest in the anthropogenic impact on the Earth's atmosphere the ionospheric parameter longterm trends are widely discussed in recent publications (Bremer, 1992(Bremer, , 1998Leshchenko, 1994, 1995;Danilov, 1997Danilov, , 1998Ulich and Turunen, 1997;Rishbeth, 1997;Jarvis et al, 1998;Upadhyay and Mahajan, 1998;Sharma et al, 1999;Foppiano et al, 1999;Danilov and Mikhailov, 1999;Mikhailov and Marin, 2000;Deminov et al, 2000;Danilov and Mikhailov, 2001). The interest in the ionospheric trend analysis was greatly stimulated by the model calculations of Rishbeth (1990) and Rishbeth and Roble (1992), who predicted the ionospheric effects of the atmosphere greenhouse gas concentration inCorrespondence to: A. V. Mikhailov (avm71@orc.ru) crease.…”

Ionospheric F1 layer long-term trends and the geomagnetic control concept

“…In these papers it is stressed: a) a positive trend in the foF1 long-term variation, b) a relationship with the global cooling of the thermosphere due to the greenhouse effect (Bremer, 1998(Bremer, , 2001Sharma et al, 1999), c) the insignificance of the geomagnetic activity (Xu et al, 2004).…”

“…The majority of analyses have been devoted to long-term trends in the ionospheric F2 and E-layer parameters since these observations are the most abundant and consistent, while trends in the F1-layer have been considered, as far as it is known, only in some papers (Bremer, 1998(Bremer, , 2001Sharma et al, 1999;Xu et al, 2004). In these papers it is stressed: a) a positive trend in the foF1 long-term variation, b) a relationship with the global cooling of the thermosphere due to the greenhouse effect (Bremer, 1998(Bremer, , 2001Sharma et al, 1999), c) the insignificance of the geomagnetic activity (Xu et al, 2004).…”

Long-term <i>hm</i>F2 trends in the Eurasian longitudinal sector from the ground-based ionosonde observations

“…But long-term changes in the thermosphere and ionosphere should also be studied seriously not only for their possible practical importance for the ionospheric HF radio-wave propagation, but also for their potential use as indicators of changes at lower heights. During recent years several attempts have been made to analyse various sets of long period observations in order to reveal the long-term effects in various ionospheric parameters Leshchenko, 1994, 1995;Ulich andTurunen, 1997, Rishbeth, 1997;Jarvis et al, 1998;Bremer, 1992Bremer, , 1998Danilov 1997Danilov , 1998Upadhyay and Mahajan, 1998;Mikhailov 1998, 1999;Sharma et al, 1999;Foppiano et al 1999; Correspondence to: D. Marin (marinsd@inta.es) Marin 2000; Deminov et al, 2000). But no final concept has been developed yet.…”