Geoscience Reference
In-Depth Information
Fig. 1.11
Magnetic storm activity, Wednesday October 29, 2003—11:00 a.m. to 4:00 p.m. EST.
Data acquired with GEM's Potassium (GSMP-40) ultra-sensitive magnetometer. (Taken from the
The main phase begins when the solar plasma clouds stream out from the Sun and
then reach the Earth's magnetosphere. This phase with duration from 3 to 20 h brings
a sequence of violent processes referred to as substorms, which result from the
solar wind energy intrusion into the magnetosphere. The magnetic storm develops
because of the substorm superposition with time.
At middle and low latitudes the main phase of magnetic storm manifests itself
as a decrease in H-component of the Earth's field by a value from 40 to 400 nT
during several hours or day and more. Ground-based observations have shown
that the magnetic substorm pattern characteristically exhibits a creek-shaped profile
(magnetic bay) similar to the indentation of a coastline. The magnetic variations
due to the substorm typically lasts for 1-2 h with a peak value about 30-300 nT
while the irregular variations on the ground surface can reach a value from 5
10
2
to 3
10
3
nT. One of the most intensive magnetic storms happened on October 29,
2003 as shown in Fig.
1.11
(e.g., see Panasyuk et al.
2004
). As is seen from this plot,
the amplitude of a positive anomaly is as much as 500 nT and a subsequent negative
anomaly is of the order of 900 nT while the change from maximum to minimum
occurred over the period of approximately 1 h.
During the magnetic storm the energy flux incident upon the magnetosphere
increases by 1-2 order of magnitude. It can reach a value
10
12
-10
13
W that
is close to the power requirements of the humanity but only 1-5 % of this
energy enter the magnetosphere. The most part of this energy penetrates into the
magnetosphere due to viscous friction at the magnetopause and via reconnection of
the interplanetary and Earth's field lines. As a result, the magnetic energy piles up
at the magnetotail.
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