Influence of solar wind dynamic pressure on geomagnetic Dst index during various magnetic storms

2011 ◽  
Vol 54 (6) ◽  
pp. 1445-1454 ◽  
Author(s):  
Hong Zhao ◽  
QiuGang Zong ◽  
Yong Wei ◽  
YongFu Wang
Keyword(s):  
Solar Wind ◽  
Dynamic Pressure ◽  
Magnetic Storms ◽  
Solar Wind Dynamic Pressure ◽  
Dst Index

scholarly journals Ionospheric and geomagnetic responses to changes in IMF <i>B<sub>Z</sub></i>: a superposed epoch study

1997 ◽  
Vol 15 (2) ◽  
pp. 217-230 ◽  
Author(s):  
C. J. Davis ◽  
M. N. Wild ◽  
M. Lockwood ◽  
Y. K. Tulunay
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Dynamic Pressure ◽  
Wind Pressure ◽  
Solar Wind Dynamic Pressure ◽  
High Latitudes ◽  
Winter Solstice ◽  
Ionospheric Response ◽  
Dst Index ◽  
The Imf

Abstract. Superposed epoch studies have been carried out in order to determine the ionospheric response at mid-latitudes to southward turnings of the interplanetary magnetic field (IMF). This is compared with the geomagnetic response, as seen in the indices Kp, AE and Dst. The solar wind, IMF and geomagnetic data used were hourly averages from the years 1967–1989 and thus cover a full 22-year cycle in the solar magnetic field. These data were divided into subsets, determined by the magnitudes of the southward turnings and the concomitant increase in solar wind pressure. The superposed epoch studies were carried out using the time of the southward turning as time zero. The response of the mid-latitude ionosphere is studied by looking at the F-layer critical frequencies, foF2, from hourly soundings by the Slough ionosonde and their deviation from the monthly median values, δfoF2. For the southward turnings with a change in Bz of δBz > 11.5 nT accompanied by a solar wind dynamic pressure P exceeding 5 nPa, the F region critical frequency, foF2, shows a marked decrease, reaching a minimum value about 20 h after the southward turning. This recovers to pre-event values over the subsequent 24 h, on average. The Dst index shows the classic storm-time decrease to about –60 nT. Four days later, the index has still to fully recover and is at about –25 nT. Both the Kp and AE indices show rises before the southward turnings, when the IMF is strongly northward but the solar wind dynamic pressure is enhanced. The average AE index does register a clear isolated pulse (averaging 650 nT for 2 h, compared with a background peak level of near 450 nT at these times) showing enhanced energy deposition at high latitudes in substorms but, like Kp, remains somewhat enhanced for several days, even after the average IMF has returned to zero after 1 day. This AE background decays away over several days as the Dst index recovers, indicating that there is some contamination of the currents observed at the AE stations by the continuing enhanced equatorial ring current. For data averaged over all seasons, the critical frequencies are depressed at Slough by 1.3 MHz, which is close to the lower decile of the overall distribution of δfoF2 values. Taking 30-day periods around summer and winter solstice, the largest depression is 1.6 and 1.2 MHz, respectively. This seasonal dependence is confirmed by a similar study for a Southern Hemisphere station, Argentine Island, giving peak depressions of 1.8 MHz and 0.5 MHz for summer and winter. For the subset of turnings where δBz > 11.5 nT and P ≤ 5 nPa, the response of the geomagnetic indices is similar but smaller, while the change in δfoF2 has all but disappeared. This confirms that the energy deposited at high latitudes, which leads to the geomagnetic and ionospheric disturbances following a southward turning of the IMF, increases with the energy density (dynamic pressure) of the solar wind flow. The magnitude of all responses are shown to depend on δBz. At Slough, the peak depression always occurs when Slough rotates into the noon sector. The largest ionospheric response is for southward turnings seen between 15–21 UT.

scholarly journals Non-storm irregular variation of the <I>D</I><sub>st</sub> index

2012 ◽  
Vol 30 (1) ◽  
pp. 153-162
Author(s):  
S. Nakano ◽  
T. Higuchi
Keyword(s):  
Solar Wind ◽  
Plasma Sheet ◽  
Dynamic Pressure ◽  
Solar Wind Dynamic Pressure ◽  
Thermal Pressure ◽  
Dst Index ◽  
Current Variation ◽  
Term Variation ◽  
Irregular Variation

Abstract. The Dst index has a long-term variation that is not associated with magnetic storms. We estimated the long-term non-storm component of the Dst variation by removing the short-term variation related to magnetic storms. The results indicate that the variation of the non-storm component includes not only a seasonal variation but also an irregular variation. The irregular long-term variation is likely to be due to an anti-correlation with the long-term variation of solar-wind activity. In particular, a clear anti-correlation is observed between the non-storm component of Dst and the long-term variation of the solar-wind dynamic pressure. This means that in the long term, the Dst index tends to increase when the solar-wind dynamic pressure decreases. We interpret this anti-correlation as an indication that the long-term non-storm variation of Dst is influenced by the tail current variation. The long-term variation of the solar-wind dynamic pressure controls the plasma sheet thermal pressure, and the change of the plasma sheet thermal pressure would cause the non-storm tail current variation, resulting in the non-storm variation of Dst.

Energy balance during intense and super-intense magnetic storms using an Akasofu ε parameter corrected by the solar wind dynamic pressure

2007 ◽  
Vol 69 (15) ◽  
pp. 1851-1863 ◽  
Author(s):  
A. de Lucas ◽  
W.D. Gonzalez ◽  
E. Echer ◽  
F.L. Guarnieri ◽  
A. Dal Lago ◽  
...  
Keyword(s):  
Solar Wind ◽  
Energy Balance ◽  
Dynamic Pressure ◽  
Magnetic Storms ◽  
Solar Wind Dynamic Pressure

Solar wind dynamic pressure enhancements and polar auroras

1998 ◽  
Vol 22 (9) ◽  
pp. 1305-1308 ◽  
Author(s):  
Y Zhang ◽  
D.J McEwen ◽  
I Oznovich
Keyword(s):  
Solar Wind ◽  
Dynamic Pressure ◽  
Solar Wind Dynamic Pressure

Statistical study of the effect of solar wind dynamic pressure fronts on the dayside and nightside ionospheric convection

2011 ◽  
Vol 116 (A10) ◽  
pp. n/a-n/a ◽  
Author(s):  
A. Boudouridis ◽  
L. R. Lyons ◽  
E. Zesta ◽  
J. M. Weygand ◽  
A. J. Ribeiro ◽  
...  
Keyword(s):  
Solar Wind ◽  
Statistical Study ◽  
Dynamic Pressure ◽  
Solar Wind Dynamic Pressure ◽  
Ionospheric Convection
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