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Abstract The effect of storms driven by solar wind high‐speed streams (HSSs) on the high‐latitude ionosphere is inadequately understood. We study the ionosphericF‐region during a moderate magnetic storm on 14 March 2016 using the EISCAT Tromsø and Svalbard radar latitude scans. AMPERE field‐aligned current (FAC) measurements are also utilized. Long‐duration 5‐day electron density depletions (20%–80%) are the dominant feature outside of precipitation‐dominated midnight and morning sectors. Depletions are found in two major regions. In the afternoon to evening sector (12–21 magnetic local time, MLT) the depleted region is 10–18 magnetic latitude (MLAT) in width, with the largest latitudinal extent 62–80 MLAT in the afternoon. The second region is in the morning to pre‐noon sector (04–10 MLT), where the depletion region occurs at 72–80 MLAT within the auroral oval and extends to the polar cap. Using EISCAT ion temperature and ion velocity data, we show that local ion‐frictional heating is observed roughly in 50% of the depleted regions with ion temperature increase by 200 K or more. For the rest of the depletions, we suggest that the mechanism is composition changes due to ion‐neutral frictional heating transported by neutral winds. Even though depletedF‐regions may occur within any of the large‐scale FAC regions or outside of them, the downward FAC regions (R2 in the afternoon and evening, R0 in the afternoon, and R1 in the morning) are favored, suggesting that downward currents carried by upward moving ionospheric electrons may provide a small additional effect for depletion.
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Factors correlated with intracranial interictal epileptiform discharges in refractory epilepsy
Abstract ObjectiveThis study was undertaken to evaluate the influence that subject‐specific factors have on intracranial interictal epileptiform discharge (IED) rates in persons with refractory epilepsy. MethodsOne hundred fifty subjects with intracranial electrodes performed multiple sessions of a free recall memory task; this standardized task controlled for subject attention levels. We utilized a dominance analysis to rank the importance of subject‐specific factors based on their relative influence on IED rates. Linear mixed‐effects models were employed to comprehensively examine factors with highly ranked importance. ResultsAntiseizure medication (ASM) status, time of testing, and seizure onset zone (SOZ) location were the highest‐ranking factors in terms of their impact on IED rates. The average IED rate of electrodes in SOZs was 34% higher than the average IED rate of electrodes outside of SOZs (non‐SOZ;p < .001). However, non‐SOZ electrodes had similar IED rates regardless of the subject's SOZ location (p = .99). Subjects on older generation (p < .001) and combined generation (p < .001) ASM regimens had significantly lower IED rates relative to the group taking no ASMs; newer generation ASM regimens demonstrated a nonsignificant association with IED rates (p = .13). Of the ASMs included in this study, the following ASMs were associated with significant reductions in IED rates: levetiracetam (p < .001), carbamazepine (p < .001), lacosamide (p = .03), zonisamide (p = .01), lamotrigine (p = .03), phenytoin (p = .03), and topiramate (p = .01). We observed a nonsignificant association between time of testing and IED rates (morning–afternoonp = .15, morning–eveningp = .85, afternoon–eveningp = .26). SignificanceThe current study ranks the relative influence that subject‐specific factors have on IED rates and highlights the importance of considering certain factors, such as SOZ location and ASM status, when analyzing IEDs for clinical or research purposes.
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- Award ID(s):
- 1632738
- PAR ID:
- 10449784
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Epilepsia
- Volume:
- 62
- Issue:
- 2
- ISSN:
- 0013-9580
- Format(s):
- Medium: X Size: p. 481-491
- Size(s):
- p. 481-491
- Sponsoring Org:
- National Science Foundation
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