Browsing by Author "Lovell, Brian C."
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Restricted Positive and negative ionospheric storms occurring during the 15 May 2005 geomagnetic superstorm(American Geophysical Union, 2015-08-10) Horvath, Ildiko; Lovell, Brian C.This study focuses on the 15 May 2005 geomagnetic superstorm and aims to investigate the global variation of positive and negative storm phases and their development. Observations are provided by a series of global total electron content maps and multi‐instrument line plots. Coupled Thermosphere‐Ionosphere‐Plasmasphere electrodynamics (CTIPe) simulations are also employed. Results reveal some sunward streaming plumes of storm‐enhanced density (SED) over Asia and a well‐developed midlatitude trough over North America forming isolated positive and negative storms, respectively. The simultaneous development of positive and negative storms over North America is also shown. Then, some enhanced auroral ionizations maintained by strong equatorward neutral winds appeared in the depleted nighttime ionosphere. Meanwhile, the northern nighttime polar region became significantly depleted as the SED plume plasma could not progress further than the dayside cusp. Oppositely, a polar tongue of ionization (TOI) developed in the daytime southern polar region. According to CTIP simulations, solar heating locally maximized (minimized) over the southern (northern) magnetic pole. Furthermore, strong upward surges of molecular‐rich air created O/N2 decreases both in the auroral zone and in the trough region, while some SED‐related downward surges produced O/N2 increases. From these results we conclude for the time period studied that (1) composition changes contributed to the formation of positive and negative storms, (2) strengthening polar convection and increasing solar heating of the polar cap supported polar TOI development, and (3) a weaker polar convection and minimized solar heating of the polar cap aided the depletion of polar plasma.Item Open Access Storm‐enhanced plasma density and polar tongue of ionization development during the 15 May 2005 superstorm(American Geophysical Union, 2015-05-20) Horvath, Ildiko; Lovell, Brian C.We investigate the ionosphere's global response to the 15 May 2005 superstorm in terms of storm evolution and ionospheric electrodynamics. Our aim is to study the global distribution of plasma and the resultant large‐scale ionospheric features including the equatorial ionization anomaly (EIA), storm‐enhanced density (SED), and polar tongue of ionization (TOI). We have combined multi‐instrument ionospheric data, solar and terrestrial magnetic data, and polar convection maps. Results reveal the prompt penetration of the interplanetary electric field to the polar region and then to the equator with a dusk‐to‐dawn polarity during the initial phase and with a dawn‐to‐dusk polarity during the main phase. This drove during the initial phase a weak eastward equatorial electrojet (EEJ) in the American sector at nighttime and a weak westward EEJ in the Indian‐Australian sector at daytime. During the main phase, these EEJs intensified and changed polarities. SED and polar TOI development was observed prior to and during the initial phase at evening‐premidnight hours over North America and during the main phase in the south at afternoon‐evening hours in the Australian sector. During the main phase and early in the recovery phase, the EIA‐SED structure was well formed in the Asian longitude sector. Then, polar TOI development was absent in the north because of the long distance from the magnetic pole but was supported in the south because of the closeness of daytime cusp and magnetic pole. Thus, the EIA‐SED‐TOI structure developed twice but each time in a different longitude sector and with different characteristics.