RADAR OBSERVATIONS OF PLASMA DEPLETIONSIN THE IONOSPHERE

INTRODUCTION

The depletions in the F region, known as ionospheric troughs

Satellite based investigations useful for studying of long-term behaviour or its general properties

Mechanisms that contribute to the formation require other ionospheric parameters data, which can be provided by the radars

Trough formation attributed to several mechanisms, with plasma convection, neutral wind effects, precipitation and heating are the most active

A high ion velocity could result in heating, turn increases the ion loss and leads to a depleted density.

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OBSERVATION METHODS

The Incoherent Scatter (IS) radar is a powerful ground based technique for the study of the Earth's ionosphere

Electromagnetic wave transmitted to ionosphere and high-power energy scattered signal by the electrons in the ionospheric plasma is detected by large antenna and a sensitive receiver

The frequency spectrum of received signal provides information about the electron density, the electron and ion temperature, the plasma composition and its velocity, and others

Radar antenna scan the upper atmosphere in north-south plane, covering wide band of latitudes between 60° and 75° N

Observed at different times of the day, during different seasons

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Fig.1 Summer, Evening Hour Fig.2 Winter, Dark Hour Fig.3 Winter, Evening Hour Fig.4 Summer, Night

• ThroughLatitude Summer higer that winter, night lower than evening, the highest is Fig.1

• Ion temperature in all cases are increased which caused higher ion loss rate and ion density are decreased, but for summer there is a temperature differention between inside and outside the trough, for winter not.

• Ion upward movement for Summer through, and Ion at the rest for Winter through

• Through formation, summer because of ion recombination, winter because of lacking photo iononization

RADAR OBSERVATIONS OF PLASMA DEPLETIONSIN THE IONOSPHERE

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CONCLUSION

• Plasma parameters seem to have same characteristics for the same seasons, summer and winter troughs including location (low latitudes during winter, high latitudes during summer),variation in the temperatures, the ions behaviour inside and outside the troughs in the similar seasons

• The plasma parameters behave differently during summer and winter, indicate the fact that formation mechanisms of the trough are different

• A more extensive study, including information about the horizontal movement of ions, which required in order to better understand the formation mechanism of the trough and their prevalence during certain seasons

REFERENCE

M. Voiculescu, T. Nygren, Radar Observations of Plasma Depletions in the Ionosphere, September 26th 2006.

M. Voiculescu, T. Nygren, Extraterrestrial magnetic field effect on the F region trough, Rom. Journal. Physic, this issue.

RADAR OBSERVATIONS OF PLASMA DEPLETIONSIN THE IONOSPHERE