skip to main content


Title: On the variation in the ionospheric response to geomagnetic storms with time of onset: IONOSPHERIC VARIABILITY
NSF-PAR ID:
10035164
Author(s) / Creator(s):
 ;  ;  
Publisher / Repository:
DOI PREFIX: 10.1029
Date Published:
Journal Name:
Journal of Geophysical Research: Space Physics
Volume:
122
Issue:
4
ISSN:
2169-9380
Page Range / eLocation ID:
4512 to 4525
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Vertical incidence pulsed ionospheric radar (VIPIR) has been operated to observe the polar ionosphere with Dynasonde analysis software at Jang Bogo Station (JBS), Antarctica, since 2017. The JBS-VIPIR-Dynasonde (JVD) provides ionospheric parameters such as the height profile of electron density with NmF2 and hmF2, the ion drift, and the ionospheric tilt in the bottomside ionosphere. The JBS (74.6°S, 164.2°E) is located in the polar cap, cusp, or auroral region depending on the geomagnetic activity and local time. In the present study, an initial assessment of JVD ionospheric densities is attempted by the comparison with GPS TEC measurements which are simultaneously obtained from the GPS receiver at JBS during the solar minimum period from 2017 to 2019. It is found that the JVD NmF2 and bottomside TEC (bTEC) show a generally good correlation with GPS TEC for geomagnetically quiet conditions. However, the bTEC seems to be less correlated with the GPS TEC with slightly larger spreads especially during the daytime and in summer, which seems to be associated with the characteristics of the polar ionosphere such as energetic particle precipitations and large density irregularities. It is also found that the Dynasonde analysis seems to show some limitations to handle these characteristics of the polar ionosphere and needs to be improved to produce more accurate ionospheric density profiles especially during disturbed conditions. 
    more » « less
  2. Dense, fast-moving regions of ionization called polar cap patches are known to occur in thehigh-latitudeFregion ionosphere. Patches are widely believed to be caused by convection of dense, sunlitplasma into a dark and therefore low-density polar cap ionosphere. This leads to the belief that patches are awinter phenomenon. Surprisingly, a long-term analysis of 3 years of ionospheric measurements from theSwarm satellites shows that large density enhancements occur far more frequently in local summer than localwinter in the Southern Hemisphere (SH). The reverse is true in the Northern Hemisphere (NH). Previouslyreported patch detections in the SH are reexamined. Detection algorithms using only a relative doubling testcount very small densityfluctuations in SH winter due to extremely low ambient densities found there,while much larger enhancements occurring in SH summer are missed due to especially high ambientdensities. The same problem does not afflict results in the NH, where ambient densities are more stableyear-round due to the ionospheric annual asymmetry. Given this new analysis, the definition of a patch as adoubling of the ambient density is not suitable for the SH. We propose a test for patches linked to long-termaveraged solarflux activity, characterized by the 81 day centered meanF10.7index. Importantly, thecurrent patch formation theory is at least incomplete in that it does not predict the observed lack of patchesin SH winter, or the many large enhancements seen in SH summer 
    more » « less
  3. Abstract

    This paper uses a regional simulation of plasma convective instability in the postsunset equatorial ionosphere together with a global atmosphere/ionosphere/plasmasphere GCM (WAM‐IPE) to forecast irregularities associated with equatorial spreadF(ESF) for 1–2 hr after sunset. First, the regional simulation is initialized and forced using ionosphere state parameters derived from campaign data from the Jicamarca Radio Observatory and from empirical models. The irregularities produced by these simulations are found to be quantitatively similar to those observed. Next, the aforementioned state parameters are replaced with parameters from WAM‐IPE, and the resulting departures between the simulated and observed irregularities are noted. In one of five cases, the forecast failed to accurately predict ESF irregularities due to the late reversal of the zonal thermospheric winds. In four of five cases, significant differences between the observed and predicted prereversal enhancement (PRE) of the background vertical drifts resulted in degraded forecast accuracy. This highlights the need for improved PRE forecasting in the global‐scale model.

     
    more » « less
  4. Abstract

    This study reports a special case of the propagation and morphology of medium scale traveling ionospheric disturbances (MSTIDs) over middle‐latitude China on the night of August 8, 2016. The MSTIDs were simultaneously observed by multi‐instruments, including the all‐sky imager, Swarm satellite, and global positioning system (GPS). The MSTIDs lasted for about 6 h in the field view of airglow imager, showing typical wavelength, phase velocity of 272–296 km and 67–250 m/s, respectively. In addition, the imagers show that the inclination angles of phase fronts for some MSTIDs were decreasing during their propagation, resulting in the propagation direction changed from southwestward to nearly westward. More interestingly, the MSTIDs began to dissipate in the airglow observation when they propagated to lower latitudes (below ∼40°N) whereas the MSTIDs at higher latitudes were still visible in the later local times. Simulation results from the Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model are fairly consistent with the Fabry‐Perot Interferometer (FPI) wind observations, which provide convincing explanation to show that the variations of ionospheric neutral winds might play important roles in the changes of propagation direction and the dissipation of MSTIDs.

     
    more » « less