Browsing by Author "Kosch, Michael J."

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    First Observations of E-Region Near Range Echoes Partially Modulated by F-Region Traveling Ionospheric Disturbances Observed by the Same SuperDARN HF Radar
    (Journal of Geophysical Research: Space Physics, 2022) Kosch, Michael J.; Hiyadutuje, Alicreance; Stephenson, Judy A. E.
    We present the first observations from SuperDARN HF radar data of E-region Near Range Echoes (NREs) whose amplitudes are partially modulated by Medium-Scale Traveling Ionospheric Disturbances (MSTIDs) propagating in the F-region overhead that have been observed by the same radar in the far ranges. SuperDARN NREs occur normally ∼180–315 km downrange from the radar at ∼95–125 km altitude. Selected observations of TID-modulated NREs are presented from SANAE and Zhongshan Antarctic SuperDARN radars for both summer and winter seasons as well as geomagnetic active and quiet times. We show that the most likely mechanism is partial modulation of the Gradient Drift Instability (GDI), which is responsible for producing the NREs. GDI is driven by the velocity difference between neutrals and ions and may appear in the E-region ionosphere wherever suitable plasma density gradients exist. GDI already present in the E-region can be partially modulated by an MSTID passing overhead in the F-region via the additional MSTID polarization electric field mapped down in altitude along the equipotential magnetic field lines, thereby partially modulating the NRE amplitudes as observed.
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    Global simulations of multi-frequency hf signal absorption for direct observation of middle atmosphere temperature and composition
    (Wiley, 2023) Mahmoudian, Alireza; Kosch, Michael J.; Baghaei, Reza Mohammadi
    This paper presents the first numerical study on a new concept for the direct measurement of D-region absorption in the high-frequency (HF) band. Numerical simulations based on the Appleton-Hartree and Garrett equations of refractive index are presented. Electron temperature as a result of HF radio pumping of the ionosphere is included in the calculations using proper numerical formulation. Both O- and X-mode radio wave polarizations are taken into consideration. A global map of HF absorption in the northern hemisphere is calculated. Detailed calculations of HF radio wave absorption as it propagates through the lower atmosphere are presented. The effect of several parameters on the amount of absorption is calculated. The best frequencies to be used for the purpose of this study are discussed. A machine learning model is developed and the capability of the model in estimation of D and E-region constituents includes N2, O, O2, as well as T and Ne is examined. Such a technique can also lead to global mapping of HF absorption and improve OTHR (over-the-horizonradar) performance.
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    Multi-instrument observations of large-scale atmospheric gravity waves/traveling ionospheric disturbances associated with enhanced auroral activity over Svalbard
    (Elsevier, 2019-09-03) Kosch, Michael J.; Katamzi-Joseph, Zama T.; Aruliah, Anasuya L.; Kjellmar, Oksavik; John Bosco, Habarulema; Kirsti, Kauristie
    This study reports on observations of large-scale atmospheric gravity waves/traveling ionospheric disturbances (AGWs/TIDs) using Global Positioning System (GPS) total electron content (TEC) and Fabry–Perot Interferometer’s (FPI’s) intensity of oxygen red line emission at 630 nm measurements over Svalbard on the night of 6 January 2014. TEC large-scale TIDs have primary periods ranging between 29 and 65 min and propagate at a mean horizontal velocity of ~749–761 m/s with azimuth of ~345–347° (which corresponds to poleward propagation direction). On the other hand, FPI large-scale AGWs have larger periods of ~42–142 min. These large-scale AGWs/TIDs were linked to enhanced auroral activity identified from co-located all-sky camera and IMAGE magnetometers. Similar periods, speed and poleward propagation were found for the all-sky camera (~60–97 min and ~823 m/s) and the IMAGE magnetometers (~32–53 min and ~708 m/s) observations. Joule heating or/and particle precipitation as a result of auroral energy injection were identified as likely generation mechanisms for these disturbances. © 2018 COSPAR. Published by Elsevier Ltd. All rights reserved.