Solovyev S.I.,Institute of Cosmophysical Research and Aeronomy |
Boroev R.N.,Institute of Cosmophysical Research and Aeronomy |
Moiseev A.V.,Institute of Cosmophysical Research and Aeronomy |
Du A.,CAS Institute of Geology and Geophysics |
Yumoto K.,Kyushu University
Cosmic Research | Year: 2011
The influence of auroral electojets and solar wind parameters on variations in low-latitude geomagnetic disturbances and Dst during strong magnetic storms on November 7-8, 2004 with Dst ≈ -380 nT and on November 9-10, 2004 with Dst ≈ -300 nT is studied on the basis of global geomagnetic observations. It is found that the impulsive variations of the western electrojet intensity with a duration of Δt ≈ 1-2 h (probably, substorm disturbances) lead to positive low-latitude disturbances of ΔH at Φ′ ≈ 10°-30° and to disturbances of the same durations with an amplitude +ΔH ~ 30-100 nT at latitudes of the polar cap (Φ′ ≈ 75°-80°). More durable (with Δt ≥ 10 h) convection electrojets whose centers are shifted to latitudes of ~50°-55° in the process of storm development are the main cause of the increase in negative values of ΔH at low latitudes and Dst. It is shown that meridional dynamics of position of the center of electrojets and the equatorial boundary of the auroral oval is governed by variations (increase or decrease) in the intensity of negative values of the IMF Bz component. It is assumed that in these storms the intensification of the magnetospheric partially ring current closes the circuit to the ionosphere with the help of field-aligned currents at the equatorial boundary of the auroral oval is the main cause of the magnetic field depression at low latitudes. © 2011 Pleiades Publishing, Ltd.
Ammosov P.,Institute of Cosmophysical Research and Aeronomy |
Gavrilyeva G.,Institute of Cosmophysical Research and Aeronomy |
Ammosova A.,Institute of Cosmophysical Research and Aeronomy |
Koltovskoi I.,Institute of Cosmophysical Research and Aeronomy
Advances in Space Research | Year: 2014
OH(6-2) rotational temperature trends and solar cycle effects are studied. Observations were carried out at the Maimaga station (63.04°N, 129.51°E) for the period August 1999 to March 2013. Measurements were conducted with an infrared spectrograph. Temperatures were determined from intensity ratios in the P branch of the OH band. The monthly average residuals of temperature after the subtraction of the mean seasonal variation were used for a search for the solar component of temperature response. The dependence of temperatures on solar activity has been investigated using the Ottawa 10.7 cm flux as a proxy. A linear regression fitting on residual temperatures yields a solar cycle coefficient of 4.24 ± 1.39 K/100 solar flux units (SFU). The cross-correlation analyses showed that changes of the residual temperature follow changes of solar activity with a quasi-two year delay (25 months). The temperature response at the delay of 25 months reaches 7 K/100 SFU. The possible reason of the observed delay can be an influence of quasi-biennial oscillations (QBO) of the atmosphere on the relation of temperature and solar activity. The value of the temperature trend after the subtraction of seasonal and solar components is not statistically significant. © 2014 COSPAR. Published by Elsevier Ltd. All rights reserved.