An official website of the United States government
Abstract Previous simulations have suggested that O+outflow plays a role in driving the sawtooth oscillations. This study investigates the role of O+by identifying the differences in ionospheric outflow between sawtooth and non‐sawtooth storms using 11 years of FAST/Time of flight Energy Angle Mass Spectrograph (TEAMS) ion composition data from 1996 through 2007 during storms driven by coronal mass ejections. We find that the storm's initial phase shows larger O+outflow during non‐sawtooth storms, and the main and recovery phases revealed differences in the location of ionospheric outflow. On the pre‐midnight sector, a larger O+outflow was observed during the main phase of sawtooth storms, while non‐sawtooth storms exhibited stronger O+outflow during the recovery phase. On the dayside, the peak outflow shifts significantly toward dawn during sawtooth storms. This strong dawnside sector outflow during sawtooth storms warrants consideration.
more »
« less
Interhemispheric Asymmetry in the Seasonal Ionospheric Outflow
Abstract A comprehensive statistical study is conducted on O+and H+outflows obtained from the TEAMS/FAST data during the 23rd solar cycle (1996–2007). The study investigates interhemispheric asymmetry in ionospheric outflows during local summer, winter, and equinox seasons. Data are classified into two distinct periods: the pre‐storm and geomagnetic storm phases. Numerous statistical asymmetries are identified. The findings indicate that the dayside cusp consistently demonstrates more outflow rates of O+and H+in the northern hemisphere than southern hemisphere during geomagnetic storms in all seasons as well as during the pre‐storm period in the summer season with the exception of H+during summer storms. Conversely, the nightside O+and H+outflow rates are higher in the southern hemisphere during pre‐storm and storm periods in the summer season. Additionally, the dawnside and duskside outflow rates of O+and H+are predominantly stronger in the southern hemisphere.
more »
« less
- Award ID(s):
- 1845151
- PAR ID:
- 10532953
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 51
- Issue:
- 14
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract We examine the statistical distribution of large‐scale Birkeland currents measured by the Active Magnetosphere and Planetary Electrodynamics Response Experiment in four unique categories of geomagnetic activity for the first time: quiet times, storm times, quiet‐time substorms, and storm‐time substorms. A novel method is employed to sort data into one of these four categories, and the categorizations are provided for future research. The mean current density is largest during substorms and its standard deviation is largest during geomagnetic storms. Current densities which are above a low threshold are more likely during substorms, but extreme currents are far more likely during geomagnetic storms, consistent with a paradigm in which geomagnetic storms represent periods of enhanced variability over quiet times. We demonstrate that extreme currents are most likely to flow within the Region 2 current during geomagnetic storms. This is unexpected in a paradigm of the current systems in which Region 1 current is generally larger.more » « less
-
Abstract Stable auroral red (SAR) arcs provide opportunities to study inner magnetosphere‐ionosphere coupling at midlatitudes. An imaging system at a single‐site obtains evidence of seasonal variations in SAR arc brightness and occurrence rates using events widely separated in time, as observed during different geomagnetic storms. The first SAR arc observed using two all‐sky imagers at geomagnetic conjugate points described seasonal effects at the same time for the same storm (Martinis, Mendillo, et al., 2019,https://doi.org/10.1029/2018JA026018). Here we report on modeling studies that enable specification of the roles of local “receptor conditions” in each hemisphere, plus the division of driving energy from a single source region into conjugate ionospheres. The geomagnetic storm of 1 June 2013 produced SAR arcs observed by conjugate all‐sky imagers yielding 73 Rayleighs (R) at Millstone Hill (L= 2.64) in the summer hemisphere, and 300 R during local winter at Rothera (L= 2.92). With incoherent scatter radar data not available to specify input conditions, we offer a new simulation approach using non‐incoherent scatter radar observations to specify local receptor conditions. These include a combination of semiempirical models (International Reference Ionosphere and MSIS) calibrated by local ionosonde and DMSP satellite data. We find that the driving mechanism (heat conduction entering the ionosphere) is not an equal partition of energy from the ring current source region, but one that is weaker in the summer hemisphere where the local receptor conditions are poised to produce fainter SAR arcs. The relationship between SAR arcs and recently discovered STEVE events are discussed and require further study.more » « less
-
Abstract We present multi‐platform observations of plasma cloak, O+ outflows, kinetic Alfven waves (KAWs), and auroral oval for the geomagnetic storm on 17 March 2015. During the storm's main phase, we observed a generally symmetric equatorward motion of the auroral oval in both hemispheres, corresponding to the plasmasphere erosion and inward motion of the plasma sheet. Consequently, Van Allen Probes became immersed within the plasma sheet for extended hours and repeatedly observed correlated KAWs and O+ outflows. The KAWs contain adequate energy flux toward the ionosphere to energize the observed outflow ions. Adiabatic particle tracing suggests that the O+ outflows are directly from the nightside auroral oval and that the energization is through a quasi‐static potential drop. The O+ outflows from the nightside auroral oval were adequate (‐ #/‐s) and prompt (several minutes) to explain the newly formed plasma cloak, suggesting that they were a dominant initial source of plasma cloak during this storm.more » « less
-
Abstract The High‐latitude Ionosphere Dynamics for Research Applications (HIDRA) model is part of the Multiscale Atmosphere‐Geospace Environment model under development by the Center for Geospace Storms NASA DRIVE Science Center. This study employs HIDRA to simulate upflows of H+, He+, O+, and N+ions, with a particular focus on the relative N+concentrations, production and loss mechanisms, and thermal upflow drivers as functions of season, solar activity, and magnetospheric convection. The simulation results demonstrate that N+densities typically exceed He+densities, N+densities are typically ∼10% O+densities, and N+concentrations at quiet‐time are approximately 50%–100% of N+concentrations during storm‐time. Furthermore, the N+and O+upflow fluxes show similar trends with variations in magnetospheric driving. The inclusion of ion‐neutral chemical reactions involving metastable atoms is shown to have significant effects on N+production rates. With this metastable chemistry included, the simulated ion density profiles compare favorably with satellite measurements from Atmosphere Explorer C and Orbiting Geophysical Observatory 6.more » « less
