The mechanism of energy release and field-aligned current generation during substorms and solar flares

In this paper, the mechanisms of field-aligned current (FAC) and westward electrojet generation are considered on the base of space measurements and laboratory simulation. Upward and downward FAC are generated in the Earth magnetotail current sheet (CS) due to the tail earthward electric field. They are connected in the ionosphere by the Pedersen current. The FAC enhancement takes place during magnetic reconnection and explosive energy release at a substorm. Electron acceleration in upward FAC produces fast electron precipitation and aurora appearance. The westward electrojet (Hall current) is located between two opposite directed sheets of FAC. The current in the jet is determined by the Hall conductivity in the ionosphere. The similar current systems in the solar corona are responsible for energy transfer to the chromosphere during a solar flare. The solar flare model is built on the base of observations and 3D MHD numerical simulation for compressible resistive plasma

In-Situ Measurement of Ionospheric E-Region Plasma Irregularities over Taiwan

One ion trap (IT) and one retarding potential analyzer (RPA) onboard the Taiwan Sounding Rocket V (SR-V) were launched to measure ionospheric plasma irregularities on 18 January 2006. After the fairing separated, voltage readings (VG1) of the first grid (G1) in the IT indicated abnormally high negative voltages appeared at the upleg between 83.7 and 120.1 km altitude for 19.7 seconds. It is postulated G1 had temporarily shorted out with the other two grids. Such the anomaly in the VG1 brought out the expansion of a plasma sheath around opening of the IT. More ions were attracted into the collector. Remarkable ion currents detected by the IT led to malfunctions of the RPA simultaneously. In this article, laboratory simulations and the International Reference Ionosphere model are performed to evaluate scale factors for the IT to the anomaly. The calibrated total ion concentration profile at the upleg indicates a peak density of the Es layer at 93.0 km altitude of about 6.9 × 103 # cm-3 with a thickness of 3.4 km. It is very similar to that at the downleg. It implies that the SR-V might encounter the same Es layer twice in a distance of 150 km away

Interferon-alpha-induced mTOR activation is an anti-hepatitis C virus signal via the phosphatidylinositol 3-kinase-Akt-independent pathway.

OBJECT: The interferon-induced Jak-STAT signal alone is not sufficient to explain all the biological effects of IFN. The PI3-K pathways have emerged as a critical additional component of IFN-induced signaling. This study attempted to clarify that relationship between IFN-induced PI3-K-Akt-mTOR activity and anti-viral action. RESULT: When the human normal hepatocyte derived cell line was treated with rapamycin (rapa) before accretion of IFN-alpha, tyrosine phosphorylation of STAT-1 was diminished. Pretreatment of rapa had an inhibitory effect on the IFN-alpha-induced expression of PKR and p48 in a dose dependent manner. Rapa inhibited the IFN-alpha inducible IFN-stimulated regulatory element luciferase activity in a dose-dependent manner. However, wortmannin, LY294002 and Akt inhibitor did not influence IFN-alpha inducible luciferase activity. To examine the effect of PI3-K-Akt-mTOR on the anti-HCV action of IFN-alpha, the full-length HCV replication system, OR6 cells were used. The pretreatment of rapa attenuated its anti-HCV replication effect in comparison to IFN-alpha alone, whereas the pretreatment with PI3-K inhibitors, wortmannin and LY294002 and Akt inhibitor did not influence IFN-induced anti-HCV replication. CONCLUSION: IFN-induced mTOR activity, independent of PI3K and Akt, is the critical factor for its anti-HCV activity. Jak independent mTOR activity involved STAT-1 phosphorylation and nuclear location, and then PKR is expressed in hepatocytes