The responses of ionospheric topside diffusive fluxes to two geomagnetic storms in October 2002

Abstract

O + field-aligned ambipolar diffusive velocities V d and fluxes Ф d in the topside ionosphere have been calculated from the observed profiles of electron density, ion, and electron temperatures during a 30 day incoherent scatter radar experiment conducted at Millstone Hill (288.5°E, 42.6°N) from 4 October to 4 November 2002. Two geomagnetic storms took place during this period. During the negative phases (depleted electron densities) of these two storms, the magnitudes of the daytime upward V d and Ф d were less than their averaged quiet time values. Whereas at nighttime, the downward V d and Ф d were sometimes larger than the averaged quiet time values. The variations in diffusive velocity and flux during the storm main and recovery phases were caused by changes in the ionospheric scale height or the shapes of ionospheric density profiles. The negative storm effect further reduced daytime diffusive flux. During these two storms, positive ionosphere phases (enhanced electron densities) were also observed. The diffusive velocity was much smaller during the period of positive storm effect, which led to a smaller diffusive flux than the quiet time one, although electron density was higher. It appears that storm time variations in diffusive velocity were more the results of storm time changes in the plasma vertical profile, rather than the cause of these plasma density changes.

Profiles of ionospheric storm‐enhanced density during the 17 March 2015 great storm

“…In the topside ionosphere (Figure 8d), storm time vertical ion drifts were small and downward, whereas those during quiet time were large and upward. Similar storm time changes in vertical ion drifts were also seen by Chen et al [2014]. They reported that the daytime upward ambipolar diffusive velocity decreased during negative ionospheric storm effect periods over Millstone Hill.…”

Physical Processes Driving the Response of the F2 Region Ionosphere to the 21 August 2017 Solar Eclipse at Millstone Hill

“…The top boundary condition for the O + continuity equation is the O + diffusive flux. In this study, we used the method described in Chen et al (, ) to specify this flux by using Millstone Hill observed ionospheric parameters from 19 to 23 August. This flux was also modified such that the TIEGCM simulated electron density profiles could match the observed Ne profiles (cf.…”

“…Figures and ). Note that O + diffusive flux in the topside ionosphere changes greatly with geophysical conditions, such as local time, solar and geomagnetic activity, and season and magnetic latitude (Chen et al, , , ). The default TIEGCM uses a simple topside O + diffusive flux that is a constant most of the time (upward during the day and downward at night), except that it varies with local time just near dawn and dusk and with magnetic latitude at low latitudes (Wang, ).…”

Climatology Analysis of the Daytime Topside Ionospheric Diffusive O+ Flux Based on Incoherent Scatter Radar Observations at Millstone Hill

“…The transition time at dusk has remarkable importance for improving the upper boundary conditions of some theoretical models, such as the TIEGCM, because after this time the ion flux flows from the plasmasphere to the ionosphere. There are some common features can be found through comparing our statistical results at solar minimum with the storm case analysis at solar maximum of Chen et al (2014). During the autumn day, the increase of geomagnetic conditions decreases the magnitude of…”