Difference in the current‐voltage relationships between dawn and duskside inverted‐V events

Abstract

We analyze 81 Freja inverted‐V events to study the current‐volt age relationship in different magnetic local time sectors. We use data from the F7 (TESP) electron detector. The events are categorized according to the current‐voltage relationship so that in categories named U, C, and O the current j increases, is constant, or decreases with the voltage V, respectively. We find that the U and C categories are the most common on the eveningside, while the O category dominates the morningside. Globally, category U is the least common. Besides the current density, we also study the behavior of the source plasma density and temperature as a function of the voltage in each category and find that source plasma density is nearly constant in U category, decreases slightly in C, and decreases strongly in O. The source plasma temperature is linearly correlated with the voltage and behaves rather uniformly in all categories. We suggest that there may be an important physical difference between morningside and eveningside inverted‐V events and discuss possible explanations in terms of different auroral potential structure models.